hi there. i am going to start a scratch build project of the waco umf-ymf biplane. i have a few questions first..i will be using muesum drawings to build by. the measurments say the real plane was 30 feet wingspan. i want to go for 45.5 inches. what scale would this come out to? also i want to keep this light as possible. i would like it keep it electric..what sized motor would you recomend? i don't want a flying rocket but at half to 3/4 throttle, keep it scale speed.. i know the drawings show top and bottom wing airolons toward the outter edge of the wings, but did it have flaps? my plans are to use 1/32 ply formers and basswood stringers to keep it strong. would this be too heavy? the wings i will have cut out of foam and skin it with 1/32 balsa.. what do you think? also about the motor, i have a spar 180 motor mci brand motor with a gear head. not sure what the gear is but it has a brass motor gear that is 1/4 the size of the larger prop gear., i guess for higher speed. i also have gws gs100 speed controller and a futuba 6 channel radio with up to 6 servo's with flap, landing gear switches. will this motor be strong enough? i know this will not need the retracts, but if there is better use for that switch, let me know..thanks tom

also, i would love to have the smoke while flying, like you see at air shows. do they make anything for electric motor planes that would work? i know the gas powered planes use somthing tht goes through the muffler if i'm correct...

Well, I can help with at least one question 30ftx12=360", so 360/45.5=7.91, therefore your model would be just a tad larger than 1/8 scale (1:7.91 scale).

As for the rest, I suggest you search for a similair sized biplane model that already exists. That will get you in the ballpark for final weight and motor selection.

Flaps? I don't think so, but I could be wrong. Good luck, the Waco bipes are some of the finest looking bipes around!

No flaps on a Waco YMF.

o.k. thanks, i didn't think it did, but before i got too far along, i wanted to make sure..i'll keep you post on progress.

I would suggest that the wings be built up with ribs and covering as the full size. Save the foam and such for the forward fuse where it had some sheet.

Power would depend on how heavy it ends up being. At 45" with sheeted foam wings I would suspect it would be well over 20oz, which means a 180 won't be near enough power. Probably a 140W system, like a bell motor on 3s or a bit more.

If you want a really good guide look at either the PICA 1/5 (?) scale or the Dumas 35" version. For lightweight I'd go with balsa formers and stringers (either a crutch with full formers or box frame with subformers). 1/16" balsa for all, or use 1/16 bass if you really feel you need to (not necessary for the structure, but, will stand up to sanding and building stresses better).

charlie

What Charlie said and, to minimize tail heaviness, try to keep structure aft of the wings light as possible including tail wheel installation and covering materials, however I like to use basswood for stabilizer and rudder frames as these take a beating during cartwheel landings, etc. I also like to use some basswood stringers aft of wings for anti-crush strength. Join elevator halves with a piece of music wire. Consider using pull-pull linkage to rudder and a pushrod for elevator supported inside the fuselage so it doesn't bow under pressure. Select your brushless outrunner motor and lipo battery pack to provide adequate power, about 100 watts per pound because of the overall drag. Locate battery pack, servos, receiver etc as far forward as possible to minimize need for nose weight. Plan on using a Park BEC if you will use more than three servos. Be careful to avoid dreaded "banana shaped fuselage" by using same stiffness sticks and adding stringers on opposite sides, etc. Good luck on this adventure.

o.k., thanks..this is helping so far..let me get some wood cut and i will post some pictures soon. how ever, after a quick cut of the ribs and threw on half side together at the size mentioned to see how much is going to be need to complete. i am now thinking, i might be in alittle over my head...i'm not sure if i'm happy with the looks..lol i havn't built too many scratch built models, exspecially when you have to make your own plans. i'd hate to spend all the time cutting alot of wood, only to have it look wrong and lost all the money spent in wood..i'm really thinking i might need to go smaller, but still keep it scaled.. with the listed equipment, what's the smallest i could go and keep it safe(not too small for the weight) if i can keep it light as possible? i believe i would be more comfortable at a smaller size. tom

How small and how light do you want to go?

I think a 180 motor is near a sp280 in power? If so then that is what the Dumas 35" version is designed for.

If you want a bit more power/wt then a 30" span might be just right.

charlie

charlie, i'm more thinking the 30'' span. i'm even thinking of going the laminate route. cut the former halfs out of thicker plywood. then, use thinner balsa strips to glue together to make different layers and clamp to the ply shape to make the formers. to save on alot of cutting and to keep halves same..hopefully also save weight too in the long run..tom

charlie, i tried to look for the dumas 35'' version you mention, but did not find it...do you have a picture of it you could post? thanks tom

Here it is on the Dumas web site
http://www.dumasestore.com/catalog/i...hp?cPath=50_51

Here is the prototype build thread
https://www.rcgroups.com/forums/showthread.php?t=356520

Your ideas for building seem perfect. Good luck with it.

charlie

o.k., i see the 35'' kit. i think i might just go with the kit route...thanks.tom