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  #1  
Old 02-21-2023, 07:44 AM
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Pounder Pounder is offline
 
Join Date: Apr 2006
Location: Rochester Hills, MI
Posts: 333
Default Carbon Fiber? (possible Cowl Change)

Gents,

For reasons I won’t bore anyone with, I’m considering replacing an existing (parallel valve) 0-360A4A with an (angle valve) IO360A1A. I have to assume a new cowl build will be required, but:

1) might I be able to modify existing cowl? Can't imagine, but i just don’t know how “exceedingly” different this set-up would be.

Regardless:

2) is there anyone producing Carbon Fiber blanks for an -8?

Thanks!
Bryan
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  #2  
Old 02-21-2023, 10:21 AM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,462
Default

Quote:
Originally Posted by Pounder View Post
Gents,

For reasons I won’t bore anyone with, I’m considering replacing an existing (parallel valve) 0-360A4A with an (angle valve) IO360A1A. I have to assume a new cowl build will be required, but:

1) might I be able to modify existing cowl? Can't imagine, but i just don’t know how “exceedingly” different this set-up would be.

Regardless:

2) is there anyone producing Carbon Fiber blanks for an -8?

Thanks!
Bryan
I think the whole cowl is wider across the front, so it might be extremely difficult to modify a parallel valve engine cowl to fit an angle valve.

Van's cowls are made with a good high-temperature resin system. Really well-made, despite the annoying pinhole filling chore. Your shortest path to success would be to just buy a Vans angle-valve cowl.

You might save a pound or two with a carbon fiber cowl, but it would be expensive to make with the same temperature tolerance. The high temperature tolerance is really only needed where the exhaust pipes go out and at the cylinder heads.

If money is no object and for some reason you really really really want a carbon fiber cowl, I think HPAircraft.com can make it for you. If someone can loan us a standard cowl, we would pull a mold off of it, and we can make carbon cowls with high-temperature resin.
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 725
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
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  #3  
Old 02-21-2023, 04:03 PM
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wirejock wirejock is online now
 
Join Date: Oct 2005
Location: Estes Park, CO
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Default Carbon fiber

Quote:
Originally Posted by scsmith View Post
I think the whole cowl is wider across the front, so it might be extremely difficult to modify a parallel valve engine cowl to fit an angle valve.

Van's cowls are made with a good high-temperature resin system. Really well-made, despite the annoying pinhole filling chore. Your shortest path to success would be to just buy a Vans angle-valve cowl.

You might save a pound or two with a carbon fiber cowl, but it would be expensive to make with the same temperature tolerance. The high temperature tolerance is really only needed where the exhaust pipes go out and at the cylinder heads.

If money is no object and for some reason you really really really want a carbon fiber cowl, I think HPAircraft.com can make it for you. If someone can loan us a standard cowl, we would pull a mold off of it, and we can make carbon cowls with high-temperature resin.
There's another option but it will be a little heavier.
Buy a Vans Cowl to fit your need. Fit everything the way you want it. Sand it with random orbital and 80 grit. Apply a layer of carbon fiber. It only noticeable from the inside. The outside looks like carbon fiber. This plenum is fiberglass with one layer of carbon fiber.
Click image for larger version

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E-mail: wirejock at yahoo dot com
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #4  
Old 02-21-2023, 06:51 PM
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Pounder Pounder is offline
 
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Default Makes sense..

Thanks guys for thoughtful responses.

99% sure Steve is correct on the (wider) planform of the angle valve 360. So a whole new cowl is almost a guarantee…

And I seem to be locked in old “muscle memory” of working with a not-so-good fiberglass RV4 cowl from a vender long ago. However, I think for years now, Vans has been getting some quality fiberglass componants, especially compared to the early stuff.

It just wouldn’t make sense to develop a carbon fiber blank.
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  #5  
Old 02-21-2023, 07:13 PM
scsmith scsmith is offline
 
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Location: Ashland, OR
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Bryan,

I think that is a good decision. The modern angle-valve cowls are really good. I remember putting some filler on the top half and block-sanding to take out a wave/lump/depression, but other than that, they are pretty smooth, fit well, and as light as you could make one in fiberglass.
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 725
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2022
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  #6  
Old 02-21-2023, 07:59 PM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
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Default

Quote:
Originally Posted by wirejock View Post
There's another option but it will be a little heavier.
Buy a Vans Cowl to fit your need. Fit everything the way you want it. Sand it with random orbital and 80 grit. Apply a layer of carbon fiber. It only noticeable from the inside. The outside looks like carbon fiber. This plenum is fiberglass with one layer of carbon fiber.
Attachment 38698
Have heard that the differential expansions of glass and CF made layering of the two ripe for problems. There was no conditions for non-structural versus other etc. would like clarity from someone with real knowledge.

Goods awfully good, BTW.
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  #7  
Old 02-22-2023, 06:47 AM
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DanH DanH is offline
 
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Default

I'm confused. Best I know, there is only one upper cowl half available. The lower cowls vary, but not due to width.

Yes, stuffing an angle valve into the RV-8 cowl can be a pain. Clearance is minimal on the left side, notably above #2 cylinder, but it's common to see some contact marking above both front cylinders. Depends on how the baffling is arranged. I hear some builders have put the baffle sidewalls inside the cylinder mounting ears to help alleviate the problem. I would try it.

Mine, on the outside of the ears, is so tight the head of the 1/4" screws in the cylinder ears rub the cowl. And I put soft spots in the plenum lid some years back.

A James or Showplanes cowl might offer a bit more room. Worth asking.
.
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  #8  
Old 02-22-2023, 06:51 AM
Southern Pete Southern Pete is offline
 
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Location: England
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I am approaching the end of a project one part of which is to fit a new cowl to an RV-6 that has an IO-360-A1A. The old cowl was substantially modified to fit, including changes required to clear an AFP fuel servo. The new cowl started as a standard O-320 RV-6 cowl. Bumps are needed on the top cowl to clear the front rockers. The bottom cowl needs some surgery to fill in the scoop and make an air inlet ... Would it have been better to start with an RV-7 injected cowl? Probably. This has soaked up many hours and we're not yet finished. I would second the idea of a layer of carbon over the cowl to give the appearance of carbon, use 120 deg C prepreg that only needs a vacuum bag and rudimentary oven for a couple of hours to cure.
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  #9  
Old 02-22-2023, 07:00 AM
Southern Pete Southern Pete is offline
 
Join Date: Jul 2015
Location: England
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Default

Quote:
Originally Posted by DanH View Post
I'm confused. Best I know, there is only one upper cowl half available. The lower cowls vary, but not due to width.

...
For an RV-6/7 the injected (flat bottom) cowl is an inch or two wider at the front. Have never built an 8.
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  #10  
Old 02-23-2023, 03:42 AM
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Pounder Pounder is offline
 
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Location: Rochester Hills, MI
Posts: 333
Default This Sight is Way Better Than Google

Hey folks, i suppose i could go to the interweb, but can anyone off hand tell me a ballpark weight ratio, fiberglass to carbon fiber?
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