My first sup!

[magentawave]

Big Dave    That's really cool that your daughter is involved. Good for you! She will never forget doing this with her dear ol dad.

[Big~Dave]

I like to cap boxes with a layer of glass and resin whenever possible.
My Bahne box router jigs are homemade. You could probably get away with other tooling methods for a one-off.
Probably easiest for a beginner (no idea of your experience base), myself included:
-glass the top and bottom, prevents damage to the board as you do the rest
-make the box hole, check dry fit /alignment a couple times, shim if needed, should only be enough around it for like 1/32" of epoxy and a layer of cloth if you desire. Too much slop/gap=too much resin=exothermic meltdown around the box=weak box to board bond.
-epoxy in box in minding the depth control tabs, alignment. Tape or weight it down if needed. It might help to have a fin in the box to check all the alignment stuff.
-trim off extra plastic with a flush cut saw (saves time and does not build up heat) to just above the fiberglass of the bottom. I usually put a layer or two of masking tape down to help keep the saw teeth off of the fiberglass.
-sand flush rotary sander low speed 60-80 grit, moving around so as not to overheat
-fill the box with flour (to catch resin leaks), tape off the slot (belt and suspenders), and glass over with a patch.
-open slot , either with an Xacto or razor blade while the resin is at 'soft set' stage or wait until hard and use a trim router with a following bit
-sand patch and file off any goobers inside the box
-congratulate the team

When I have HD foam around, I add that to the board around the box first and then do the rest of the steps. I prefer genuine FU Bahne boxes to the less expensive ones.

Dude, I must say that it is the best step by step on how to install a fin box I have read. I just ordered a bahne 10.5" center box. Most of my research is indicating only a single fin is needed for my length and the type of water I'll be on,mostly rivers lakes and occasionally the Gulf of Mexico. I assume I'll use this technique for installing all of my accessories i.e. Handle, vent,leash and bungee holders ?

I will be laser cutting my router jigs would you say it is better to have an exact fit or a couple thousands loose to add a layer of glass?

When you say hd foam are you referring to divinycell? If so what thickness are you using? Man is that stuff pricey lol.

[Big~Dave]

Big Dave    That's really cool that your daughter is involved. Good for you! She will never forget doing this with her dear ol dad.

Thank you for the kind words! She is my partner in crime! We were just out kayaking yesterday and all she was talking about was how she can't wait till she gets to surf down the river.

[jrandy]

Dude, I must say that it is the best step by step on how to install a fin box I have read. I just ordered a bahne 10.5" center box. Most of my research is indicating only a single fin is needed for my length and the type of water I'll be on,mostly rivers lakes and occasionally the Gulf of Mexico. I assume I'll use this technique for installing all of my accessories i.e. Handle, vent,leash and bungee holders ?

I will be laser cutting my router jigs would you say it is better to have an exact fit or a couple thousands loose to add a layer of glass?

When you say hd foam are you referring to divinycell? If so what thickness are you using? Man is that stuff pricey lol.

Thanks. I have been talked through stuff by others as well. I have a couple 12'-6" build threads here if you want to see the good, bad, and ugly of my processes and the advice given to me.

You will need more that a few thousands just to overcome manufacturing tolerances of the box itself. I would figure .020-.030" or .5 to .8mm a side.  The key is not to pool the resin to the extent where it exotherms wildly and melts the surrounding foam. You could test your resin and rout on a scrap piece of foam with a block of wood that mimics a box. Try the install and cut it apart a couple ways to check for defects. There are also methods like applying ice bags or doing multiple pours to reduce exotherm but I prefer a one-and-done approach.

My last score on HD foam was Divinycell from one of my suppliers. They had an odd sheet about a half inch thick and I cut it up on a CNC mill into box surrounds and little surrounds for leash plugs.