Weight of fiberglass sheet

[Daan]

Hello everyone,
Recently I built my own little boat and I want to cover it with fiberglass and epoxy. I watched on a website where they sell fiberglass and epoxy and I noticed that you can buy different weights per square meter of fiberglass sheet. I am fairly new to using fiberglass so can someone explain what weight I should buy?

Thanks in advance!

 

[BlueBell]

The weight that suits your needs.
You're going to need to do some research it appears.
Come back with specific questions vs general knowledge questions.
OR
Tell us more about the boat with some pictures and someone more generous than I may reply.

 

[Daan]

This is the "boat". I tested it a few days ago and it was able to hold at least 3 people but there were some small leaks but I hope to fix that with the fiberglass and epoxy and I want to reinforce the bottom and sides with the fiberglass and epoxy.

 

[bajansailor]

Daan, the only reason as to why it is leaking is most probably because you have not glassed the joints.
But I see that you have used three very short sections of plywood for the sides, and they are simply butted together on narrow frames, which is not good practice.

Here is a link to your previous thread started in September re this boat - Coating for plywood boat https://www.boatdesign.net/threads/coating-for-plywood-boat.64487/

If you really want to keep this boat, and stop the leaks, then just use glass tape and epoxy along the joints to start off with.
And coat all the plywood inside and out with epoxy.

However I still think that you would be better off quitting with this design now, before spending lots of euros on epoxy and glass.
Start from square one again, and buy a 'proper' set of plans for a boat that will have a proven history and which will be MUCH safer than your boat.

You mention that you had three people on board - what was the stability like?

 

[Daan]

what was the stability like?

It was more stable than you would think. The only moment it felt like it wanted to tip over was when we all decided to lean to one side. To be more certain of the stability I will glass the joints as you mentioned and perform a better testrun.

 

[fallguy]

It was more stable than you would think. The only moment it felt like it wanted to tip over was when we all decided to lean to one side. To be more certain of the stability I will glass the joints as you mentioned and perform a better testrun.

the stability has nothing to do with the joinery


to glass that boat; you need to define the horsepower plans and the plywood thickness, but probably two layers of 6 oz woven on the bottom and overlapping a single layer on the sides, only you cannot do so with square edges, so all the edges need rounding where glass goes

still think it best to build a bit wider boat instead; the amount of freeboard and the odd beam are a recipe for tipping; if you insist on that boat; you could, however design seats that keep people on the centerline more

 

[Daan]

the stability has nothing to do with the joinery

What I meant was when I have glassed the joints there will be no water leaking into the boat so I can test it a lot better.

you could, however design seats that keep people on the centerline more

This was indeed my idea. My idea is to make seats in the exact middle so the weight will be in the middle for the most part.

 

[bajansailor]

Daan, there is so much wrong with this boat - I know that you must have sentimental attachment to it, as it is your design, but realistically it is only 1 metre of beam on 3.3 m. length - or approx 3'3" on just over 10' in length - and even if you make watertight box seats they will not do anything to keep people on the centre (people are unpredictable) - they will just add buoyancy to help to stop the boat from sinking if you capsize.

How much power is in the outboard engine that you are planning on using?
Be aware that most boats have more deadrise near the bow, getting less aft - your boat is the other way around, with virtually no deadrise at the bow, and a fair bit at the stern. This is fine so long as you are going slowly, but if you want to get the boat to plane...... I think it could be 'interesting' re what happens.
It would be worthwhile (if you do keep this boat) to have some buoyancy bags on the sides.
Or even lash a couple of sausage shaped fenders on each side, to effectively turn it into a basic type of RHIB.

Rather than spending (more) money now on fibreglassing the hull, I still think you would be much better off starting from scratch with a proven design.
There are literally hundreds of good small boat designs out there on the internet, and with many of them, the plans are free or cost very little.

 

[fallguy]

I must second Bajansailor.

Build a better boat. Make this one into a shelving unit in the build area.

 

[Daan]

Make this one into a shelving unit in the build area.

Might be a fun idea in the future.

I will see how far I can come with what I've built. I am going to do some tests and see if I like what happens and if everything goes wrong I will try something else.
Thanks for all your advice because I am learning a lot of new things thanks to you guys.
Maybe I will post the results of whatever I am going to do later on on this forum.

 

[hoytedow]

I like the shelving idea. When I retired a boat I always tried to repurpose the materials. One of the TEOTWAWKI hulls became the console in my skiff, which in turn morphed back into a simple rowboat in its decline. The other hull is now a garden bench.
My intent is to say don't become too attached emotionally to a design upon which you can greatly improve.

 

[bajansailor]

Daan, maybe do your 'tests' before you go and spend a lot of money on glass and epoxy.
Boatbuilding is a bit like gambling - it is very easy to get into it so deeply, that you feel you cannot pull out, you have to keep going. When very often it is best to cut your losses early and start again.
I would agree with Hoyte and Fallguy re building some shelves now with the plywood and timber currently in the boat - that is really the best thing that you can do now with those short sections of plywood, and lengths of timber framing.
Then find a nice small craft design online that appeals to you - and please do ask on here if you have any specific questions about any particular design.
It would be useful if you could come up with a statement of requirements listing everything that you want this boat to do for you.
Such as load capacity (re number of people), speed required, and if it is for smooth water only or slightly rougher water capability as well.
And if a design calls for using (eg) 8' lengths of plywood, please do try to get hold of this size, rather than joining 4' sections together.

 

[DogCavalry]

If you can afford the experimentation -because while you can't turn a sow's ear into a silk purse, you can certainly amuse yourself and your audience trying- add a stiffener in the form of a gunwale on either side. Fillet and tape all inside joints, then grind off enough wood outside to round all the corners like a 2.5cm dowel, then glass all. A single layer of 450gm/m² biax will do.
It still won't be a good boat, but it will keep you out of the casinos, and you'll get some epoxy practice for your next boat.