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Direct mast mount to board? (wooden board build)

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chesapeake
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Direct mast mount to board? (wooden board build)

Postby chesapeake » Fri Jan 24, 2020 3:53 am

Anyone have experience building a mast slot into the board (i.e. no bolt-on mast base)? I was thinking about sandwiching to carbon fiber plates, one inlayed into the deck with the 2 bolt holes and one on the bottom with the cutout for the mast. I would then fill the middle with high strength casting resin using the mast as a mold to pour the resin around. The carbon fiber plates would then be glassed over with the rest of the board. One question I had is whether the mast bolts can be countersunk directly into the carbon plate or if some kind of reinforcing grommet is needed to prevent stress fractures. Also considering aluminum although I prefer the CF for its aesthetics and better bonding with fiberglass. I sketched up a diagram. Would love to hear other ideas/thoughts on how to do this.
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bacon2109
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Re: Direct mast mount to board? (wooden board build)

Postby bacon2109 » Fri Jan 24, 2020 11:20 am

like tenon and mortise type of connection.
tuttle box, power box, Kfbox (ketos foil box) , and more.....
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chesapeake (Fri Jan 24, 2020 3:51 pm)
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kollac
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Re: Direct mast mount to board? (wooden board build)

Postby kollac » Fri Jan 24, 2020 1:00 pm

yeah, windsurf and regular surf foils use box-type connections. There are several standards and they achieve basically what you're describing. The box itself handles the loads and is bonded into the board with some reinforcement. I bet you that assembly is LESS burly than what you're describing because it's not nearly as integrated into the board as your idea.
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chesapeake (Fri Jan 24, 2020 3:51 pm)
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BWD
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Re: Direct mast mount to board? (wooden board build

Postby BWD » Fri Jan 24, 2020 1:32 pm

The part where the mast goes in that you have indicated as resin needs lots of carbon fiber in it too, or the mast will almost certainly crack it. Probably 6-8 layers of 200gsm carbon in the walls would be enough if well supported by high density foam or wood. If no fibers, it would definitely put your resin to the test. Buying a premade box and setting it in the board is also a good
option.
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chesapeake (Fri Jan 24, 2020 3:51 pm)
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RalfsB
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Re: Direct mast mount to board? (wooden board build)

Postby RalfsB » Fri Jan 24, 2020 1:44 pm

It can be done but then you would be married to that mast forever, can't switch to anything else. It would be better to use some standard (KF box, Deep Tuttle, etc), you can buy adapters for building into boards, then there is way less worry about strength and fractures as well. Also, the standard mast connections have some angle built into them -- connection tightens as you tighten the screws and there is no wobble.
If you still decide to go with your initial idea, don't just use plain casting resin, have some fiberglass or carbon cloth around the mast base, don't make the connection too tight (you can't get the mast in/out) or too loose (then it will wobble).
For the screw that comes from the top it is better if you can put it lower than the deck level so that your back foot is not on the screw head. Also have some metal washer between the screw head and the carbon plate.
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chesapeake (Fri Jan 24, 2020 3:51 pm)
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chesapeake
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Re: Direct mast mount to board? (wooden board build)

Postby chesapeake » Fri Jan 24, 2020 3:55 pm

Thanks all! I wasn't aware of the tuttle adapter option. Although, that doesn't get rid of the bulky base in the water so maybe I'll go back to an earlier idea of mounting the LF base normally but running the two mast bolts through to the top deck (see pic). Countersunk so they are flush with deck. I like the idea of being able to release the mast w/ 2 bolts and it also distributes the load from 4 connection points to six...
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TomW
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Re: Direct mast mount to board? (wooden board build)

Postby TomW » Sat Jan 25, 2020 4:31 pm

Chesapeake,

You only need to embed 4 bigheads into your board before lamination. The bigheads should be in high density foam, at least 80kg/m3. I have used HD plate over entire mast plate area and just 4 local blocks and both hold up on strapless boards.
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chesapeake (Sun Jan 26, 2020 11:43 am)
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chesapeake
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Re: Direct mast mount to board? (wooden board build)

Postby chesapeake » Sun Jan 26, 2020 11:58 am

TomW wrote:
Sat Jan 25, 2020 4:31 pm
Chesapeake,

...bigheads should be in high density foam, at least 80kg/m3. I have used HD plate over entire mast plate area and just 4 local blocks and both hold up on strapless boards.
Hi Tom, would you use HD foam in a wood build? I had been planning to use solid paulownia or balsa blocking around the base but would consider HD if it is a worthwhile weight savings..
Thanks!

TomW
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Re: Direct mast mount to board? (wooden board build)

Postby TomW » Tue Jan 28, 2020 11:53 am

No need for HD foam on balsa or paulownia. Just bed the bigHead directly into wood with epoxy plug as big as the base.


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