I need to put a foil box into a board, how do I do it?

[jrandy]

Thanks Bill!  This is all great info!  By next week I'll have all my stuff and can get started. 

All good on the inserts, I already have two coming from Jose at FiberGlassSupply.  He also had a private stash set aside from when they stopped producing them.

I really appreciate the sharing of all the great wisdom and experience here!

Stopped producing them...is this to say that Chinook does not have them, does not make these boxes at all, or now makes them at a different level of quality?

https://chinooksailing.com/collections/board-building-part-accessories

[sharksupper]

Thanks Bill!  This is all great info!  By next week I'll have all my stuff and can get started. 

All good on the inserts, I already have two coming from Jose at FiberGlassSupply.  He also had a private stash set aside from when they stopped producing them.

I really appreciate the sharing of all the great wisdom and experience here!

Stopped producing them...is this to say that Chinook does not have them, does not make these boxes at all, or now makes them at a different level of quality?

https://chinooksailing.com/collections/board-building-part-accessories

I can't remember who, but someone I spoke with in my hunt for the fin boxes told me everyone stopped using the Chinook boxes in the past.   I guess windsurfers went to tuttle/powerbox and everyone wanted lighter weight, cheaper boxes, like the futures/etc so production sounds like it came to a stand still out of lack of demand.  Suddenly this foiling craze has come about and now everyone wants stronger boxes again, so they ran out of old stock and have kicked into production again, that's why they're backordered for a few weeks currently.

[sharksupper]

Ok, I just about have all the parts needed to build my foil track cassette using Chinook fin boxes.

I have the RideEngine cassette (left side in photo), Two Chnook 10" fin boxes, and some 1" H100 Divinycell sheets.  While I wait for more Divinycell to arrive I made a router template for the Chinook fin boxes to go into the Divinycell. 

How much gap should I leave on either side and bottom of the boxes in the Divinycell?  My template leaves a hair under 1/16" total on the sides as it is, pretty tight.

The Chinook boxes have 5/8" of material from where the T-nut holds and the top of the box.  The RideEngine box has 1/2".  So the Chinook boxes have 1/8" (25%) more thickness.  They are all the same length and width.  I'm going for strength on this one so that's the reason for making my own cassette with the Chinook boxes.  However, this RideEngine box doesn't look bad, I will use it on a smaller board which sees less forces than my big board.

[sharksupper]

I'm trying to figure out how best or even if I want to add the carbon to the Chinook boxes when they go into the Divinycell cassette.  I'm assuming I'd just run one sheet of carbon over the whole cassette and then sink it down into the routed out holes when I put the boxes in?  It's going to be tough to keep the boxes lined up right and get that carbon flat on the top surface.

What do you think?  Is the carbon addition really necessary?  I'm going to be putting a few layers of carbon over the whole thing once it's in the board, seems like it should be pretty tough, then again, I've never made one of these before!

The RideEngine cassette I have doesn't have this carbon bit, they just sunk the boxes right into the Divinycell using thickened epoxy... that's what I'm leaning toward, if not just because of the complexities mentioned above.

[jrandy]

I'd worry more about keeping the boxes parallel to each other and square to world than adding a lot of carbon fiber underneath them. It sounded like your rout was going to be pretty tight...maybe I'd just add one piece of wetted 4oz glass in the holes or go commando like the Ride Engine. Were you going to use one of your foils as an alignment jig for gluing in the boxes into the routs? How deep do they recommend setting those boxes?

[sharksupper]

Yea, getting them square/parallel is something I've been thinking about for the past hour.  So far what I've identified as possibilities are:
1.  Bolt the boxes tightly to one of my adapters at the exact width and then sink them in as a unit with mylar between adapter/boxes with waxed up screws/nuts.  The boxes end up flush with the top of the cassette this way too.  I just worry about overflow getting down in the boxes or having no where to escape.
2.  Sink the boxes in free and very carefully measure and use sticks to wedge the sides to get everything just right.

I like the first way because it's going to be damn exact, but I like the second way because there is space for the overflow to come out and I can scrape it away.  What to do...

I think I'll skip using carbon under the boxes and go with glass, since it flexes a lot easier.  I test fitted the carbon though, it fits fine, but not much extra space left after that.

I'm leaning toward the first way and maybe just make sure I'm a little short on the thickened epoxy so it doesn't overflow and fill the boxes up.

[sharksupper]

I threw the aluminum CNC adapter (from Foilmount), for the most accuracy, together with the boxes and put a sheet of 0.01" Mylar aka PET (Polyethylene terephthalate) as a barrier between.  Boxes exactly at 90mm apart.  I think I'll just tape over the unclamped down areas of the box to avoid spill over and call it good.  Bolts were waxed too just to be safe, but I don't see how they could get contaminated.  Interestingly enough the bottoms of the Chinook boxes were not quite square after tightening it down to the adapter.  I don't know what to think about this.  Either the bottoms of the boxes are off (both off the same bit exactly) or the tops are off.  Off by about .5 to 1 degree or so each, close enough I guess?  I suppose the better way to be exact would be to have fins in both boxes and get them vertical and parallel... but of course doing it this way that's not possible.

I tested the fit in a test piece made by using my template and they drop right in both ways with only about 1/32 on all sides to spare, good fit!

I think I'm ready to go and do the final cut and fit.

[PonoBill]

Don't post that on Swaylocks. The beards will start explaining why XPS will delaminate and how the expansion gases will rot your feet.

[sharksupper]

Ok, ready to lock and load it in....  I guess I'll use 6oz glass and drop them in.  Nice tight clearance so shouldn't need much thickened epoxy.

[jrandy]

Right on 'Supper.
I would add some baking flour to the boxes and cover the middle portion up with masking tape.
I got that tip from a Hawaiian uncle on Swaylocks who is also not afraid of XPS.

[sharksupper]

Nice, is that a joke or for real?   

I just covered the exposed box ends with tape, I'll have to chisel out any that gets by, if any does.

I was out of 6oz glass so used two layers of 3.7 instead.  Currently curing with about 300lbs of granite and other random heavy shop items on it.  It look a lot of weight to get the boxes to finally sink all they way down, the fit was pretty tight.  I think I used a little over 100g of epoxy.  Probably about 15-20% of it squished back out and I wiped it away.

[jrandy]

The flour trick is for reals and I have used it.
The aforementioned XPS-phobia is also real except for those who have already freed their minds.
A couple of these dinner tray foil boards would be  good candidates for proving or disproving the theory.
Sounds like you may have been 1 layer too tight and a bit generous with the epoxy.
I probably would have done the exact same thing...

[PonoBill]

^^My plan exactly. I think I could make a super light foil board with XPS. Maybe do some radical things like an internal skeleton and no skin other than the standing area.

[sharksupper]

Ok, so too bad I didn't hear about the flour trick before I sunk it in.  Not a major disaster, just had to chip out the spill over, and there was a bit more than I thought there would be.  I happen to have just the right size chisel for the box width, some good hardened picks, and made a custom angled chisel out of a flat head screw driver (to clean the T-nut slot).  In 30min it was like it never happened, easy recover, whew!

The tight fit was only because the gaps were so close around the boxes that the thickened epoxy had a hard time escaping, and all the glass in the way didn't help.  There was no pinching as I test fit everything dry first.  However, it came out perfect, the top skin is about 1/64-1/32, just enough to hit with some 80-120 grit for later skin attachment.  There were no dry spots, which I was worried about, and everything is fitting great.  All three of my adapters fit loose and slide smoothly to the ends.

Had to do over, I would definitely seal or create a non-stick surface in the box interior.  The cassette is 200g heavier than the RideEngine at this point, although mine is 1/2" wider overall, is 7.4oz glass sunk/capped, and uses H100 (I think the RideEngine might be H80, it's not as dense/strong as the H100).

Now just waiting for a couple more 1" sheets of Divinycell to get the thickness I need and then in the board it goes!

[sharksupper]

Yet another template to make.  Too bad I'm not producing this work since I have all the templates now.

How exact should the cut out for the cassette be in the board?  Right now it's a slightly snug fit in the template.  I can lightly press the cassette into the template and it has just enough friction to hold the template up at the top of the cassette.  I'd imagine minimal adhesive will be used with this tight of a fit.  From the sounds of it, maybe this is a good thing as the harder adhesive can create point loading between the foams.  Thoughts?

Other than that, looks like I'm ready to route out the board with this crazy long bit <cautions noted>.