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Thread: Carbon fibre cowl

  1. #1
    cgoldy's Avatar
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    Carbon fibre cowl

    Well I have finally finished my new cowl including cowl rails. (Still to be painted) I haven’t any weights to report but I am guessing that my empty weight is about 1100lb. She is a real performer. Now I just have to pretty her up a bit. I had some concerns re going to a small square filter box but I reckon she performs better. Maybe a bit of rammed air, I don’t know. CHTs are down but not sure about oil temps yet as I’m still waiting for a hot summer day.

    The big change was to scrap the sea plane lip as it was advised that it would be causing turbulence and inhibiting the flow of exit air out the bottom. I have continued the lower cowl to just past the boot cowl. Seems to have improved temps.

    Cgoldy

    .Click image for larger version. 

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    Last edited by cgoldy; 09-27-2020 at 05:24 PM.
    Javron O-375 wide body extended wing cub

  2. #2

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    Nice work!

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    cgoldy's Avatar
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    Javron O-375 wide body extended wing cub

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by cgoldy View Post
    No pictures


    Sent from my iPhone using SuperCub.Org mobile app

  5. #5
    tedwaltman1's Avatar
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    Great job on the cowl!

    How wide is your exit at it's widest point?

    How many layers of carbon fiber & what weight (e.g. 5.9 oz) cloth?

    Hand layup, vacuum bag?

    Did you reinforce the aft curve to retain its shape during flight with additional strip(s) of carbon fiber or aluminum or a stand-off?

    Thank you for the pics!

    Ted
    Thanks mike mcs repair thanked for this post

  6. #6
    cgoldy's Avatar
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ID:	51332Three layers of 120 gram vacuum bagged onto glass. Pulled in the curve I wanted after then stiffened with three strips of unidirectional about 1" inch wide double thickness. The shape held nicely. The airbox was cut out of some CF flooring I made and has honeycomb core. Heat is the enemy. I have had to lag the exhaust and use some heat shielding on the lower cowl. The cowl rails were vacuum bagged on glass. I just laid heaps of mat over the original rails and then prised them out when I was done. They were 1/3 the weight and way stronger. I found some really neat carbon fibre / Kevlar hinges made here in australia for the cowl hinges. I'll report on them after a few more hours. I think the cheeks are 4" Ted. The new Javron square airbox is much lighter than the round filter box. I was experiencing allot of cracking in the old cowls. So far so good. I removed the heater muff. Im finally geting rid of that forward c of g that comes with a O-375

    A tip for anyone who wants to vacuum bag on a budget. Buy those vacuum storage bags and the hand pump that comes wit them. They are surprisingly good. I normally use a refrigeration vacuum pump but if I have a little job to do, just use the storage bags.
    Last edited by cgoldy; 09-27-2020 at 07:08 PM.
    Javron O-375 wide body extended wing cub

  7. #7
    cgoldy's Avatar
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    Javron O-375 wide body extended wing cub
    Thanks tedwaltman1 thanked for this post

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    That looks really good Colin you would have to be happy with the result.

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    I've thought about giving a try at vacuum bagging copies of the belly panels on my -18 (full length/aluminum in 5 to 6 panels). For sake of estimating costs of materials, how many layers of a 3K 2x2 twill should I plan on to achieve a sufficient level of rigidity? If it makes a difference on layers required, all the panels besides the narrowest tail cleanout have a couple ribs which have been pressed into the sheet metal longitudinally.

    Cheers,
    Jeff

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    tedwaltman1's Avatar
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    How rigid do you want it? Equivalent to say 0.032" 6061 T6? More? Belly panels--I assume you mean underneath the aircraft rather than inside floor panels--then 3 layers would likely be more than enough. 3 layers would be far more durable and puncture resistant than fabric. FYI, 3 layers of CF are still quite pliable.

  11. #11

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    Quote Originally Posted by tedwaltman1 View Post
    How rigid do you want it? Equivalent to say 0.032" 6061 T6? More? Belly panels--I assume you mean underneath the aircraft rather than inside floor panels--then 3 layers would likely be more than enough. 3 layers would be far more durable and puncture resistant than fabric. FYI, 3 layers of CF are still quite pliable.
    Yes, by belly panels I mean underneath fuselage/exterior. Re-build notes I have from the previous owner show they used .025 2024 T3.

    Thanks for the input. Without having started anything yet, it's hard for me to know what 3 layers vs 4 is like. And reading articles and watching vids on youtube has any number of different suggestions. I suppose it's easy to start with the tail cleanout in 3 layers, see how that turns out, and if need be try 4 on one of the wider pieces.

    Jeff

  12. #12
    cgoldy's Avatar
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    Many of my panels are 2 x 240 gram bi axial. And then I add a strip of 1” tape in areas that I want to stiffen. If you want real rigidity, I would do 2 x 240 with the thinnest of core material you can buy. The core is the secret. Jut stop it short of the edge you are going to fasten. If you want to polish it up you will have to use some twill.
    Javron O-375 wide body extended wing cub

  13. #13
    cgoldy's Avatar
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    The thing that stops me from doing too many panels, eg tank lids, is that the edges are straight. With aluminium you can turn down the edges and get a neat intersection without waves. I hope I explained that ok.
    Javron O-375 wide body extended wing cub

  14. #14

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    Quote Originally Posted by cgoldy View Post
    Many of my panels are 2 x 240 gram bi axial. And then I add a strip of 1” tape in areas that I want to stiffen. If you want real rigidity, I would do 2 x 240 with the thinnest of core material you can buy. The core is the secret. Jut stop it short of the edge you are going to fasten. If you want to polish it up you will have to use some twill.
    I get what you mean. The panels are curved a little as they hug the lower longerons just a bit. Since in this case I'd be using my existing panels as a mold more or less, it would end up working out well I think.

  15. #15
    cgoldy's Avatar
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    Quote Originally Posted by Tgskillskill View Post
    I get what you mean. The panels are curved a little as they hug the lower longerons just a bit. Since in this case I'd be using my existing panels as a mold more or less, it would end up working out well I think.

    The best result will be to vacuum onto waxed glass and cut down to the size you want. You have to have a very strong mold to vacuum onto or it will distort.
    Javron O-375 wide body extended wing cub

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