13-Inch Fokker D-VII for RFFS-100

[gjohnson]

Ok, I've barely started. But, there's a D-VII trapped in that contest grade balsa trying to get out. Thanks for the GIF files Allan.:)

Regards, Gordon

[pease1]

Looking good Gordon! You're a little ahead of me - keep it that way buddy! I really like that scalloped trailing edge on your wings - really makes it look like a WWI bird! Almost makes me wish I'd done a Spad XIII!

I've got my wings framed up and started on the tailfeathers, but I have to go back to the photocopier. I need to enlarge the tail/rudder 10%-15%. It's just too small at true scale for me to be comfortable that it will have enough surface area to keep the model stable AND have enough rudder authority. On the wings I went for 2 ribs on each wing half, and on the top wing a 5th rib on the center section was necessary, although it's trimmed way down to a sliver. The ribs are at the outter strut and cabane strut locations on the wings. I figured I'd need something to attach the struts too. I plan to make all of my struts from .5 mm CF rod.

The stabilizer is cut out - I'm only making half of the elevator moveable, but I think it will be plenty. It's much easier that way since it keeps me from having to make a joiner for the two elevator halves. I was suspect that a joined surface would not deflect well with the actuators.

http://pease1.sr.unh.edu/aew/rc/DU-Se5a/parts.jpg
(so do you want me to post my photos here or in my own thread? ;) )
More and larger photos here: Al's Micro Se5a (http://pease1.sr.unh.edu/aew/rc/DU-Se5a/)

I didn't see any dihedral in your wing - are you going for aileron control? I bet these would fly fine with one aileron. You have a nice advantage with the Fokker, in that all the control surfaces are aerodynamicly balanced in scale!

I have my ribs framed up and the dihedral in my top wing (which is 1 piece). The lower wing halves will get dihedral when they're attached to the fuselage. I went for 3/4" dihedral at each wingtip, I hope that's enough. It's much more than scale, but little enough that it doesn't look too much unscale.

So are we aiming to try to run these on 3 cells? I think I'll need at least 3 to balance my model.

Al

[gjohnson]

Al,
The reason you don't see any dihedral is there isn't any yet. I haven't even got the ribs cut out.:( The dihedral on the D-VII is further out from the center than on the Se5. So, I'll put a rib at the dihedral break, and out where the struts attach.

I used a light ply doubler on the elevator and planned to make both sides move, which means cutting an area out of the rudder. I like your one side idea. I made the elevator out of 1/32nd, what is yours? I ended up gluing pieces together to get the grain running in different directions, those rounded tips are pretty weak. I also wicked some light CA into the rounded tips to stiffen them up a bit. I'll do the same on the wing as they are just asking to be broken off.

I have to enlarge my rudder too. That's why you don't see one.

What are you going to do about rib lines and control surface breaks? I was wondering about a Q-tip with pencil graphite on it and then smudge lines near the LE and TE of the wings to give some emphasis for the ribs. I'll try this on a practice piece of heavy balsa first to see how it covers with paint. BTW, are you good with an airbrush? I've never used one. Maybe I should try.

These little planes are just too much fun. I started a new thread because I didn't know if it would confuse people having them both in one thread. On the otherhand, they are basically the same, just different profiles. Doesn't matter to me.

Gordon

[gjohnson]

Al,
The more I think about it, maybe we should not discard the printed tissue covering method so quickly. There is a site http://www.fidelersgreen.net that sells PDF files that can be printed on a color printer and folded up to make quite detailed planes. I've wondered for a while about using these on Depron to get nice looking planes. The problem is they are PDF files. But, I think it's possible to copy all or part of them and paste into a graphics program and then resize to our planes. The detail on these if pretty good. Their Piper Cup (their free downloadable trial plane has about a 10 inch wing span). But, if we can master the printing to tissue and then covering, we could make more scale looking micro planes. Especially if we wanted camoflage schemes.

Do you know anything about the tissue ink jet printer technique? I once tried taping some tissue to a sheet of paper and running it through my printer. I didn't get great results, but I don't know how it would have looked had I glued it to balsa. Maybe we should do a search on Ezone and Google.

Gordon

[pease1]

All my surfaces are 1/32. I plan to run a 1/16" wide strip of CF ribbon along the LE of the top wing to strengthen it up. The tailfeathers I'm planning on leaving untreated. I picked some of my stiffer stock for them.

I've been to the fiddlers green site. I'm not sure I want to go that route though. His fold-up models have extra material in them that may be counter-productive. They make nice 'looking' models, but who knows how they'll fly.

I don't know anything about the tissue method, but I'm willing to experiment!

Rib details I plan to draw on with technical pen, colored pencil, etc. Actually in this scale they wouldn't be that pronounced - leaving them off is even a possibility! I'm going to draw on the ailerons for sure though. I have to scratch build some engine bits out of balsa and a Lewis gun on a foster mount for the top wing - that's going to be a challenge! I refuse to send an Se5a up unarmed though.

Maybe a profile pilot if I get sick about things, we'll see. Also, some minimal inter-wing rigging will not only look good, but be very functional - If the plane can handle the extra drag.

Al

[Ralph B]

Al, Gordon:

I think printed tissue would be the way to go on both of your projects. In case you didn't know about it, I wanted to let you know that my brother authored a detailed feature article on the printed tissue process which was published in the July 1998 issue of "Flying Models". If you don't have access to that back issue send me a private email and I may be able to help you track it down.

Ralph

[gjohnson]

Ralph,
Thanks for pointing us in the right direction. I've sent you my email address. I think with the Fiddlers Green DVII, which I now need to figure out how to resize, and your brothers and your techniques I should be off and running. Will take too long to get the Flying Models back issue from them, and I've had a subscription for only a year or so.

Regards, Gordon

[pease1]

Thanks for the offer Ralph, if you get a copy to Gordon I'm sure he'll be happy to forward a copy to me :D

The nice thing about the tissue method is I can print the rib detail, control surfaces, and insignia and drop them all down at one time.

I just need to make sure I can keep it LIGHT.

Al

[gjohnson]

Al,
Have you checked out the Fiddlers Green site yet? They have a nice SE5a as one of their planes. You are better at and have access to more graphics packages than I am. Perhaps you could take a stab at resizing one of the PDF files? For a single plane the cost is $2.95 (the full CD is a much better buy when we get this technique down) and you just download it. They have a Piper Cub that can be downloaded for free which you can try on if you want. Also, included with each plane is a three view of it. In the case of the Fokker DVII, it's exactly the same one you sent me a GIF of.

Gordon

[Ralph B]

Gordon:

I got your private email and replyed to the new address that you sent.
Ralph

[gjohnson]

I found a post by Ralph's brother on the EzoneBasically, spray photo mount on a sheet of paper, then stick it against and pull off cardboard about five times to reduce the stickiness. Stick tissue on and print out on inkjet printer on economy setting. I'll wait for Ralph's email and the finer details at home tonight.

You can use the graphics capture tool in Adobe Reader 5.0 to select sections of a PDF file to copy, then paste into any paint/graphics program, use resize to enlarge to dimension of wing, and then print. I know there will be a few other details to be worked out. But, with this Al, you should be able to download the SE5a and put it on your wings tonight. Family allowing, I'm going to give it a shot tonight for my D-VII. Otherwise, my wife has book club Thursday night ...

I started turning my scale balsa wheels on my Dremel this morning before work. I want to get that tapered slight cone look on the wheels and a rounded tire. One trick I've learned here is to use very light balsa for the wheels, and laminate the sheets together with Super Phatic glue since it's lighter than CA.

Ralph, please continue to give us the benefit of your experience.

Gordon

[pease1]

Tissue method: sounds good, I'll look into that soon.

Wheels: I'm turning the 'cone' on the dremel, but then I plan to put a rubber O-ring on as the tire. It's easier to paint the hubs the correct color that way and they're more durable. I should be able to get an O-ring thin enough to be light.

I worked on the fuselage for an hour tonight - I made some progress, but there's a long way to go. You have a slight advantage on me there - your turtledeck is much less curved and you don't have a headrest to contend with :p

For the tail and rudder I went with 110% of scale. Anything larger looked really silly.

I'm not sure how much more work I'll get done before my vacation this Friday. I have a lot of commitments and some shopping to do to get ready. Count on more productivity from me after Easter. By that time I expect you'll have yours flying or darned near close. Maybe I can ride your coat-tails and learn from your experiences!

Al

P.S. Check the DU-IFO thread for movies of my RFFS-100 IFO, may be the last flights before I decomission it to put the gear in the Se5a!

[gjohnson]

Al,
I was planning to paint the cone of the wheels through a cutout hole in a piece of paper, then chuck the wheels up again but in my drill press (which turns way slower than a Dremel) and apply the tire with magic marker. Let me know what your wheels weigh with the o-ring. Right now two of mine without aluminum hubs weigh 0.2g combined.

On your wing, what did you do for ribs? Were they 1/32 or 1/16? Did you end up doubling the ribs where the dihedral breaks are? Just curious as I'm not entirely happy with the way my top wing came out. It weighs 1.8g bare. I used 1/16th for the ribs and doubled them at the break, but I'm now questioning it. I wonder how much weight the tissue adds?

I have a set of bitmap files mostly ready for printing from the Fiddler's Green PDF file. When you get yours, there's something to consider. They have fuzzy grey lines at the edges and corners. The question is, if we are covering a fuselage in sections (sides, top, bottom) do we want to leave these grey lines on, or instead do some manipulation in a graphics program to fill out with(in my case) red? that way we could have a bit of overlap and have the fuselage color blend together where they overlap. I'm going to give it a try on the top wing Thursday night if I can.

Also, I'm wondering if 0.5mm CF rod will be too small for a scale strut look. I also wonder if it will be heavier than balsa struts. I read a technique for larger planes where a guy makes a pot of tea with a bunch of tea bags and dips his struts to make them look the color of varnished wood without the weight of paint. I'm thinking of trying this on the struts before gluing them in place. They should glue just fine after drying out.

Gordon

[pease1]

I'll photograph the underside of my wing to help you out. I'm happy with it with the slight exception that I didn't align the surfaces carefully enough on one joint and had to do some sanding. My ribs are 1/16" but some of the lightest stuff I had. I don't have any rib at the dihedral break, I sanded the edge the correct angle and just butt-glued the two sheets - it's plenty strong because it's two curved surfaces. Balsa glues up fine end to end with CA at this scale. I was going to run a 1/16" wide CF ribbon along my wing as a spar, either at the LE or across the top in traditional spar location, but now that it's built I think this is overkill.

I want to use CF rods for my struts for strength. I'm afraid balsa in scale size will be too weak. I think the rod I'm going to use is .7mm

Al

[Ralph B]

Al, Gordon:

It sounds like you have decided tp go with the printed tissue so let me suggest that you also use printed tissue on the wheels. You can make very light weight wheels by laminating 1/32 balsa onto 1/64 plywood disks. After laminating the balsa you can sand it to the desired tapered cross section (use thicker balsa if you require more taper) in a dremel tool. I use the small size yellow tubing that comes in the Sulivan cable type push rod sets as the bearing. Cut the tube about 1 inch long so you can use it as a turning mandrel in your Dremel. I glue both wheel blanks about 1/4" apart on one end of the tube. Chuck the other end in the Dremel and you now have a hand held lathe that will allow you to turn the pair of wheels to the final diameter. You can use a stick about 1/16" X 3/8" X 6" with sandpaper glued to the flat side to sand the taper into both wheels. After sanding take a sharp razor blade and cut the tube flush with the hub on both sides and you now have a nice light pair of vintage wheels ready for covering. The tire, spokes etc. is printed on the tissue and while it adds to the looks of the model it also makes the wheel very strong for it's weight. You can also eleminate the plywood for a little more weight savings for the lighter models. In this case laminate the balsa so the grain of the two pieces is at 90 degrees to one another. I'm looking forward to seeing your finished product.

Ralph

[gjohnson]

Ralph,
Thanks, that's pretty much how I do it, except I've been gluing in aluminum tubing from Peck after I'm done turning. I have a light ply circle with a hole glued to a piece of CF rod with slightly smaller dia than the od of the aluminum tubing. I stack two glued up 90-degree balsa blanks and then another ply washer and then chuck it up in my dremel. I remove and flip wheels to do both sides. This way they are both the same diameter. Like you I have a small stick with sandpaper on it. Using your technique I may switch to gluing the tubing in first so I don't have to worry about alignment after the fact (except this requires a pretty small CF rod going through the whole thing). Can you guess I had a wood lathe as a kid?:D

Gordon

[Frank]

As an alternative strut material, check out the strip woods available in the model railroading section of your LHS. Most are basswood and available in sizes down to a scale 2x4 in HO. They take stains well and the tea method will work great with them. Much stronger than balsa and still in keeping with the natural wood effect that looks so good for struts on WWI and golden age planes.

[mcalicchia]

Frank you beat me to it. I used the basswood strip wood for my wing struts on my 24" SE-5a. They are very strong and weighed little if any more than the balsa struts that they replaced.

Mike

[mcalicchia]

Gordon and Al,

You guys never cease to amaze me. Your models look great and I've been following your progress. I love the WWI scale planes and have built both the D-VII and SE-5a but at 24". I don't have an indoor site to fly in so I've had to keep to the larger scale that can handle a little wind.

Good Luck guys and I'll be watching your progress reports and look forward to the test flights.

Mike

[pease1]

Mike - thanks for the encouragement - I saw your Electric Mite - you're no slouch youself!

Frank - thanks for the suggestion - I'll go check out the scale RR hardwoods.

Gordon - I'll be packing tomorrow then off on vacation - I can't wait to see what you've done when I get back on the 1st of April!

Al

[gjohnson]

Allan, Enjoy your vacation!

If you have a chance before you leave, could you post a pic of the underside of your upper wing?

I just got some new gears and motors last night and my new RFFS 100. It will be tough to keep working only on this plane with all those new goodies to check out.:D

Gordon

[pease1]

http://pease1.sr.unh.edu/aew/rc/DU-Se5a/underwings.jpg

There you go Gordon, I posted 6 more photos of my fuselage partially done, wings upper and lower sides and a mock-up of what it will look like with the wings mounted, plus the photo above is much larger on my site.

http://pease1.sr.unh.edu/aew/rc/DU-Se5a/

Have fun building while I'm gone - I'm sure when I get back you'll be way ahead of me!

Allan

[gjohnson]

Here's the covered wing.

[Dave Robelen]

HelloGordon,
That is really nice! have you weighed the wings along the way as you added the detailing? For reference, the Pixel wings weighed 4 grams finished and colored, while the fuselage weighed 3.5 without the wheels.
Cheers, Dave Robelen

[gjohnson]

Dave,
You know me, I weigh everything. Was having trouble with the RC Microflight server yesterday and got tired of typing details and having the posting fail.

The top wing weighed 1.8g before covering and 2.2g after covering. Yikes, a 20% increase.:mad: I may make the wing again as one wing tip has more airfoil for some reason and I'd like to perfect the technique of applying tissue. I used 3M photo mount spray, but am wondering about using spray dope instead (which I don't have).

Here's the fuselage, no turtle deck (think that's what it's called) until I decide on the elevator size, which will be slightly enlarged. Can't wait to put tissue graphics on the fuselage as they have some nice details. I need to figure out where to mount everything inside. I'm thinking of mounting the RFFS100 to the inside side of the fuselage (half over the wing) where I've doubled the 1/32 sheet. I've got to think of some way to mount a home geared M20 inside. Dave, do you have a picture of the underside of yours? I was plannng to leave the fuse open on the bottom in the front area. I'm toying with using the magnetic method for battery mounting as velcro might prove too problematic in such a tight area. I have some litz wire from Cloud 9 and am thinking of running it up a strut to the wing and then around the perimeter of the wing for an antenna.

Also, what gearing and prop did you use on your Pixel? From your Pixel posts it sounds like you've used different props. I've got some super light 0.18g 60t 0.3 mod spur gears from Didel and can use a 12t or 10t pinion for either 5:1 or 6:1 gearing, but I'm thinking those might be to much. I'm thinking of initially using a 4-3/8" white Takeoff prop from Cloud 9 or something similar from GWS, since I've never carved a prop. I'd like to keep it scale so I don't have to put long landing gear on. Did you give it any down or side thrust?

[Dave Robelen]

Hello Gordon,
First, I do not have pictures of the bottom of Pixel. However, the bottom is basically 1/32" sheet with the lower wing serving as a hatch. My battery and the RFFS-100 board are essentially "stuffed" in place with small bits of foam to anchor the location.
I have had resonable success with 3M Super-77 spray contact cement misted on very lightly for this type of application. Dope would be a bit of a mess. It soaks into the wood like a sponge instead of staying on the surface, and then starts curling the wood with the shrinkage. You may have a bit of an issue with curling as the humidity changes, since the tissue shrinks at a different weight than the wood. I have found tissue to be very humidity sensitive on my stick and tissue models.
The finish on the Pixel is automobile trim spray paint that I sprayed into a container and then diluted half & half with auto paint thinner. I then sprayed this on to get the effect of a stain with minimal weight.
I used a couple of the 1mm ID ball bearings from Dave Lewis pressed into a tube and bonded on top of the M20 with balsa spscing to get the gear mesh. With the 4.2-1 gears I ended up with a 5.2" dia X 4" pitch prop which is pulling nicely on 3 cells and the current drain is substantially lower than the KP-00.
I did use down and right thrust, about 3 deg. down and 3-4 deg. right (depends on the prop). I have always found biplanes work best with right thrust, it is only the amount that varies.
Take care, Dave
PS What method are you using to post pictures? I tried extensively last night, but it would not take one off of my hard drive as it usually does.

[gjohnson]

Dave,
Thanks, you just saved me a trip to the LHS (three towns away) for spray dope, that would have made a mess. I'll stick with the photo mount, which seems to be slightly lighter than 3M77 (but could be my imagination.

I post using the dialog box for attaching a file. Yesterday the server was really slow and it would fail to load because it took longer than 30 seconds. Text only posts take less time, so even though slow did not violate the 30 second rule.

The gearbox I'm planning sounds very similar. My aluminum tube is a bit too small, so unless I figure out a way to swedge it out, I'll have to do something else. I'm planning to glue the lower wings on the side of the fuselage (wondering now if I should have made the lower one piece and cut out the fuselage to match). Because of the struts, neither wing will be removable. So, I'm planning to leave the fuse open in front of the wing. I hadn't thought about using foam. Did you have any CG problems with all your equipment further back at the lower wing? I havent got that far yet, but Al thinks his won't balance unless the battery is almost all the way forward.

Regards, Gordon

[Dave Robelen]

Hello Gordon,
First, my battery is way forward ahead of the landing gear. Those tail mounted actuators need something to offset their moment arm. The receiver deck is pretty much over the lower wing. A friend showed me a long time ago a neat method for mounting struts in this situation. He glues small wire "posts" to the top of the lower wing, and the bottom of the top wing. Then thin plastic tubing is plugged onto the wire ends. Very damage resistant, looks pretty convincing once it is painted.
I sure would vote for a removeable lower wing if it is not too late. That is one of the first things to snag the surface on rough landings and if you had a magnet mounted wing with those plug on struts, there is a much better chance of surviving a session without serious gluing. Without major reinforcement, the fuselage side is a tough place to mount the wing for survivability. And finally, with a removable wing, you can "tweak" the incidence if necessary.
Cheers, Dave

[Dave Robelen]

Hello Gordon,
It was the "slow server" thing that was killing my picture post. The strange thing is, even though it did not post the picture at the tine, When I checked in this AM the picture was up?
Ah well, Dave

[gjohnson]

Dave,
Thanks for all the suggestions.:) It's probably too late to make the wings removable.:( Oh, well, I'll probably build it twice anyway. I started from Herr plans and reduced them to the correct size. Tom's plans have the wings as separate, glued on the side of the fuse, connected by a spar. As I've progressed I've realized that the outline is what matters with this type of model, not the construction details for a larger stick and tissue model.

It's also fairly time consuming to take a file from Fiddlers Green break it up into the appropriate pieces and scale them up, cleaning up the graphisc, and getting it ready for covering this plane. The good thing is this only has to be done once. I'd like to get a size and set of techniques down for this because there are a lot of WWI planes on Fiddler's Green I'd like to do. So, I guess this plane is a learning excercise.

I've got to start searching for thin plastic tubing!

I have a small red prop with a spinner I got from Cloud 9. The takeoff props turn out to be way out of balance. This one is scale, so I've put together a gearbox for the M20 that uses the standard gearing for the Echarger. It looks like at 3.3v from three cells I get about 17.5g thrust (very quick test with small boys underfoot). This seems reasonable so I don't have to resort to a large prop that would hit the ground for ROG. BTW, I doubt this plane will ever fly outside.

Regards, Gordon

[Dave Robelen]

Hello Gordon,
I expect we all have lot to learn to get the best structural designs for these tiny models. For example, if you are working with decorated tissue, it is a bit wasteful to apply it to a complte sheet of balsa. This is a case Where a single surface frame would be a neat compromise. Maybe even some of the fuselage on those delightful WW1 birds. More realistic, and more efficient structurally.
I get my thin tubing by stripping it off of insulated wire. A choice of color, and about the right wall thickness. Congrats on finding a prop combination that is working, this is another area that will benefit from experience and testing.
Are you going to Toledo? I will be there with a box full of fun stuff, and you could even meet the original Punkin II and Pixel.
Take care, Dave

[gjohnson]

Dave,
With small children and a demanding job, unfortunately I'm not able to go to shows. But, I hope to make it to NEAT next year (9/11 last year made it so I had to skip it and worry about the portfolios I manage). Maybe I'll see you then.

Gordon

[gjohnson]

Dave,
The more I progress on this plane, the more I think you may be right about a combination of paint and tissue. Originally I was going to make a D-VII that was red for the forward half and white for the aft half (flown by Goebbels I think) -- primiarily because it would be easy to paint -- and use tissue insignias. Then I remembered Fiddler's Green when Ralph suggested tissue. So, I'm viewing this plane as a 100% tissue covered experiment. By the time I'm done I'll know how much weight was added by tissue covering, and what other refinements I need to make on the second version (like removable wings.

Regards, Gordon

[Dave Robelen]

Hello Gordon,
Weight control is even more important on your DVII due to the reduced wing area with the smaller lower wing. This whole micro model thing is a steady learning experience. It really pleases me that we can share info publicly so that someone can pick up on it and keep the ball rolling. As scale models go, the WWI machines are super subjects. So many biplanes and colorful too. My goal lies in the direction of getting actuators that may be mounted inside the model and leave the tail "clean".
Cheers, Dave Robelen

[gjohnson]

Dave,
Has Carl shown you the actuator servos he's working on? They look nice. Don't know if they will fit in a fuse this tiny. Then there are always those neat actuator servos Nick Liechty makes. But, they run $50 to $125 each. I haven't gone for them yet ...

Here's how I spent the Oscars.

[Dave Robelen]

Hello Gordon,
Boy, that's looking neat. I forgot to mention, but the "wire and tube" trick works great on landing gear struts as well. Make the front strut a full wire strut, and use a flexible tube for the rear strut. Sure worked well for me on a Sperry Messenger years ago.
I had not heard about Carl's work, and Nick would only post a phone number, so I never got back to him. Based on your price numbers, it is just as well. I have found with the RFFS-100 actuators that they start to interact when they get to close together. The pair on my Pixel just barely show this, but it got my attention. I may try to rework the parts that are sols with the RFFS-100 into a pushrod style actuator. So many projects, so few hours.:-)
Regards, Dave

[gjohnson]

Dave,

Carl has posted pictures of his actuator servos over on the Ezone in the micro forum. Search on "A control-arm actuator", as for some reason this BB won't let me post a link directly to his thread. Yes, Nick prefers a phone call to an email and his stuff is made to order on a semi-custom basis.

I'll have to see if I have any suitable wire for stripping insulation off of. I'm sure to have more questions if I have what I need.

I'm worried about the weight of the fuselage. It's 3.2g. But, about 0.3g of it is in a thicker nose block to get that "pointed" look the the D-VII had. Tissue covering added 0.6g. Yikes again! I dusted the top and both sides with glue and then started tissuing. By the time I was ready for the sides, the glue was beginning to dry. Plus, I hadn't thought about the fact that I needed fresh glue where the seams overlap. So, I had to dust each side again, right before I tissued it. More weight from glue. :mad: So, depending on how much everything else weighs before assembly, I could end up building the fuse again as I think I could save between 0.4g and 0.5g.

I hadn't thought about the smaller bottom wings till you mentioned it. Al's choice of a SE5a may have been a better choice as I think the lower wing has a chord and wingspan similar to the top. I think it's time I computed a wing loading for this plane. The thing my Punkin II convinced me of was that a small amount of weight can make a big performance difference.

Thanks for all your input,
Gordon

[Dave Robelen]

Hello Gordon,
Yes, it is that wing loading vs power loading that keeps us scrounging for grams. The thrust we are able to get from a 3-cell pack is beginning to define the size and weight of the planes. My Pixel has a wing area similar to the Skeeter, and the weight is close. With the efficiecy cuts of a biplane I figure that my effective wing area is about 80% of that. The performance envelop of the Pixel is quite resonable, although it is hardly overpowered. One day we will find that magic coreless motor that will weogh no moe than an N20 and put out good power at a low voltage. The RFFS-100 does not really offer the option of using voltage boosters withit's voltage range.
Regards, Dave

[gjohnson]

More pictures of my construction of the D-VII can be found on my Fokker page http://home.attbi.com/~gordonjohnson/FokkerDVII.htm

Also, I'm not sure about the insignias that Fiddler's Green put on this plane. If there was a white border, I wonder if it is too thick. Plus, the basic black crosses seem a bit two thick to me as well. But, I'm not an expert on these things yet, and editing and creating separate graphics files was enough trouble as it was. Maybe in a second version. What's important to me is that a Guillow Fokker D-VII kit was my first ever model airplane built with my Dad when I was about 4 years old. That started my interest in biplanes. My brother's plane built at the same time was a J3 Cub. Maybe that's why he wasn't obsessed with biplanes.

Regards, Gordon

[pease1]

Gordon,

You've outdone yourself! I'm speachless.

I'm not sure I'm worthy of participating though! Those graphics look great! It will be a couple more days before I get back to working on the Se5a. I'll have to go to the Fiddler's Green site and see if they have any graphics for me. :D

Al

[all_fly_all_day]

Hey Allen, Gordan,


You guys are using tissue to cover your planes, i was wondering what kind of tissue this i and where i could get it? This model looks so cool, im wondering where i could get the plans for it. I am itching to build it!

Thanks a lot guys, and keep up the good work!

eat-sleep-fly

[gjohnson]

eat-sleep-fly,
We are still figuring it out as we go along. The tissue is just store wrapping paper tissue.

Dave,
See if this sounds possible. I think I may be able to get the D-VII to come in at an AUW of 27-28g with an M20 motor. With a 4-3/8 Takeoff prop (from Cloud 9) geared 5:1 and 120x3 NiMH, I can get about 14g static thrust. With a BitCharger 3.0 motor and everything the same I can get about 10g thrust, but save 2.5g on the weight of the motor. This has the potential to bring my "projected" AUW down to the 25-26g range. Do you think a 10g thrust would fly your Pixel (I'm not talking loops at this point)?

Another alternative would be to use the BitCharger motor on 2 cells, which generates about 6.8g thrust, but saves an additional 3.9g battery weight. So, could your Pixel fly on 6.8g thrust if it weighed in the 22-23g range?

Anyway, just thought I'd ask.

Regards, Gordon

[Dave Robelen]

Hello Gordon,
actually, the Pixel is a bit of a "power hog". I suspect we will find this to be true of most of these small biplanes. The Skeeter is really in another class with a large stab and rearward CG. Being a monoplane it also only has two sets of tip vortices.
I remember a free flight article that discussed power requirement relating to very small planes. The gist of it was that you could divide the glide ratio (distance/height) into the weight to get the needed thrust. From what I have experienced, this appears to be a valid measurement. Unfortunately the glide ratio of a peanut size biplane is pretty steep. This is not talking loops, etc. either, but just enough power for level cruise. I took some measurements of RPM vs. time with the 4.2-1 M20 on 3 cells, and the drop off after a minute was really significant. In other words, to be able to have cruise thrust into the flight, you will need well over cruise power at the start.
As time goes on and we get a better handle on the power requirements of these really small biplanes the answers will be easier to come by.
Cheers, Dave

[gjohnson]

Dave,
So, what do you estimate cruise thrust to be? I just don't have an idea. I think if I have thrust equal to 1/2 the AUW I should be ok, but I don't know if 1/3 will do it. Everything you say about bipes makes sense.

Gordon

[Dave Robelen]

Hi Gordon,
If I were pressed to answer, I would expect that My Pixel needs between 10-12 grams of thrust assuming that the pitch speed is also reasonable.
My takeoff static thrust with a 5" pitch prop turning about 2900 RPM is near 14 grams. At one minute that is down to 2750 RPM static, and 2500 at 2 minutes. All this at full throttle. My cruise stick setting is about 75% after a couple of minutes of flying. We really do need that wind tunnel data from small drives to begin to assign quantities. Also, these little bipes probably have a best glide ratio 1n the range of 3-4. I have noticed that the Pixel drops right quickly when I power down. Unfortunately I have never even seen a Skeeter fly (or flown one) to see how large this difference is. That should get cleared up this weekend at Toledo, but rght now I am short on quantitative material.
Regards, Dave

[gjohnson]

Thanks Dave,

I just got around to computing wing area. It will only be 47 sq inches. Ouch!

Weights so far:
Fuselage = 3.1g
Top wing = 2.1g
Lower wing = 1.0g
Elevator = 0.6g
Wheels (pair) = 0.3g

Regards, Gordon

[Dave Robelen]

Hello Gordon,
Sneaky stuff that weight, eh? Actually you are not that far from the 7.5 gram airframe weight of the Pixel, but that wing area is what is going to push the power requirement right up there.
I suppose we should be scaling these things by area rather than limiting the wingspan. You would only have to elarge that beauty by a few percent to get up to around 60 sq. in.
From what I am seeing with my activities, the area will climb much faster than the weight since so much of the total is R/C and power equipment. It may well turn out that building the WWI scale models a little larger still will give that "floating" flight style that is so realistic.
I still believe that it would both possible and desirable to use some open frame where you are applying the colored tissue. The lightest white tissue I have seen and used came from the indoor supply house ( I can't find the URL at the moment). The sheet balsa has been a good option for speedy construction and reasonable weight control. I sure appreciate the durability of the Pixel when I am handling it too--I am all thumbs at times :-)
Till later, Dave

[gjohnson]

Dave,

As I said several posts up, I'm sure I'll be making this plane again. I wonder what's the best way to make sure the actuators can be removed? Minimal CA might do it.

I had the same thought, that If I were doing it again I'd scale the plane up slightly. I'll also lose the thick nose. I computed the estimated flying speed for your Pixel, using your formula, to be 9.5mph. I have a better estimate of the likely weight for the D-VII with M20 and 3 cells at 31g. :mad: At that weight it has a projected flying speed of 11.7mph.

By my calculations, using your formulas, at the 1.5x rule of thumb for pitch speed to flying speed this implies a minimum pitch speed of 17.5mph. A M20 geared 5:1 with a 4-3/8 Takeoff prop has a static rpm of 6120 after four minutes. I don't know the pitch of the Takeoff prop, but at a pitch of 2.0 this would give a pitch speed of 17.5. My guess is this prop has a pitch more like 3 (but I haven't measured it yet). I also don't know what the pitch speed will be unloaded. All this seems to indicate to me that the plane could fly with this weight and motor/prop/battery setup. I have a couple of small Aeronutz CF props on their way. The advantage of them is they have wider blades and I set the pitch and then glue. So, all these calculations may help me figure out if those props correctly pitched might be a better choice.

Any thoughts?

[Dave Robelen]

Hello Gordon,
First the part about actuator removal. The best glue to mount the coil seems to be a cellulose type such as Ambroid or Testors. A small amount is adequate. I have removed and remounted mine using a brush with acetone several times with ease. Some one else reported serious problems removelnd the coil that had been mounted with CA. It seems the debonder has metallic salts that shoted the coil, and he had to jump through a lot of hops to save the coil.
As cute as it is, I have some real concerns about you getting that Fokker airborne for extended periods. The best shot will probably be with a high gear ratio (6-1?) and a larger prop. This was a big help with the original Punkin effort, and I have seen improvements in the Pixel when I move to larger props. It's a shame no one has come forward with a series of props that can be used "off the shelf".
Regards, Dave

[gjohnson]

Dave,

We posted at the same time. Did you see my pitch speed calculations above?

The nice thing about spreadsheets is how quickly "what if" analysis can be performed. The effective span of my D-VII (not counting the ailerons that poke out on the ends of the top wing) is 12.25 inches. If I scale this up 22.5% I get a span of 15 inches and an area of 69.2 sq inches. If weight stays the same at 31g (no thick nose block, and use of cutouts in fuselage) the flying speed drops to 9.6 mph

Gordon

[Dave Robelen]

Hello gordon,
I did miss the part about pitch speed. When I am reffering to this, it is strictly a static reading. Those "unloading" effects are what the wind tunnel tests would be useful for.
Those Aeronutz props sound like a good idea, could you post an address? For my personal stuff I can carve props and be happy as a clam, but that does not solve the issue of passing it on to others.
At 69.2 sq. in. and 31 grams, that Fokker ought to have plenty of margin. As the wing loading drops and the weight stays the same, it just gets better and better. Now if you can push the weight down a bit too, that would be great. That probably is a pipe dream with the equipment weight where it is, so I am anxious to here about the little coreless motor compared to the M20. I really should get back to the motor from the KP-00 and set it up with a large ratio and larger prop. I did this with the motor from the GWS EDF motor with very good results in another project.
So many ideas, so few hours :-)
Dave

[gjohnson]

Dave,

The Aeronutz to contact is Dr Chris JFouweather@aol.com, who makes this stuff in very small quantities.

I need to test the coreless motor. But, I'm waiting on an adapter that goes on the front of the 60/12t Didel gear, that will have a 2mm shaft sticking out the front. I just didn't want to start slapping CA all over a $52 motor, plus I was busy with BitChargers, etc. Remember, that it is slightly lighter than an N20, but is still heavier than an M20. So, it might find a home in a Punkin sized plane.

Gordon

[gjohnson]

Progress so far. Time to start installing actuators.

[Chris]

Just a few thoughts...

First of all, your D-VII is looking great, I really need some free time to build something similar for my RFFS-100.

For adding color to these planes, weight is obviously a large factor. Take a look at this: www.currys.com/airbrush/letrajet.html
It's basically an airbrush that sprays ink from the tip of a special marker instead of paint. I had one years ago and it worked quite well. While it wouldn't have the same coverage as paint, I assume the ink would add an almost (if not totally) imperceptible gain in weight. As for the coverage, I wonder if it'd be possible to bleach balsa to a lighter shade so blues don't end up green, reds orange, etc.

For a removable actuator glue, I used rubber cement on my Skeeter. If you coat both the coil and control surface with cement and let it nearly dry before assembling, the bond will be pretty strong but still separable without destroying anything. It also helps to have the coil fit fairly snug into the control surface. Unfortunately, it's been far too windy here to fly my Skeeter, so I can't comment on the long-term durability of using rubber cement, but considering there's little if any force being placed on the coils, I don't foresee a problem.

Anyway, just a few random thoughts...

[gjohnson]

Chris,
Thanks for your ideas. I'll check that ink sprayer out. Another Idea I've had, which might be much harder to accomplish, is to modify an inkjet printer so sheets can be fed straight through, and then print directly on the balsa. If anyone has ideas on how to accomplish this, please let me know.

Gordon

[Dave Robelen]

Very pretty work Gordon. Thanks for the contact info on the prop. I am just back from Toledo and the indoor flying session. The Pixel did just fine although I did not do a bunch of manuevers. I was able to climb to the 65' ceiling a number of times in one flight.
Static electricity is a critical issue with the RFFS-100. One of the other flyers blew his receiver aftev walking on the carpet and coming near (or touching) the antenna. Be sure and ground yourself on a table or something in dry weather before handling the unit.
Regards, Dave

[pease1]

OK Gordon, I'm back working on my Se5a. I have the airframe complete: Wings mounted (including top wing with cabane and outer struts), landing gear and wheels mounted. Masking tape holding the elevator and rudder on for dry-fit. With no equipment the complete airframe weighs a portly 14g. I can save 2g by making my own balsa wheels since the ones I have are almost 4g themselves.

I haven't painted it yet, I figure I'll fly it first and see how much extra weight it can stand and that will determine how 'hog wild' I'll go with the paint.

No pics, sorry, I lent my digital camera to a friend for a week or two. I'll try to borrow a camera soon. Next step is to put the RFFS-100 in it.

Test glides with some appropriately placed clay show that it will glide, although I wouldn't call it a 'floater'. I shouldn't have any trouble getting it to balance, empty it's only slightly tail-heavy.

Al

[gjohnson]

Allan,
No pics.:( You're ahead of me on putting things together. I'm about to glue wings on and start building the landing gear and struts. I've got actuators in both rudder and elevator. I have to figure out how to mount the motor gearbox. I'm going to mount the RFFS-100 with foam sticky tape, or I may just hold it in place with Dave's method of foam pieces. I'm still working on motor/gear/prop possibilities. But, I think it will be M20-LV, 3:1 gearing, 4-3/8 Takeoff prop, but I have a couple of others to bring and try too.

Dave,
Thanks for the warning about static electricity. I had wondered about DU's waning. Now I know to take it seriously. BTW, you have mail.

[pease1]

I'll be mounting the actuators next. I've been holding off as long as possible, not wanting to disassemble my Micro-IFO, but I guess it's time to decomission it.

Al

[gjohnson]

Al,
I forgot to mention it. I think you can save a lot more than 2g on the wheels. Mine weigh 0.3g for both! I used contest grade balsa, and laminated it together with Super Phatic glue, which doesn't dry as fast, but is lighter than CA. Also, I flipped each wheel around and carved the back side to save further weight.

Gordon

[Dave Robelen]

Hello Gordon,
You have mail now. Considering the hassle with message length, how about using my regular E-mail adress of aplusfarm@hovac.com?
Al, you are going to need some serious thrust to get that SE5 going. The Pixel airframe weighs 7.5 grams with wheels and I would not class it as overpowered wit the 4.2-1 M20 and 3 cells. I am looking forward to those pictures also, the WWI machines are great candidates for the RFFS-100 system.
Regards, Dave

[pease1]

Yeah, I'm not happy with how heavy the frame is, but that is assembled with struts and (heavy) landing gear. I'll give it a go this way, but I'm planning on it being a pig. I'll just have to consider it a first effort, that's all.

Going right to scale with the RFFS-100 may be too big of a leap all at once for me. I don't even have 'contest' balsa. Just picking some light stuff from my modest stock.

Al

[gjohnson]

Al,
Put in an order to Superior or Lone Star (not National, their definition of contest grade is considerably higher than Dave's). Superior has a minimum order of $25. 1/32x4x36 contest grade costs $1.47 and 1/16 costs $1.29. Mine ranged between 5 and 6 pound density. One $25 order will have you set for contest grade for a long time.

Gordon

[pease1]

I did just that this morning. I ordered 1/32, 1/16, 3/32 and 1/8 sheets, plus some misc. essentials I needed for larger projects. Between this micro stuff and my HLG 'habbit' I think I'll be able to put it to good use :)

Up to now using 'light' stock from the LHS has been fine (you've seen my Punkin fly) but now that I'm trying to 'keep up with the Jones' or rather the 'Johnsons' I needed to pull the trigger on a contest order.

Al

[pease1]

http://pease1.sr.unh.edu/aew/rc/DU-Se5a/se5a.jpg

There you go Gordon. Tons more and larger image sizes on my page at: http://pease1.sr.unh.edu/aew/rc/DU-Se5a

I've had some warping problems with the wings - storing the plane in the basement puts a lot of humidity into the wood. I needo to get the wings straight again, then hit the wood with a coat of Nitrate Dope thinned 50/50. That should 'set' the wood without adding much weight. Then the airbrish with a dusting of thinned paint. - probably going to cost me a gram.

Al

[gjohnson]

Allan,
Looking good. I'm about to start work on my landing gear. I may go with wood, but haven't decided yet. Ditto for struts.

Gordon

[gjohnson]

Here's the progress update. More pics are on my site at my
Fokker Page (http://home.attbi.com/~gordonjohnson/FokkerDVII.htm)

Dave, what did you use as a counterbalance weight? I was thinking of using a short piece of piano wire CA'd on the bottom of the elevator.

Regards, Gordon

[pease1]

Gordon,

Outstanding work man! I'm afraid you're pulling away from me big time! I'm not even sure my brick of a plane will fly. Your's will AND looks fab!

Maybe I should do an E-III instead :(

Al

[Dave Robelen]

Hello gordon,
I used a length of 1/32" soft wire. It is not all that critical except to help keep the centering precise. That bird sure is colorful. I would like to persuade you to make the front landing gear strut from music wire, with the rear being a tubing dummy. It would also be good to add some .020" music wire in the cabane struts against those unplannd events. The old VK kits of the Nieport and Fokker DR1 had a wood strut that was grooved to take the wire reinforcement. They were downright tough.
Take care, Dave

[gjohnson]

Al,
Don't forget mine is considerably down on wing area. It could end up hanging in my two-year-old's bedroom.

Dave,
I'll try to incorporate your landing gear and strut suggestions. I'll have to weigh the piano wire. I might reinforce the struts with .02 inch CF rod. I was just going to use balsa, so I need to do some thinking. I have the landing gear wing done and am making printed tissue covers for the wheels. I proceed at my usual snail's pace.

Gordon

[Dave Robelen]

Hello Gordon,
It is partly that wing loading that is leading my suggestions. I have repaired a fair share of balsa struts on small biplanes to appreciate the strength of music wire. The chances of your VII making smooth landings are somewhere near slim. The 1/2 gram spent on flexible wire can make the difference in surviving a test session to get some trimming and evaluating done.
Have fun, Dave

[gjohnson]

Dave,

Here's a picture to see if I understand. Would the front strut be one piece going from one side, up to the fuse, across, and down the other side? Or, would it be two separate wires? Also, I think I would bend it under the axle and up toward the rear strut. In the picture, the long box represents the insulation. Is this right? Is the wire CA'd into the insulation? Or is it just a snug fit. Is the insulation supposed to flex slightly to give a shock absorber effect? Or, are we just going for strength here?

And, how the heck do I strip thin insulation this long off a wire?

Thanks, Gordon

[Dave Robelen]

Hello Gordon,
That's the idea. Works for me.
Dave

[gjohnson]

Dave,
You may have missed my questions. I kept reposting till I got the picture right.

Gordon

[Dave Robelen]

Hello Gordon,
Boy, did I miss them! I prefer to use two front wires that go across the bottom of the fuselage in opposite directions to give a "torsion bar" effect. The way you show the wire in the picture pretty much covers the rear portion. As far as attaching the insulation, I have been fortunate to have found stock that plugs snugly onto the wire. If not, then CA. My method of stripping is simply to nick the insulation with a blade, and then use my thumbnail to pull it off of the wire. I was pleasantly surprised that it comes off reasonably well. I hope I got it this time.
Regards, Dave

[gjohnson]

Dave,
Someone in my local club who's a good rubber FF builder told me that biplanes often need a bit of down elevator. He told me this as I was trimming my Punkin II. I've noticed in Fokker three views that it looks like some of the Fokkers like the DR-I and the DV-II have the elevator pointing slighly up at the front, giving the effect of some down elevator. Am I misinterpreting the three views, or is there some truth to this? Could you comment?

Regards, Gordon

[Dave Robelen]

Hello Gordon,
Your friend made a very true observation. There are a couple of reasons for this arrangement, and since Reinhold platz ( Fokker designer) is not available for comment I will boldy step in.
In these same 3-views you might also note that the wings have positive incidence with an airfoil that is definitely in the "high lift" class. This sets up a strong downwash flow behind the wing system and in turn the horizontal tail is rigged with the LE up to compensate. In fact, in the flight shots I have seen (Blue Max, etc) the elevator is drooped below neutral in level flight.
The result of all this is a setup where the airplane trims a bit nose low in cruise, with much improved visibility. Even today the biplane crop dusters use the same setup for the same reasons. Finally, This rigging gives a slight down thrust effect which is very helpful during the takeoff acceleration.
In making application to our models, especially the micro class, this can be useful to a point. Due to a weaker down wash field, models like the Pixel do not need as much (if any) positive incidence in the tail. I hope I answered your question. :)
Regards, Dave

[gjohnson]

Dave,
Yes that answered it. Which means I don't have to be true, or completely true, to the original. Now that you mention it, the guy in our club said it was downwash that caused this effect.

Gordon

[gjohnson]

It's time to resurect this thread. When I started this plane LiPoly cells were not available, and I didn't have any BitCharger motors. The problem with a 13-inch D-VII is that because of its shorter lower wings with less chord, the wing area is less than with something like an SE5 where the wings are the same size. So, this plane has languished on a shelf till now. I decided to finish it up and see whether it can fly with its reduced wing area. But, now I have more tricks for keeping the weight down. So, it uses a BitCharger 3.0 motor (~1g) geared 5:1 with Didel gears, and a U80 prop. This setup weighs 2.5g with wires and prop and generates 13g static thrust. The AUW of this model is looking likely to come in between 21 and 22g. The wing loadins should end up around 2.5 oz./sq.ft. So, now this plane has a chance of working.

Here are a couple of pictures, before the landing gear was permanently glued on.

[gjohnson]

And another

[FLB]

Very nice work and amazing finish...

Hope you will have good flights. So we will have nice pictures to see :D

Regards

FLB

[Dave Robelen]

Hello Gordon,
That sure is a cutie. If the Bit Charger motor proves to have inadequate thrust, for just a couple more grams you can get 20gr static from an E-Charger at 6-1 with a 5-4 prop and still be under 1.0A max. Hang in there with those delightful early bird aircraft, they sure are cute.
Regards, Dave

[gjohnson]

The little D-VII finally flew. AUW with a BitCharger 3.0 and reworked DU actuators to be remote actutators and use push rods was 22.4g. It would ROG and is a very stable and predictable flier. More pictures, equipment details, and a detailed weight breakdown can be found on my Fokker D-VII (http://home.attbi.com/~gordonjohnson22/FokkerDVII.htm) page.

The RFFS-100 is mounted with small magnets to facilitate plugging in the actuator leads, and to make the receiver removable for use in other planes. The LiPoly battery is similarly mounted.

Many thanks go to Dave Robelen for his help and encouragement along the way with this plane.

Gordon

[Fwilly]

very nice looking plane. Did you get the gears from the bit charger kit? I have the radio shack version of the bit charger that has the equivalent of the 2.2 motor in it and I have the two motors below it. When I get the 2.6 (the highest radio shack offers) the 2.2 may get canibalized.

[gjohnson]

I used the Didel gears. To use the BitCharger gears, which are a different mod, I would need to buy one of their axle kits -- which I never have. I've only bought the motors from a hobby shop in Hong Kong, and the motors come with just a pinion (6 or 7t I think). I've never actually had one of the BitCharger cars.

Gordon

[Fwilly]

I made a single gear drive using the car's gears and the 2.0 motor. It may end up in a peanut scale Jenny biplane found unbuilt, hiding in a drawer. I haven't decided whether or not to convert it. I guess it will depend on the weight once I've finished building. The wood seems heavy but theres not much wood to it.