panhndl

My Feedback: (10)

I asked this in the Warbird's forum and didn't get an answer I was satisfied with, so I thought I'd ask it here and maybe someone could explain some stuff to me. :-)

The two airplanes linked below have similar stats. The KMP T-28 will have an 80 inch WS and should weigh about 16-18 lbs AUW with 1015.3 sq. inches of wing area. The ESM P-39 has an 80 inch WS, 1224 sq inches of wing area with an AUW of 16-18 lbs. From the 3 views of the planes, both seem to have very similar dihedral. The only things that are significantly different is the wing area and shape of the wing.

Anyone want to explain how or why the T-28 would make a better 1st "warbird" than the P-39? Let's try to ignore whether the T-28 is really a warbird or if the P-39 will be sorry because of the full size version's mid engine issues. Also, the KMP calls for a 40-50cc engine while the P-39 calls for about a 30 cc engine. Why?

http://www.kmp.ca/product_info.php?c...roducts_id=238

http://www.vqwarbirds.com/product_in...5e1d32d5ede344

Thanks a ton!

Shoe

The similar weights, planforms, control surface layouts and landing gear arrangements lead me to believe that you could expect similar flying qualities between the two models. The extra wing area with the P-39 suggests it might be a bit more forgiving in the landing pattern.

I can't speak to the P-39, but I've had the chance to fly the full-scale T-28. My biggest impression was that the stick/pedal forces were much lighter than I expected... perhaps the T-28 just looks like it would be a handful, but I was pleasantly susrpised, both in the landing pattern and doing basic aerobatics. As long as your servos can keep up, control forces aren't a factor for RC flying qualities, so there's probably not much value to this antecdote. Bottom line: subtle design differences can sometimes lead to unexpected flying qualities "features", but to the extent that you can predict behavior from gross design specifications, I would expect similar behavior for these two models. However, as a Naval Aviator, I would have to recommend the T-28.

panhndl

My Feedback: (10)

Thanks Shoe. I have the T-28 on order already but have been waiting on the P-39. I'm sort of planning on eventually purchasing both planes but have been hoarding some money for a sec. Unfortunately, no one seems to have actually flown the P-39 so we don't exactly know how it handles. The T-28 is a fairly common rc plane design, but like you said, small changes can have some big results. As far as I know, the new version of the KMP T-28 (available around Aug. 1st if they haven't all been pre-ordered) will be closer to scale than the original model pictured in the links. I guess there were some pretty legitamite complaints with the "scale-ness" of the original T-28 and KMP responded to their customers' requests.

I really like the P-39 and was thinking that I could order the model and put my Syssa 30cc gas engine in it down the road.

Anyway, thanks for the insight.

rmh

FWIW.
The design requirements for the t28 was far different (and at a much later time) than the P39.
both are trike setups but the p39 does not lend it'self to hiding other than an electric motor setup-simply because the P39 had a poorly concieved engine location.
A lot of "what would this do" designs came out of the 1930's some good -some not so good.
IF you build both models with same wing areas and wing loadings - expect similar performance in a model simply beacuse in these sizes and the fact that all flying is conducted by watching and then making inputs, wing loading and power loadings directs the actual feel of all designs.
I can make either P39 or a T28 which is a fully aerobatic setup or a very tricky setup by changing just one factor
wing loading. This is unfortunately, the most difficult one to control

Some kit designers can make nice looking models but they are not good weight/strength guys