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Upper Longerons Installation

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I'm getting ready to layup the insides of the fuslage but can't figure out how to place the upper longerons.

 

The upper longerons have a small piece of wood floxed to them about 5" from the front edge of the long wood strips. I assume they are only meant to provide support for the F28 Bulkhead. When looking at the plans it looks like you "eyeball" it so there would be an inch or so of this wood piece forward of F28.

 

The longerons have a tapered doubler that will be installed facing down. It looks like if you moved the longeron and therefore this taper too far forward it would interfere with the controls.

 

There are doublers installed almost all the way aft on the longerons. I have not been able to identify thier purpose. I can only guess they are used to provide bracing in front of the firewall to load from engine thrust. Given this assumption it seams important to place them correctly.

 

Are we meant to "eyball" this installation based on the F28 bulkhead or is there a dimension I'm not seeing here?

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I followed someone's recommendation to have equal overhang on the jigs at each end when bending the longerons. And, then again have equal overhang when attaching the longerons to the sides.

 

The bottom line is that the doubler must be far enough forward for F-28. And, anything forward of F-28 gets cut off later. At the aft end, you must have enough doubler to get through the firewall. It all worked out when I followed the above recommendation.

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I'm getting ready to layup the insides of the fuslage but can't figure out how to place the upper longerons.

I recently just completed this step.

 

The upper longerons have a small piece of wood floxed to them about 5" from the front edge of the long wood strips. I assume they are only meant to provide support for the F28 Bulkhead. When looking at the plans it looks like you "eyeball" it so there would be an inch or so of this wood piece forward of F28.

I measured 6.25" back from the forward edge and did just as you said -- eyeballed so that there would be enough doubler AFT of F28. Your approach is fine as well.

 

The longerons have a tapered doubler that will be installed facing down. It looks like if you moved the longeron and therefore this taper too far forward it would interfere with the controls.

Read further in the plans and you will see that approximately a 5"x5" square of the upper fuselage sides forward of F28 will be cut out to make room for the canard.

 

There are doublers installed almost all the way aft on the longerons. I have not been able to identify thier purpose. I can only guess they are used to provide bracing in front of the firewall to load from engine thrust. Given this assumption it seams important to place them correctly.

I'm equally intrigued by their purpose, but I believe they are setup to travel through the firewall (all 1/4" of it).

 

Are we meant to "eyball" this installation based on the F28 bulkhead or is there a dimension I'm not seeing here?

I believe so -- setup so that there's a good portion of the forward doubler that will be aft of F28 (which will placed 6.25" aft of the foremost edge of the sides).

Jon Matcho :busy:
Canard Zone Member & Administrator
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Building a Cozy Mark IV

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Thanks Guys!

 

Did/are you going to layup the 4 layers of unidirectional along the entire length of the longerons and thus covering up the doubler in the front and the strange doubler all the way aft? If we are to glass the entire longeron it looks like we will need to do some shaping of the wood to allow the glass to lay flat...

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Did/are you going to layup the 4 layers of unidirectional along the entire length of the longerons and thus covering up the doubler in the front and the strange doubler all the way aft?

I just finished this layup minutes ago. I covered most of the front doubler, and all of the rear doubler.

 

If we are to glass the entire longeron it looks like we will need to do some shaping of the wood to allow the glass to lay flat...

I used a router to make a uniform radius wherever I could (once I remembered I had a router after sanding for an hour). Don't be shy with the radius... maybe 1/4"?

Jon Matcho :busy:
Canard Zone Member & Administrator
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Building a Cozy Mark IV

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That's what I'm planning to do tonight when I put the 4-uni layers on the upper longerons. I'm going to use some flox to make a smooth transition from the longerons to the fuselage sides, then put on the cloth.

I just remembered that since the UNI runs in parallel with the longerons and easily wraps around the longerons. You need a radius on the edge of the longeron, and a flox fillet, but they can be relatively small -- say 1/4" radius.

Jon Matcho :busy:
Canard Zone Member & Administrator
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Building a Cozy Mark IV

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I have read some stories about a tough time with the 4 ply upper longeron layup, so I did what you did Jon. 30 grit sandpaper EASILY put a rounded edge on the longeron in about 10 minutes, and I did a micro fillet where the longeron meets the fuselage side. I just mixed up a small batch of micro, and used my finger (with blue glove) to put a "wipe" down the inside corner. Very easy, much easier than caulking a sink or tub. After cure, I sanded away the unwanted bumps of micro, and sanded the fillet till it was dull. Took about 20 minutes or so worth of sanding.

 

 

RESULT... The layup went great! The UNI was happy laying there, and did not try to lift up off the longeron anywhere during its curing. I was mentally prepared for a tough layup, but this one took three hours from start to finish.

 

I did NOT peel ply this layup, because I know the peel ply would have shifted my layup and messed it up (in all the corners of the various doublers and such).


Andrew Anunson

I work underground and I play in the sky... no problem

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Cool, you're building! I trust your shop is built and in working order now?

 

I did NOT peel ply this layup, because I know the peel ply would have shifted my layup and messed it up (in all the corners of the various doublers and such).

Good move. You *could* have put peel ply on the top horizontal surface if you felt like it (I didn't), but can always sand well enough. Peel ply in certain tight corners will definitely pool the epoxy, add weight, and just not add any value over not using it in those situations. Just my opinion.

 

Shop pics?


Jon Matcho :busy:
Canard Zone Member & Administrator
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Building a Cozy Mark IV

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Yeah, the shop is great! I bought a used $50 hotel type heat pump, and half of the shop is kind of a play area for my daughter for now. I'll get some pictures this evening and post them tomorrow.

 

What is the best way to post pictures here, and what is a good file size?


Andrew Anunson

I work underground and I play in the sky... no problem

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What is the best way to post pictures here, and what is a good file size?

Check here.

Jon Matcho :busy:
Canard Zone Member & Administrator
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Building a Cozy Mark IV

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