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Building Tips and technical articles. => Building techniques => Topic started by: Bootlegger on August 07, 2018, 04:41:30 PM
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Guy's what way have you found best to mount the bell crank in a foam wing, and please be specific, I need all the help that I can get..
and THANK'S...It will be suspended between upper and lower b/c mounts...
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https://stunthanger.com/smf/open-forum/how-do-you-mount-belcrank-in-a-foam-wing-core/msg388732/#msg388732 (https://stunthanger.com/smf/open-forum/how-do-you-mount-belcrank-in-a-foam-wing-core/msg388732/#msg388732)
Reply #7 answers all your questions, plus the ones you forgot to ask.
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litle different solution
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then the glass goes over the all and joins all together
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Igor, that bellcrank is a work of art. I assume from the soldering that it's steel with brass tubing soldered on. Is the body plain steel or some fancy hard steel? How much does it weigh?
Interesting use of ball joints, BTW :).
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It is steel used for car caroseries, so standard, not hardened, not plated, but high tensile, not soft.
BTW I do not use ball bearings, it is standard bent pushrod from welding wire in brass tube bearing.
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https://stunthanger.com/smf/open-forum/how-do-you-mount-belcrank-in-a-foam-wing-core/msg388732/#msg388732 (https://stunthanger.com/smf/open-forum/how-do-you-mount-belcrank-in-a-foam-wing-core/msg388732/#msg388732)
Reply #7 answers all your questions, plus the ones you forgot to ask.
Okay, forgive the obtuse question. If the wing and fuselage are built separately, you have to cut a slot in the fuselage to clear the top and bottom of te pins when you slide the wing in place. Looking at the photos of Bob's plane, I don't see how he did that. The fuselage and ply doubler look intact. How did he do it?
Mark
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Slid the fuse sides onto the wing separately (from each tip) then built the fuse jigged to the wing on his bench?
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It is steel used for car caroseries, so standard, not hardened, not plated, but high tensile, not soft.
I usually understand Igor just fine, but "car caroseries" has me puzzled. ??? Steve
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body bodywork chassis frame coachwork (of a car ) car body
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"Not hardened but high tensile" sounds like a bit of an oxymoron to me -- but car body steel is weird stuff these days. It comes out of the mill soft, and age hardens. The idea is that it's soft for the punching process, and then hardens itself by the time the car gets out of the factory. That way you can have a strong, lightweight car body without having to even think of heat-treating sheet metal (which would be nuts).
I don't know where you'd get flat pieces of the stuff -- steal the tailgate off of Helmick's truck, maybe. There should be several bellcranks in that.
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My solution is:
https://plus.google.com/photos/117790355930193335731/album/5715088163776972593/5715089616610138770
Can it be more simple? :)
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Okay, forgive the obtuse question. If the wing and fuselage are built separately, you have to cut a slot in the fuselage to clear the top and bottom of te pins when you slide the wing in place. Looking at the photos of Bob's plane, I don't see how he did that. The fuselage and ply doubler look intact. How did he do it?
Mark
The very worst part of that question is that you made me realize that I have this beautiful fuselage, and this beautiful wing with the bellcrank axle sticking about 1/2" from the top & bottom. The project has been idle for a couple of years so I can't remember my plans, but I think I'll take a Dremel Dangerous Disk and whack the axle down so it's sticking out about 1/8", and then just notch the wing opening on one side. That'll be easily covered by the wing fillet, so everything should be just fine.
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"Not hardened but high tensile" sounds like a bit of an oxymoron to me -- but car body steel is weird stuff these days. It comes out of the mill soft, and age hardens. The idea is that it's soft for the punching process, and then hardens itself by the time the car gets out of the factory. That way you can have a strong, lightweight car body without having to even think of heat-treating sheet metal (which would be nuts).
It is material for cold molding of car body - especially that which must surive and to break during molding process and also during crash (must bend, not break, but still must be strong and not heavy)
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Okay, forgive the obtuse question. If the wing and fuselage are built separately, you have to cut a slot in the fuselage to clear the top and bottom of te pins when you slide the wing in place. Looking at the photos of Bob's plane, I don't see how he did that. The fuselage and ply doubler look intact. How did he do it?
Mark
The answer is easy; I cut a saddle section from the bottom of the fuselage crutch and install the wing. Then I glue the saddle piece back in place and reinforce the joints with a hard balsa doubler piece. Been doing it that way for more than 50 years with great results.
In the attached photos you should be able to see (at least in the second one..) the angled cuts that were made in the fuselage crutch to allow a saddle piece to be removed and the wing to be dropped in.
One thing that helps is the fact that the opening in the fuselage sides are dead accurate to the wing shape where it passes through the fuselage sides. If the wing I am using is made from sheeted foam, I make a "dummy" foam panel that is the same as the one being used in the actual airplane, cover it with the same thickness balsa that is used on the actual wing, sand it about the same amount as I sanded the actual wing panels, and then measure out to the point where the fuselage sides will pass over the wing and draw a chord-wise line. I then place the dummy panel back in its lower cradle (piece from which the wing panel was cut) and, using a band saw, cut the dummy panel chord-wise. What I then have is a "plug gauge" of sorts. I measure very accurately to find the centerline of the plug gauge and scribe a pen line. This gauge is then used to mark the opening shape onto the fuselage sides when I lay them out and cut them. Next I cut the dummy panel chord-wise at a point several inches out from the center and make another plug gauge that will be used to make two alignment plates that will slide onto the wing when it's time to install the wing into the fuselage. The center line on these plates is the same distance up from the alignment board (in my case a piece of 2-pound foam that has been cut extremely accurate to be absolutely flat...) as is the center line of the wing on the fuselage sides. Next I cut out the saddle piece and align the fuselage crutch, upside down over a center line on the assembly board and weight it down. Then I drop the wing into place. The bellcrank post will protrude upward, and because of that I have to make a hole in the foam assembly board to allow the wing to seat in the opening perfectly. Next I test fit the saddle piece to ensure that it fits perfectly. And, it always does because of the use of the plug gauge. The outward alignment plates are slid into place and the skew alignment is checked carefully. There is no need to check the incidence of the wing because of the inherent accuracy of the above procedure.
Once the skew is correct, I glue the saddle piece in place and let it dry thoroughly. Then I can remove the assembly from the foam assembly board and detail glue the top of the wing to the fuselage sides. This process has been used to accurately assemble dozens of models in my shop (mine and those of many others...). Plywood bellcrank mount pieces can then be cut and fit over the bellcrank post and glued to the wing and the fuselage sides. Hopefully the photos will help to make all this more clear.
Bob Hunt
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Bob, thank you very much for the description and the photos. It is clearer now. I hope to one day be able to build close to your level. I have a set of foam wings in the corner that I need to build a fuselage for, and this will help greatly.
Thanks,
Mark
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Thanks, Mark! Hey, you build fine.
Bob