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Author Topic: (Non) Flexible Noses  (Read 786 times)

Offline Tim Wescott

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(Non) Flexible Noses
« on: July 20, 2010, 02:36:53 PM »
Argh!  I can't find my issue of Flying Models that has the profile Smoothie article with the inboard nose reinforcement details!  I had planned on shamelessly copying what they did.

Profile, for a old .25, fuse is 3/8" balsa.  I'm thinking (in the absence of better information) of just slapping on a balsa block that goes from the nose to the high point of the wing, roughly airplane shaped in the front, to a maximum thickness at the wing LE, tapering down to little or nothing at the end.  I'm thinking maybe 1/2" to 3/4" think, to lend rigidity to the nose.

Good plan?  Good idea but dumb execution?  Just put a nice set of doublers on the thing and go fly?
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Offline Steve Helmick

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Re: (Non) Flexible Noses
« Reply #1 on: July 20, 2010, 09:35:40 PM »
The Excalibur was one of the first profiles to use no plywood doublers. The inboard doubler is a duplicate of a inboard plywood doubler, epoxied on, and shaped nicely. The outboard doubler is roughly the same as the ply equivalent, but cutout to receive the fuel tank. Both were 1/2" sheet, but I built mine many years ago ('67/'68).

Some recess the tank into the fuselage plank itself. Be sure to make tank height adjustable, and the tank removeable. Your 3/8 plank seems a bit thin for a .25. Maybe a layer or two of .5 oz CF mat would help, applied with epoxy and not sanded too aggressively. One thing, tho...if you can't mount the engine on aluminum, phenolic, or epoxyboard plates, then mount it directly on maple bearers...not on plywood, even if you use a piece of plywood for the outboard doubler. It squarshes down somethin' turrible...

You might consider building a plywood "shelf" about 3/32 or 1/8 thick by 1" > 1.25" onto the outboard side, under the tank, from the front of the tank, back into the wing. Tie it into the wing, and you'll increase the stiffness a whole bunch. Strap the tank down onto the "shelf", and use plywood shims to adjust height. Consider neoprene 0-rings to sub for rubber bands.  #^ Steve
 
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Offline Tim Wescott

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Re: (Non) Flexible Noses
« Reply #2 on: July 21, 2010, 05:06:37 PM »
Your 3/8 plank seems a bit thin for a .25.
It's a tall fuselage, and a wimpy .25.  I got stuck on deciding between 3/8 (light!) and 1/2 (sturdy!) for long enough that I just decided to build the darn thing already!

If it breaks too soon I'll do the next one with 1/2.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline john e. holliday

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Re: (Non) Flexible Noses
« Reply #3 on: July 22, 2010, 08:25:53 AM »
Thanks for the memory of the Excaliber.  One of the first schools the company let me drive to in Dallas, we were out of class the following Monday.  I drove to Fort Worth hobby shop that made the kit.  First kit I ever had that had no plywood for the nose.  Three layers of balsa with the hardwood engine mounts.  Yes the fuel tank was embeded into the fuse.  Was a great flying airplane.  Also the engine was sitting right on the hard wood. H^^
John E. "DOC" Holliday
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