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  #1  
Old 10-26-2021, 01:16 PM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 821
Default Skybolt flanges and Cowl Stiffening

Im getting ready to order the Skybolt firewall kit for my -7.

Couple of questions for those that have gone before me:
  1. Should I order the flanges or is it easier to drill the holes in the cowling by making your own flanges?
  2. I've read Dan Horton says add some carbon fiber strips for stiffness, is this just on the inside?
  3. Hinge or Skybolt for the horizontal section of the cowl?

Any other tip appreciated
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Joseph, OR
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RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017
Started on QB fuselage 01/2018
Sliding canopy mostly completed 10/2020
Wiring and Avionics harness completed 9/2/2021
FWF Started 9/3/2021

Donated for 2021 and so should you
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  #2  
Old 10-26-2021, 02:22 PM
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DanH DanH is offline
 
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Location: 08A
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Quote:
Originally Posted by mfleming View Post
[*]I've read Dan Horton says add some carbon fiber strips for stiffness, is this just on the inside?
I don't know what you read, but I run with high cowl pressure, and adding a few glass plies didn't stiffen my cowl edge as much as I would like. So, for the next one...

Carbon is higher modulus, i.e. less stretchy than glass fiber. In this application, apply a ply or two of unidirection carbon tape on both the inside and the outside of the cowl edge. The tapes become tension and compression members separated by a core. One side only won't do anything useful.

A glass tape over the carbon tape on the inside will serve as a wear buffer, minimizing carbon contact with the aluminum parts. You'll need some micro on the outside to blend the tape. Shim as needed to match surface height with the boot cowl.
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  #3  
Old 10-26-2021, 02:22 PM
agent4573 agent4573 is offline
 
Join Date: Aug 2019
Location: Mountain view
Posts: 418
Default

1. Order the flanges. Its a huge time saver.
2. I didn't, but I also didn't use the maximum suggested spacing. I ordered a few extra fasteners and kept the spacing closer together. I'm also using a plenum which should keep some of the pressure off the upper cowl, so I'm prepared to go back and add carbon reinforcement but I'm hoping it isn't needed.
3. User preference. I went skybolt for everything.
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  #4  
Old 10-26-2021, 02:22 PM
ryankhallcpa@yahoo.com ryankhallcpa@yahoo.com is offline
 
Join Date: Jan 2018
Location: Taylor, AZ
Posts: 85
Default My Skybolt kit will be for sale soon

Hi Michael,

I just went through this same decision and actually purchased the "Upper Firewall" kit for my RV-7 ~$200, including the two tools needed for installation. However, being a newb I found it a bit difficult and a bit too complicated to understand the installation work required (I know I'm just running out of patience). At the suggestion of a multi-builder friend, I abandoned the Skybolt idea and decided to install a flange with nutplates and simply use screw fasteners along the upper firewall. I extended the flange down each side just far enough so that the upper portion on each side of the lower cowl could receive a screw fastener; below that, the vertical/straight portion of each cowl side has the hinge installed.

Sure, the screws don't look nearly as neat and professional as the Skybolts (screws are the domed cadmium plated (I think) #8 screws with a nylon washer underneath). But, the final fit is excellent, very secure and the procedure was something I was familiar with. I'm super happy with the results. This was one area that I didn't want to go with the hinge. I used the .02 shim with the flange and it helps to reinforce and make a flush finish between cowl and skin.

Hinge for the horizontal portion and very happy with the result there too.

I don't mean to dissuade you at all! I found that my "keep-it-simple" mindset was being a bit challenged here with the Skybolts. I haven't had time to post my kit for sale, but I figured that when I do get around to it, it would likely sell quickly since the Skybolts are a very popular thing, and for good reason.

Ryan
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  #5  
Old 10-26-2021, 03:12 PM
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DanH DanH is offline
 
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Found a photo Mike. This one has multiple plies of glass tape on the inside edge. It's not bad, certainly not like some I've seen. Still, it does bulge and I gotta look at it. Oil door too, and got about 8 plies of 9oz. This was a job for carbon/core/carbon.
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  #6  
Old 10-26-2021, 05:35 PM
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wirejock wirejock is offline
 
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Location: Estes Park, CO
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Default Carbon

Excellent timing!
I am right in the middle of the process and ordered a 20 piece kit to do the cowl split.
My notes are on my blog. They are edited as I go so be careful.
Dan's carbon suggestion will be done.
Sorry. Never figured out how to post a vertical image
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  #7  
Old 10-26-2021, 05:58 PM
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DanH DanH is offline
 
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Use plain strips down the sides of the fuselage. The scallops can catch the corner of the cowl when you slide it upward into place...paint chips!
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  #8  
Old 10-26-2021, 06:06 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Location: Meridian ID, Aspen CO, Okemos MI
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Quote:
Originally Posted by DanH View Post
Use plain strips down the sides of the fuselage. The scallops can catch the corner of the cowl when you slide it upward into place...paint chips!
This is very true. It is like a chainsaw hitting your cowl.
For me, I would either use a hinge at the split or make the strips myself. I didnt like having to cut down the pieces to match the spacing I wanted. It would have been much easier to fit the cowl, mark and drill pilot holes, then expand the holes to fit the fasteners.

Maybe on my next one I will do a left and right split so I can take off 1/2 at a time!
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  #9  
Old 10-27-2021, 01:23 AM
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rv8ch rv8ch is offline
 
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I just made the flanges myself, but this was before they sold them with the kit or I probably would have bought theirs.

Looking back, it's probably better to make your own so you can be sure all the holes are perfect.

Not much narration, but a few photos here:

http://www.rv8.ch/installed-camloc-fasteners/

As you can see, I used the skybolts around the firewall, and hinges along the horizontal interface between the top and bottom cowl. I'd do it this way again.

I also get the bulging but I'm too busy looking out for bogies and mountains and my magenta line to really let it bother me.

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  #10  
Old 10-27-2021, 05:54 AM
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 1,181
Default Another cowl stiffener option

I took Danís comments seriously regarding cowl bulge. On my recent build, I fabricated a U shape channel of glass and bonded in just forward of the Skybolt fasteners on the inside of the cowl. Minimum weight, maximum stiffness !
If you would like pics, email decamplarry@Gmail.com.
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