Bomb proof board from XPs insulation foam

[TomW]

Dart,

I'd shape the foam without stringers. It's easier. Stringers add some problems shaping and are stiff rib in soft foam, causing problems later.
Seal the blank with epoxy and micro balloon, mayonnaise mix. Squeegie it on thin, almost nothing left on board. the foam is so soft, you have to be very careful handling it. You can't even grip it too hard. You'll need well padded shaping and work stands.
Then I'd drop in the boxes with some sort of reinforcement. You could glue boxes to a piece of plywood/ HD foam so boxes are in correct position. drop that into board from the deck, making ply/HD foam flush with deck, and boxes flush with bottom. I'd probably add HD foam around boxes too so strut base doesn't compress foam on bottom. Or Basically a block of HD foam with fin boxes embedded into it and then entire HD block embedded in foam. HD block is all the way through from deck to bottom.
You need HD inserts if you are adding strap screw inserts on deck.
Then hand layup bottom with 3-4 layers 6 oz glass, wrap rails. Bomb proof it by adding 2x 6 oz on tail by strut base.
Then vbag on a wood veneer to deck 1 or 1,5 mm. You can use 3-5 mm HD corecell if it's easier to get. Put glass under this as glue layer. Clean it up and hand layup 3x 6oz, wrapping rails.
This will be pretty strong board but not super heavy.

You could make blank and Shape it in one weekend, drop in HD reinforcements next weekend + glass bottom, glass and vbag the 3rd weekend, sanding coats 4th weekend, finish it up 5th. Final polish and deckhand the 6th. Extra nice cosmetic add a weekend.
If you can work during week, you can do some steps in evening after work and do it faster.

Now get off the Internet and start making mistakes!

[DartBoard]

Dart,

I'd shape the foam without stringers. It's easier. Stringers add some problems shaping and are stiff rib in soft foam, causing problems later.
Seal the blank with epoxy and micro balloon, mayonnaise mix. Squeegie it on thin, almost nothing left on board. the foam is so soft, you have to be very careful handling it. You can't even grip it too hard. You'll need well padded shaping and work stands.
Then I'd drop in the boxes with some sort of reinforcement. You could glue boxes to a piece of plywood/ HD foam so boxes are in correct position. drop that into board from the deck, making ply/HD foam flush with deck, and boxes flush with bottom. I'd probably add HD foam around boxes too so strut base doesn't compress foam on bottom. Or Basically a block of HD foam with fin boxes embedded into it and then entire HD block embedded in foam. HD block is all the way through from deck to bottom.
You need HD inserts if you are adding strap screw inserts on deck.
Then hand layup bottom with 3-4 layers 6 oz glass, wrap rails. Bomb proof it by adding 2x 6 oz on tail by strut base.
Then vbag on a wood veneer to deck 1 or 1,5 mm. You can use 3-5 mm HD corecell if it's easier to get. Put glass under this as glue layer. Clean it up and hand layup 3x 6oz, wrapping rails.
This will be pretty strong board but not super heavy.

You could make blank and Shape it in one weekend, drop in HD reinforcements next weekend + glass bottom, glass and vbag the 3rd weekend, sanding coats 4th weekend, finish it up 5th. Final polish and deckhand the 6th. Extra nice cosmetic add a weekend.
If you can work during week, you can do some steps in evening after work and do it faster.

Gold!! Sounds like a plan. I'll let you know how it goes.

Now get off the Internet and start making mistakes!

That's DIY in a nutshell!!!

[max]

Dart,


Then I'd drop in the boxes with some sort of reinforcement. You could glue boxes to a piece of HD foam so boxes are in correct position. drop that into board from the deck, making HD foam flush with deck, and boxes flush with bottom.

hey Tom . . .

would you use the poly glue to put the HD foam into the XPS or do you think it would be better using epoxy?

Regarding glue lines, the PU glue line is much easier to sand than epoxy glue lines where pieces of the foam are joined.

[max]

Max I think your goal of 3kg with this build will be pretty easy to achieve. My beast is 4.3 kg of which the ply is 1kg+. With smaller stringers and not using hardwood blocks around the mast connection and footstrap inserts (Tasmanian Oak) I am sure mine would have been well under.

I have to agree.

Using some scrap pieces of HD foam for my reinforcements so these should not be adding much weight. Also, have decided no stringers.May end up kerfing the deck to get the rocker and then no vac bag or may just use the vac bag and weight to the rocker bed. Am looking at only setting up about 2" of nose scoop for the 1200mm board length possibly starting around 600mm from the nose.

[TomW]

Foam to foam, i prefer the PU glue- it foams and sticks to all other foam around- so you have to tape off .
Plastic parts to foam, i prefer epoxy with fumed silica or microballoons mix.
If structure is needed i will glue parts together with epoxy and silica and then layers of glass over joints.

[max]

Foam to foam, i prefer the PU glue- it foams and sticks to all other foam around- so you have to tape off .
Plastic parts to foam, i prefer epoxy with fumed silica or microballoons mix.
If structure is needed i will glue parts together with epoxy and silica and then layers of glass over joints.

and it starts . . . only one placement for strap inserts and foil mount based on my current board and foil.

HD inserts for footstraps do not go right through. Glued in using PU glue.

[DartBoard]

Foam to foam, i prefer the PU glue- it foams and sticks to all other foam around- so you have to tape off .
Plastic parts to foam, i prefer epoxy with fumed silica or microballoons mix.
If structure is needed i will glue parts together with epoxy and silica and then layers of glass over joints.

and it starts . . . only one placement for strap inserts and foil mount based on my current board and foil.

HD inserts for footstraps do not go right through. Glued in using PU glue.

File 18-1-17, 9 12 35 pm.jpeg

Good stuff. Whats the plan for putting the rocker in?

[TomW]

Max, I shaped my rocker. Towards nose I glued on an extra layer. Then cut outline, then shaped rocker. Used a hotwire and templates.

[max]

Good stuff. Whats the plan for putting the rocker in?

Could do what Tom suggests but this is a one off trial at this stage so my plan is to kerf the deck towards the nose and glue while pressed on rocker table. Not done this before so we will see.

Alternative is to glass the bottom and bag it weighted done on the rocker table. Am only going for about 2" nose scoop so foam bends easily to that without any stress.

[BWD]

You can get that rocker I am fairly sure without kerfing, it is helpful to thin the board toward the nose as flexibility relates to the cube of thickness.
Having made a couple of (non-foiling) boards similarly, I think if you use birch ply no glass is needed where you have ply. softwood ply or okoume, maybe some glass.
Also you will probably not need ply on the bottom, glass should do it, or glass plus some veneer or extra thin ply.
Maybe a ply inlay in the area of the box running forward to beyond your front foot position... just throwing experience/ideas out there, best luck!