RIBS

[Marc]

It's been a while since I have posted, but here goes;  Has anyone ever or is it possible to put ribs in a boat for strength.  I'm considering it,  maybe spaced 16 - 24" apart going from gunwhale to gunwhale,  and the material would be 3/4 treated plywood.  Got laid off just this morning, but for only two weeks.  (it was voluntary)  annd I need something to do on my boat.  Marc

[CharlieJ]

Sure, it's possible. I wouldn't use treated ply though.

Dave Martin added stringers to Direction while he was rebuilding her for his round the world sail. by stringers I mean longitudinal ones.

You can also use the foam insulation tubes they sell for piping- cut it in two length-ways, tack it in place with a hot glue gun and glass over each one. That's a urethane foam and you could use either epoxy or polyester resin.

I stiffened an old fiberglass boat using the foam and polyester resin  one time- worked well.

Even if you used plywood, I'd use regular un-reated and glass over it. Cut the edges on a 45 degree angle so the glass will run up and over easily, then use a layer or two of matt to glass them in. Again, you could use either epoxy ( my choice) or polyester resins in the glass work.

The reason I said no to the treated is that there have been problems with either resin adhering properly to treated wood. If the wood is COMPLETELY dry after the treatment, it would probably be ok, but why chance it?

[AdriftAtSea]

I'd recommend going the foam route, as it will be easier to work with on a curved surface and lighter as well. :)

[Marc]

Thanks alot guys!!!  Grogs to you.  But just how much and how wide should the matting be?  I'm trying to get ready for the scoot.

[CharlieJ]

I like the glass to extend at LEAST 1 1/2 inches on each side, depending. Tabbing in main bulkheads I let it run 2 or even 3 inches out . Tabbing the new ribs or stringers, I'd use 2 layers matt and finish with a layer of cloth, preferably 10 oz. Make the first layer the widest, then cover that with the cloth for a smooth finish.

On bulkheads I might use twice that. On shelving and non load bearing things I'd probably use a single layer of cloth, just for smoothness.

By the way- if you use fillets on each side, lay the glass while the fillet is still wet, ALL of it, In fact, lay all the glass in one shot while the underlayer is wet. That way you get a chemical bond.

Here's two pictures of some tabbing pn a customers boat. In the first one, the tabbing is structural- it holds the Dinette seat in place and is done on both sides. The tabbing in this case was a layer of heavy roving, with a layer of matt.

The second is a small shelf that will be inside a locker- it got a single layer of 10 z about 2 inches wide





And actually Dan, matt works quite well with epoxy. Very little is now on the market that won't. I t doesn't wet out as clearly as with polyester, but it works well anyway. If you'll go to the Gougeon's online Epoxyworks mag, there is an article where they tested Matt. I used to not use it either, but after contacting them, I've used it quite successfully

[AdriftAtSea]

BTW, if you're using EPOXY RESIN, don't use matt.  Most of the Chopped Strand Matt isn't compatible with epoxy resins, since they are made using a binder that is designed to dissolve in polyester/vinylester resin.  If you're using Epoxy Resin, which is often a better choice for structural repairs or modifications due to the higher tensile strength of the secondary (adhesive) bonding, use fiberglass cloth or roving instead of CSM. 

As Charlie said, you'll do much better if you layup everything at once and have the edges filleted properly.  The foam doesn't have to be epoxied to the hull as it isn't going to be needed for the structural strength.  It is just there to create a "box beam" out of the fiberglass you lay down—unlike what would be the case in a cored-laminate construction, like a flat deck section, where the foam is an integral part of the construction and needs to be properly adhered to the fiberglass laminate on both sides—since it provides a tension web for the laminate layup.

[CharlieJ]

Just in case it slid by unnoticed, I made some comments about epoxy and matt when I modified my previous post.

If it works, here's the link to the article on epoxy/CSM

http://www.epoxyworks.com/21/chopped.html

[Marc]

I am going with epoxy resin and the foam pipe thingies,  sure do wish I lived down south in Texas,  I am entering an unknown area on the rebuild of my boat.  I'm figuring foam for 3/4" pipe, cut in half, then hot glue it to the inside of the hull, mix up my resin  and cut the mat 6'' wide, add the cabisol the the resin  to makge the fillets then apply the matt over that and more "plain" resin over the matt to smooth it out.  I'm not going to start any of this till after I hear from you all.  I hope we meet someday.  Marc                                                                                                                                                                         P.S.  I am ordering a new main sail today from Blue Water Yacht in Seattle

[CharlieJ]

If you are using the foam, you mosty likely won't need to fillet. CSM will lay in quite nicely

Use a disc sander or angle grinder with a flap wheel , grind where each rib will be, and as far out each side as the glass will go- getting out further won't hurt. Not getting it ground make cause trouble in bonding. No resin works well on dirty surfaces. Then tack the ribs in place.
.
Once your ribs are tacked in place- you don't need to glue all along- just enough to hold it still, you can begin the glass work.


Here's another tip for you. -

Cut the CSM using a roller cutter for fabric and a straight edge- you can buy a cutter at Walmart in the fabric department- costs about 10 bucks and is worth 4 times the price.

On to glassing-

Cut the strips as wide as you want, then cut those into about 3 foot or 4 foot sections.. Get a piece of stiff cardboard, lay the CSM on that and wet it out. I use a ribbed roller and a 1 1/2 inch brush. You CAN do it all with a brush. Then roll that piece up and set it aside. Do enough to do one rib.

Carry the rolled pieces into the boat (if you aren't working inside- I do this on the bench), along with your brush and a small quantity of mixed neat resin, wet out a strip each side of the foam with neat epoxy and unroll onto the foam, starting at one end. Use the brush to push it into place on each side and smooth the whole thing. Then lap the second piece about 1/2 inch and work it. Keep on til you finish that rib. Mix some neat epoxy and lightly smooth and coat everything.

A point on the above - the idea is to use JUST enough resin to thoroughly wet out the glass, but no more. You want the glass to look wet, but not have any puddles of resin anywhere. But you don't want it resin starved either. It's pretty easy to tell and if you get too much in one spot, just move it around with the brush.

If you are applying multiple layers, start the second layer immediately you finish the first, without letting the epoxy cure. Work gently so you don't disturb the first layer's positioning. This gives you the best bond, plus enables you to soak up any excess resin from the first layer

Then move to the next rib..

This keeps you working with small batches of epoxy, and small sections of CSM that are easy to handle without rushing because the epoxy is starting to kick. Plus should you HAVE to stop, you have multiple stopping points.

Once all the ribs are glassed and have partially cured- to the point where the epoxy isn't sticky anymore, you can LIGHTLY sand any fibers that are sticking out or obvious rough spots, and recoat. Do it as soon as you finish means chemical bonds, rather than mechanical bonds. I try to lay in the glass and get two coats of epoxy over it in one day. Usually in taping, that's enough, but it all depends on  A) if the work will be visible and B) how good you glass work is.

Oh- my assumption is that you WILL be wearing disposable gloves?- Yeah- buy a box from the pharmacy of choice and USE them.

By the way, white vinegar makes an excellent tool and hand cleaner for epoxy. Clean the roller not the brush-throw that away. Wipe up any drips or runs with paper towels as you work- MUCH easier to work clean and get rid of them while they are wet, than it is to sand them later.

[AdriftAtSea]

One thing—clean the hull before grinding, with a good degreaser, like TSP.  If you don't clean the surface before grinding it, the grinder can often embed contaminants into the ground area, making it less likely to bond as well as a cleaned surface would. 

Working with the epoxy and adding additional layers when it is just setting up but hasn't cured fully means you also don't have to worry about rinsing the amine blush off. 

Charlie-

Good to know that about CSm... I know the binders were a problem in earlier CSM products...but they may have changed to the binder to something that is more epoxy friendly.

[Marc]

I have all your instructions and just came back from home depot with the foam,  I'm going to try to get some done today bt can't pass up a golf date with a friend.  It's 33 degrees here now, and if memory serves me right this stuff does'nt work to well until above 40  what do you guys think?  There should be no contaminants on the boat (inside).  I have it ready for primer and paint.  I came up with the idea for ribs the other day while talking to a guy who restores stinkpots.  I want my boat to be as strong as possible so that I will not be worried for the scoot.  That REALLY is my goal.  Marc

[Marc]

Oh and I will try to get you gus pics of my progress

[AdriftAtSea]

Good enough. :) Look forward to seeing photos.