Author Topic: I need to put a foil box into a board, how do I do it?  (Read 40472 times)

sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #30 on: April 17, 2018, 12:02:20 PM »
I would have probably sourced the same materials from the same places, or maybe used thinner D-cell layered with epoxy.
Be careful with that long router bit.
Will you be wrapping and capping the boxes with glass or carbon fiber?

I'm new to this, so any advice is appreciated.  From the looks of other cassettes it looks like they just sink the boxes into the Divinycell with thickened epoxy, but I could be wrong.  I certainly could wrap the boxes in something first.  I have plenty of carbon and glass.

surfcowboy

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Re: I need to put a foil box into a board, how do I do it?
« Reply #31 on: April 17, 2018, 08:04:17 PM »
+1 on the router bit being dangerous. That's easily the most dangerous thing in your house/shop. Don't want to spook you but just be cool and aware whenever that thing is live.

Glass wrap and cover the boxes if you can and it sounds like you are on the way to a bulletproof install.

sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #32 on: April 17, 2018, 08:35:16 PM »
I hear you guys on the bit.  My router is fixed at 25k RPM too, so yikes.  I'm going to use shorter bits until I have to cut through the very bottom.. and then go REALLY slow.  I'll probably armor up my body and face too to be extra safe.

By wrapping the boxes I'm assuming you guys mean that after I cut the slots in the Divinycell for the fin boxes that I first lay in and wet out some carbon or glass, and then shove the box down into the hole/slot over it?  I suppose then I should take that layer all the way to the edge of the Divinycell on top?

Lastly, by glassing/carbon(ing) over the box you do mean when I put the final layers on for the board bottom skin that I cover the box openings with the layers (without masking off the boxes) and cut them open again after curing?  This was my plan and I have a flush trim bit to accomplish this.

Thanks for the help!

Dwight (DW)

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Re: I need to put a foil box into a board, how do I do it?
« Reply #33 on: April 18, 2018, 03:33:05 AM »
You don’t even need to mess with a router.

Multi tool to saw cut the skin.

Drywall saw to cut the EPS hole.

Gorilla glue to lock the divinycell in place.

PonoBill

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Re: I need to put a foil box into a board, how do I do it?
« Reply #34 on: April 18, 2018, 10:08:16 AM »
+1 on gorilla glue. The only time I use epoxy is with glass or carbon. Gorilla glue is superior in every way for gluing stuff to foam.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #35 on: April 18, 2018, 01:43:31 PM »
How much does Gorilla glue exotherm?  Any concerns with melting the EPS?

Dwight (DW)

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Re: I need to put a foil box into a board, how do I do it?
« Reply #36 on: April 18, 2018, 01:50:36 PM »
No heat generated.

Gorilla glue is better than epoxy when the hole cut is less precise. It fills every void giving more complete bond.


Dwight (DW)

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Re: I need to put a foil box into a board, how do I do it?
« Reply #37 on: April 18, 2018, 03:48:13 PM »
But don’t use gorilla glue between your divinycell layers. You don’t want expansion there.

Beasho

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Re: I need to put a foil box into a board, how do I do it?
« Reply #38 on: April 18, 2018, 05:29:05 PM »
If you can bond ahead of time with the gorilla glue and apply pressure it should work.

sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #39 on: April 18, 2018, 05:36:46 PM »
Since I'm going for bullet proof and I'm going to have tight fitting parts I'm going to stick with the epoxy.  The big thing is that I might stick carbon around the cassette cut out and/or between the Divinycell layers.  There shouldn't be any excessive gap to have to fill.  If I line the cut out with carbon wrapped through to both decks first, any exotherm will be unable to get to the EPS too... not that I'm expecting that gap to be big enough to even exotherm much at all.  I'm also using slow cure epoxy on that.

jrandy

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Re: I need to put a foil box into a board, how do I do it?
« Reply #40 on: April 18, 2018, 08:28:16 PM »
There are a couple ways to think about it...
You can overbuild it and create additional stress points in the system or you can imagine how to best couple each member to its neighbor. We use D-cell because it is stronger than EPS. If you line that joint with fiber and resin, both foams may want to shear away from the rigid cloth. If you use GG, it expands into the porous foams and provides a connection with a little flex. So if you liken it to anatomy then it is fat muscle tendon bone  to EPS GG D-cell finbox. I would do a layer of  epoxy and cloth between D-cell and the box and for sure capping it ( the big foam insert)  both sides and lapping onto the old skin. I do a mild version of this on my SUP finboxes to protect the EPS from taking in water if I smack a fin on something.
Will your plan work? Most likely Yes but you could be inadvertently adding some stress points.
« Last Edit: April 18, 2018, 08:31:18 PM by jrandy »
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sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #41 on: April 18, 2018, 08:40:37 PM »
I hear you, I've been thinking the front and rear edges of the cassette I put in could cause strain points for the whole board breaking in half.  Perhaps the better way to reinforce for this is to just add carbon/glass layers on the board surface which go continuously past the length of the cassette, rather than try to create an I-beam effect along the sides of the cassette, which will, like you said, increase point loading in the area.  Interesting, I'm going to have to plan this carefully.  How worried should I be about disturbing the sandwich skin of the board construction?... because I'm basically replacing it with a single skin attached only to the top skin of the boards existing sandwich.


PonoBill

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Re: I need to put a foil box into a board, how do I do it?
« Reply #42 on: April 18, 2018, 11:01:30 PM »
The cassette shouldn't be isolated from the rest of the board. I've done it that way and when I thought about it, regretted it. I was taking a good practice for inserts and applying it to foam cassettes without thinking it through.  That's one reason Gorilla glue, which is both strong and flexible, works so well. Jrandy's explanation is excellent. The tracks themselves can have glass under them--they are much stiffer than the surrounding material and anything you do to support them and keep them from moving is good. A common failure for inserts is for them to work against the surrounding foam. If the foam is pushed to the point of yield it won't spring back, and the resultant void often causes delamination because there is no support for the insert other than the skin. The insert gets pushed down with mo support under it and breaks away from the skin. Presto, leak. Your cassette can probably just be set into the foam and attached only to the bottom. The surface area increase makes even the soft EPS capable of resisting a fair amount of force. Still better to tie it to the deck, but make the bond of PVC foam to EPS as resilient as the foam. Epoxy is hard and doesn't penetrate into the interstices of the foam.

EPS has a compressive strength of 10-60 psi. Even if your EPS is just 20 PSI the cassette has increased the surface area that is bonded from about 16 square inches for each track to what looks like at least 200 square inches for the cassette. And the PVC has a compressive strength of 200+ psi. Your tracks won't move in the PVC foam, and the cassette won't move in the EPS until you put a huge force on it. Tying it top and bottom to the glass takes the structure to another level. Belt and suspenders, and it doesn't cost anything in added weight unless you get as sloppy as I did with the carbon patches. Literally, you need a patch about an inch bigger than your cassette. My rail to rail carbon patch was just a waste.
« Last Edit: April 18, 2018, 11:13:34 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

PonoBill

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Re: I need to put a foil box into a board, how do I do it?
« Reply #43 on: April 18, 2018, 11:16:57 PM »
Too bad I'm not in Hood River, I have a box of 10" chinook mast tracks with maybe four missing. I think there's 25 in the box--but for all I know it might be 50. Anyway, a lifetime supply. Glad to give you a couple.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

sharksupper

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Re: I need to put a foil box into a board, how do I do it?
« Reply #44 on: April 19, 2018, 10:47:57 AM »
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!

 


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