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Building Tips and technical articles. => Building techniques => Topic started by: Bruce Guertin on March 27, 2020, 04:09:40 PM
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I need to build a Nobler fuselage. I have a Green Box kit to duplicate parts from and I have a copy of the "Green Box" plans Tom Dixon did in May 96 collaborating with another gentleman. This plan set has the former shapes and all of the ribs.
I was surprised the kit Nobler had no plywood doublers at the engine bearers. The bearers attach directly to the fuse sides with an eighth inch balsa doubler above and below it. Seems like not such a hot idea to me. Mr. Dixon's plans, on the other hand, call for a 1/32" doubler extending to the landing gear former, a 2" tank compartment width, and a one piece 1/2" top block from the prop to the back of the cockpit. I'm not sure if he meant to install the 1/32 ply between the engine bearers and the fuse sides and the 1/8" balsa doublers or sans the 1/8" balsa. I was thinking of 1/16" ply doublers and do away with the balsa doublers.
Any additional ideas? Thanks Bruce
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I would have to check the plans to sure I understand this, but for certain many have been built this way. An alternative would be to build it as designed but put a layer of carbon mat between the sides and the engine bearer/1/8" doubler and such. Lots of models been built with no ply doubler, but just a sandwich of the fuse side, carbon mat,hard balsa doubler then engine bearer.
Type at you later,
Dan McEntee
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I would have to check the plans to sure I understand this, but for certain many have been built this way. An alternative would be to build it as designed but put a layer of carbon mat between the sides and the engine bearer/1/8" doubler and such. Lots of models been built with no ply doubler, but just a sandwich of the fuse side, carbon mat,hard balsa doubler then engine bearer.
Type at you later,
Dan McEntee
I'm guessing a lot have been built per the kit instructions. When I left modeling CF was just starting to appear. I and Steve Kott had built a number of 1/2A foam wing combat planes with CF arrow shaft booms. We also sanded a wide, shallow flat groove on the upper and lower surface of the foam wing and filled that with a mix of CF roving and epoxy prior to covering with FasCal.
Getting back to the subject, your comment on CF between the fuse side and the engine bearers led me to use the most important part of this forum, the search function. There I discovered a thread on the use of CF as a doubler complete with photos. .5 CF mat was used and it had been obtained from Randy Smith. Additionally, there was a thread on this Randy had commented on. I'll have to contact Randy and see if he still sells this material.
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Check recent columns on the main forum for sources of carbon mat. That has been discussed a lot also. There are some different weights and styles and some one suggested that a part number had changed or something like that. It's available at several vendors.
Type at you later,
Dan McEntee
Try this
https://stunthanger.com/smf/open-forum/carbon-fiber-mat/
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I have had three Noblers built according to kit and plan from when it first acme out. Have one of them hanging on the wall that is still flyable. Back then there was no carbon mat or epoxy glues. Just good ole Duco Cement from the drug store and Testors Dope. Guess I need to clean it up and fly it again. D>K
By the way almost every Nobler I seen broke the break was either just in front of the wing or just behind it. H^^
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Spent time today getting reacquainted with an old friend, the pressure washer.
So what's best? .2 carbon veil or .5 carbon mat?
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Don’t count on either for strength.
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You want to distribute the load of the maple motor mounts to a large part of the fuse. I recommend plywood doublers (1/64) from the nose to 1” aft of the flap hinge line
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I think maybe Howard's comment sailed over many heads. Little or no strength is gained with CF layered between the motor mount and anything else. Might as well take a ten dollar bill and use it, cost is close to the same and you'll get the same effect.
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Might as well take a ten dollar bill and use it, cost is close to the same and you'll get the same effect.
LL~
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I think maybe Howard's comment sailed over many heads. Little or no strength is gained with CF layered between the motor mount and anything else. Might as well take a ten dollar bill and use it, cost is close to the same and you'll get the same effect.
Well, I included the kit supplied 1/8" doublers in my answer. That should give you a sandwich from the top of the fuse side to the bottom. Like I said, I don't have a copy of the kit plans at hand here. If you had a tight fit at all joints with a good, thin application of epoxy and applied some pressure while it cured, I would think a layer of carbon veil would be of some help if one was concerned.
Type at you later,
Dan McEntee
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I think maybe Howard's comment sailed over many heads. Little or no strength is gained with CF layered between the motor mount and anything else. Might as well take a ten dollar bill and use it, cost is close to the same and you'll get the same effect.
It has a minor effect, specifically, it adds some protection from splitting along the grain. It does nothing for rigidity, however.
I built a lot of Noblers straight out of the box, with the stock kit balsa doublers. I never had any problem with them being balsa, I would probably do it that way if I build another one. Of course the kit wood was typically 8+ lb.cu ft, so, pretty sturdy.
Brett
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Well, I looked over the kit wood. The "crushwood" fuse sides appear to be heavy (16g) each and 1/4 grain. I have some 1/8 balsa but it's 5lb+ stock and this is not a good use for it for a returning flyer. I've got a couple of sheets of 3/32 that's probably heavy enough to use. I have enough 1/32 ply to use as doubler material but, not enough 1/64 or 1/16. There's a Hobby Town in Brandon with a fairly large supply of balsa. Given the situation going to get any of it is not an option at the moment.
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I built several Green Box Noblers in 1950's early 1960's stock with my old Fox 35 and the nos e held up fine but they all cracked from the trailing edge to the first large cut out in the fuselage side. Later built with ply doublers and no cut outs. Those planes are still around in Florida and upstate NY.
EddyR
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I have a brodak Nobler kit sitting in my workroom (birthday present). I was thinking of trying a take-a-part for practice and to see how it's done. Would anyone recommend 1 piece wing, or two piece wing take-a-part. It seems like the two piece method is much more precise. So precise I can't envision it really. But two piece seems to fit in a travel case much better.
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A few more questions. On this Nobler fuselage I'm building I'm going to use one of the Tower .40s I have hanging around. It's longer than the Fox the Nobler was designed for. .8125 to be exact. In order to keep the prop in it's designed location the cylinder ( the heaviest part of the engine ) will be closer to the CG. I will be extending the engine bearers to the rear a bit but, how far forward beyond the front of the engine mount flange does the engine bearer need to be? Can I cut it 1/2" beyond the flange and make up the space between the bearer and nose ring with balsa? That would make tapering to the spinner a lot easier.
Also, with the prop in it's designed location there is room for a 6oz DuBro plastic tank. Is this enough fuel for the Tower?
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I've been plugging along. I finally got a free photo editor I like so here are a few photos I took a while back.
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If I remember correctly he Brodak Vector 40 kit had no ply. It was a balsa doubler carbon sandwich. Seemed to hold up just fine.
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I would use a lite ply former behind the engine. I mean how much weight are you saving vs allot more strength.
Motorman 8)
I can see now there are a lot of places I could have saved some weight. Some I can rectify now and some I can't do anything about. These ply doublers could have been thinner or lightened with triangular hole leaving an X shape in the middle.