Lay up- what cloth to use?

[Bob T]

In my previous threat 'Adding a pad-a new question 'I forgot to ask several important ones.When fiberglassing the wood i.e.covering it,what type/weight of cloth should I use ?When bond ing it to the hull should I place a layer of mat in between the pad and the hull?I've also heard of a gelcoat additive that allows it to cure while exposed to the air.Anybody know what it's called?Brought the wood home today,getting ready......Thanks!!BT

[Reese]

Polyester resin has really poor bonding strength and I would strongly recommend using a waterproof glue or epoxy adhesive for the initial bonding.

Once it’s bonded, you need to make sure that the wood surface is 100% sealed before you put on the first layer of fiberglass. If you try and fiberglass directly over raw wood the resin will soak up unevenly leading to dry spots and poor adhesion.

I start out with a first coat of thinned laminating resin (use MEK acetone or styrene monomer for thinning) wait a few hours and recoat a second time. Usually 2 coats will completely seal the wood face (end grain takes about 3-4 coats) and you ready for your first layer of glass. The actual fiberglass itself is not critical…most use the standard 6 oz. cloth…two or three layers should be plenty.

Can’t help you with epoxy or gel coats…only use polyester and urethane paints.

[Bob T]

Thanks Reese.That helps a lot .I'm using Bondo marine epoxy through out and thought cloth to cover was correct.What about 'mat' between the pad and the hull?BT

[Reese]

cause that whole explanation was for polyester resin and yes covering with cloth is correct.

I'm sure that mat between the pad and the hull with bondo epoxy is fine...but I've never used epoxy resin for the initial bonding.

I'm also putting a new pad on my boat (hopefully very soon) and will probably use waterproof glue or two-part epoxy resin (not fiberglass epoxy resin) for the bonding. Epoxy used for glassing is generally too thin for my taste but lots of folk on this site have used it without any apparent problems...hopefully some of them will chime in.

[Reese]

forgot one thing...most mat fiberglass is supposed to be used with polyester resin because there is a binder present that does not disolve with epoxy...cloth does not use binders.

[Bob T]

You just saved me a BUNCH of grief!I'll use an epoxy/fiber mixture along with the cloth to fill the gaps.Thanks for teach'n me some thingBT

[Reese]

don't forget to post some pics of you progress...BTW, did you ever say exactly was it is you're padding?

[Bob T]

Reese,it's a 19 ft Jcraft .Another member'Flat Out' has one just like it with a 200 Venom.He has a picture on his posts.I plan to take some pics as I proceed but I haven't got a scanner.My computer buddy calls me a techno -peasant.I'd rather spend mydollars on boats/cars.You've
replied to one of my previous threads'Adding apad a new question',and your words have been a big help!My buddy just calledand he's finished cutting the wood!!!!!!! Gonna pick it up right NOW! BT

[Reese]

forget the scanner...someone you know must have a digital camera...hell I borrow my nieghbors all the time.:D

[Racemore]

The additive for the gelcoat is Duratec Clear High Gloss Additive.Mix 1:1 with gelcoat,thin with fast lacquer thinner if desired and catalyze at a full 2% mekP (20cc per quart).prep80-180gt.

Yes you can put mat between the hull and pad.36-80 grit prep:cool:

[Bob T]

Racemore.THANKS for the tips.What about the previous statement about not using mat with epoxy.Can you educate me a little?I'm getting real close to doing some tests then getting to the itchy work.TRhanks again BT.

[sho305]

I was planning on fitting my pad parts to the hull dry, then putting a layer of mat on the hull and piecing the pad on top of it; all with epoxy. Is there a better way? I figured I could not make it fit good enough otherwise, or get enough surface area where it bonds together and I would have to bolt it or something.

When I did a transom with Wests, some dripped under to the shiney bottom. I hit it with a chisel and knocked a piece of gel out, then did it again in another spot! I learned my lesson, the stuff sticks. However, I have been told to lay mat and press into it wet or layer on whatever you are attaching to your hull for good adheision since it gets beat under there and a hull flexes.

Got my scanner for $20 at Officemax and it works fine.

I will have to make my pad wider than this pic, to the inside of the small strakes.

[Techno]

Polyester is oxygen starved to cure non-tacky. This is usually a wax additive. Layup poly doesn't have it so it stays tacky when cured for the next layer. Non layup needs this wax layer removed for hte next layer and don't sand it off thinner it off.

I use epoxy with mat or whatever. It is said that the binder doesn't dissolve but it does. Also there is a wet out coating on glass and is supposed to a special one for epoxy but I've never had a problem I don't normally like to use mat. To me it's inferior. Resin rich. Some use it as a bonding layer but if using epoxy I don't think it's needed. I only use it for print through protection.

Epoxy cures with a possiblility of amine blush this is washed off with water and not thinners. Poly is washed off with thinners and not water.

When coating wood with either resin you saturate the wood with resin. After awhile it has soaked up what it will and you can start lamms or wait for it to cure and do the sequence from a cured start. Clean, sand for bite and all that.

If you want to bond a part on thicken some epoxy with structual filler, I think it's silica. This should be fairly thick mix and shouldn't be to fill a bad fit, just to bond the parts together. You coat the dry surfaces with liquid epoxy let set a bit and then put the filler on much like a tiling, a scored knife or a regular one.

Don't know anything about bondos epoxy but probably more $$ than many other choices out there.
Epoxy is always 2 part. If it's not a liquid there is filler in it, like bondo or gellcoat. Both are polyester resin with fillers.
Actually a thin flowing resin is better. You only want enough resin to wet out the material- whatever it is. Any more is heavier and weaker.
Epoxy has a huge choice of fillers to choose from. Light weight, easy sanding, to heavy duty strucural bonding. Some cross over a bit.

Non stop laminating is best for both resins. You have to stop and let it cure If going thick which I think is around 1/4" so the heat doesn't distort the lamm or destroy it.

There is a 3rd resin I don't know nuthin about but hear it's pretty good. Now I got brain lock and forgot, Vinyl???

Also the advantage to thin glass( light) and thicker like roving is the thin stuff bends direction easier to the extreme of roving which wants a large radius, or a clamping system. The heavier the weight cloth, the less lamms needed. Mat is pretty agreeable to many direction changes and can be shoved around too. The cloth can only handle so much and then wrinkles.

[Bob T]

Thanks for the info. I thnk you're talking about vinyl ester resin.. don'tknow a single thing about it,so Ill proceed with what I have.Fumed silica or maybe some milled fiberglass soaked in epoxy,in conjuction with some 6oz. cloth to sandwich in between the pad and the bottom of the boat and fllets on each side.BT

[sho305]

I agree with you Techno, the epoxy bonds very well. Still see many that do not recommend not using mat, I can't see the difference since I plaster the wood with epoxy before laying anything on it anyway. So you should have 100% surface bond to the wood then reguardless of what you put over it. But, I'm not a pro with that so I ask and get many answers. I like the epoxy a lot, but I would have to figure out how to slow it down for a large area. I only used the fast for my stuff so far.

On the last transom I did I started with a few repair kits from a bondo type company that had two part epoxy 1:1 mix. It was on clearance, and got all covered up with west sys when I ran out. Mostly just sealed the transom wood and floor panels I made with it. Seemed the same as the west.

[Techno]

To slow epoxy down, mix smaller amounts or/and put it in a spread out container. Like a roller pan vs a tall pot. The resins generate heat and the more contained they are the more they generate. You can mix in a convenient chip dip container then pour it into the larger flat one.

Another thing about epoxy, I like the west system mostly because of the pumps. You pump 1 hardener-1 resin or 3&3 or whatever the amount. The non pump kinds you pour into containers and is quite the hassle. Other epoxy systems do have these calibrated pumps though. With the pumps it's no big deal to mix smaller amounts many times. Measuring it out does become a big deal.

[sho305]

I got the pumps on a gallon and a qt., now they do not work anymore as there are no hose on them to the bottom??? I have to find some or get the smaller containers. I been leaning them over but now that don't work.

[Techno]

You might have the wrong pumps or forgot to put the little extenders on.
I think 1 kit has them with and with out is for 2 sizes. Then there is a tiny pump set for the pint size?
Stick a hose on or buy more and pour it in. Or cap the old and save it.

[sho305]

These were the only pumps there, and came with no hoses. They are about half empty, so maybe these are qt pumps. They are pretty big pumps, and the line on the end is only about 1/2" past the plunger where an extension needs to be attached. I'll find something, just hope it don't react in there. I have measuring cups, but the pumps are great.

[Techno]

I think the cans and pumps have an A B C thing to show the size. Not sure but think thats right.

[sho305]

I think for the next project I'll just buy the smaller cans and use them; keep refilling them after. I been glueing all kinds of stuff together with it, sure is nice stuff. Fixed a running board, a plastic kitchen do-dad, etc:cool: I might have the wrapper for the pumps, I'll check.