Hello to all,
I have been building balsa aircraft for many years but am relatively new to R/C. I saw this web site: [link]http://home.mindspring.com/~telemark/sopwith/index.html[/link] and I have the same kit. I would like to convert it to R/C and am looking for some direction. I did a similar conversion to a Fokker Tri-wing, but the .049 with a 7x3 prop did not have enough power to get it past a slow taxi. I have other balsa kits of the same size and am wondering if there is a specific thrust to weight ratio when looking for engines. Currently I have two cox .049 engines and I would like to know how many pounds of thrust they generate at max RPM with different props so I could gauge my building accordingly. Does anyone know of a R/C website that lists such information? Also, what size servos would be best suited for such conversions: ie. standard, mini, micro.... servo tourqe and speed. I have been looking at a 6 channel radio with micro reciever and servos at tower hobbies but would like some recommendations before I shell out some cash. Any information that can lead me in the right direction would be helpful since I plan on designing a 1/2A P-3 model with retracts and operable bomb bay. I want to keep the models small and highly detailed so power to weight are my biggest issues.

That has got to be probably the most grossly overpowered WW1 scale model that I have ever seen.

The flying speed and overall performance would be so totally out of scale that it would be sad to see.

ewalters4, welcome to the Universe and hopefully we can guide you in your quest for a scale like but still satisfying performance.

There's no reason at all why a model of this size or even a little bigger cannot be built to 16 oz or less and powered very succeffully with an 049 running a 7x3. But bear in mind that if you were trying to take off from grass then yes, things can get messy in a hurry. It's quite possible that you would need to handlaunch this sort of model. After all, to a 28 inch model the normal grass is a scale foot or more tall.

It's not just thrust to weight but also wing loading that determines what flies successfully and what is a dog.

But for my 1/2A tecaco model the weight is 19 oz, area is just a bit less than 300 and the engine with an 8x5 puts out 10 oz of static thrust. The climb is very much like what I would expect of a WW1 scale model. A bit lazy in other words.

Thanks for the reply,
I am not sure of the weight of the aircraft, that will be checked, but I was trying to take it off from a paved area. I only have one of the cox .049 black widow engines installed with an old r/c receiver and standard sized servos. The model kit is a Guillows Fokker Tri-wing 1/16 scale with a 20" wing span. It is supposed to be control line capable but I added all the r/c stuff inside and the model doesn't want to fly. Could changing the pitch of the engine assist? The control line directions had me pitching the engine downward by about 2 degrees with shims. If it needs to parallel with the cord of the aircraft I can do that simple enough. What type and size r/c receiver and servo do you use in your 1/2a models?

MICRO size equipment, is the weapons(equip.) of choice.Lighter=better,there`s a,lot of options available,dollar/weight wise.Everyone has thier own preferance,just try ,and keep your weight down,including your battery..You`ll find the micro/smaller stuff, fits in, the little planes, better too.

Yeah, you better believe it! They were puttin some big honking gear in that sopwith. Way heavy! If you are into tripes, look at my 1/2 A DRI build along, its by no means a traditional build, but its light and it flies on a .049. Also, very important as everyone here has mentioned, the internal stuff can be soooooo much lighter. I use cirrus 4 channell RX's usually, why do you need six!!?? Bombs rockets and aerial photography!!?? Lets just get the X@$%G!f%$ thing in the air 1st. Little guys this size dont really need payloads. Little HS-55s or HS-88's (I dont recall which but I can check) servos are fine, and probably 1/5th the weight of a standard. Look around here and keep asking questions, we'll have you airborne before long.

THE ZZ.

A 20 inch span Fokker is not going to have much wing area and with the larger equipment the loading would be high. I'll bet it high speed taxi'd all over but just never had a chance to run fast enough to fly. And yes the 7x3 may have reduced the revs and thus speed limited it so it did not want to take off. But if it had the regular sized gear in it I'm sure it was a bit heavy so perhaps for the sake of the radio gear the non takeoff was all for the best.

If I was doing an 049 Tripe I'd enlarge it until there was about 230 to 250 sq inches of area and build it with sticks with lightweight covering. Power would probably come from a 7x4 or 7x3 on the engine set up with a couple of extra head gaskets to reduce the compression ratio in order to make it more big prop friendly. The weight in this size should not go much over about 18 to 19 oz. At that size and weight it would fly fairly well and scale like. In otherwords you would need to dive slightly to do a loop but consecutive rolls would be easily done.

[8D]That sounds about right BM. With mine, I went the opposite route engine wise, I turn a 6x4, and have the head gasket/washer removed to increase the compression. Either way though, he'll be a lot closer to success than trying to build an undersized flying brick.

The ZZ