little skeeter parts

[Fwilly]

I built a small biplane using the 2 horizontal stablizer from the little skeeter plans and test flew it today. good news is it flys. Bad news is it's tail heavy and was hard to control. I ran out of daylight before I could correct the problem. It seemed very manuverable and before I adjusted the rudder throws it would roll when I didn't want it to. Didn't try a loop but as soon as I fix the cg I will. It climbed very well on an m20 with 3 cells. I figured the wing loading to be around 5oz per square foot and it seems to fly well with it. I figured the W.L. using a weight of around 25 grams becuase I thought the smaller airframe wouldn't weigh as much as the other planes for this system. I would of used a weight of around 23 grams but the balsa I used wasn't contest grade(I used 1/32" balsa incase you were wondering). any one know where to get a cheap scale that will be acurate to around a gram. are any of the m20s better for 2 cells? I have a kpoo and an e chargers drive and if it would be better I wouldn't mind ordering a toy tronics m20.I used the kpoo and couldn't get it to fly using 2 cells. Does the weight I estimated seem reasonable? Any one else trying planes with around this wing loading for the rffs?

[dow]

Scales

Cheap and accurate don't belong in the same sentence. Dave Lewis sells a digital scale with a 200 gram capacity for $63. Tough to beat, as his shipping is free and he is a great guy to work with. A less expensive trade-off would be a Lyman Pro 1000 powder scale for $45, very accurate, but limited to 65 grams and would need a bit of adapting. You can see it on cabales dot com web site. By the time you are done paying cabales shipping there will probably be about $10 difference.....for that small amount I would go with the one from Dave Lewis.

Dave W.

[gjohnson]

As I understand it, the M20 from an E-Charger or KP-00 is a lower volt higher amp version. The one from Toytronics can handle higher volts and does not pull as many amps. But, Ralph Bradley is the expert on the Toytronics version. I think if you want to go for two cells, the low-volt version is what you want. You will also do better going for more reduction in your gear ratio and a larger prop. Try a GWS 5x4.3 and 5:1 or 6:1 gearing using readily available gears and props. I'm still working on static tests for the M20-LV with various gear ratios and props. Everything I've found so far is consistent with what Jean-Louis Coural of France has said that the M20 needs higher gearing. The optimal is supposed to be about 10:1 and a big prop -- for a floater. Since you can't do that on a plane this size, you will have to go somewhere in between. Use as big a prop as you can get away with and then the gearing that is consistent with that. It's becoming more and more clear that the 2.7:1 gearing on the KP-00 is far from optimal, but may be a good choice if a small prop is all that you can use. I'm probably going to go with an E-Charger M20 geared 6:1 and around a 5x2.5-inch prop on my Fokker D-VII.

I have the scale that Dave sells, and it is a very good choice.

Regards, Gordon

[Fwilly]

so the kpoo m20 is one of the better ones for 2 cells. then maybe it's my battery pack, its kind of old and I used to fast charge it off of other batterys for free flight use. Now I use the new diamond super peak charger. What diiferences in thrust do you notice between the 2 and 3 cell? I'd say mine gets 50% or less than the 3 cell. the 3 cell is one from an echargers intruder that I took a cell off of and the 2 cell is a sanyo. both are 1/3AAA. The prop and gearing It has caused it to roll very quickly at stall so I think I'm at my limit with the u80. Think I can count that as a tourque roll:)
Thanks
Mike Feuilly

[Dave Robelen]

Hi Fwily,
I just bought a digital kitchen scale from WalMart the other day. The cost wa $30.00, and using my calibration weight set, I found it accurate to less than one gram up to 200 grams. It would be a very simple matter to arrange a "multiplying beam" across the scale that would cause it ti read 10X the weight of a small object. Put stand beside the scale and weight it at the base for stability, then put a pivot bearing in the top of this stand( could be smoe brass tubing), then fix a piece of wire through the end of a long arm that passes across the scale. Glue a piece on the arm that presses down on the scale, and then move out 10X the distance from the pivot/scale piece and notch the beam for a hanging weight pan. I make a pan from 1/16" plywood and 1/16" music wire to place the small stuff on. A sheet of 1/32" balsa that weighs 5.1 grams will read 51 grams on the scale. Plenty good resilution for our work.
Regards, Dave

[Fwilly]

thanks for the idea one gram is good enough for me for now. I've fixed the cg and it is still unstable. Its not in the pith axis its in the turning. It flys around alright by itself but when I turn it starts to turn but then starts tipping side to side kind of violently until I release the rudder. any Ideas? The only thhing I can think of is to add more side thrust because it kind of turns to the left with no control input. The left turn could be because the control suface rests toward that side but it has a really free moving hinge and I think the air moving over the surface would center it. If I can ever get it working right it will be pretty aerobatic because I have accidently made it roll a couple times and they were fast rolls and I think it will loop equally as well. please help if the side thrust doesn't help and no one can help me I'm going to give up and build an ultra simple floater type plan

[Dave Robelen]

Hi Fwilly,
It sounds like there are a couple of possibilities. There may be a bit too much dihedral for the size of the vertical tail. A vertical tail that is too small would cause the same problem. Possibly a little stronger centering on the rudder would help also. It's hard to make a clear call without seeing it.
Regards, Dave

[Fwilly]

trying to post a rough scetch of it

[Fwilly]

OK it's not a good drawing but I tryed to get the dihederal and rudder size as acurate as possible. sorry I don't have a digital cam or scaner

[Dave Robelen]

hi Fwilly,
That's a neat looking concept for a tiny bipe. I really do believe that ther is too much dihedral for the vertical tail area. Part of this is due to the short moment arm of the center of area of what wiold be the vertical tail (fin + rudder). It has been a big help to me to temporarily tape pieces of 1/32" balsa to a model like this to enlarge a surface. With the amount of dihedral you have drawn in, the rudder would be very powerful, so I would go easy on adding more area there.
It is always a help if you have someplace with soft grass that you can hand glide a small model into wothout risk of damage. No power, no control, just tape the controls in center and glide it a few times. Does it want to rock from side-side with a rolling motion? Tail too small for the dihedral. Any turning tendencies would be likely to a warp somewhere. You can expect that a small bipe will need right thrust, usually 3-4 deg. although it sometimes takes more when there is a lot of side area.
Hang in there and have fun.
Regards, Dave

[Fwilly]

would taking out the dihederal be the same as adding rudder/fin size. I just totaled the plane so I can try a little of both when I rebuild the boddy. whats the minimum dihederal I can use and still get good rudder turns? I totaled the plane by adding to much side thrust(I think) it spun into the ground after launch. I had somewhere around 10 degrees to the right with about 4 down
thanks
Mike Feuilly

[Dave Robelen]

Hi Mike,
Sorry to hear that you are getting to rebuild the hard way. Removing most of the dihedral would be a very good move. With a biplane 3-4 deg. is adequate for good turns, and yes the original tail may be adequate under those terms. Apparently soft grass is in short supply where you are located. Testing a new design with such novel features can be a rough experience over a hard surface. If you need to go beyond about 5 deg. side thrust for straight flight, something else is acting up. With lower dihedral everything will be less critical, so maybe that will do the trick.
Regards, Dave

[Fwilly]

It was actually over grass it just wasn't tall enough in the spot it hit at . the broom weed should start coming in soon and that will catch even a heavy 280 sized plane but by mid summer they get so large that a stalk is big enough to take the wings off my little bipe and milk weed is scattered in the grassy areas wich has taken chunks out of my j3 stick wing before. there like small evil trees!

thanks for the advice I will use it on the rebuild and hope that this plane lasts longer. the original body had about an extra gram or two worth of repair ca anyhow

[Fwilly]

got the wal mart scale and weighed the wreckage. turns out it weighs 22 grams. tack on another gram for small missing pieces and that should be what it weighed with a 3 cell. weighed the new body which was built from what I believe is heavier wood and it weighed 4 grams. When I get it stable I will seek out some contest grade 1/32" balsa. maybe I can get that down to 2.5-3 grams. all the gear alone(rffs100+actuators+kpoo+3 cells) weighed in at 18 grams. I cut most the excess plastic away from the gear drive to save weight and I used short wires to batt and motor because they didn't have far to go. I think I'll set up the 10x beam thing after I get the new plane assembled.

then I went crazy with the scale and started weighing every thing I could get my hands on. My previous lightest plane weighed 4.5oz and used gws gear and dd ips motor on an 8 cell 120 mah nicd with a 16" ws. an empty j3 stick body weighs 3oz, an empty cox viper mustang weighs 36 grams with some lightening, and a gear drive I made using a motor and second gear from an hs55 servo with homade balsa prop weighed 2 grams(got plans to use that in a free flight plane in the somewhat near future)