Fibreglassing a marine ply hull - costs

[kitkats]

I'm very new to boats, so please forgive any lack of acumen.

I'm thinking of buying a boat to convert into a weekend-houseboat. It will be permanently moored in shallow (0 - 16ft) sheltered coastal waters (an estuary).

I have come across a hull which I think may be suitable, a 24" x 9" motor yacht (I think). The present owner has suggested that the whole hull be fibreglassed, which seems sensible.

I'm looking for advice on what type of glass would be best, and roughly how much I'd need, and how much that would cost. I'm based in the UK so if anyone knows of the best suppliers here that would also be useful.

Thanks in advance.

http://i325.photobucket.com/albums/k390/stevekrazykats/boat.png

[apex1]

http://www.r-g.de/en/

cheapest and best you will find...

[kitkats]

I only just noticed the sub-forums... Guess this should be moved to the Wooden Boat Building and Restoration forum. Apologies. Perhaps an admin can move the post?

[FAST FRED]

The present owner has suggested that the whole hull be fibreglassed, which seems sensible.

WHY?

Slathering on a layer of GRP does almost nothing for a leaky teaky in terms of adding structural strength , it mostly adds weight.

The GRP also give problems as the wood wants to move , expand and contract which breaks the bond to the GRP, even is EPOXY (the only choice) was used.

I would contemplate weather the boat is suitable AS IS , a wooden vessel, and if so simply maintain what you get.

FF

[petethai]

Doesn't wood contract and expend only when level of moisture is changing.
If we apply epoxy over the wood we make this level constant.
The movement from the mechanical stress, can make some damage.

[FAST FRED]

Doesn't wood contract and expend only when level of moisture is changing.
If we apply epoxy over the wood we make this level constant.

Doesnt it rain snow and at rare times the sun shines in your place?

Any and every hull or deck penitration is simply sealed with a goop which may pass moisture , new or old.

The downfall of the various Tiawan boats with teak overlay decks was the hundreds of fastenings, which eventually watered the incapsulated ply below.

YRMV

FF

[kitkats]

I'm not planning on this boat being powered, strange as that may seem. So the internal stresses would be less than normal perhaps.

I'm not planning on the GRP adding any strength, and adding weight could even be an advantage if it increases her stability. The reason for coating it in glass and epoxy would be to provide greater scratch resistance and seal the hull so that I don't have to take her out and repaint her every few years. It would be a thin coating not an inch thick. She will be moored up near a marsh, beached roughly half the day. I'm planning on towing her out there and then ideally leaving her in situ for as long as I can. So the idea is to reduce the frequency of maintenance.

I've not heard people suggest that marine ply would come away from a GRP coat before... but perhaps that is a danger.

[rwatson]

Marine ply and GRP are a bad mix. They separate eventually because Polyster resin permists water to pass thru it. There are dozens of discussion about this in the forums.

Epoxy over a sound surface is the most reliable way, and adding even very lightweight fibreglass will vastly improve the epoxy lifespan.

But thats not enough - you also need a good paint to keep the UV off the Epoxy (or Polyester) - so that needs to be factored in also.

[PAR]

GRP structures include epoxy folks.

Plywood should always be sheathed in fabric, if good durability, increased abrasion resistance and water proofing is desired. Of course as has been mentioned, epoxy is the choice, though if done properly polyester can offer an option. This said, polyester has it's issues and personally I would never use the stuff on wood, but if you happen to have barrels of this goo laying around, then it too can be employed, though you'll pay a weight and application difficulty penalty using polyester.

The photo you've posted Kitkats, doesn't appear to be one of a plywood boat. Are you sure it's plywood?

Since you intend to moor the yacht, it should have a fairly thick sheathing, to protect the wood from the likely infrequent haul outs, it'll have to tolerate for the remainder of it's life. I would recommend at least 24 ounces of fabric sheathing, in multiple layers on the outside of the hull. A considerable increase in abrasion protection can be had if you use Dynel instead of regular 'glass fabrics. It will use twice as much resin, but it is a lot tougher then 'glass.

[Fanie]

Polyester is not the material to use for glass to wood, you have to use epoxy.

I had a discussion recently with someone on this. The polyester does not penetrate the wood sufficiently thus does not really seal it and the glass may delaminate from the wood due to a more 'shallow surface' bond.

Epoxy does make for better penetration in wood and a better seal and bond process is achieved, even better still if you can vacuum it to the hull.

[petethai]

[QUOTE=FAST FRED;295126]
Doesnt it rain snow and at rare times the sun shines in your place?

It looks like you have too much sun.
Some snow can help.

[Commuter Boats]

Gentlemen, there is a completely different track on covering wooden boats that does deserve some consideration. Now I'm not suggesting that somebody builds a beautiful cold molded 44 foot hull and then goes after it with polyester but a vessel that has put in a good service life and is a little on the tired side can have a good bit of life restored with a structural polyester-fiberglass skin applied. There are enough successful examples that the technique should be given consideration when the vessel warrants it.
A brief rundown on the technique, replace rotten wood, removed through-hulls fittings, apply a minimum laminate of one mat and one roving, mechanically fasten the laminate to the wood, complete the structural laminate in such a way as to prevent freshwater from getting to the wood. Although not wet the hull is not dried ( kept as swollen as it will be) and little effort is done to promote bonding. There is at least one boat ( I think it was a 76 foot herring schooner) were a product similar to 3M 5200 was troweled over the hull and C-flex was laid into it and wet out, fastened, and overlaid.
There is a good book on the subject and I have scanned the cover.
Gerald

[kapnD]

I like the idea of the 5200 layer between the wood and glass--an expansion joint of sorts that adheres to both sides yet allows some movement without delamination. Still sounds expensive though.
Getting back to the original question/requirements, it looks more like a floating dock than a boat, so
Since weight is not an issue, only strength, how about cement plaster?
It can be mixed with polymer admix to be very strong, somewhat flexible and quite waterproof. It is also sprayable, could be a one day job.
Also, if it is to be stored in the same location always, you could build a cradle on the seafloor for the boat to rest comfortably on at low water. A couple of pilings to guide and moor it, and there's your floating concrete dock!
Good Luck, Don

[cowobyisking]

I am learning about boat building, and I wanted to know if I can only locate marine plywood online or can it be found in most hardware stores?

[kitkats]

Just wanted to say thanks for all the replies. It sounds like epoxy is the way to go, although I'm hoping now to simply find a fibreglass hull instead. If I don't and I go and see this boat, I'll maybe post back here for more specific advice on the different types and weights of fabric, as there seem to be far more available than I realised.

If anyone cares to comment on the surface preparation, that might also help. Presumably ALL the paint would need to be sanded off, and back to bare ply - to what grit? C-Flex etc etc?

[mark775]

Par - it just looks like it has shape because of the reflection - look again.
Cowobyisking, in Texas, one can purchase Joubert okume plywood which, IMO is the best for most purposes. Okume, itself, is not that rot resistant, but this stuff has a fungicide that makes it wonderful. Marine plywood, however does not exist as we came to know it, which is doug fir plywood made in one Simpson Timber plant in Oregon. There are other plys that are suitable for some projects just steer clear of anyone trying to sell you exterior grade ply ("It's just as good", "The glue is what matters", etc.).

Frome the Glen-L site;
Marine-grade plywood is made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better. B-grade veneer may have knots but no knotholes. A-grade veneer has no knots or knotholes. Both A and B grade may contain wood or synthetic patches. Panels are sanded on both faces or Medium Density Overlay (MDO) or High Density Overlay (HDO). The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a "premium" panel grade for use in situations where these characteristics are required. It is available in 4x8-foot sheets of 1/4, 3/8, 1/2, 5/8 and 3/4-inch thickness. Sheets up to 5x12-feet are also available. Available grades are A-A, A-B, B-B (face-back), MDO and HDO.

Marine-grade plywood is not treated with any chemicals to enhance its resistance to decay. If decay is a concern, it should be pressure-preservative treated to an appropriate standard.

The detailed description of veneer grades and Marine-grade plywood is contained in Voluntary Product Standard PS 1-95 Construction And Industrial Plywood.

Sample Specification For Marine Grade

APA 3/8" B-B Marine Grade 4x8 10 pieces

Other Exterior Plywood Grades

Plywood panels rated as EXTERIOR but not Marine, such as A-B, A-A or C-C EXTERIOR, may contain any other permissible species and contain C-grade veneer. Unless specially improved, C-grade veneer is permitted to contain knots and knotholes up to approximately 1-1/2 inches across, and the inner plies may have core gaps up to 1-inch wide.

Exterior glue probably cannot withstand submersion. Gaps, filled knots are a bad thing.
Also, note that it says voluntary product standard. It is the same with BS1088, as well. One needs to trust who they are dealing with. If your local search fails, try Boulter, http://www.boulterplywood.com/

[SamSam]

Finding another boat is a good idea as there are a lot of them available dirt cheap, especially considering you are not planning to move it around.

Commuter Boat's post #12 is the one you would be doing best to follow if you go ahead with the boat in your original post. Here is a thread similar to the same situation as yours, post #13 is mine and describes the process a little.
http://www.boatdesign.net/forums/wooden-boat-building-restoration/advice-hull-restoration-28953.html
In the book, and Vaitses is talking about boats that are actual commercial working boats or pleasure boats that are actually used a bunch, he says that a chemical bond between the wood and frp (polyester resin) is not required, the mechanical bond of the staples is enough. He describes that on some boats, as the wood drys out, being no longer in touch with the water, the boats end up weighing less and actually floating higher, the extra weight of the frp being less than the water that evaporates from the wood.

[mark775]

I don't even want to get into it but sheathing this thing with stapled fabric in poly, troweled 5200, etc., is counter to everything I know (When troweling 5200, make sure to let someone know to come check - you could end up a permanent fixture somewhere).
Notice the cribbing under that boat. To my eyes, it looks like a piece of plywood on end is keeping that thing upright...

[SamSam]

That fin does look like a weak link.;)

We stayed on Homer spit one night in '95 or so, in the furthermost motel on the end in the furthermost room in the motel. Nice.

I took a series of photos to get a panoramic picture of the marina, where there were what seemed like hundreds of small boats lined up on the first docks. I don't think any two were alike, I was amazed by that and everything else in Alaska.

[kitkats]

I'm not sure about how the keelband is constructed but the chap did say the bilge keels were inch thick solid steel plate..!! I thought that sounded strange but I'm no expert.

[hoytedow]

Cowobyisking,
Specialty lumberyards located in coastal cities like Galveston, Port Arthur or Corpus Christy should have what you are looking for. Specify AA for hull or AB for superstructure/decking and expect to pay more for the superior quality over normal exterior grade plywood. Copper napthanate wood preservative is something you should research also.

[cowobyisking]

Okay so what you are saying is that I could more then likely just go to a boat repair shop and buy the plywood from there, which would probably be easier then ordering it online. Can copper napthanate be used in conjunction with glass.

[Ike]

PAR and I have differed in the past on this fiberglass over old wood idea for extending the life of a wood hull. My take is that it would be better in the long run to fix it properly rather than try to save money by glassing it and then waiting for the almost inevitable rot to set in.

However, if you are going to glass it, do it right as many have suggested above. Use a good epoxy resin and make sure the glass is well bonded to the wood.

Wood does expand and contact even when coated on one side with fbg. just the moisture in the air will cause expansion and contraction. Wood is aliving thing, and to completely stop the exspansion contraction you have to completely seal the wood inside and out such as in the WEST approach.

Also, vitually all boats leak, or get water in them. (Even mine, which I have always prided myself on a boat that doesn't leak.)

So, if you don't buy a fiberglass boat, and do buy this one, get it done right. Spend a little extra up front and it will pay you back in the long run.

[hoytedow]

I did not purchase my plywood from a boat repair shop. I purchased it from a lumber yard in Tampa that does business with boat repair yards and sells the stuff retail. The boats I built were painted with copper napthenate and allowed to dry before I fiberglassed them. The boats were under 16 feetlong and I had no problem with delamination due to the treatment.

[cowobyisking]

Okay thank you for all the great incite, you all are a lot of help thanks.

[scotch&water]

Hello all you great boat craft folks, we are finishing a wood boat project and coated with Epoxy 2 sheets of boat cloth and paint will be polyurethane. I ran on to a web of Stancraft Boats Post Falls Id. Sid over on the other side of the mountain builds great looking composid wood boats with 5200 must get the stuff in 55gal drums and make 3m smile, check it out. Well its short of 1800Hr and wine time! Fritz