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Fastback Bulkhead & Canopy questions

R

RogerG

Active Member
I have read others comments about the HR bulkheads being almost of no use since so much cutting and fitting had to be done. I like Arlie's approach in fitting flanges to the skin, then bulkheads to the flanges. My fuselage is built with the Vans bulkheads installed per plans, and almost ready for turtle deck. Definitely want to go fastback, but not sure how I should proceed.

What parts should be purchased from Harmon if any, and how to get the correct turtle deck dimensions if you don't have these parts to at least get you in the ball park? Perhaps the HR skin is the answer, then fabricate bulkheads to fit the skin.

Another interest is in comments I have seen about building canopy skirt, and frame out of glass like the EZ amongst some who would do it different 2nd time.

Anyone know what advantages this might give like weight, strength, better fit etc? I have looked at some builder logs of some EZ builders, and think this might be a great idea. Has anybody built the canopy skirt, and frame out of glass on a RV4?
 
I believe, not positive, that the HR uses a stretched fuselage, and a widened forward fuselage section.

Considering the above, it is not surprising if you need to do a bit of custom fiddling to make these parts fit in a stock RV4 fuse.
 
HR bulkheads for standard RV-4

RogerG said:
I have read others comments about the HR bulkheads being almost of no use since so much cutting and fitting had to be done. I like Arlie's approach in fitting flanges to the skin, then bulkheads to the flanges. My fuselage is built with the Vans bulkheads installed per plans, and almost ready for turtle deck. Definitely want to go fastback, but not sure how I should proceed.

What parts should be purchased from Harmon if any, and how to get the correct turtle deck dimensions if you don't have these parts to at least get you in the ball park? Perhaps the HR skin is the answer, then fabricate bulkheads to fit the skin.

Another interest is in comments I have seen about building canopy skirt, and frame out of glass like the EZ amongst some who would do it different 2nd time.
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RogerG said:
Whoever told you that there is too much involved in using HR bulkheads 407, 408 and 409, converting to a fastback, do not know what they're talking about, if I can be rude and say so. If I understand your statement correctly. If I misunderstood, I stand corrected.

I converted my standard RV-4 to a fastback RV-4 about four years ago and used only the parts that I purchased from John Harmon plus the Rocket canopy from Todd's Canopies.

The issue of the width between a Rocket and standard RV is really no big deal. I figured this out myself, and didn't follow anyone else's lead. If you buy John Harmon's 3 bulkheads, you merely cut each of the 3 bulkheads in half. Just like taking a buzz saw and run it down the middle of each bulkhead. Do not touch 410, it is the correct size in standard form. Now you attach each half of the original station 407 (the bulkhead the seat rests against). Now stabilize bulkhead 407 by cutting a piece of plywood shaped like the top of the turtledeck. Take a long straight edge, place it on top of bulkhead 410 and place about a 1/2 inch to 3/4 inch spacer on top of the attached roll bar. That is the line you hope to achieve with the turtledeck when you're done. You stabilize the cut 407 so it touches the straight edge resting on 410. When you have that accomplished, put 4 to 6 pieces of nylon fish line around the circumference of 410 and the new raised position of 407. After you have the lines established where the new turtledeck skin will be, add each half of 408 and 409 to their respective positions. Now you can see what little strip you have to add to 407, 408 and 409. I was even able to reuse the empennage fairing without modifications.

All I can tell you it worked like magic and I couldn't believe it myself. It takes longer to explain it than do it.

If you have any interest, please contact me and I can send you some progress photos I took. As far as the canopy frame start with a Van's frame and in the end you remove all of the 7/16 aluminum tubing and replace it with new tubing and have it welded up, etc. You also cut most of the square tubing at the aft end.

I made my own side pieces, without too much trouble. I think I added a few pounds to the weight of the aircraft when I was done.

I recommend this mod to any RV-4 owner, there is some free speed involved too.

My email [[email protected]]
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Jake,

Thank you, makes perfect sense. I have seen some FB that appear to have a Vee at the intersection of the canopy, and the turtle deck. Your method should eliminate this, along with fitting canopy properly. Did you buy the skin from Harmon?

Thanks,

Roger
 
Turtledeck skin, etc.

RogerG said:
Jake,

Thank you, makes perfect sense. I have seen some FB that appear to have a Vee at the intersection of the canopy, and the turtle deck. Your method should eliminate this, along with fitting canopy properly. Did you buy the skin from Harmon?

Thanks,

Roger
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Roger,

Yes, I did buy the turtledeck skin from John Harmon.

Your comments of the "dog leg" in some builders version of a fastback to me takes away from the purpose of the modification. Looks to me was primary.
In the fitting of the canopy bubble, I did take one piece of information from Axel (AX-O) in the forums that was key. Move the new bubble about 4 inches forward of the standard bubble position. You got to give credit where it's due. I thanked Axel in the past, but I give him credit.

If you're interested, go to Todd's Canopies website, then go to the gallery of his canopies on various aircraft. Look under "Harmon Rocket" and go through the photos until you see a yellow/green trim converted RV-4, with the unpainted turtledeck installed and the canopy in the raw. N 44TK is my airplane. Send me an email address and I'll share some photos with you.

Jake
 
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