Peter Miller plans question

Looking through the ring binders of plans that few will ever get built, I came across a Peter Miller plan for a CAP 21, in the August 2007 RCM&e

The main heading ends "THE PERFECT HOME FOR YOUR .25 TWO-STROKE"

Many of the free plans are too small for my liking, but this one is 53" wingspan, which is just right.

At the end of the article, in the spec box, it says for .25 - .32 engines.

My question is, does that motor size sound right? If it does, then it is the perfect candidate for fitting a more advanced and eco-friendly power plant.

Construction is nice and simple, would fit two servos for ailerons and not bell cranks, but it may be something to do instead of changing to model submarines.

Yep - the motor size sounds about right. I've got the same plan in my "not likely" file so I had a sticky beak at it. With a 25 you'd be looking at a pleasant Sunday flyer - go up to a 32 and it would be a bit of a missile. Always taking into account of course that if you build it from lumps of recycled Oak it probably wouldn't fly with a Merlin up front!

Grumpy42 wrote: Yep - the motor size sounds about right. I've got the same plan in my "not likely" file so I had a sticky beak at it. With a 25 you'd be looking at a pleasant Sunday flyer - go up to a 32 and it would be a bit of a missile. Always taking into account of course that if you build it from lumps of recycled Oak it probably wouldn't fly with a Merlin up front!

Thanks, my initial calcs show it would fly very well with a 3548 with a 3s lipo, and a 400mAh battery giving around 8 minute flight times.

It will move up to my "very likely" folder. Mine are colour coded, long green bar for "very likely", short green bay for "likely", yellow bar for "maybe another look one day", orange bar for "unlikely", and red bar for "what the heck am I keeping this plan for"

That also means I can find things that others may talk about by looking how I would rate it

Eric wrote: Don't forget that the real CAP 21 is a competition aerobat, so would be - to the weekend flyer - grossly overpowered!

www.airliners.net/aircraft-data/stats.main?id=32

That is one of the things that puzzled me, a "semi-scale aerobat" nearly 5' span on a 25, didn't seem powerful enough to me, but I'm not very good with IC, it is more than 30 years since I flew with one.

Looking at the plan Sangoma it seems to me that it was designed as more of a sunday flyer rather than an attempt to duplicate the real aircraft's performance. If you wanted to have something approaching a scale version of the performance of a real CAP 21 you'd probably need to go to the electric equivalent of a hot 40 or 46. I'd think that would require a certain amount of redesigning of the plan to cater for the increased performance.