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Old 12-21-2010, 04:25 AM
Gettin' Lower!
busso wa
Joined Dec 2010
74 Posts
Help!
gp cap 21 73 inch

hi guys

been given an almost finished cap 21 from a club mate. only been in the hobby for about 1 1/2 years so don't realy know heaps about this stuff. I'll soon be working on a 30cc mx2 so don't expect this progect to get finished in the near future. i've got some questions but any additional info will be helpful. back to the questions, how much should it weigh? how well does it fly? would a satio 100 be any good? and can i paint it or will that make it to heavy? and finaly what aerobatics does it exel at.

thanks lachlan.

sorry about the spelling.
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Old 12-21-2010, 05:06 AM
Gettin' Lower!
busso wa
Joined Dec 2010
74 Posts
Re: gp cap 21 73 inch

hi

one more thing. whats the best way to keep balsa from warping ect.
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Old 12-21-2010, 06:44 PM
Flyin' Around
bellingham,Washington
Joined May 2007
5 Posts
Re: gp cap 21 73 inch

This is about a 20-25 year old model. I was teaching at the university of Illinois when GP develpoed this model. In the hands of a competent pilot it can be a very erobatic aircraft. But it did develop the repuatation as the Snap 21, not the GP model but Cap 21 models in general. Do your stall tests at a decent altitude to give yourself time to recover. Keep decent power on it during your first landings as it can snap into disaster in a hurry. Although the Cap 10 was very stable the 21 was not. It became a much better aircraft in the 231 and 232 when they put the extra wing on it. I have a GP Cap 21 in the crawl space under my house here in Washington, powered by an ASP 72 2 stroke.
The Sato 100 4 stroke should be a good choice for power. The Cap 21 is not a light plane bye todays ARF models standards. The slab fuse with ply doublers etc can not match the light ply truss type structure that the ARF's use. The GP Cap 21 is a rather robust structure, and thus a bit on the heavy side. I don't know the weight of mine. I haven't done anything with it since before I left Illinois. I think it is robust evough that warping is not a particular problem.
I assume the fellow who gave you the plane gave you the construction manual and plans. Keep the CG at or infront of the location shown on the plans. The throws that are suggested aren't bad.
I wish I could remember the name of the former pattern flyer who did most of the flying of the prototype. I think Dave Eversen or something like that. Last I know he was in Oregon somewhere. But don't hesitate to contact Don Anderson, he was and still is the power behind GP. He is a hell-of-a nice guy and I am sure could answer any serious questions you have about this model.
Bill Schnobrich Bellingham WA
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Old 12-21-2010, 10:09 PM
Gettin' Lower!
busso wa
Joined Dec 2010
74 Posts
Re: gp cap 21 73 inch

thanks Bsschno

if you don't mind me asking what did you teach at uni. right now i'd like to go into aeronautical engineering after school if i get the grades even if it means traveling to America.

lachlan.
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Old 12-22-2010, 03:39 PM
Flyin' Around
bellingham,Washington
Joined May 2007
5 Posts
Re: gp cap 21 73 inch

I taught civil engineering, the structural option. Several of the classes I taught were selected by a number of aeronautical engineering students to take as the courses dealt with design of plate and shell structures.
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Old 12-27-2010, 06:16 AM
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Australia, WA, Kelmscott
Joined Aug 2010
2,151 Posts
Re: gp cap 21 73 inch

lachlan i had the 55in span 40 size gp cap (snap) 21 i know of a few guys that had them and had big problems with them snaping and tip stalling. so what i did with mine was set up spoilerons on my ailerons for landing like flaperons but they go up insted of down by doing this i could land it at walking pace. Alot of reasonds why airobatic models snap is because they have too much elevator throw. That is just setup. If i remeber rightly i had my c of g set on the spar set your elevator throw to around 15 degrees on low rates with expo and try around 20 degrees on hi rates with expo. If it snaps when you pull in full elevator (try this at a high altitude) then you have too much throw. With the 72in span cap that was designed for a 120 4 stroke or 90 2 stroke but these days the newer motors have more power. I personally would be looking at putting either a 120 to 140 2 stroke or a DLE30cc petrol in it. Also what is the MX2 you are building? I have the Dolphinco goldwing 1 here. What club do you fly at? Ill be flying mine at the imac comp in capel at the end of the month if you want to see how it flys.
regards Bill
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Old 12-31-2010, 07:16 AM
Gettin' Lower!
busso wa
Joined Dec 2010
74 Posts
Re: gp cap 21 73 inch

Hay Bill

I have a gold wings mx2 haven't started the build yet because I've been on holidays. I fly at swarms (capel) with Scott who will help me with the build if need be.
How many degrees did you spoiler go up to? might try that on my cap 580 gp .46 size.

lachlan
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Old 01-01-2011, 09:20 AM
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Australia, WA, Kelmscott
Joined Aug 2010
2,151 Posts
Re: gp cap 21 73 inch

can't remember now was years ago think was only a couple of degreese though. ok cool the mx2 is a nice model, It will fly well on 15 deg throws. Unlimited vertical with the DLE30, will do all imac manoververs.
Good luck with the build.
regards Bill
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Old 01-07-2011, 04:40 AM
Gettin' Lower!
busso wa
Joined Dec 2010
74 Posts
Re: gp cap 21 73 inch

Hay

getting futaba brushless sevos for the mx2. NOT CHEAP!!!!

lachlan
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Old 01-07-2011, 05:08 AM
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Australia, WA, Kelmscott
Joined Aug 2010
2,151 Posts
Re: gp cap 21 73 inch

ok i'm just running 12kg hitec in mine
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