Stage Two

[Richard Miller]

I have completed and flown the 14" glider with the tail that tilts by virtue of a balsa dowel in an aluminum tube. The horizontal surface has about 31% of the wing area and the moment arm is about 1/4 span and the tail pulls the nose around very smartly with only a little bit of tilt. I mean with only 3 or 4 degrees. And the model glides in a satisfactory manner, keeps on course with a total vertical surface area about equivalent to that of a nickle. I'm pleased and I'm surprised, mainly at the directional stability with so little area.

On now to State Two. This will be the same configuration, but with an RC installation that will incline the wings differentially *and* tilt the tail at the same time. From what I've seen thus far I expect this one to turn on its own vertical axis.

I've been jusgling things to see how small a box I can get it all into, and have ended with 1/10th [linear] of the proposed 36-ft. full-scale design. Since it is to weigh 90 lbs., and the pilot twice that, I must make do with 2.88 oz. of electronics, which should be fairly easy, and 1.44 oz. of structure, which may not be. [That's provided I've done the math right. I frequently find I make dumb mistakes in this realm, but have (re)checked a few times.]

Thus, and now I need help, I have arrived at the Hitek Focus3 system, available for $84 currently from balsapr.com as item number 147721. I will, I assume, need a battery and a charger, unless the transmitter-battery charger suffices for both. Neither weight nor duration appear to be much of a problem at this point, but I'm likely to be using the equipment on projects where I do want less weight and more duration. Suggestions please. [The whole battery business mystifies me.]

I assume JST is a term I should know and deal with. The little plug/jack common to mini and micro servos? I have a big battery and charger with a plug/jack with a cross section of 5X10 mm. Is there a patch cord for these two?

Thank you all, especially you Dave. You're always there and I'm sure I'm not the only one who appreciates that.

-Richard

[Dave Robelen]

Hello Richard,
Welcome to the wild world of dynamic scaling! If you look at some of the free flight endurance model designs, you might pick up some ideas for the structure. Just curious, did you represent your area and CG with the small glider? That small rudder (or fin) may change if you were not scaling a pilot. But, you probably were.
The Hitech Focus system comes with a dual output charger that is meant to charge a 500 mah flight pack as well as the transmitter. You will likely be using a much smaller battery and will need to add some resistance in the receiver charger side. The HS-55 servos that come as part of the package have worked out well for me. Not quite the smallest or lightest, but they have decent torque and will work in a variety of applications. You may find that the "Double time" ni-mh cells will make a very useful battery for your application. A 4 cell pack weighs about 1/2 ounce, and they have a rating of 120 mah. The best ones come from Cloud 9 Micro R/C ( check the vendor links in R/C Microflight). They may also have an economy charger for these cells.
Take care, dave

[Richard Miller]

Dave,

As regards the 14" glider, there was no discernable relation between the scales, and yes, I'm prepared to have to use a larger vertical surface.

I contemplate using none on the basis that the two vertical vectors, those of the wing and the horizontal surface, will provide some sort of directional stability. Almost immediately I see the fault in that: It's like pendulum stability. There's nothing there at the zero [both vertical] setting. In a dynamic situation, which is to say while the turn is in progress, yes. In the end, whatever is required, but the least possible so as not to impede the turning responsiveness of the glider.

Back to the battery. I will go to Cloud Nine and endeavor to further educate myself. Meanwhile, how about some utility battery from balsapr, even if it weighs a couple of ounces, which I have to play around with. One order. One shipping cost. The saving there could pay for a good share of the purchase, and I really only need it for this one transient operation.

And THANKS,

-Richard

P.S. I managed to contact Bob Hoey, also it appears a NASA alumnus - you are aren't you? We had some very valuable exchanges regarding tip elements and the dispersal of tip flow. One item that's kind of surprising: The initial, forwardmost of the vanes/feathers has a (-)21-degree angle of attack! Who would have guessed?

-RM

[Dave Robelen]

Hello Richard,
You caught me! I am also an NASA alumni. Any ni-cd 4.8V battery with a capacity of 110 mah or greater should meet your needs. I suppose what had me thinking more fin is both the dynamic behaviour, and the possibility of unwanted sideslips. You are quite correct, My old employer has been looking at tip feathers as well as other devices to reduce votex drag. There was also a program to clean up the flow around the tip of a crop duster wing to improve the dispersal of light materials. Such fun.
Take care, Dave

[Richard Miller]

Dave,

Among the problems with the vertical on the little glider is the pylon, full dimension of the wing, flat on both sides, so no telling what would happen with a rounded fuselage with a lower profile.

I'm going to round out a second balsa dowel and attach another horizontal surface to it, this one with a bit of dihedral, see what happens.

As regards modifications to the wing tip, I have been a voice crying in the wilderness since the mid-70s. About half way through that decade I wrote a paper entitled "End Play" that covered diffusor tips and [what I call] emarginated dispersion. I put special emphasis on the work at Cranfield where it went from theory to full scale with very positive results. The use on crop dusters, for obvious reasons, dates from then.

[Submitted to "Soaring" - of which I had been the editor not long before - given peer - What??? - review, rejected. Ha!]

In recent times I opened a Yahoo egroups site, WingTip, which has fewer than anybody else members. "End Play" is in the files there if you should want to see it.

I had a letter [co-directed to a Jonathan] from Bob Hoey this morning with pictures of his current project. It looks as if, finally, some serious work is in progress. [I hardly need say that I envision emarginated elements on my full-scale glider.]

PLEASE, please do direct me to any work being done on tips. I'm trying to get it all under one roof, and if you should want to be put into contact with Hoey [and Jonathan], included in this little loop, let me know and I'll arrange it.

Off to find a ni-cad of the specifications given.

-Richard

[Dave Robelen]

Hello Richard,
I deeply appreciate your offer to be included in this "circle". Considering my genuine lack of theoretical (or practical) knowlege of any tip system beyond winglets, I best stay clear. my field was more evaluating the stability and control of complete configurations, and my contact with the more esoteric top systems was more one of a general awareness of a work in progress. There were two principal investigators at Langley NASA that would have published a number of papers in this area. One was Frank Jordan, The other Claude Patterson. Both, like myself have been retired for some years at this point The papers would have been both NASA TP's, and AIAA papers. A search by author or topic might turn up something useful.
Good luck, Dave

[Richard Miller]

Good Morning Dave,

These items: I shaped another blank into another dowel and added another set of horizontal pieces to it, these with 14 degrees [each] of dihedral. [My aim here is that *all* surface be lifting surface; all wetted area working area. Like the birds.]

Under duress, a disproportionate gust case, the whole model rocks. Otherwise it flies fine with a very loose sense of direction, which I take, for my purposes, a glider meant to milk little bits of lift in the morning sky, as a Good Thing.

I have forwarded the names, Jordan and Patterson, to Bob Hoey, who, it turns out, is also a stability and control guy. I let him know you're here, at this site, and what you do.

My prospective order - to balsapr - is now the Hitek Focus3 outfit, @ $84 and a Sanyo 4.8v, 110mAh Ni-cad, for which add $11. I await your assurance that these are what I need and all I need: transmitter, receiver, servos, batteries, charger, the lot.

-Richard

[Dave Robelen]

Hello Richard,
From the sound of it you are on your way with the gear. The only area that will take a bit of "fiddlin" will be the charge rate on the wall charger for the Hitech receiver output. The 50 mah output would overcharge the 110 battery if left on for extended periods. If it were me, I would occasionaly feel the battery temperature and stop the charge when you can feel a little warmth.
It will be interesting to see what your contacts turn up in the old NASA connection.
Cheers, Dave

[2NG]

Hey DAVE!!!!!:)

Thanks, I just got it in the mail:cool: Your super!!!!.

Thanks, Man,:)