Dremel instead of sander to avoid finbox burn-through when opening up taped and hotcoated boxes?

Hey all — board #5 looking good. I did a post-lam finbox instal (FCS 2, RR expoxy, EPS foam). post finbox install i did football patches over my finboxes for strength. i’ll hotcoat and then sand. 

in the past i’ve had problems when using the electric sander to open up the taped-closed finboxes post-hotcoat. often in the process of sanding those open, i expose the weave around the finboxes. 

i’m wondering if anyone ever uses, like, a dremel or something to specifically bust those taped-up finboxes open to avoid having the sander do it and possibly get down to weave. 

anybody every try that? 

I would be more likely to use a razor blade or exacto knife than a dremel, but either way there is going to be sanding involved, and if you hit weave you just follow up with a bit of resin over the exposed weave, so not really sure what the issue is?




you are pretty much always going to hit the weave a little bit when sanding the boxes flat, especially on a post lam with the patches sitting slightly above the lam. you will also most likely hit the weave in other spots on the board sanding your hot coat. this is why most do a 2nd thinner finish coat to seal all the weave.

my go to routine on epoxies lately is sand hotcoat with 60-80 grit on a medium red pad to get the board nice and flat. tape off and do finish coat  with 1oz resin hardener mixed per foot of board.  then all that is needed is a quick sand with 320 or 400 grit on a soft yellow pad. smooooth and deadly

okay so you think i should bust those taped finboxes open during hotcoat sand? – so i can make sure board is nice and flat? (then hand-tape again for gloss coat?) or do i leave them untouched until gloss coat sand and just swipe a little epoxy on any exposed weave there at very end? 

Not sure whom the question is directed to, but you are welcome to use whichever method you want. I’m just saying if you hit weave, then resin is called for. If its just a small spot here and there, all you need is a touch up. If you haven’t yet applied a final coat, then it will be handled with the final coat.

I generally leave the boxes covered until the resin work is complete, then cut the masked area away, and maybe hit the cut edge with a very fine grit.

okay, thanks very much all!

Yes bust them open then because im assuming they still have the raised flanges since the board has been hotcoated but not sanded correct?  Sand the board flat. Then retape for gloss/finish coat  most of the fcs boxes come with two sets of the little tape stickers to do 2 tape offs for this purpose.

If you’re feeling OCD about it… I’ve rigged a box install jig plate with some strips of 1x2 under it, and then carefully lined it up over the box and hit it with the rigid trimmer router. tricky but if successful very clean

Paint stirrers.   

My most recent probox install after I capped the boxes,  I was waiting for epoxy to thicken to the right consistency for cutting with several brand new razor blades just outside the tape covering the grubscrew holes and  fin base slot.

 

I have adopted the use of a dremel for many things.  The right angle attachment for the dremel, in my opinion increases control and precision of the cutting head to a great degree, and I basically have only removed it once since I got it, using  the right angle attachment even when it is not required, as it allows me much better control and precision.

 

The right angle attachment seemed to be lacking in the grease department when i opened it up to satisfy my curiosity. Easy enough to take apart and stuff it with more grease.  The tool gets hotter than the attachment.

Why don’t you try sanding the boxes flush directly after the lam cures (assuming Epoxy which has a sandable lam). Then put on new box-stickers and hot-coat over that. This way, when you sand your hot coat, you have much less work to do around the boxes, significantly reducing the likelihood of exposing weave. This method is also great because any bubbles around the lam will be exposed in the first sanding and filled in during the hotcoat.

This method does work well but as a newbie he has a much higher chance of sanding thru his patches and reducing the strength of the install this way.

Tape a piece of equal thickness wood 1/8" or thicker on either side of router base. This makes a sled like cutter. Set router 1 or 2mm deep by eyballing and free hand the router cut of the tape over box. Sand to perfection by hand, problem solved.

Use a harder pad to flatten the box.  It is less likely to compress and hit the surrounding box.  I use a hard disk and the boxes are set in such a way that the opening can be ground flat without hitting any surrounding area, box or board.  Then I start sanding with a medium or a soft FlexPad or Ferro and the proper grit.  A common mistake is to try to use the same pad on everything from grinding boxes and leash plugs to sanding the overall board. I would not use a Dremel. The barrel attachment and other attachments are sometimes useful for repairs, but require a lot of skill. A Die Grinder with a 3M ROLOC Disk is a better alternative.

AH! that makes sense. yes, i do use a general-purpose softer pad and i can see it physically compressing as i press to bust through the taped box. i tried angling the pad to get the “sharp end” but the compression makes sense. victory!

Yes glad to be of help.  If you use a hard disk no matter what type, flat pressure is the key.  Don’t tip it and try to use the outside edge of it too much.  When you do use the outside edge of the disk you have to lighten your touch.  About the only time I tip the disk on edge is if I have to clean up the inside edge of the fin slot.  It is very important to set the boxes or plug at the proper depth.  Then you are able to flatten the raised part without hitting the surrounding area until you start overall sanding with your pad.  These days I am using a Makita 5 inch sander(about $100 at Lowe’s) with a 4 or 5 inch red resin disk.  Works great because it is lower RPM’s than an angle grinder.  My opinion is that an angle grinder with all those high RPM’s shouldn’t be anywhere near a surfboard.  You have to go easy with whatever you use.  The plastic box will melt if you get on it too hard.  One of the reasons people use white boxes and plugs is that white residue from the box doesn’t show if it gets in the weave of a clear board.

This method works well too.  Just be very careful with that router.  I’ve got so many fin jigs around my shop that require a Makita trim router that I don’t have an extra to use for that method.  So I just grind them.

In case anyone else comes across this looking for help this is how the master does it. https://www.instagram.com/p/B-R5blUn0Gp/?igshid=724ibpduj8k3

Grid down boxes post lam with 80 grit. After grind down of box i smooth the plastic on box by hand with a little 220. This helps 2nd sticker stay on. First try after 80 grit grind down and sticker started to come off as soon as hot coat was applied… 

Reapply 2nd sticker before hot coat. He pulls sticker off as soon as resin hits a point where its stops dripping. I wait about 15-20 minutes on epoxy hotcoat and pull sticker off. 

 

Grinding post lam with a die grinder and then pulling the sticker on the hotcoat is probably best.  Old habits die hard.  I’m used to the production method which is generally not to interupt the Lam/hotcoat process and sand after.