Author Topic: Wood Fin Support  (Read 651 times)

Cruisinby

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Wood Fin Support
« on: October 22, 2016, 06:39:04 AM »
I knew this day was coming, cracked fin box.   Sailing a sup with to large a fin for the board structure. Damn shore break !   I seem to remember in the 80's glass sailboards had two strips of wood next the fin box for support.   I plan on installing a new fin box embedded in a brick size section of high density foam.   Any ideas on installing two strips of wood as well.   What type of wood ?  wood thickness ?   How long and deep ?  Do the wood strips butt up to the box or is there foam between the fin box and wood ?   Any and all ideas are welcome.




SUPflorida

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Re: Wood Fin Support
« Reply #1 on: October 22, 2016, 08:03:35 AM »
If your foam is high enough density you don't need "woodies." Woodies were a method some builder used to solve high loads on sailboats fin boxes in the early days. They were not always 100% sucessful long term...I'v seen more than a few fin boxes folded over dispite woodies.

PonoBill

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Re: Wood Fin Support
« Reply #2 on: October 22, 2016, 08:21:28 AM »
Amen Florida, hard to make wood strips really work. You don't need a huge block of foam either. An inch on either side is fine--or even less. You don't even really want super-high density, just more than the EPS has. Everything flexes. The way to make a stronger area is NOT to make it rigid--that creates a stress riser. It's to make it progressively stronger as the structure moves toward the hard fin box. Restricted flex without delamination or crushing the foam under expected load is what you're aiming for. Wood strips distribute the load a little, but don't do much to keep the foam from crushing--too hard.
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starman

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Re: Wood Fin Support
« Reply #3 on: October 22, 2016, 10:43:06 AM »
For windsurfing and the increased loads I would consider boxing the finbox in divinycell. Then install it so it is bonded to the deck as well. The structural strength of the board is in the outer skin and not the soft foam core. Here is a good picture of what it should look like.

http://www.boardlady.com/cross1.jpg

Cruisinby

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Re: Wood Fin Support
« Reply #4 on: October 22, 2016, 12:04:13 PM »
Thanks guys for all the info, you saved me some extra work.   I have installed Chinook mast tracks in 3 different sup's with no issues to date going back over 3 yrs.   I will get a piece of divinycell and we are back in business.   


 


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