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HELP WITH MODEL TECH CAP 21 MODEL..

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Old 06-30-2007, 02:03 AM
  #1  
<<KJ>>
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Default HELP WITH MODEL TECH CAP 21 MODEL..

I posted this in another page, but I really need help so I'm adding it here.

I have a CAP 21 plane made by Model Tech (.40 - .60 size).
It appears in ok condition - it is dusty though and it has some cracks in the surfacing (not sure if they are structural cracks or not) but the surface is made from some kind of painted fiberglass material.. (not sure what it is really)
It has an SC .61 engine to go with it.
I am just wondering if the cracks will stop it from flying correctly and also I need to know where to mount servo's, petrol tank etc.. I have no instructions.. is there anywhere that I could possibly get a set of instructions for one of these so I can make sure I have everything correct before attempting to fly it?

Regards

KJ
Australia.
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Old 06-30-2007, 10:39 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

This really depends on how bad the cracks are. Could you post some pictures?
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Old 07-05-2007, 03:20 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Pics of cracks
The plane feels structurally sound but I haven't attempted to fly it yet..
Any help would be greatly appreciated! Especially Instructions!

KJ =)
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Old 07-05-2007, 05:40 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Some of those cracks, especially the ones along what looks like the top of the horizontal stab could be cause for concern. One thing you don't want to lose while flying is your horizontal stab. You may wish to have someone more experienced take a good look at this fuselage to make sure that these are not structural in nature.

If these are just surface cracks, well, perhaps a little repair, some covering, or just leave them alone.. and give it a try. But be careful.

Don't just think 'well, if it crashes, well, so what' because that could cause you some severe heartburn. The what if.. could be what if it does break apart in flight and hits someone on the flight line? Then what would you do? Losing the horizontal stab during flight means you have completely lost control of that aircraft and where it is going to go next.

DS.
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Old 10-19-2007, 02:39 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Thanks for that,
I will get someone at my local club to check it out.
Does anyone know where I can mount petrol tank, servo's etc?? I have a Hitec Transmitter and Servo's (4 channel)
I Need some instructions!

Anymore help would be greatly appreciated!

Thanks.

KJ :-)
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Old 10-19-2007, 03:55 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

there are holes in the firewall for the fuel lines....isn't there mounting holes for the servos in the fuselage? If not you may have to get a servo tray.
You're not a beginner are you?
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Old 10-19-2007, 09:50 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Your not going to like hearing this,but DO NOT fly this plane untill you strip all the paint off it and re-glass the entire fuse! The fuse has been glassed,and all those cracks are structural fractures and breaks and need repaired. By looking at the pic's,the plane was painted not covered in covering,and sustained a severe crash to crack all the paint,wing hold down blocks and stab hold down blocks. Crash was most likely due to the infamous Cap-Snap on a take off.Repair the plane completely,then remove the main landing gear from the wing and place them in the fuse about 1 inch in front of the wing.This simple trick will stop the cap from snapping on take off only because it forces the cap to only lift it's tail off the ground when it is at it's true and actual flying speed. The Cap is a fantastic flying plane when set up correctly,i used to have 3 of them at one time,but thinned out my plane numbers over the years. Fuel tank goes in fuse just behind the firewall,reciever goes just behind the fuse former at the wings leading edge where the wing goes into the fuse,servo's ( throttle,rudder,and elevator) go into a tray located just past the mid-way point of the wing saddle,and aileron servo is located in the wing it's self. CG of plane is located between 3.5 to 4.5 inches back from leading edge of wing at the fuse with the plane inverted. Hope this information help's you out!


Good Flying

Art
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Old 10-19-2007, 09:53 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Some advice from an old timer who has been in this hobby for 23 years. Your Cap 21 question is posted in the "Beginner Forum" so my assumption is that you are a beginner. Welcome to the hobby, it's a lot of fun. My advice to you is that the Cap 21 is a hot plane and, as a beginner, don't try to fly it on your own until you have some good flying experience under your belt. I have made and flown a Cap 21 and it is a fun plane to fly, but it also is a fast and hot plane to maneuver and land. This is the type of plane that an intermediate flyer with a lot of flying time can handle. I also recommend that if you have access to a simulator with a Cap, get on it and practice. The Aerofly Professional Dekuxe Simulator by Ikarus has a Cap in it.
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Old 10-19-2007, 07:59 PM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

I don't think this plane was fiberglassed. Looks like they doped the wood and then painted it. Without Dacron, that finish would crack along joints very easily. And then some of the scars look like crash damage. Wiggle everything and see if anything moves. The plane is likely air worthy.
Snap21's were nasty, ill tempered planes that bit many a pilot early on. But they can be tamed. Limit the elevator travel. Crank up the ailerons slightly to reduce the tip stall tendency, and add nose weight. You can never completely remove the snappy tendency of these planes, but you can improve thier personality with these few changes.
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Old 10-20-2007, 09:23 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Thanks for that everyone.
Yes I am a beginner, well I would class myself as one. I used to fly a bit.. a friends plane though, not my own.
I would like for this Plane to fly, so I am going to try everything possible to get it to do so!

abacro wrote: "remove the main landing gear from the wing and place them in the fuse about 1 inch in front of the wing.This simple trick will stop the cap from snapping on take off only because it forces the cap to only lift it's tail off the ground when it is at it's true and actual flying speed."

Is this necessary? I don't really want to remove the landing gear from the wings if I don't have to.
The wings are in great condition. the plane overall seems structurally sound, I applied a firm pressure to all the area's with cracks and it all seemed strong enough, but is strong enough to fly? I am not sure.
Just for looks I would like to fix up these cracks anyway.. what is the best way to repair over the cracks and achieve that glossy plastic look that they have used from factory?

Also......

PilotFighter wrote: "I don't think this plane was fiberglassed. Looks like they doped the wood and then painted it."

Forgive me for not knowing, but what does Doped the wood mean? do u mean dipped? and if so, in what?

All the help I can get would be fantastic!

Thanks everyone!

KJ :-)
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Old 10-20-2007, 12:52 PM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

THe old way of finishing models, and it still works great, was to paint the wood with a product called dope. Dope is a thick, but very light weight , clear substance, that dries very quickly and allows the grain of the wood to be made perfectly smooth. Typically, two or three coats of dope are applied. Then Dacron, a man made cloth similar to silk is applied using another coat of dope, or other adhesive. Then the weave is filled in with another few coats of dope. And the whole thing is then sanded smooth with 400. Its fast, easy and allows a great paint job to go on top. Actually, they even sell colored dope, so this would complete the project.

It appears , that your man only applied dope before painting. He didn't apply silk or Dacron. So the plane has no "hide". A fingernail could easily be depressed into the finish and the vibration and stresses of flight often cause cracks to appear in the finish all along the structure. Many of the cracks in your pictures appear to be the result of the technique in which the modle was finished. And a few appear to be the result of a minor crash. He might have used a product called silkspan. Its very much like tissue paper. Its great for small models. But doesn't offer the strength needed for an aerobat of this size.
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Old 10-20-2007, 10:12 PM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Wow!
That's very interesting information! Thanks.
So to repair the surface, I would need to re-apply this "Dope" Substance? Where do I get it from? Do hobby shops sell it? Being an older plane, is this "Dope" still available?
And with this method, can I just replace the damaged sections or do I need to re-coat the whole plane? (I would loose all the Decals and colors if I was to do this)
Also, would I need to replace any of the balsawood? It doesn't appear to be broken anywhere, but then again, I can't really see inside the plane or underneath this "Dope" covering.
Would a wood glue be ok to apply to repair some of the cracks?
What is the process for repair using this "Dope" Method? If you know, please post here or E-mail me - it would be ever so helpful!

Thanks

KJ :-)
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Old 10-20-2007, 10:46 PM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

You should still be able to find butyrate dope or paint at the hobby shop?

http://www3.towerhobbies.com/cgi-bin...loss&search=Go

http://www.sigmfg.com/cgi-bin/dpsmar...humb_02Dope_01
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Old 10-21-2007, 07:43 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

I am in Australia, are these parts available here too?
does this Dope material come with instructions as to how to apply it?

Cheers,

KJ :-)
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Old 10-21-2007, 08:07 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

These specific brands may not be available but I'm sure some brand is available to you in your country but maybe not in your town?

Even in the populated area where I live, I would have to order these paints as the local hobby shops do not carry them any more.

The paint does not come with instructions. You will have to gain that knowledge from the forums.
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Old 10-21-2007, 08:40 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Ok THanks!
Does anyone here have that knowledge that could help me out?

Regards,

KJ :-)
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Old 10-21-2007, 08:47 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

http://www.rcuniverse.com/forum/m_38.../printable.htm

http://www.randolphaircraft.com/html/australia.html

R/C Warehouse in Logan City, south of Brisbane, stock SIG dope.
Go to
http://www.rcwarehouse.com.au
Then enter dope in the search box at the upper left.

Phoenix Lacquers in Bankstown, Sydney manufacture and sell a variety of aircraft dopes; Nitrate shrinking, Nitrate non-shrinking and Butyrate which can be tinted if you want. These need to be well thinned with cheap thinner for use on models. Ian Smith has been using it and has had favorable results.

Use Acetone for thinner

They also sell TCP plasticizer
.
And then you can mix your own colors by getting dry pigments from a good art supply store - Fun Fun Fun (until you try to match the color for repairs)

Aeroflyte dope is/was nitrate. Butyrate, as favored by our US friends is nominally fuel proof against low nitro glow fuels. My experience is that it isn't very durable in our conditions. The tinter used is normal auto paint tinter, So a gazillion colors are available.

Non-shrinking nitrate is useful on fragile or easily warped (like solid sheet) surfaces. Nitrate is proof against Diesel fuels only.

The best nitrate was made in Oz by Bostik, Peter Lloyd had a ready supply many years ago. I'd be confident that the FF guys have this problem under control.

Cellulose dope is becoming the latest bio-hazardous material and is banned in the EU from September 2007. Apparently, model materials are exempt from this, but the amount now sold for modeling won't be worth anybody’s while.
I've always understood that cellulose was just about the safest of materials and that the body could break it down. 60+ years ago I used to sleep in a room full of dope fumes...

Unfortunately you are stuck with hazmat charges too. Imported (Randolph for example)dopes are horrendously expensive because of the shipping halfway round the world charges. Randolph dopes are available at virtually any major GA airport thru Aviall, Spruce & Specialty or Hawker Pacific.

Get an old CD case. Break up the clear plastic and drop into a glass jar of acetone. Keep the lid on. Leave overnight. The plastic will dissolve in the thinner and that is dope for my use. Thin it further to the right viscosity if necessary. I mix it with paint tints and apply onto my plane. Some plastic cases give clear dope, some are slightly hazy.

Xylol seems to be used to slow the rate of evaporation and I guess because it's a solvent it dilutes the dope as well and hence the rate of shrinking.

Buy dope at the airport? Most of the quantities are pretty large when people are restoring airplanes and the people doing that might have a pretty good handle on the best economy and products Randolph comes in any size you want: quart, gallon, 5-gallon, 55 gallon drum, 550-tote, and bring-own-tanker

Try an aircraft supply store at a municipal airport near you ...they should have butyrate and nitrate dope clear and colors...its the real stuff.......airplane butyrate clear is about 10 dollars a quart...colors are about 20 bucks......you may be able to order it direct from Randolph... http://www.randolphaircraft.com/
tin of Aeroflyte lists the composition as:

Acetone 27%, Xylol 38%, and I guess the other 35% is Randolph's type dope (Cellulose Nitrate ?). Nitrate is not fuel proof. Butyrate is.
http://www.awm.gov.au/events/confere...nt/nitrate.pdf.
Gents, Model Engines are/were supplying dope under their own label, nitrate/27%Acetone/38%Xyelene
Supposedly the furniture lacquer used in Asian countries by (usually Chinese) cabinet makers is supposedly identical to nitrate dope. I've been meaning to try it, I've heard it yellows with age.

CD jewel cases are, I believe, polystyrene. So you'd get the same results if you dissolved Styrofoam, of which there is usually a free supply in shopping mall dumpsters, or near a MacDonalds. Some guy in Brazil wrote to the MACA Newsletter a long time ago about melting sprues (from plastic model kits) to make dope.

Too bad CDs themselves won't dissolve, being made of Lexan. Lots and lots and LOTS of those lying around, the result of mis-burnings by Nero. We call them "coasters", but you only need a small number of coasters..
http://smallflyingarts.com/Current_C.../floor_wax.htm
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Old 10-21-2007, 09:01 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Wow, that a lot of info! sounds complicated but I guess it can be achieved!

So this will fix/repair the cracks and have the plane back to a safe flying state then?

Thanks for your help,

KJ :-)
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Old 10-21-2007, 09:15 AM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

Be cautious, you do not know what kind of finish is on your plane.

Different types of finishes may react with each other and cause wrinkling or who knows what kind of reaction? Try you new finish in a small area first.

There has been a trend in recent years away from Dope with the use of Urethane paints and in particular of using spray enamel for color and then using Polyurethane clear over the top as a fuel proofer. Therefore your plane may not have dope on it?

I personally have not used dope in 20 years. But I used to think I couldn't live without it.
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Old 10-21-2007, 10:13 PM
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Default RE: HELP WITH MODEL TECH CAP 21 MODEL..

I rather doubt the top coat is dope. And dope might react poorly with it. I'm afraid that a quick coat of dope is not going to repair those cracks in the paint. I was simply trying to explain the possible process that the builder appears to have used to paint the plane.
I suspect the top coat is not dope. Therefore, you could 1.) try sanding everything off, and starting new. 2.) sand everthing off and then use iron on film, 3) fill in the cracks, shoot primer, sand and then repiant it. But if my assumption is correct about the builder not using Dacron or some other fabric, your paint job could easily show stress cracks also within a short time.
I would suggest that you simply fly the plane as it is now. Those cracks are hard to see at 60 mph and fifty feet away. Then maybe some day later you can give the plane a proper restoration.
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