Deck fiberglassing technical questions

[mattb1974]

Great site, been lurking for a while.

Have a few questions about replacing the deck in my 1998 Glastron GS209. I would like to do a good and safe job, as I will be taking my family out in it and I will be selling the boat in a few years. Dont want the next owner to have headaches either.

1. What Plywood to use?
2. What resin to use?
3. What glass to use, how many layers, what weight, wieve, etc.
4. OK to use screws to fasten deck to bulkheads? GRK screws OK?
5. Resin coat on bottom of plywood? 1 coat?
6. what else do I need?

Im sure I will think of more questions as soon as I post this, but if these questions have been answered before please direct me to that thread.


The Story:
Got the boat this year, had it out 1 time to test. All went well except the boat was listing to starboard. Got home started doing research here. Checked the foam under deck and it was saturated. Pulled carpet, cut out deck to about 6" from hull, found waterlogged foam,removed all foam, (12) Contractor bags full, about 400 lbs Deck had a few soft spots. Luckily no rot to stringers, bulkheads, transom. PO was a slob and didnt keep this boat covered.

Glastron GS209
Volvo Penta 5.0 GI
SX Cobra Drive

 

[mattb1974]

Re: Deck fiberglassing technical questions

Ohhhhh..... and how much resin would I need to do the deck? It will be about 70 square feet.

All help is appreciated!!

 

[bigredinohio]

Re: Deck fiberglassing technical questions

These are all questions you'll have to decide for yourself unless you're (re)building by comittee but here are some options.

1. What Plywood to use?
Options are Exterior grade, Treated, Marine, Composite. Your call but I'm using exterior grade. Highly recommend doing research and/or determine what your budget allows for.

2. What resin to use?
Polyester or Epoxy...your call again with price as epoxy is expensive. There are some great threads right now discussing the cause/effect in regards to dangers from exposure to each.

3. What glass to use, how many layers, what weight, wieve, etc.
IMO, I would use a lightweigth to midweight to the underside. I'm pre-glassing both the top and bottom of the deck with 10oz. cloth and then tabbing with the same in tape. Then I'm going to blanket the entire top section with 1708 biax.

4. OK to use screws to fasten deck to bulkheads? GRK screws OK?
You can just use weights to set the deck if it's not crowned too bad otherwise you can screw it down. Once set in place (glued in), you can remove and fill the screw holes with thickened resin.

5. Resin coat on bottom of plywood? 1 coat?
You want to apply at least one or two coats of resin to the bottom then add a light weight cloth. Resin by itself is brittle and the glass reinforces and adds an extra barrior to moisture.

6. what else do I need?
Read some theads in here with the yellow stars. They will give you a good insight as to what you are about to plunge into.

As for quanitity, it depends on the fiberglass you use and the resin. When you order your supplies, they should be able to help you.

 

[ondarvr]

Re: Deck fiberglassing technical questions

Can't add much to that. After you read some more threads you'll have different questions related to details of your project.

 

[prolinews]

Re: Deck fiberglassing technical questions

I personally like good glass on both sides some boats just have resin and csm. If time is not an issue precut the floor set it in the boat weigh it down for a week or so it takes shape then glass both sides top first but don't tab it in yet flip it glass bottom flip it then use pl or pb on top of stringers bulk heads etc. If at all possible I would avoid screws, on some boats there is just no way around it . If you use screws dry fit it screw it remove and make sure to add pb around screw hole in stringer bulk head etc. before final install . A screw that is not square in the stringer can crack the glass and cause delamination of stringer predrill holes for best results . I hope all of my rambling is not to confussing.

 

[andgott]

Re: Deck fiberglassing technical questions

Most everything is covered pretty well already- But a few notes that might be helpful

An epoxy resin is going to saturate wood better- when you put it on the ply to seal it, it will soak and bond better than a polyester. You can still add glass if you want to, but it won't be 'brittle' at all, so there wont be a NEED for it.

As mentioned, the company you get the resin from can help with how much you'll need. 9 gals sounds like a lot, but it is really easy to underestimate it, too- And you don't want to run out right in the middle of your project!

If you use Biaxial and or csm, and are using epoxy, make sure that the cloth is compatible with epoxy- Some of them use binders that are not.

And- Get yourself a laminating roller for when you wet out the glass- It makes things a lot easier for you!

 

[bigredinohio]

Re: Deck fiberglassing technical questions

Most everything is covered pretty well already- But a few notes that might be helpful

An epoxy resin is going to saturate wood better- when you put it on the ply to seal it, it will soak and bond better than a polyester. You can still add glass if you want to, but it won't be 'brittle' at all, so there wont be a NEED for it.

As mentioned, the company you get the resin from can help with how much you'll need. 9 gals sounds like a lot, but it is really easy to underestimate it, too- And you don't want to run out right in the middle of your project!

If you use Biaxial and or csm, and are using epoxy, make sure that the cloth is compatible with epoxy- Some of them use binders that are not.

And- Get yourself a laminating roller for when you wet out the glass- It makes things a lot easier for you!

You have been misleading in your posts with regards to the properties of epoxy.

__________________
Obtained from www.fibreglast.com - (fundamentals_of_fiberglass.pdf)

Introduction
Composites are materials made up of two individual components who?s combined physical strength exceeds the properties of either of them individually. The reinforced plastic composite consists of a fibrous reinforcing network embedded in the cured resin matrix. The thermosetting type resin is a plastic that cures from a liquid to a solid through a chemical reaction of its two components. Once this reaction occurs, the material can not be reformed.

A typical thermosetting epoxy resin has a tensile strength below 10,000 psi and is quite brittle. When such a resin is reinforced with glass fibers the resulting composite can have a tensile strength between 45,000-50,000 psi. It also becomes extremely resistant to impact damage. This high strength for the relatively low weight is the fundamental reason that fiberglass composites are popular. Another significant reason is their tailorability. Since the reinforcement can be added in any direction, layers can be built up which are perfectly oriented with the stress the part is to encounter. This saves additional weight by removing unnecessary material from areas with little stress. Other reasons for composite popularity are how easily these materials can be formed into complex shapes, that they have superior resistance to most environments and they can be used by most individuals without a major investment in equipment.
__________________

In short, it's brittle without fiberglassing reinforcement.

Additionally, I do not find epoxy or poly soak into wood any differently unless you thin the resin with acetone which is not recommended. For doing a deck, I wouldn't recommend around three gallons which is probably overkill for overhaulling a deck. Nine gallons for a deck repair will cost nearly $500!

Lastly, cloth is compatible with both epoxy and poly. It's the mat that is a problem with wetting out with epoxy. You can do but it requires a lot of resin and it doesn't break down the mat like poly.

 

[Knightgang]

Re: Deck fiberglassing technical questions

In reading, I just noticed one item that was not addressed. What thickness os plywood to use for the deck. I know most people use the ACX exterior grade, but what thickness is most commonly used. 3/4 on transoms, at least 2 layers thick, but would you use 3/4 on the floor, 1/2 inch or 3/8. I will probably be re-doing my boat next winter so this is a question I was wondering as well...

 

[andgott]

Re: Deck fiberglassing technical questions

You have been misleading in your posts with regards to the properties of epoxy.

In short, it's brittle without fiberglassing reinforcement.

Yes- It is brittle without reinforcement, however when used to saturate the surface of a piece of plywood, the plywood IS the reinforcement. It is common practice building small boats with epoxy encapulation an no 'glass- I have built several boats that way, and THOUSANDS are built that way each year.

Additionally, I do not find epoxy or poly soak into wood any differently unless you thin the resin with acetone which is not recommended.

Not the case, if you read any of the 100's of technical documents, discussions, and other resources available on the web. Do a google search on epoxy vs. polyester, specifically for bonding wood, you will find 100's of resources that support what I have said.

Lastly, cloth is compatible with both epoxy and poly. It's the mat that is a problem with wetting out with epoxy.

Sorry, I was referring to the Biaxial that was recommended in a prior post- I have run across biaxial that has been 'bound' like CSM with a glue rather than stitched. Sorry if my wording was misleading.

 

[bigredinohio]

Re: Deck fiberglassing technical questions

It's best to replace what was original to the boat. The standard for most boats is 1/2" for a deck.

 

[Knightgang]

Re: Deck fiberglassing technical questions

I think that may be why I boat sits so low at the stern while in the water. The PO of the boat replaced the floor, and installed a 36 gal fuel tank under the deck. The deck is 3/4 ply and the tank is under the floor from the CC to the splashwell. With a full tank, that is alot of weight in the stern and almost none in the bow.

That is one reaosn I want to redo my boat. I want to build a different console, move my tank forward, rebuild the front cast deck to add forward storage and bring my batteries to under the console.. I hope to unclutter the floor area in the stern and better distribute the weight around the boat.

Did not mean to hijeck this thread, just added my thoughts...

 

[ezmobee]

Re: Deck fiberglassing technical questions

I put a 3/4" floor in my Jupiter and love it. I'll be going with that for the SS as well. Incredibly solid. The SS currently has a 1/2 floor and it's much too springy for my tastes.

I think on a glass boat I'd go with thoroghly dried PT ply.