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 Post subject: When failure is the only option...
PostPosted: Mon Sep 22, 2014 8:23 pm 
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Joined: Tue Sep 04, 2012 3:21 pm
Posts: 312
Location: Canada
Thought Id post about my board that when horribly wrong in every way.

So while I wait for some parts to arrive to finish my custom free race build, i thought I would quickly pop out a new twintip. I am familiar with using foam core construction, and decided to give my hand at a wood core. Seemed easy enough, requiring less work than shaping foam. Kind of a 'press and go' solution.

I picked up a sheet of 1/4" marine plywood. First mistake.

Attachment:
20140919_172634.jpg
20140919_172634.jpg [ 1.8 MIB | Viewed 168 times ]


1. Notice the massive gap between the table and the center of the core. What you cant tell in the picture is that the springback of the core is very strong, not remotely close to a 1" foam core. Will come back to this issue later.

2. After prepping the table and cutting my glass and vacuum plys, i change ppe and get the resin out. The west system pumps weren't closed correctly and half my container of resin has crystallized making it unusable. (this can be reversed using a hot plate or bucket of hot water and time, but I wanted to get done quickly) I rush to the store to grab another resin.

3. I lay the glass on the table and begin to wet it out. I use two layer on the bottom, cut oversized to wrap the rails. I place the core on the table, press it down and begin to wrap the glass over the edge. Immediately the core springs back to flat and my edge wont hold. To counter the spring back I weight the core (this works with foam) and finish the wrap with difficultly. At this point Ive realized that I should have cut the fibres to shape, and not wrapped. After I would be able to trim the excess. Cannot do this now as the two top sheets have been cut smaller than the core for the overlap.

4. I decide to press on and deal with the edge clean up afterwards. Using cabosil maybe ill be able to cure the rail and the fibres together. I add the release film and peel ply, add the breather and place the vacuum film over the table.

5. An hour goes by and I am still trying to find the leak to the vacuum. ive double tacky-taped the edge, tried the valve, but no luck. Has to be a slow leak in the bag. Most likely a defect (Have had pitted film before). I tear off the bag, retape the edges and go to get a new piece of film. My roll ends and Im 6 inches too short. Now i have no other option but to wet lay. Its possible to weight the board to the rocker, but ive have a concave trim as well and cannot remove it once the sheet is in use. I flatten the rocker and leave it for 24 hours.

Attachment:
20140920_192320.jpg
20140920_192320.jpg [ 2.17 MIB | Viewed 168 times ]


I basically have a half fibred wood panel. The concave line raised the centre so the edges didn't hold.



Things to change for the next one:

- Use 1/8" ply and sandwich together with fiber between
- Cut glass to shape
- Check vacuum supplied, verify film for defects

After a very frustrating 5 hours, the next morning we got 25 kts of sunny warm wind and I wasnt so pissed. Hopefully this weekend Ill have a decent photo to post of a proper wood core board :thumb:


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 Post subject: Re: When failure is the only option...
PostPosted: Mon Sep 22, 2014 11:14 pm 
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Joined: Thu Jul 24, 2014 10:42 pm
Posts: 10
Location: Portugal
The import was: You tried! And learned with your mistakes! Just for that you deserve my Respect :thumb:
I´m also building my own board. But for my first one, I will just use Two pieces of plywood (4mm each), wood glue, vacuum pump, rocker table, vacuum bagging and breather (windows bug screen ), I want to keep it simple and cheap. The point of this board it´s to familiarize with vacuum, board rocker and concave! If she works I will pass to next level.
I guess it´s a good starting point for your Kite Board! So this is my advice for your first board: Simple and cheap!

Best regards,
Brainsold


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 Post subject: Re: When failure is the only option...
PostPosted: Mon Sep 22, 2014 11:48 pm 
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Joined: Sat Aug 29, 2009 11:25 pm
Posts: 2489
Location: The Naki
You could change to mechanical press. That way there is no chance of failed vacuum destroying your work.

For my last build i used a mechanical press combined with vacuum. The vacuum conforms the complex shapes of the top skin and removes excess resin. Once the resin has go green there is no more need for vacuum and the mechanic pressure holds the board in shape for the desired duration of cure.

Check it out here

viewtopic.php?f=107&t=2385345


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