I could use some help... opinions.... hot coat and sanding

[Bradley]

I’ve been posting a lot the last few days trying to finish up my board. I have really appreciated the feedback I have gotten. It has helped so much.

Using polyester Resin FYI.

I did the hot coat on both the deck and the bottom.

Questions:

1. I felt like the resin pooled a bit in my concavity upon setting and kind of filled it in. It is a lot shorter now and doesn’t transition into a double concave like it did on the foam. What did I do wrong? How do I prevent that in the future? I have like a tiny single concavity now.

2. My resin cured a little “tan”. Any ideas why that happened? I did the glassing at about 60 degrees in my garage. I thought I was pretty close on the MEKP ratio. Although, I did go a little light on it to have more working time. You can see the color best on this white garbage bag.

3. Burn throughs - I honestly don’t even know what I’m looking at. Part of me thinks I have sanded WAY to much, and part of me still feels like I have a lot of sanding left to do. I just don’t know, what I don’t know. On the flats of the board there are still “Pock Marks”/ small divots in the hot coat.

On my fin box (which i totally screwed up) I think I have gotten all the way to the foam some how.

I can’t tell if these are burn throughs or need more sanding? You can see my crappy lap line on that last pic. Is it possible I have just sanded all the way into the weave either side of that? Because you can’t even see the lap anymore…

Anyway, I have looked through a bunch of forum listings this morning and think i’m pretty screwed here.

Any help/advice on where to go from here would be great.

[jrandy]

Hey Bradley,
Your experiences sanding hotcoat are not uncommon. I am by no means a professional so take what I say with grain of salt…

The pooling in the concave may have something to do with the lower shop temp and lower amount of MEKP used, which would give the resin more time to flow and regroup in low spots.

The color of the resin, I don’t do much with polyester but I do remember the color changing a bit after the MEKP is added. Which resin, is it listed as having a brightener?

The folks who do more with polyester resin can confirm if the above theories rings true.

Sand-throughs… The fin box will have to be handled. An old trick is to fill the box with flour before taping it off to catch any resin that get past the tape. The screw holes can be filled with surf wax. Then do a patch, hand sand, and recoat. The lap lines might just need to be sanded a little more and re-coated. Are you thinking of a gloss coat?

[Bradley]

It seems like there are a lot of posts on here about this. Its just so hard to know what your doing and looking at the first time around. I appreciate the feed back

That makes sense with the lower temp. I wish I would have thought of that before hand.

Regarding the Fin Boxes: So I need 1. Tape the fin box. 2. cut a new patch of fiberglass that covers the entire find box and overlaps onto the board. 3. Glass it on. 4. This is where I get confused: How do I sand the box down flat without going through the cloth at this point? I don’t have that elevated flange to cut down anymore. Seem like I will just end up burning through again. Am I missing something here?

I hadn’t decided on the gloss coat. But sounds like that might be the easiest solution to covering up my burn throughs, right? Or should I just do another hot/wax coat?

[OSS1]

Blow off the whole board with air. Be sure to blow sanding dust out of pores and cloth weave. Wipe down your burn thrus, over sanded laps etc. with a clean soft cotton rag and styrene. Wipe completely dry and let sit overnight. Fill any divots with a resin cabosil mix. Like the ones on your fin boxes. With 4oz. add a small football patch over the fin boxes. Re-hot coat both sides(deck and bottom) of the board. Sand both sides by hand. No sander for you. You are NOT sanding fin boxes down flat! They are already flat. You’re sanding all the dings that you got while building the board. The idea is to just sand Things smooth. If you let resin pool in the concave, sanding is the only way to get it back. If you try that; do it before you start the repair process I have described.

[lemat]

Do exactly what OSS1 write. Welcom at board building. Better you come less problems are problems.

[arlosilva]

hello,

congratulations on your board and on the nice paint or resin tint its cool!

now from the pictures, you made ultra common mistakes.

i made so many mistakes in the process of learning that many times i was ansious , angry ot frustrated and thinking of giving up. ( i am happy i never gave up)

also don’ t rush nothing in the process(think about things) and it turns out better.

i am no professional shaper and what follows is my opinion, it took me arround 15 boards to be able to have something looking more or less ok.

1 - sanding ( sand the rails by hand, remember that the hard edges will sand faster, sharper)

one trick i got from someone is before i sand i draw lines with a pencil (pattern like if i was waxing the board) and then i sand untill the pencil marks disapear ( that gets me even sanding all over the board)
i repeat this pencil marking everytime softer as i progress the sanding paper grits.

also ( first 2 hot-coat sanding passes with 100 to 200 grit, i use sanding machine with 8" soft pad)
but after that i use a small sander with a hard pad and variable speed and i wet sand to finish.

2- hot coating.

remove the excess resin with horizontal brush strokes ( that way it does not pool on concave)

when i mix resin i add parafin (for easy sanding and gloss look)
i mix it for longer time because i have not to do laps.

i was told also by an experienced shaper that just because i am using a brush that i should not use the resin as paint.

so use the brush like a squegee 45 degree and spreading the resin not aplying pressure.

one time vertical spread, one time horizontal to remove excess, and one last time vertical to finish.

3- fin boxes.

i had lots of issues, the trick is to use the sander with the pad at an angle ( instead of flat) and sand only the bit of tape until it pops out, then sand flat to lower the edge of it.
sand the paper out before the hot coat.
put another piece of tape for the hot coat.
you will find it easier this way, you can even cut it out with a razor blade when the resin gels, before curing.

you can also add the boxes after you laminated, before the hot coats( some people like it better, to cut on the harder surface)

also i find future fin boxes nicer to work with.
cheers and good waves

[Bradley]

Haha… No sander for me! I couldn’t agree more.

Thanks for your help. Working on my second hot coat this evening.

[Bradley]

I appreciate the tips. I really like that pencil idea. I’m definitely going to use that after hot coating this board for a second time.

[OSS1]

Depends on how nice your hotcoat is; but you can probably start with 150 or 180#. When sanding by hand I take 1/2 sheet and fold it into 1/3. If you were working on that concave you might start with 120# or even 80#. It’s better though for the inexperienced to use a lighter grit and more elbow grease. That way you don’t have to stop and fix another burn thru. Remember “NO SCRATCHES”. So if you finish with a grit and still have scratches; You need to go to the next grit and get rid of them. Be it 180, 220 or 320#.

[OSS1]

Be careful using a sander on edge. You can do some major damage that way. Sand the fin boxes flat when you start to sand the hot coat. Flattening the fin boxes and leash plug are the first step in sanding the hot coat. A lot of sanders use a hard pad and coarser grit to do this and then switch to a softer pad to sand the board overall. I try really hard to lay down a nice even(no brush marks) hot coat. My goal is always to sand with the finest grit possible. I shoot for putting down a good enough hot coat to start with 180#. Check out the video available on this site. “Glassing 101 John Carper”.

[OSS1]

PS. The voids and bubbles at the fin box are a result of your install. Use a little Cabosill to thicken your resin in the fin box. If you don’t get enough resin in the hole to come up through the slots in the box you will have to work extra hard to get resin to drain down into and fill the cavity when you start to laminate. The voids are caused by lack of resin around the box and under the flange. It all looks good, but the next morning you find that the resin has drained down into the fin box cavity and left a void or bubble under the glass at the fin boxes. Putting a football patch over the box as you laminate helps prevent this because the fin box will be resin rich.

[Bradley]

Thank You! I totally messed up the fin box. Not to blame futures, but I bought there one pass system. When I used it, the router bit did not cut the area for the flanges. I then added the washers they included and it cut the boxes too deep. It just became an entire fiasco. Pretty frustrating when you pay the high fee for a futures install kit and then have to add spacer washers to make it work correctly. Anyway, lesson learned.

I will take your advice moving forward on the box install and the extra patch. I appreciate the feedback.

[Bradley]

My second hot coat came out way smoother. So i’m going to try and start the sanding on 150 or 180 grit. Should go pretty quickly.

[OSS1]

Right on. Easy with the elbow grease.

[OSS1]

Yes I heard about those kits. The washers are there to compensate for the new style bits that Futures came out with. The bit is thinner at the cutter head. I’ve got the old style bit so there is nothing to compensate for. I’ve got two routers with each bit mounted. It’s hard to believe they didn’t see that problem coming. I’ve got an old shortboard that I run a practice pass on when I haven’t done a cut in awhile. PS. It’s nice to have “dummy” fins so that you can lift up and push down the fin boxes in the cavity when you are setting the boxes. Doing that helps force the resin in the cavities to come to the surface and up through the slots.

[resinhead1]

use a 1/4 sheet variable speed orbital sander when learning, keep sander moving, do not stay in one place ever…ever, just keep moving. Once you grow up you can move to a 7in sander. Understand the issue areas are going to be where you pile up resin and fiberglass, ie, laps, boxes, fin plugs etc…so when glassing take extra effort around these areas so they dont get all piled up…ez right. Also learn to prep your laps before next glassing schedule or hot coat. You filled in your concaves because you flooded the board with too much Hot coat. The hot coat is only on the board to fill the weave of the lam. Use just enough hot coat to fill top of weave…flood board, go side to side twice, go tip to tail pulling off resin and smoothing out…then walk away, should take no longer than 3 mins max. Then after you sand the board flat…the gloss makes it all pretty. Gloss should hide the spots where you nicked the weave…gloss resin has lots of styrene in it.

[resinhead1]

Gloss resin is slightly different than hot coat. Gloss has a harder barcol strength which makes it easier to get a shine. I’ve done hotcoat gloss coats, you just need to use more grits longer. 320, 420, 600, 1200, 2000 etc…it will work. Gloss resin is usually pink. Hot coat resin is bluish aka 249. Styrene is used to thin the resin out. if you are using hotcoat resin for gloss put a cap full of styrene in, Ive never added wax? Kick it super hot with MEK, you want it to kick in 5 mins or less. If the gloss / hotcoat has a chance to sit too long before it kicks…it will slab off or brain slide leaving exposed non waxed resin (aka sticky areas). So do about 20 cc per pint +/-. work fast, brush side to side 2 times, tip nose to tail 2 times…walk away…let it self level, the wax must rise. Don’t slam a door behind you, and don’t have any air movement in the room. …walk away. if you did it right, after you clean your brush it will be time to pull tape. like i said about 5 mins

good luck

[arlosilva]

cheers, thank you very much.

here is a pic of the latest hot-coat i did with
600 mils hagart resin and two caps of parafin.

i do catalise fast like 2%.
but the strangest thing is that when i brush it i always get the feeling the resin is not liquid enough and is hard to spread.

room temperature this time of year arround 17 degrees celsius.

cheers and good waves

[resinhead1]

I like warm resin, and a cool room. Stick the gallon of resin in a warm water bucket for 15 mins, that will thin it out a bit. That hotcoat looks fine…but you should prep those laps a bit better. Grind them down, hit them with styrene, then hot coat. That way you won’t have any burn throughs. Do all the burn throughs before the hotcoat if possible.

When I do epoxy my hot coats look close to gloss coats… meaning i don’t have to remove wobbles and flatten stuff.

[OSS1]

Thin it with just a little Acetone. Don’t over do it. You can tell by the way it runs off your stick when you stir it. Overdo it and you’ve got nothing but Acetone. I am sure I will be criticized for this, but it works. Been doing this for years. Hot coats and Gloss both.