Chapter 4 -Bulkheads

[CFernandez]

Okay, I have studied the firewall plan...a lot...perhaps not enough b/c I'm asking this question. Anyway, here it is: What size are the pieces between the lower and upper firewall pieces? Where do these pieces go in relation to the outside edge of the firewall? Should the upper firewall and lower firewall pieces be the same width?

 

Thanks,

 

Carlos Fernandez

AeroCanard FG #206

Chap. 4

[CFernandez]

I slept on it (almost literally) and it came to me.

[Kraig]

It's kinda funny how that works. I have had questions about a certain step, or how to with the plans and mulled over them in my head for a while. Then later I would re-read the area, and the answer would almost jump out at me.

 

If I have not seen my question in one form or another on these forums, I really look deep w/in the plans. The majority of the time I have missed or not understood something.

 

Kraig

[Jon Matcho]

I slept on it (almost literally) and it came to me.

I'm just about to do this step of the firewall too. What were the specifics of this 'gotcha' if you don't mind sharing.

[CFernandez]

I'm just about to do this step of the firewall too. What were the specifics of this 'gotcha' if you don't mind sharing.

 

The outside edge of the pulley mount pieces (approx. 5" x 9"). I was confused with the "foam" line on the outside of these pieces. I just had to study the lines more to see what I was looking at. What I did to make it work was eliminate the "foam" portion. We'll see what it looks like when it goes together.

[argoldman]

The outside edge of the pulley mount pieces (approx. 5" x 9"). I was confused with the "foam" line on the outside of these pieces. I just had to study the lines more to see what I was looking at. What I did to make it work was eliminate the "foam" portion. We'll see what it looks like when it goes together.

 

If it is of any help in orentation, In the aerocanard, the firewall is cut out as one solid piece, the foam (for lightening purposes is placed into the appropriate area as are the aluminum engine mount hardpoints) when your firewall is totally assembeled the outside borders will be smooth and will fit into the confines of your fuselage and turtle deck.

 

The Cozy uses 4 pieces and the foam internal for ease of construction. The result is the same.

[Jon Matcho]

Rich, Carlos and I are building plans-built AeroCanard FGs. With the exception of a couple measurements, the plans and steps for building a plans-built AeroCanard SB/FG are IDENTICAL to that of a Cozy Mark IV.

 

I'm sure the kit-built AeroCanards are different, and as you describe. A positive thing about building a plans-built AeroCanard is that you can, theoretically, buy complete molded assemblies, such as the firewall as you point out (although I was previously under the impression that even with the kit-built AeroCanard, you still had to plans-build your bulkheads).

[Jon Matcho]

Carlos, what did you need to do to get your bulkheads to fit in Chapter 6? Did you have to cut one? Also, did you have to eliminate the outside angle so that the sides would go straight up?

[CFernandez]

A couple things now that I'm past it.

 

I had to cut the aft lg bulkhead down width wise about .7" to get it to fit with the fwd lg bulkhead and firewall.

 

Also the turtle back portion of the FW caused the fuse sides to angle out at the upper longeron. This required a small wedge (0" at the bottom of the upper fwd lg bulkhead to .2" at the top of the upper fwd lg bulkhead) of foam on both sides of the fwd lg bulkhead.

 

Knowing what I know now...:/... The aft lg bulkhead needed to be shortened further and the firewall (lower and upper portion) needed to be cut differently to allow the fuse sides to come in at the longeron approx. .2"-.4" each side. It's a minor detail that I hope won't bite me later.

 

 

Let me know when you get to the plywood in Chap.7. Positioning those pieces was a stumbling block for me.

[Jon Matcho]

The fuse width is wider at the FW than at the seatback by .4"-.8" at the upper longeron.

This doesn't surprise me... are you saying this is bad? or good? Or just as a reference?

 

Let me know when you get to the plywood in Chap.7. Positioning those pieces was a stumbling block for me.

Yes, I recall, and am looking at those too -- definitely going to be a custom job in that area.

 

I was also looking at your firewall bulkhead -- nice and rounded with the sides at 90 degrees vertical -- NOT LIKE the plans AFAICT. I wonder how you came up with that given the "stock" AeroCanard FG firewall drawing?

 

I pity anyone attempting to build an AeroCanard FG from plans (without a kit). The bulkhead measurements are simply and needlessly incorrect. Very frustrating! Think twice about plans-building an AeroCanard FG over a Cozy Mark IV (equivalent to AeroCanard SB) -- so far I've wasted a LOT of time trying to get an extra 4 inches into my rear seat!

[CFernandez]

This doesn't surprise me... are you saying this is bad? or good? Or just as a reference?

I stated it incorrectly. The sides are not vertical by that much. The fuse does taper back to the FW from the seatback.

I was also looking at your firewall bulkhead -- nice and rounded with the sides at 90 degrees vertical -- NOT LIKE the plans AFAICT. I wonder how you came up with that given the "stock" AeroCanard FG firewall drawing?

 

It's stock FG.

I pity anyone attempting to build an AeroCanard FG from plans (without a kit). The bulkhead measurements are simply and needlessly incorrect. Very frustrating! Think twice about plans-building an AeroCanard FG over a Cozy Mark IV (equivalent to AeroCanard SB) -- so far I've wasted a LOT of time trying to get an extra 4 inches into my rear seat!

Here we are. What are you going to do? I'm thinking Arby's! I will say it's been more difficult than I imagined, not the building part, more the interpretation of information or lack there of.

[Jon Matcho]

Here we are. What are you going to do? I'm thinking Arby's! I will say it's been more difficult than I imagined, not the building part, more the interpretation of information or lack there of.

I didn't get the Arby's reference, but I got by my bulkhead issues today. I misinterpreted the mark-up for the upper half of the forward landing gear bulkhead and built it much wider than it should have been. The AeroCanard plans are horrible here, since the drawing convention changes from relative measurements ("increase by X on each side" in the aft LG bulkhead drawing) to absolute measurements in the other bulkhead drawing ("increase by Y in total"), but leave you to assume that a single convention is being used. Luckily I built one oversize and was very easy to cut down.

 

The AeroCanard FG firewall also moves the upper and lower longerons out by 2 5/8" on each side, but shows LWY out by 3" on each side. That's NOT going to happen, so I'm setting the LWY hole the same relative increase as the others -- 2 5/8".

 

After a day's worth of head-scratching, and fixing that one bulkhead, I'm now expecting a good fit for fuselage assembly. What a relief!

[Jon Matcho]

Actually, I *may* be less confident now...

 

I had to cut the aft lg bulkhead down width wise about .7" to get it to fit with the fwd lg bulkhead and firewall.

I can almost see this, as the width of this bulkhead per AeroCanard FG plans is 37.45", which is 1.45" wider than the forward LG bulkheads. Divide 1.45 by 2 and you get "about .7"

 

Also the turtle back portion of the FW caused the fuse sides to angle out at the upper longeron. This required a small wedge (0" at the bottom of the upper fwd lg bulkhead to .2" at the top of the upper fwd lg bulkhead) of foam on both sides of the fwd lg bulkhead.

Good to know. I'm thinking of test fitting all of the bulkheads except the firewall so that I can measure where the AeroCanard longerons naturally end up (as opposed to apply major forces to bend, etc.).

 

The aft LG bulkhead on the Cozy Mark IV is 0.15" more narrow than the forward LG bulkheads on each side. So how would the AeroCanard FG achieve this bend? Answer: it doesn't... the plans are incorrect here.

 

So... I expect to have to cut the same or more as you did, and possibly bring the longeron through-holes in the firewall a bit more closer to the centerline.

[CFernandez]

I didn't get the Arby's reference

I was probably hungry and was thinking of getting something to eat.

 

I think you have what you need to know to proceed with putting the fuse together. Have fun!