86 SN rebuild

I thought that if you were using epoxy, you wouldn't necessarily need to use mat. Epoxy supposedly has enough strength without it.

I would like to bed my stringers in at least 1 3oz strip of mat. Maybe 2. Then take the 2, 4 and 6 inch cloth and tab the stringer to the hull, using opposite 45% angles for each. Then, wrap the entire stringer with a 3 oz mat and cloth. Once each stringer is finished, use mat and roven in the bilge, between each stringer and outboard of the secondary stringer up the side of the hull. (Hopefully this makes sense) I'm assuming that I can use biax in place of the mat.

What do you think?

As far as green versus cured, I would certainly like to complete the entire layup before it cures, but I don't think I can move that fast.

I'm going to call a couple of distributor’s tomorrow, but what am I missing?

Jeff

Jeff,
I don't feel you missed much and your plan sounds good except the 3oz. is on the light side. The biax is worth considering but I've never seen any decent comparison figures on it.

I am glad Greg mentioned the green layup. It's preferred for max strength and if you have all the glass precut lay up does go fast. If it does set up on you, all you need to watch out for is the amine blush but it comes off with a light soapy water.

Whatever glass you do you use, make sure it's "E" glass.

Ranger wrote: What would you use to bed the fir to the hull. West systems says use a mixture of their products, but I think I would feel better with something like mat or maybe biax between the fir and the hull.

If the stringers are scribed well to the hull, not much is needed. Some have used a strip of mat but I feel thickened epoxy (with cabosil) is just as good and sure is easier. Lay a bead down and set the stringers in place. You'll be filleting the bottom edge with it anyway so you can actually fill the minor gaps at the same time. Get some of the empty caulking tubes, make a batch of cabosil/epoxy and force it into the gaps. Then go over it with a squeegee with the radius cut into the corner.

I agree with Pete on bedding the stringers instead of using mat. I don’t think you can scribe them perfect enough to not have gaps larger than the mat can fill.
I laid a bed of epoxy thickened with cabosil and milled fiber for extra strength (like your laying brick)
Gently set the stringer in place and let the weight of the stringer squeeze out the excess (give it a tap or two if need be) like edge gluing boards you don’t want to squeeze all the adhesive out.
I also put a layer of mat on the stringers before installing them.

As for lay-up it’s I found it was pretty hard to do the whole layup at one time you only have about 20min. of pot life and that time goes fast while you’re trying to adjust everything as you go. It’s better to take your time and do a little sanding between coats if need be.
And don’t forget to coat everything with CPES before you epoxy it.

gun-driver wrote: As for lay-up it’s I found it was pretty hard to do the whole layup at one time you only have about 20min. of pot life and that time goes fast while you’re trying to adjust everything as you go. It’s better to take your time and do a little sanding between coats if need be. And don’t forget to coat everything with CPES before you epoxy it.

Limiting the mixed batch size of resin to what is needed in 20 minuits really helps. Keep in mind it may "kick" in 20 but is still "green" for hours.

Make sure you buy the metering pumps along with the resin/hardener.

If in doubt about the hardener speed, favor a slow hardener.

YES, don't forget the CPES!!

Ranger-

While you are doing the rebuild please consider replacing the shift system with a morse MV-2 which has a safety lockout. The MV-1 which is original on your boat does not have a lockout.

Tim

JoeinNY wrote: In terms of Mat I disagree with Pete's comment on the 3oz being too light... 3oz would be a massively oversized mat for general use.

Correction!! Sorry as I missed it was mat! I thought it was cloth!

I cant say enough about how good the biax is. My friend who built offshore race boats for 25 years said that when they were not using kevlar they used biaxial and that was it.

I just spoke to U.S. Composites and here is what he suggested.

First, use Fasco 110 Epoxy Glue to bed the stringers. Then use the 2, 4 and 6 inch E-Glass tape for the stringer to hull joint. Then use 2 layers of 6 oz cloth over the top of each stringer. Tie all of it together with a layer of biax in the bilge and between each stringer. Since I have gel coat cracks that will need to be addressed, he recommended that I run roven up the sides under the gunnels.

He also said that I should use the 635 epoxy with medium hardener.

What do you think of the Fasco product?

I have not heard of anybody using fasco. I would stick to either milled fiber or cab-aer-o-sil. It is not easy to fair at all and is not recommended where fairing is needed. While it is true milled fiber is the strongest, fumed silica is a lot stronger than talc or microballoons which are used where fairing is needed and adequate for this application, and as pointed out makes great fillets.

I agree with the medium cure 635. You can always add less hardener for a slower cure time, but if the temp is below 70 you need that hardener or else you will be waiting forever for it to cure. When I got my 10 gallon kit of 635 it came with 3 and a third gallons of hardener. I never touched the small third bottle because it was getting hot here so I was using less hardener. Digital scales are great for mixing small batches. When I was bedding the stringers and making the fillets I mixed a few 40oz batches which is a PITA using the 1 oz pumps and the scales I had did not read that high. FOr those I used cheap pitchers from the dollar store that were graduated. The biggest favor you can do for yourself when you get into the glass work is buy a small paint mixer for your drill. It is impossible to mix thickener into a 40 oz batch fast enough by hand. Its hard enough in a 9 oz batch!

I also used the eglass tape but I used 2, 4, and 8 instead of 6. I would eliminate the 6 oz cloth from the layup they recommended and just use the 12" biaxial. A layer on each side and then one over the top, and I put 2 layers over the top from the pylon back to 6 inches past the tranny mounts. Bulletproof!

There are many different ways to skin this cat and most of them are going to be better and stronger than original. Just sharing my experience.

I was thinking of using biax over the stringer as well, but U.S. Composites said it’s very difficult to work over the top of a stringer and back down. He said it can be done, but it's not user friendly. Did you have any issues with it going over the top of a stringer?

Jeff

Jeff,
Run a router with a round over bit (1/4" to 3/8" R) around the tops of all the wood. It makes it easier to glass over the tops.

I was planning on using a router to round the edges. Does anyone else have any experience using biax over the tops of stringers? Is it worth the hassle?

Jeff

Great Info, Thanks!

TRBenj wrote: I wrapped the tops of the mains in our BFN with biax. PITA and not user friendly- but it can be done.

I routed the tops of my stringers everywhere they were to be wrapped as Pete mentions and I loved the biaxial. In a lot of ways I thought it was easier to deal with than the lighter cloth. As long as it was completely saturated with resin I was surprised at how easily it would make the radius and then stay put after laying it down.
Here you can see the CPES finish, the fillet, and the raius on the edges


Biaxialed over

TRBenj wrote: Im not sure I agree that 3 layers of cloth is a sufficient layup on the stringers though- especially the mains that support the engine. Personally, Id double that (2/2/4/4/8/8) and then add biax or mat up the sides, and wrap the top as well.

This is the schedule I used as well sorry I forgot to mention that there are 2 layers of each cloth tape. I was just impressed by how strong the biaxial is over the cloth.

I did my entire rebuild largely from Pete and Tim's suggestions They know their stuff!