Construction of a fin

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Re: Construction of a fin

Postby PK » Sun Oct 02, 2011 8:48 am

OverTheTop wrote:An extension of this idea would be to fold an aluminium strip and fold it at an acute angle. It could go 10mm or so along each side of the fin. This would be fitted over a rebate on the leading edge. Heat generated on the leading edge would be rapidly moved backwards to cooler areas, keeping the front edge cooler and cloth veneer happier.


Here's one I prepared earlier.
Image

In researching composite fins at supersonic velocities, I observed a common failure mode where the resin softens due to heating, and the airstream 'gets under' the laminate at the leading edge, peeling the layers off.
To prevent this, some 0.8mm stainless steel sheet was folded in a press brake and secured over the leading edges with about 6 M3 bolts which went through the laminate and core material (the stainless was tapped M3). These bolts were then ground flush and the whole thing faired to the fin.


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Re: Construction of a fin

Postby OverTheTop » Sun Oct 02, 2011 9:33 am

Is it a case of "Great minds think alike" or "Fools seldom differ" ? :lol:
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Re: Construction of a fin

Postby PK » Sun Oct 02, 2011 9:37 am

OverTheTop wrote:Is it a case of "Great minds think alike" or "Fools seldom differ" ? :lol:


Not sure about you, but aparantly, "PK is idiot" so it must be the latter for me.
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Re: Construction of a fin

Postby Kryten » Sun Oct 02, 2011 10:36 am

PK wrote:
OverTheTop wrote:An extension of this idea would be to fold an aluminium strip and fold it at an acute angle. It could go 10mm or so along each side of the fin. This would be fitted over a rebate on the leading edge. Heat generated on the leading edge would be rapidly moved backwards to cooler areas, keeping the front edge cooler and cloth veneer happier.


Here's one I prepared earlier.
Image

In researching composite fins at supersonic velocities, I observed a common failure mode where the resin softens due to heating, and the airstream 'gets under' the laminate at the leading edge, peeling the layers off.
To prevent this, some 0.8mm stainless steel sheet was folded in a press brake and secured over the leading edges with about 6 M3 bolts which went through the laminate and core material (the stainless was tapped M3). These bolts were then ground flush and the whole thing faired to the fin.


PK


I think this is the way to go.
Composites are stronger than metals on a weight for weight comparison, but they're not infallible - and should not be seen as the ultimate.
A combination of metal with carbon/kevlar reinforcement and phenolic resin would be worth a try 8)
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Re: Construction of a fin

Postby OverTheTop » Sun Oct 02, 2011 11:09 am

It is still a composite if you add metal, just a different mix of materials!
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Re: Construction of a fin

Postby Kryten » Mon Oct 03, 2011 6:48 am

OverTheTop wrote:It is still a composite if you add metal, just a different mix of materials!

Point taken!
I probably should have written fibreglass or carbon/epoxy
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