Guillows Curtiss Robin R/C

[Bill Gaylord]

Thanks David and Phil

I glued the balsa manifolds on, and it now looks like it's supposed to. Just wasn't quite there without them.

[Konrad]

Don't know, she looked great even before you added the manifolds!

All the best,
Konrad

[Bill Gaylord]

Thanks for the good words Konrad.

After a bit of flying, the model is now at 117gms AUW. I added a gram of lead ballast under the cowl, as the plane proved to be just a slight bit tail heavy. The climb tendency, few clicks of down elevator required, bit of over-responsiveness, and calculated balance point all made it pretty obvious. Ideally proportioned planes like this are pretty forgiving, and it should be reasonable now at about 27mm from the LE, or 29% chord. The warbirds often like a good bit further forward CG. The plane now also has a small scale sized spinner, figuring I may as well get the combination of added looks and nose ballast from it.

[davidchoate]

Bill, glad it woked and flew good. I am all but complete a vwry simolar plane. Thanks for the info. I also have been uncertain of my exact CG settings. Though pretty balanced, I want a bit nose heavy. I hav in her now a 150 2300 kv, and a 7.4v 2mah 20c batt. My Auw is around 130Grams. Can you suggest a Prop, and is this a strong enough motor. I also hava a Eflite park 250, but It may be too much.I Have never had a success yet, but I think this one is it. If you think i'm not in a good way as far as motor size and battery please advise me. You seem to have found a feel for these things, and I appreciate any advice. Thanks.

[Bill Gaylord]

The GWS 4530 should be a good prop for the setup David, with your 2300kv motor. I would think the motor should be fine. Depending on the kv, you could use a 5030 or 5040 prop on 2s, but given the added current draw the returns are diminishing. With a slightly lower 2000 kv motor, the 5030 and 5043 are certainly useable on a 10gm outrunner, but there's probably no need for the added thrust on your model. While I like scale sized props on models, the smaller props have a lower P-factor "torque effect" also, which makes flying them easier. As you go larger, the right thrust angle really has to be tweaked to offset the left hand turn tendency caused by torque effect, if you want the model to be reasonably flyable. I have a Guillows Spitfire with a scale 9" 3-blader that has an insane right thrust angle. Once properly set, it turned out to be a good flying model, but a smaller prop would have made things easier.

A good CG setting would probably be around 25%. These high wing, ideally proportioned trainers are the only planes where I'm bold enough to go further, such as on this model. With some of the warbirds, I wouldn't have them anymore if I had flown them at 29-30% MAC. For whatever reason, a number of people on the forums seem to suggest dangerous aft CGs, which I certainly haven't had success with. A lot of the plan CGs are picked out of a hat also. The bipes are really fussy. The Guillows Sopwith for example flies beautifully with the CG at 10mm from the LE of the bottom wing. Don't even try it at 15mm, unless you have really tall grass/weeds like I did, when I first tried it at that setting.

[Konrad]

Well, I'm one of those guys that recommends what some might call "dangerous aft CGs". I like a model that does NOT fight me in pitch attitude as the model changes speed. I like to make touch and goes with my models. Nose heavy models don't allow a nice nose high flair for a slow touch down.

That having been said, I set up my models so that the equipment allows the placement of the CG at 25% MAC (biplanes at 20% MAC). Then as part of my flight testing I move the CG aft and turn down the control throws. With aft CGs one does not need as much control throw on the flight surfaces. I move the CG aft until the plane becomes slightly divergent. Then I hope a pray I can land her. I then move the CG forward a bit for some added margin of stability. My best flying gummy band to R/C models are trimmed this way

I find that far too many folks confuse over responsive controls with being tail heavy. Many Quote, "tail heavy" models actually just have too much control throw. Recall that I lower the control throws as I move the CG aft.

For R/C use on most Guillow (and just about all gummy band conversion) I lower the declarage (angle between the wing and stabilizer) by raising the leading edge of the stabilizer. On most Guillow 300 series models I raise LE of the stab by 1.5mm. I also try to remove the sharp bottom part of the wing's LE. I try to build in some Phillips entry on the front bottom part of the airfoil. Now most Guillow series 800, the series 1000 Hellcat, series 1000 Dauntless, and series 700 Edge 540 don't need these modifications.

All the best,
Konrad

[davidchoate]

Bill, I think it was you who put up a link for Heads Up RC? Well anyway, not only did I order every size prop and then some, but I got a motor 250 to use on a later build,and I found mini servos that dont require adapters llike the Eflites I've been using. I noticed the motor was cheap,and that usually means low quality, But I do have to try it.