Hey pv,

Your best chance at getting advice and suggestions would be if we had more information about what you were doing and what kind of advice you actually want.

Also, keep in mind that this is primarily a support forum for CLC products so most of the folks here, while quite familar with stitch and glue kayaks, canoes, rowing and sail boats and even the occasional power boat, may not have much experience with a small pontoon boat.

That said, since CLC's product line includes tools and materials, as well as boat plans and kits, there's lots of folks here that could help out with the how-to's of boatbuilding. Just give us a bit more info and try and tie it to something that people on this site are likely to have run into.

Have fun,

Laszlo

My main concern is with the use of Epoxy and Fiberglass which I have no experence. I need a experienced estament for these materials. Boat will be built with 3/4" & 1/2" marine plywood, 4 - 10' runners the length & 5 - 6' stringers across.

Demensions: 10' L x 6' W x 1 1/2' H total.

Pontoons: 10' L x 2' W x 1 1/2' H.

Spread between pontoons: 8' L x 2' W x 3" H.

At least you have an idea of what you want to build pv, that's a good place to start.

Looking at those numbers I hope you're prepared for what this project will weigh once completed. There's a lot of plywood lurking behind those dimensions, then adding fiberglass and epoxy's gonna bump the poundage higher yet.

If, eventually, you don't gain answers here, there's another forum (membership's necessary to post to but membership's free) run by the folks who put out Woodenboat magazine.

Contributors there from all over this wonderful globe we inhabit, their collective experience with boats (in general) and fiberglass + epoxy for building them (in particular) ought to help fill any gaps in your current knowledge.

pv,

Here's a link to CLC's Shop Tips for Working with Epoxy and Fiberglass. It should answer a lot of your questions.

As spclark points out, you're building your boat like a tank, so you won't really need fiberglass & epoxy for strength. All you need is the abrasion resistance and sealing. For that, if it was my boat, I'd use 6 oz cloth on the bottoms where the pontoons are most likely to scrape and 4 oz everywhere else. if you think that certain areas will not have to stand up to scraping against docks, other boats or people walking on them, you could even skip the glass and just use an epoxy coating. Be sure to varnish or paint the surfaces. Bare epoxy doesn't like the UV in sunlight.

Browse through the Shop Tips (all of them, not just the epoxy/fiberglass section). There's lots of good info on boatbuilding in general to get you started right.

Laszlo

   Glen-L has plans and a forum that deals with these

https://www.boatdesigns.com/12-28-Huck-Finn-trailerable-pontoons/products/169/

http://www.glen-l.com/phpBB2/index.php

   sugestions as to material thickness

The image is invisible without a google login.

Laszlo

It's 'invisible' to me, despite my being logged into google.

Error says '...can't be loaded, try again later.'

Doubt I'll bother. 

   WHAT SIZE PLYWOOD DO U RECOMMEND?

Still can't see the picture, google still wants me to sign in. Is it supposed to be plans for your boat?

Laszlo

   https://www.dropbox.com/t/AeN5BU1u5gD3OqTW

OK, I was able to download the image from dropbox. I've hosted a copy on my personal server so that it can be displayed here so that other folks can see it and weigh in if they feel like it. Your question is, based on the "built like a tank" comments, what thicknesses of plywood do we think that you need, right?

Give me a day or so to think about this.

Laszlo

Click on the picture to see a larger version. Right click on that and select view image to see it full-sized.

Laszlo

   Thanks much.

I used the Dropbox link earlier to look at that plan; Laszlo's picking it up & hosting it gives it a wider audience....

All that 3/4" ply + fiberglass & epoxy's gonna be pretty heavy, like I said earlier.

I have to wonder too if, with that dry weight, what kind of displacement it'd have once afloat? Load capacity?

Little if any apparent reserve buoyancy in that slab-sided design... stability's going to be minimal.

What kind of deck layout's planned?

What's the anticipated use

Propulsion?

Should I eliminate the 3/4" ply and build it with all 1/2"ply?

The pontoons will each be filled wilh styrofoam for additional bouyancy.

Deck will be carpeted with 1/2" aluminum railing all around fitted with 2 pontoon style chairs and 2 pedestal swivel fishing chairs.

Boat will be used only for fishing and propelled with a bow mounted trolling motor only.

   I'm all for having fun in the shop, trying out new ideas, gaining satisfaction from building it myself, etc., etc.

And adding the caveat that this is only one person's unsolicited opinion and you've probably had all these thoughts yourself and rejected them for your own good reasons anyway...

Why not just buy yourself a beat up old aluminum jon boat for less than a couple hundred $$ (in other words, much less than you'll spend on materials per your planned wooden boat). Or even a new one?  Or, still a deal if you start thinking about the labor of your build, maybe one of these for $799, which is basically what I think you are planning to make on your own: https://www.dickssportinggoods.com/p/field-stream-angler-10-fishing-boat-21fnsunglr10fshngpso/21fnsunglr10fshngpso?sku=21820646&camp=CSE:DSG_92700048853077568_lia_pla-824969399649&segment=&gclid=Cj0KCQjw1PSDBhDbARIsAPeTqrf0OsiBm6dWJfxEs6563M50N32-8PU6dhm2ExL3Z2tE6V3LJxtwgWEaAgDiEALw_wcB&gclsrc=aw.ds 

You'd be out there on the water fishing in no time.  With plenty of time, and mabe even some money, saved to put towards building yourself a nice CLC kit of your choice?

And with my unsolicited 2 cents added, if you go forward with your build, all the best to you and I hope it turns out well.

 PV, I'm adding another note just to ensure that you understand the physics involved.  Filling the pontoons with styrofoam doesn't add any buoyancy, in fact it minimally decreases your reserve buoyancy due to the small added weight of the foam.  Buoyancy will be determined solely by the dimensions (displacement) of your pontoons.

There will be positives and negatives with the foam fill idea.  The positive is that the thing will be basically unsinkable should a pontoon leak.  The negative is that you might be increasing the chances for decreased air flow and thus for rot.  If your plan is to completely seal your pontoons with no access ports for bailing or drying, that is OK so long as you never have even the smallest leak.  In my opinion is almost invevitable after some period of use - a seam will get a hailine crack or whatever.  So, if it were me, I'd think about building in some access ports on top of the pontoons so that they could be opened, inspected, dried out, etc..  (Even a couple of these will add some cost...)  But then again, your current design doesn't include drainage (limber) holes between your frames, and even with limber holes I dont think you'd get good drainage between compartments. 

I don't think there are easy answers, just things to think about here.  Based on experience I get VERY nervous about any sealed wooden compartment.  Taking liberties with the quote from Jurassic Park - "Rot finds a way."

PVS what Bubblehead's telling you truly is worth your careful consideration.

He's pointing you to a solution that will provide you with the recreation you want, for about the same out-of-pocket costs, as well as a properly designed and constructed craft you'll enjoy.

If you still desire the experience of building something with wood and epoxy, build one of CLC's kits. Hundreds have been built by folks with as much desire and likely a few with as little experience as you claim.

It's fun, it's not at all hard, and the forumites who come here will have answers to what questions you might have along the way.

OK, so I've had a chance to look at the plans and think about the question of scantlings for the boat. First off, I am not a professional boat designer. This advice is worth at least 50 times what I'm charging you for it, you take it at your own risk. If you really want to be sure of what you're getting, contact CLC and use their consulting design service. There you get some truly excellent and inspired professional designers who can help you out. Of course, they'll charge you, but that's how they feed themselves.

Next, there's a disagreement in the dimensions. The length at the top of the runner is 9'-10-1/2", but if you add up the dimensions at the bottom of the runner you get 10'-10-3/4" and the text refers to a 6'x10' top. Based on all that I'm assuming that the 9'-10-1/2" number is the correct one.

I'm also assuming that the boat will draw 3" so the total displacement comes out to be 600 lbs. That means that everything - structure, propulsion, furniture, people, beer, fishing rods, etc. - combined needs to weigh 600 lbs. Every 200 lbs above that takes another inch of depth. So, for example, if you go to 1/2 ton of displacement you'll draw 7 inches, not 3.

That is one heavy boat as drawn. Assuming DIY store mixed conifer plywood, the framework, a 6'x10' deck and the skinning for the pontoons is 430 lbs, leaving only 170 lbs for all the other stuff mentioned above.

You can immediately reduce that to 290 lbs by using Okoume plywood, like the kind sold here by CLC. That will leave you 310 lbs for everything else. Note that these weights do not include paint, fasteners, additional wood for chines, etc. This is one heavy boat.

The next big weight reduction would be by using less wood. This is a plywood scow, so it will never go fast. Unless you're extremely unlucky or extremely foolish, it will never operate in rough water, either. The most it should have to stand up to is the wake from an inconsiderate motor boater and grounding on the bottom. Because of this you don't need such thick wood. If it was my boat, I'd use 3/8" plywood for the frame, 1/4" for the skin and 1/2" for the deck. That would give 250 lbs in pine and 170 lbs in Okoume.

If the thinner wood makes you uncomfortable, you can add lightweight strength by putting a sheet of 1/4" plywood under the connecting frames between the pontoons. That will form a box girder with the deck that will hold the pontoons together for only 13 lbs pine and 9 lbs Okoume.

The other thing you could do is run a piece of 3/8" plywood on its edge down the center of each pontoon bottom. Make it the same height as the bottom frame and use nesting notches to lock them together. That will make the bottom into a t-beam that will strongly resist flexing front-to-back for only 3 lbs in pine and 2 in Okoume.

To summarize, weights are:

original -            430 lbs pine,  290 lbs Okoume
reduced -           250 lbs pine,  170 lbs Okoume
extra strength - 266 lbs pine,  181 lbs Okoume

Payloads are:

original -            170 lbs pine,   310 lbs Okoume
reduced -           350 lbs pine,   430 lbs Okoume
extra strength - 334 lbs pine,   419 lbs Okoume

That's still pretty heavy, but that's because you aren't getting any help from the shape. Those slab sides are easy to cut and build, but they make no real contribution to stiffness. If you curved the sides toward each other and had rocker on the bottom (both ends curve up), you could use thinner sides since the opposing curves would provide stiffness. But that would make layout and assembly more difficult.

I've also got a few thoughts on construction. Even the really thick plywood doesn't have good fastening area, especially since the fasteners would have to go into endgrain. If you want to build it plywood on frame, you'll have to add chines along the edges to hold the nails or screws.

If you build it stitch and glue, then you won't need chines. You'll be using fiberglass taped fillets to join the pieces. The glass tape will bond to the wood with lots of surface area and the fillets will support and smooth the bend.

Speaking of fiberglass, if it was my boat I'd put a layer of 4 oz cloth on all the surfaces (inside and out) except the top of the deck. For the deck I'd use a single layer of 6 oz glass. On the bottom, once the boat is assembled, I'd add a layer of 6 oz glass over the 4 oz that was already there, being sure to run it up 2" on the sides, back and front. That kind of glassing schedule would seal the wood against water, prevent any leaks at the joints and protect against abrasion. Since the boat is slab-sided, all the glass, except on the bottom of the pontoons, can be put on after the pieces are cut but before they are assembled. That lets you work flat on a table.

I would not put foam in the pontoons. That is just extra weight for nothing. With the construction described above it'll never leak. Instead, you could put hatches in the deck and use the pontoons for storage. Just keep the load balanced and use leak-proof hatches.

Finally, a word about balance. Every 100 lbs on one side of the boat that's not on the other will make that side go down an inch or so, until the deck tilts to where the loose weight falls in. One person walking around will make the boat wobble a bit, but not too much. Two people could start making it more interesting. This kind of boat has great initial stability, but lousy secondary stability. It'll handle some decent imbalances, but once it goes over it's not coming back. So keep the crew towards the middle laterally. Front-back you have a lot more leeway. What you really want to avoid is anyone standing on the outside front of a pontoon. make that area unattractive for loiterers.

Hope this helps and let us know how it turns out,

Laszlo

Excellent post Laszlo. You touched on all the salient points of this design that will affect both stability and safety in use.

There're reasons why watercraft hulls are shaped the way they are, why so much effort goes into selecting proper materials to build them, then using them to their best advantage. 

One correction to my numbers - increasing the displacement to 1/2 ton woukd increase the draw to 5 inches, not 7, leaving 13 inches of freeboard. I wish there was a way to edit these posts.

Laszlo

"I wish there was a way to edit these posts."  

I'll add my second to that sentiment...

You’ve researched a lot of pontoon boat prices and you can’t help but balk. It seems like even if you’re looking at used boats, they’re just so much money! You’d rather spend the time and make your own DIY pontoon boats. How do you even go about doing this?

To make your own DIY pontoon boats, you can either buy a kit that comes with most of the materials or procure these materials yourself. Then it’s just a matter of following instructions and building your boat!

In this in-depth guide, we will tell you everything you need to know about making your own custom pontoon boat. From detailed steps to what kind of finished product you can expect, you’re not going to want to miss it.
Can You Use a DIY Pontoon Boat Kit?

If you’d prefer, rather than build your own pontoon boat from nothing, you can always rely on a DIY pontoon boat kit. This comes with everything you need to make your very own pontoon boat, including the instructions (at least, most of the time). Here are some kits you might consider if you want to go this route.
U-Fab Boats
The pontoon boat kit from U-Fab Boats is ideal if you want to make a full-sized vessel. The company says you can use the kit to create houseboats, tour boats, utility boats, work boats, or party boats like a pontoon.