New stringers and floor question on fiberglass resins?

[wguttrid]

Hi guys in the process of a restoring a 1979 18' Wilker boat. Right now the floor has been ripped up and stringers removed and also managed to grind down the old fibergass that was used to hold the flooring and stringers down.

Here is my plan of attack for next stages once I have the new stringers and flooring cut and ready for install. The flooring will be exterior grade 5/8" plywood, and cross members will be pressure treated 2x4 and stringers will be 5/8' exterior grade plywood cut to same dimensions as orginal.

1.) Cover the flooring, stringers, and cross members with finishing polyester resin that has been thinned with acetone to allow it to really soak into the wood.
2.) While the 1st coat is still tacky apply a second layer of finishing polyester resin.
3). Maybe apply a 3rd coat (not sure if really needed).
4.) Use an epoxy resisn and 3-6" fiberglass tape to attach the stringers and cross members to hull and join all together by covering each seam and bulkhead.
5.) Use an epoxy resisn and 3-6" fiberglass tape to secure the flooring to sides of hull.
6.)Use epxoy resisn and fiberglass top side of flooring with 1.5 oz. fiberglass mat (1-2 layers).
OR
5.) Use fiberglass resisn instead of epoxy.
6.) Use fiberglass resisn and fiberglass mat.

Trying to save a bit of cost by going this route and also I understand that epxoy is a true adhesive so hoping I can save a bit on the bottom hull prep work (grinding and more grinding) of attaching stringers to hull.

I would like to use polyester resin (cheap) and f/g for the top side of the flooring but understand I will really need to grind down and prep the sides of the hull and grind down the old layer of fiberglass used to hold the floor down.

What are everyones thoughts?

 

[clockwatcher]

Re: New stringers and floor question on fiberglass resins?

I think that no matter what you use, you need to grind the mating surfaces and at least 6 inches on either side as smooth as possible. That way your glass will lay down nice and smooth. Otherwise you will get air bubbles and voids instead of a good solid bond. I know that grinding stinks. Just protect yourself and mix up a stiff drink.

 

[jonesg]

Re: New stringers and floor question on fiberglass resins?

Use polyester laminating resin, not finish resin.
Order it online for best prices.
You wanna use wax free resin.
Laminating resin stays tacky for a day or two but it will cure dry to the touch after that, especially if it see's the sun. Its nice not to have to sand between coats, just keep sloppin it on almost as fast as you can cut mat.

Epoxy is nice glue but you don't need to use it, especially if money is key.
On large surface areas thinning with acetone is a waste because it will gas off before you can utilize it, I've done it on small areas but its gone before I can get all the resin brushed on. I like to pour it out and use a big 4 inch cheapy brush to spread it, a plastic scraper is ok too, once you apply cloth a roller is better ...but I still resort to the big brush.
Save the acetone for cleaning your tools.

Cutting your own strips of cloth is cheaper than tape, but glass tape is nice to work with.

 

[tschmidty]

Re: New stringers and floor question on fiberglass resins?

A solid plan, the only thing I would change is to make sure you put at least one layer of colth on the bottom side of the decking for waterproofing. And you shouldn't need to thin the resin just make sure you lay it flat and you should be set, not too thick.

 

[wguttrid]

Re: New stringers and floor question on fiberglass resins?

Hi guys thanks for the messages...yep grinding is fun dirty sweaty work....respirators and safety glasses all the way.

A grinding question..do I need to grind the fiberglass that was used to attach the stringers to the hull completely down to the fiberglass hull or do I only need to smooth out.

Drew up a quick cross section to better understand what I mean.

 

[wguttrid]

Re: New stringers and floor question on fiberglass resins?

Think I will go with the polyester resin. Will I be able to use laminating resin for everythng I need here or should I pick up some finishing resin?

Might make my own tape to save some cost.

For the top of the floor should I use mat or cloth and how many layers should I build it up?

 

[ondarvr]

Re: New stringers and floor question on fiberglass resins?

jonesg covered most of it.

Don't mix and match resins.

Don't thin resins.

Use glass on all surfaces.

5/8' ply may be too thick, most use 1/2, but just replace what was there to begin with.

The surface prep is the same for both resins, so there's no time savings.

Do a search here and read the huge number of threads on this subject, they will walk you right through it.

 

[wguttrid]

Re: New stringers and floor question on fiberglass resins?

Will heed the advice and put one layer of glass on bottom side of floor decking.

 

[Greg Mrozinski]

Re: New stringers and floor question on fiberglass resins?

wguttrid,

One other note, you really don't need to sand/grind bewtween layers of applied glass. At most a quick wipe down with some acetone if dust collects on it between coats. On my boat I did all the prep grinding and totally cleaned everything real well and washed the surfaces down with acetone before starting to lay the glass. but once I started laying on the glass I kept on going until the end. I didn't have any problems with bonding. Finishing glass work will require sanding and smoothing before paint, but that's understood.

For the underside of the deck you could do two things - glass it as the folks here suggested or just give it a good coat of resin. It's up to you and depends on how long you plan on keeping the boat. For the top of the deck, glass will add stiffness, strength and waterproofing to the floor. Cloth will give you a smoother finish than CSM. More layers give longer wear protection as well. Just watch how much weight you are adding. Have fun.

 

[rockyrude]

Re: New stringers and floor question on fiberglass resins?

All of the important points except one have been covered, don't use pressure treated. if you read the threads on the subject you will find that your lumber needs to dry pressure treated comes pretty much wet, it also eats most fasteners will probably consider using.

 

[wguttrid]

Re: New stringers and floor question on fiberglass resins?

Thanks for all the advice guys...intend to keep the boat next couple years or so and sell off...so thinking I will only glass the top and resin the underside.

Will match up the lumber to old...boat orignally had 5/8' stringers and 1/2' floor. Pressure treated is off the list now..was another thing I had on my list to research but thanks for the quick tip rockyrude!!

How many layers op glass would everyone sugguest for topside of floor deck if I intend to use 1.5 oz mat? I was thinking 2 layers from what I have read on other threads.

Thanks again guys it is very much appreciated.

 

[bugzy_1]

Re: New stringers and floor question on fiberglass resins?

I agree with the rest of the guys. DONT use treated lumber.
Marine ply is best if you can afford it. Otherwise I would use at least a B-C ext. panel. CDX is not designed to carry a load and has open knot holes and defects that make it hard to glass. I'm using 3/4'' marine for stringers,etc. and 1/2'' for the deck w/ 6oz fabric on both sides. Bed the stingers in PL poly. const. adhesive, glass over. I used epoxy resin from U.S. Composites, best price I could find.
I think epoxy is abetter choice for repairs because you never really know what the hull is made from. Pobably is Polyester resin and poxy will adhere better. Just my opinion!
Happy building!
Scott

 

[ondarvr]

Re: New stringers and floor question on fiberglass resins?

Pressure treated works fine in boats, I would say most of the small boats (at least my customers) made now use it in construction. As far as eating metal, you shouldn't be using anything but SS hardware anyhow. There are several brands of PT that are made just for the marine industry, the big difference is that they have been kiln dried.

http://www.greenwoodproducts.com/moreproducts.htm

999.9999999% of the boats made use polyester, I don't think there has been a single boat discussed on this forum that's been made from epoxy. Either resin will work fine, just coating the underside of the deck with resin is sort of a waste though, both types will crack when stressed or with age (polyester sooner though) without glass.

I'm not saying this to slam anyone, just so that inaccurate information doesn't get repeated so many times it becomes fact.