US Box sealing

Hi everybody,

Try to find this one one the forum but it looks that I’m the only dumb to have this trouble.

I glued my US box on a longboard, with some fiberglass and a mix of resin, bit of cabosil (silice, same thing?) and white tint. I glued it with a fin in it to check the cant. I remove this fin I think to early and I can see that the box is not sealed to the resin/foam. Any advices?

 

I can’t tell anything from that microscopic close up pic.  Sand it flat and put a glass patch over it.  Who told you to you to use Cabosil and pigment on a longboard box anyhow?

Hi McDing,

Sorry for the picture I though it was the best way to show the little flaw in between the foam and the box.

I don’t know… I was sure that it was the way to do it. There’s so many informations to retain that I feel this one was an easy one and so I didn’t double check. 

I’ve been on the forum and I’ve seen a post from proboxlarry saying just lam resin and fiberglass…

Why we shouldn’t use pigment there? 

 

Hi McDing,

Sorry for the picture I though it was the best way to show the little flaw in between the foam and the box.

I don’t know… I was sure that it was the way to do it. There’s so many informations to retain that I feel this one was an easy one and so I didn’t double check. 

I’ve been on the forum and I’ve seen a post from proboxlarry saying just lam resin and fiberglass…

Why we shouldn’t use pigment there? 

 

Next time ask around about installing a longboard box.  Cabosil has it’s uses (primarily as  thickener).   Works well for basting around inside tight fitting fin box cavities like FCS Fusion and Frutures.  Not something you would use to fill gaps or dings.  Your best result would have been to use ground milled fiber.  Some shops sink the box in the slot with a piece of 4 or 6 oz. cloth.  The lower quality shops sink the fin box in Q-cell.  It’s always a good idea to put a patch over the finbox primarily to make sure that it is water tight.  Also strengthens the install.  At this point just sand it flat, fill any holes or cracks with Q-cell and put a layer of cloth over it.  Q-cell is a filller, can be mixed really thick paste like and applied with a hard plastic squeege.  Sands easy.  Cabosil on the other hand sands poorly.  I use 1/32 milled fiber.  I mix it fairly thick and spread it around inside the cavity.  Then I pour the slot about half full, press the box down into the slot forcing the saturated fiber up around the box in the slot.  I put masking tape around the box so that the mix doesn’t get all over the bottom of the board.  Then I clean up the excess and wipe things off with a paper towel.  I wait for it to gel and pull the tape.  Then I grind it flat when I sand the hotcoat.  Off course the install is done after the hot coat.  A standard Fins Unlimited or other brand longboard box should not be installed before you glass.  That just creates problems.

Thanks for your patience McDing.

Actually sometimes I try to find things with the research thing and I struggle to get answers, and for something like fin install I’m a bit shy for asking because it looks like this subject has already been discussed hundred times…

Anyway I’m gonna lay a patch of glass over that thing. Thanks again for your time and advice, I really apreciate. 

By the way I found a thread were you and other ones are talking about Qcell, cabosil and aerosil https://www.swaylocks.com/forums/cab-o-sil. Here in France I can’t find the correspondence, we have silice or micro ballon (and I don’t really know how to use them). So actually I’m not even sure that I’ve putted CAB-O-SIL in my box… I think it’s Silice. I’ve poured some in my box hole because I though it was the way to do it for leash plug.

I should ask Balsa for the correspondences…

Yes You should get in touch with Balsa.  I am sure he would be very helpful. Don’t be shy.  I’m not a harsh person.  I just hate to see people get bad advice.  You can private message me anytime and I will do my best to answer your question or steer you in a direction that will make your attempts at board building a success. If you use Milled Fiber you will need to put a little white pigment in it.  Q-cell is naturally white.  But for now on this one;  just make sure it is filled, sanded flat and cover with a layer of cloth.

All good advice from McD.  This might also help:  When the box is in (installed after glassing the board), I put a sheet of newspaper on the bottom and layout a cut strip of fiberglass that will be placed over the box to “cap” it.  I wet out the cloth and carefully  squeegee excess resin from the fiberglass so it won’t drip in the box, then ligt the fiberglass from the newspaper and lay it over the box.  Neatly.  Of course the box top and area around it have been lightly sanded to give a better bond.  Actually I usually use a couple of layers of cloth, but you get the idea.  WHen the resin reaches cheese consistency, you can cut it wilth a razor blade leaving just the slot for the fin.  Then blend the cloth on the border with a sanding block.

The fiberglass placed this way will seal the box from potential leaks, and bond it to the surrounding glass so it won’t wiggle and open up a seam to leak.

This is a box that I did the other night.  Looks good, but not perfect.  There is one little bobble due to a slight divot in my Jig.  Gonna have to break out the Bondo and fix my jig.  I used Ground Milled Fiberglass with blue tint.  Tint color is same as the board (Jamaican Blue) so it looks good.  Taped off and ready for Gloss.  Lowel

Thanks Greg and Mc Ding for your advice.

I glassed my box like you told me, it looks great. When I finish the board I’ll post some photos to show you on what I’m working.

 

Coming to the rescue… Cabosil and aerosil are -I think- the same thing and it’s known in France as “Silice colloïdale”. Basically used to make a kind of putty that doesn’t flow along vertical surfaces. When mixed with resin, its original white color dilutes to become almost clear (actually a bit blue tinted and not totally clear). Q-cell is what we call “micro-ballons”, actually microscopic glass spheres, used to lighten resin when filling cavities, for instance. Its white original color stays white when mixed with resin, making it the material of choice for fixing dings on clear boards (although it will never be exactly the same white as foam, it’s still better than a chunk of blue resin that will turn brown with the sunlight…) And then you have milled fiberglass (“fibres broyées”) which is basically fiberglass powder. Also whitish but will turn greenish when mixed in resin. This does add strength to resin.

Polyester resin is known to retract somewhat when curing and fin boxes are made from a thermo-plastic material. Thermo-plastic means that if you heat the material to the right temperature, it will melt and become “moldable”. (Unless thermo-setting plastics such as polyester or epoxy for instance which, once set, won’t ever come back to their liquid initial state). When polyester resin cures, the polymerisation reaction produces heat and the more stuff in the resin (be it glass, Q-cell or cabosil), the more heat is produced. Fin boxes will tend to shrink somewhat under this heat (while resin retracts) and ultimately separate from the resin mixture as it sets, hence the cracks you have had. I personnally do the same as you did -insert an old fin in the box to prevent box shrinking- and I under-catalyse the mix so that it sets slowly, overnight is good. Once cured, I replace the fin with a piece of foam forced into the slot, allowing me to sand the box flush with the bottom. (Sanding also produces heat, so…)

Using pigment in your resin mixture is not that bad, it actually enhances your job when you are good enough to perfectly center your box in the slot: having a black box with a perfectly regular white line around it is the top of the top in my book. But usually you will use black pigment for installing a black box and white pigment for a white box.

Hi Balsa!

Thanks for the precisions, so silice colloïdale is what we called silice? I mean it’s not two differents things? In my mind silice and micro-ballon were the two same things.

  Also I’m used (kind of ahah) to route the slot by hand, I don’t have a jig. Like many others I’m using the us box as template, I draw it and route it. Then I just need to sand the edgde straight. Doing that I think my box fit almost too perfectly in the slot and I was wondering if I shouldn’t over route it a bit in order to have more room for resin and thus more strengh around the box. 

By the way balsa, this is off topics but I just watched a lamination video of you wich has been made 10 years ago I think. Like normal lamination until the 6th minutes when you have to turn down the laps and we can see your racks rising up just by pushing a button. I don’t know if anyone has see it on swaylocks but it’s super ingenius and also super funny. 

Very good.   A piece of cloth over it and now you wonder what all the stress was about.  And look at the education you got from that single post.    Glad it worked out for you.  You should connect with Balsa.  He’s a master at his craft.

Thanx Balsa,  I had all those alternative names rolling around in my head, but I couldn’t put it in writing.  So thank you for that explanation.  And you are right about the white line around a black box.  If you can rout the hole nice and straight, center that box perfectly and get that perfect white line around a black box, that is top of the top.   A couple of little things to add;   I got into the habit of using white boxes because I shaped so many boards with thin tails.  If the box is in the stringer, it is strong enough, but if you install a black box you can see a black shadow thru the deck.   Another thing is that a lot of guys keep a quart or a gallon of white Gel-coat around the shop and use that in place of polyester laminating resin for fin installs.  Eliminates the need to use pigment in your slurry.

Hey Greg. I saw a video ages ago of someone cutting out a fin box that had been glassed over but somehow didn’t get any resin in the box. I didn’t realise that’s how it was done. Cheers for the insight 

Kind regards

 

simon

Without tape to cover the box you mean?

Hi everybody!

I’ve finished the board I was working on and I just wanted to show you the result. It’s a 9’3 with Volan deck and patch.

Big thanks to you all. Can’t wait to try it!!

Cheers!




Very nice board.  Did you special order that blank?  Lowel

Thanks Lowel!

No it’s artict foam blank that I ordered thinking it was a stringerless one. Initially I wanted to make the stringer and I eventually gave it a try. I don’t really know what to expect, more flex in the tail just sounds fun for me. I’ll tell you.