Author Topic: Rail Structure and Impact Resistance  (Read 3636 times)

Beasho

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Rail Structure and Impact Resistance
« on: April 08, 2023, 09:57:52 AM »
My ultralight board has shown its first signs of wear on the rails.

Specifically the Port (Left side) rail.  I was surprised it was ONLY one rail until I realized that was the side I normally crawl on the board.

The board is XPS foam, which means it has a compressive strength significantly higher than EPS foam.  Example 15 psi vs 4 psi. 

Structurally it should be more sound, but I found cracking of a rail that was a combined 6 oz Carbon and 4 oz S-Glass.  Granted my rails were very sharp.  Probably less than 1/4" radius, or half inch diameter (problem #1).

My standard SUP EPS boards have not worn on the rails like this board.   

So is it

1) Simply how hard the rail was?  Make it a 1/2" radius (1" diameter), or 1" radius (2" diameter) curve.

2) Bolster the rails?  I don't think carbon works well on the rounded rails.  I could use 1X 4 oz S-Glass and then a 2" Kevlar strip. 

Other suggestions?

Note:  Because this board is XPS I don't care about dings or water intrusion.  I can also just modify the rail after the fact, use a router and just re-route a larger radius rail, and then re-laminate.  The photo shows cracked rails, sanded down, then modified with 2" Fiberglass strip covered with 1" of Kevlar fabric Gorilla glued on to rail.
« Last Edit: April 08, 2023, 10:02:18 AM by Beasho »

sflinux

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Re: Rail Structure and Impact Resistance
« Reply #1 on: April 08, 2023, 05:18:27 PM »
Here is the current build schedule.

I assume you are running the carbon fiber linearly.  For the deck, are you running the S-glass on the bias?  That is what Stretch does for his boards:

Rounding the deck will give you the strength of a round carbon fiber tuber versus a square tube which should definitely help.
I like how Nathan Fletcher has thumb rail indentations on his boards, which adds to their strength.
« Last Edit: April 08, 2023, 05:33:30 PM by sflinux »
Quiver Shaped by: Joe Blair, Blane Chambers, Jimmy Lewis, Kirk McGinty, and Bob Pearson.
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Beasho

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Re: Rail Structure and Impact Resistance
« Reply #2 on: April 08, 2023, 06:27:54 PM »
. .  are running the carbon fiber linearly.  For the deck, are you running the S-glass on the bias?  That is what Stretch does for his boards:

Stretch definitely knows his stuff.

I am running ALL carbon on the deck, but this makes me realize that running a few layers at different BIAS would add strength per his recommendations.  I had 2 layers on TOP deck, but in parallel. 

I am getting dents but I have discovered that they are exclusively KNEE dents. Knees MUCH harder than feet.  Feet, toes and heels, are soft and squishy.  Knees are probably 1" of area with 100 lbs + each side, or more if your knee is only covering ~ the size of a Quarter.  Putting multiple carbon KNEE patches on the BIAS may help this. 

JohnnyTsunami

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Re: Rail Structure and Impact Resistance
« Reply #3 on: December 17, 2023, 08:37:29 PM »
A rounded section with 10oz of carbon/glass should be quite strong, although you might be pushing your paddle handle on it when you get up to your feet like I do.

People have been mentioning your construction around and I'm curious. I think you use XPS and gorilla glue? Isn't gorilla glue just foaming PU resin? PU resin that is foamed (or any resin foamed) at all is likely far, far weaker than a composite using neat resin. It might be an order of magnitude weaker, for example. It's really impossible to know anything besides that it is far weaker. Have you done a test of a flat sheet using GG vs epoxy on carbon to test the strength?

 


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