Need help and advice - fiberglassing new wood boat

Hi
I have just completed the wood part of my home made boat and I am preparing to fiberglass the exterior. My original plan was two layers of cloth and resin. I contacted fiberglassite.com and they advised me to use fiberglass mat with two layers on the bottom of the hull and then sealing with marine paint. I am somewhat concerned with the weight as it is heavier than I had hoped. I would like to hear from anyone who has experience with this and would also like advice and opinions on marine paint. I won't be able to complete this project until next Spring or Summer as the weather is starting to turn but I still have plenty to do on this project a trailer to build and the motor. I am planning to use an 18 horse Briggs vertical shaft and the bottom and possibly the mid section from an outboard. More on this later

Thanks in advance
Dave T

 

If using epoxy, you don't need or want any mat in the laminate. If using polyester or vinylester then you don't have a choice and mat must be in the laminate to bulk it up.

Neither vinylester and especially polyester stick very well to wood, more importantly they don't waterproof it, which frankly is the whole point. If using these materials, I'd strongly recommend you switch to epoxy for the exterior sheathing.

I'm not surprised "Fiberglasssite" has suggested mat for your sheathing. They'll assume you also will buy their epoxy and since it take 3 - 4 times as much epoxy to wet out mat, as it does the same weight cloth, then they've just made a good business decision. Their epoxy is a good product, but not priced very well compared to other reformulators. In fact, I suspect their product is just a rebadged name brand.

What boat are you building and what sheathing schedule do the plans recommend?

Also welcome aboard . . .

 

Thanks PAR

I'll do some more research on epoxy. I'm guessing that you have worked with this so I would like more details such as what weight cloth to use and any other hints you can give me. I was planning on polyester resin and that was I guess why fiberglasssite said I would need to use mat because the resin needed to be that thick to be waterproof. Can you tell me where to look for epoxy resin at a reasonable price. If it costs twice as much and I only need half as much it would be the way to go. Here are some more details on my homemade boat. There are no plans only my notes and drawings in a notebook it is built from my own ideas of what should work. It is a twin hull design this allows the boat to be fairly wide and the bows to be shorter and still be well pointed. The twin hulls are separated by a 7" tunnel. It has a 5'x7' main deck and a raised front deck extends over the twin bows. This is the first boat I have ever built so I don't claim to know what I'm doing but this has never stopped me in the past. If you get a chance check out our website at thomas-superwheel.com and you will see a lot of the the things I have designed and built

thanks for the reply and keep in touch
Dave T

 

The main deck is 5'x9'

Dave T

 

Epoxy resin?

Looks like epoxy resin is the way to go. I briefly looked at automarines site and a couple of others but I'm still confused as to what resin and weight cloth I need and how much. Do I need more than one layer of cloth. My boat has a surface area of about 205 square ft. to cover it completely. any suggestions and advice would be greatly appreciated.

Dave T

 

You will need to provide more info than you have to get a sensible answer ... pictures are worth a thousand words

 

greeting shawn here. i know just enough to be dangerous- im not exspert
im not real sure what type a boat you are building? but for paddelcraft of any sort i would never use mat, its way to heavy and has poor strenth weight ratio. cloth is best but if its too exp/ you want build up? boat is bigger and motor powered maybe some roving layer betweem is an decent compermise...........

watch your bonding to wood, ive never got good bonds to polyester- epox is surpose to excell there

 

Need expert help

I need to contact someone with experience in using both polyester and epoxy resins. I've contacted fiberglasssite and got pricing for polyester and mat. Evan though they sell both they reccomend polyester and 1.5 oz. mat with two layers on the bottom of the hulls. this would take 25 yds. of mat 10 gal. resin and 2 gal gel coat at a cost of 570 bucks plus shipping and would add about 120 lbs. to the boat which I don't like. To coat the boat with epoxy would be cheaper and lighter if I used 1 layer of 6 oz. cloth and resin but I have no idea if this would be Ok. Again the total sq. footage for my boat is about 205 sq. ft. that needs to be covered it is all wood. If anybody knows of a good place to buy resin and cloth let me know fiberglasssite is the cheapest Ive found.

Dave T

 

As Mr. Watson has suggested, without considerably more information on your project recommendations to a laminate schedule is imposable. As to with resin system to use, well the hands down preference is epoxy on wood. This isn't debatable, it's well establish fact, regardless of what Fiberglasssite, might be trying to blow up your butt. As to where to get good prices, Bateau.com and Epoxyproducts.com are about the cheapest for epoxy and supplies.

 

Dave T

Are you counting on the fiberglass for strength? If your wood structure is strong enough without it, just go with 6oz cloth and 3 coats of epoxy. That will seal the wood and provide waterproofing until you damage the glass by scraping along a rock shore. then you need to repair the damage after drying out the wood. If you want more damage resistance add another layer of cloth.

If you are counting on the glass/ epoxy for strength, everyone who asked for more details of the boat are right. No one can help you without lots of information.

How much will you have sunk into the boat cost wise when you finish? Typically it will be enough that skimping on the glass / epoxy is wasting the money you have already spent. I suggest you use one of the 3 or 4 more popular epoxys rather than look for the cheapest thing you can find. Mostly I have not used the cheap stuff, so someone else with experience may have a better opinion.

Don't ruin your boat at the last minute. However, some boats have lasted a long time (with maintenence) with just paint and TLC.

Good luck

 

All of the lower cost marine grade epoxies I've run into, are acceptable and comparable to the major formulations.

6 ounce fabric is a finishing cloth and doesn't offer much by way of abrasion resistance and as noted zilch (technical term) in strength. A heavier cloth or preferably Xynole instead will offer better abrasion qualities.

 

Par,

I'm building a cedar strip kayak right now. 6oz cloth on the inside and outside of the 3/16" thick hull is the only real strength there is. From experience on a similar construction for a row boat, epoxy by itself is next to useless compared to epoxy and 6oz cloth for abrasion resistance, and painted wood would have been much worse.

As I said above, if the strength is primarily in the wood, then there needs to be a lots more information provided. If this is to be a military landing craft being driven up on the beach, then I accept your statement that 6oz is too light for abrasion. It does depend upon the usage of the boat.

Perhaps you would like to suggest another lamination schedule for my Kayak? If so please estimate the extra weight and cost you are adding to my 35# (designer estimate) kayak. 18' 4" long by 21" wide, 3/16" "planking", used for lakes and will be cartopped.

I had a similar experience with a plywood Tornado catamaran. Also a light weight boat which had a significant amount of care in use.

As stated by you and others above, more data is needed before making statements about "zilch" strength of 6oz cloth. BS is also a technical term, appropriate in this case.

Thanks for the comment on the lower cost epoxies.

 

Par

I left out the fact that the Tornado was 4mm ply (Occume - 0.160") with 6 oz cloth inside and outside, similar to the kayak. When I sold it it was 20+ years old and in need of sails but the hull was still sound - with appropriate TLC.

 

Thanks to everyone who has or will reply

I am going to go ahead and go with epoxy and 6 oz. cloth. My boat would be plenty strong enough with out sheathing I am only concerned with protecting the wood from water. I followed the golden rule for engineering which states if any doubt build hell for stout. I'll check out the sites mentioned for pricing. If anybody can tell me how much epoxy resin it takes to wet out 25 yds. of 6 oz. cloth and base and top coat about 205 sq. ft. I would appreciate it

Thanks,
Dave T

 

Check out the West System Website ( http://www.westsystem.com/ss/estimating-epoxy-amounts/) for an estimator.

West is one of the name brand high dollar epoxies, however, the same amount would be used for most any epoxy.