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How can I mount a foil on an old directional board?

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kiteband
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How can I mount a foil on an old directional board?

Postby kiteband » Thu Feb 25, 2021 10:04 pm

I have a nose crashed directional board that really cannot be used for anything else. So I cut off the nose and I thought about fitting a foil under it.

I could mount a US Box (this or alike https://de.aliexpress.com/item/10000294716408.html ) but getting it shipped here takes a while, so I would rather not do that.

Instead I thought why not drill four holes through the board and put some load distributing metal plates from below and above the board. A kind of sandwich construction.

To make the holes water tight I plan on drilling them bigger than necessary, then filling them with epoxy and filler and then redrill them.
I could also laminate some layers of fiberglass on the bottom if that helps.
(I do have some rubber to account for the rocker of the surfboard.)

Do you think this could work?

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Re: How can I mount a foil on an old directional board?

Postby Trent hink » Thu Feb 25, 2021 11:59 pm

Probably not.

Easiest and possibly cheapest is just get one of those stick-on foil mounts and hope the board can handle the stress.

If you already have the materials and tools, it is not that big of a deal to drill four oversize holes, fill them with epoxy and filler, then drill the mounting holes.

You might want to slap a bit more glass over the top and bottom in the general area where the foil gets mounted.

The hardest part is figuring out where is right place to put the holes.

kiteband
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Re: How can I mount a foil on an old directional board?

Postby kiteband » Fri Feb 26, 2021 12:06 am

Thanks. The stick on foil mount costs $160. Before I do that I will rather invest in a used board.

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fluidity
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Re: How can I mount a foil on an old directional board?

Postby fluidity » Fri Feb 26, 2021 2:16 am

I think it will work just fine but you would likely need absolute minimum of 4mm thick aluminium plate on the underside or 3mm stainless steel. And it would have to extend in front and behind for some way. You should be able to drill the slot ends and nut entries and then jigsaw between unless you have cnc or plasma cutter. I've been considering something similar for a budget EPP surfboard only I was going to cnc some thin plywood plates for top and bottom and then vacuum glassfibre reinforcing over it. With T-nuts fitted on underside.

If I get bored this weekend with the current lack of wind I'll do some CAD drawings and pass them on.

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Re: How can I mount a foil on an old directional board?

Postby jumptheshark » Fri Feb 26, 2021 4:46 am

Use the search:

viewtopic.php?f=196&t=2388827&p=896007& ... rd#p896007

Takes more than just through bolts and washers.

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Re: How can I mount a foil on an old directional board?

Postby kiteband » Fri Feb 26, 2021 8:31 am

@fluidity
I don't quite get what you are suggesting to jigsaw. I also do not have access to any cnc. My plan was to simply put those load distributing plates on top and below the board.

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Re: How can I mount a foil on an old directional board?

Postby kiteband » Fri Feb 26, 2021 8:38 am

@jumptheshark
I have been reading endless threads (also the one you linked to), however, I did not get the information I wanted. I am not looking to invest a lot of money or time. The board is trash anyways and I am looking for an easy way to mount a foil to it. No need to be pretty.
In the thread you linked he did not use any load distributing plates but relied on the glass only. I can also not make out how much of the old surface he took off before adding the new layers of glass.

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Re: How can I mount a foil on an old directional board?

Postby drone » Fri Feb 26, 2021 9:11 am

kiteband wrote:
Thu Feb 25, 2021 10:04 pm

To make the holes water tight I plan on drilling them bigger than necessary, then filling them with epoxy and filler and then redrill them.
I could also laminate some layers of fiberglass on the bottom if that helps.
(I do have some rubber to account for the rocker of the surfboard.)

Do you think this could work?
worked for me,
no plates, just many layers of glass, top and bottom. Only choose hole position wisely.

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Re: How can I mount a foil on an old directional board?

Postby snitkjaer » Fri Feb 26, 2021 9:24 am

You can put more than 4 holes 8 or 12 then you can move the foil to find balance

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fluidity
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Re: How can I mount a foil on an old directional board?

Postby fluidity » Fri Feb 26, 2021 9:28 am

I've done up a design. The PDF can be printed actual size in A0 sheet size at a commercial printer.
If I get around to doing my one it will be on a budget Expanded Poly Propolene surfboard which for me will be a sinker.


For two foot straps with front foot strap single only.
The rectangular piece should be in 4 or 5mm thick aluminium.

Drill all the plate holes out to 5mm, tap to M6 or your imperial equivalent. Drill 8mm end holes for the slot ends and jigsaw betwee, keeping 8mm width and 90mm between track centers.
Cut or file out the nut insertion holes.
Drill all the wood bottom holes out to 8mm. Fit M6 T-nuts into the back hole and front 2 holes from underneath and fill the insides up with melted wax.
Drill all the top wood holes out to 6mm.

The other pieces should be cut from 4mm plywood. The top ply should be clad with surfboard cloth top and bottom over glass fibre patches around the holes.
The bottom ply needs a few layers around the plate attachment area and out to another 20 mm or so, top and bottom sandwiched between surfboard cloth. Be sure to put some extra fibre thickness around the rear of the plate attachment which takes all the shock loading from the foil attachment plat if the foil hits the bottom at speed.

Redrill all the holes through after fibreglassing but take care not to damage the T-nut threads.
Fit short countersunk screws through the bottom plate into the aluminium piece on the 8 side holes and the 2 centre holes and do them up.

Line the top plate up with your board centreline. Google foilbox placement and figure out where the boxplate centre needs to be based on board length.
Drill all the holes through top to bottom.
Check alignment with bottom plate, you will need 5 long screws fo fix front and rear foot straps and a more robust leash attachment at the back hole.

Squeeze silicon sealant into all the holes and do up the last 5 screws through straps or board leash fixing clip, top plate and bottom plate, T-nuts or last two (tapped) holes of the bottom plate.

If you follow the instructions then the loadings will be spread out by the plates and you can fit to even a fragile or bendy board. :D
Attachments
FoilAdaptorPlates.pdf
(6.85 KiB) Downloaded 62 times
FoilAdaptorPlate.PNG
Last edited by fluidity on Fri Feb 26, 2021 10:20 am, edited 1 time in total.


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