Building My Own Pontoons

First time posting, but I have been viewing for some time. I have been wanting to build a small pontoon boat that will fit into the back of my Ford Explorer. First step is to build the pontoon. I have been looking at the best ways to do so. Here is what I came up with.

I took a 4x8 sheet of aluminum that is used for race car bodies or signs. Cut a piece 3'x8', and bend it long ways into a u 1'x1'x1'. Take the same kind of aluminum and cut into pieces 14"x13 1/4" to make the bulk heads.

Position the aluminum piece so it is 14" wide. Measure in an inch (left and right) on each side and make a 90 degree bend the length of the side. Do the same on the 13 1/4" (top and bottom). If you measure the 14" wide, it now should be 12" wide and the 13 1/4" should be 11 1/4" high.

Take one bulk head and pop rivet in place at one end making a cap. The bulk head will fit inside the u pontoon. Pop rivet the cap at all three sides. Use bathtub calk and 3/16" pop rivets. I made a bulk head every two feet. The inside bulk heads I only pop riveted the two sides. I angled one end of the pontoon to make it go though the water better.

Now this pontoon will leak. Trying to make something water tight is very difficult. If you fill the chambers with foam, the foam will displace any water trying to come in. You can use the foam that you mix to fill the chambers, but you better know what you are doing, and it is expensive.

The spray foam from Lowes or Homedepot may soak up the water. I tested the blue high density foam from lowes and Homedepot. I immersed the foam for 24 hours and found no water soaking into the foam. I will be placing 2" thick foam pieces cut to fit into the bulk heads. Five pieces will give you 10". Place another piece of foam 1 1/2" on top to give you 11 1/2". From the top of the bulk head to the top of the foam will be 1/4" of space.

Place a piece of wood sheeting 3/4" thick ontop of the bulk head to make the top of the pontoon. Measure the sheeting to make sure it is 12" wide. Most sheeting is only 11 1/2". This will make it difficult to finish the top of the pontoon. My sheeting is 11 3/4" wide, good enough. Drill holes in the sheeting and fill the chambers with spray foam. I know that I said this foam may soak up water, but the water should not reach this foam.

Tee-nuts look like the bottom of golfing shoes where the spikes thread into. Place 3 tee-nuts in the underneath of the sheeting. I will be making my deck out of 3/4" plywood. Drill holes through the plywood deck and trough the sheeting. Bolt the deck to the sheeting to keep the deck in place. You can also screw 1" aluminum angle under the deck and on top of the pontoon to keep the deck from moving. Drill holes in the deck and anchor the deck to the pontoons with ratchet straps. I'll get more detailed later.

My calculations are 1 cubic foot of air will float 60 lbs. That is total immersion. The pontoon is 8 cubic feet, less the angle at the front. 8 time 60 is 480. Two 8' x 1' pontoons should float 960 lbs. Total weight at 6" draft should be 480 lbs. I am attaching pictures of what I have built so far.

 

Your work looks very neat and workmanlike. Properly, this is a catamaran--- crude but I think it deserves the name. Sealing the seams and keeping them watertight will be a challenge. It sure would be worthwhile to weld the seams at bow and stern but perhaps it's too late if flotation is already in place. While this would cost a bit, it would make for a world of difference over time.
Note: Tee-nuts are zinc plated? They will corrode in contact with aluminum.
Better to use self-drilling/tapping stainless screws. "Decks" of 3/4" ply works okay, but epoxy the inside surface... and roofing tar in the gallon can, if brushed on, will make for a good cheap substitute. as a matter of fact, roofing tar is fabulous as a water-proofing sealant. Where no one can see it, it's messy gooey qualities won't matter.
Beware of pressure treated ply in contact with aluminum! The newer formulations have a copper base. The copper is more "noble" than aluminum, and so the aluminum suffers a galvanic change, and corrodes when immersed in water (essentially, the water----especially saline---- is an electrolyte, and the boat becomes a battery, with the aluminum as the anode.
Tar, again, coating mating surfaces, will reduce this problem. At least you are making the hulls take-apart, which is wise.
Looks fine so far. What's next?

Alan

 

Nice job Jim. Alan made some excellent points. The galvanic relation between the ply & aluminum was new to me (thanks Alan).

Smaller rivets placed alot closer may provide a better H2O proof seal. If you check out a good aluminum skiff such as a Lund, you will see what I mean.

I would put limber holes along the bottom pontoon partions at center & each side of all mid-ship panels. That in conjunction with a drain plug at the aft end of each pontoon will allow any water out. Never count on anything being 100% leakproof.

Once again, nice looking work. Not shapely like a "proper" boat but functional & practical looking for what you are after. If you ever buils another I'd suggest angling the aft ends of your pontoons. It looks more balanced and allows you to get out of trouble as fast as you got into it (almost).

You going to use it on the Mon & Allegheny or area lakes & ponds. I live over by the Chestnut Ridge (Mt Pleasant area). Hopefully I will get to take the sea kayak down the Yough with the month.

Welcome to the forum and keep us updated.

Tim

 

Jimith welcome.

It would make it easier to read your post, I didn't because it is too hard to read, if you used paragraphs.

Like this.

Also look at Timgoz post.

He also used paragraphs

Paragraphs are in simple terms a gap between sentences to make it easier to read.

Kindest regards






Poida (Now I'm being silly) But it's what I'm good at.

 

Thanks For The Feedback

Alan and Tim, thanks for the input. I'm trying to build someting that is easy for others to copy, and be an easy build. So far I have about 4 hours in the pontoon. I will keep you posted with more pictures.

I am a videographer and I live about a mile from the Raccoon State Park. I need something slow and smooth to shoot the shore line in the fall. If it works, I hope to travel to other lakes. Tim, one of my videos is called Mountain Streams. It is a relaxation video and I shot it at Linn Run State Park. I used to just about live my summers near Roxbury.

Poida, Thanks so much for the comments about the pontoons that I am building for my boat.

I am very sorry for the rambiling posting, but I found myself caught up describing details.

Paragraphs are a group of words dealing with a particular thought. They may be one or many sentences.

I could engage you in pointless vollys of postings that will show you how silly you really are, but I do not entertain myself with such childish pleasures.

 

Thanks Jimith, it would be a waste of time indeed as I am sillier beyond your wildest dreams.

Poida

 

Jim,

I've spent many a fine day on Linn Run at a friends private property. He had a awesome stretch of water by Rector. Practiced catch & release, and ALOT of it.

Not done much video work. I studied media technology but with a photography emphasis. Hope your boat proves useful.

If you ever want to do a vidoe on the Bottom Yough River let me know. I'd be willing to go down with you. Used to guide the Ohiopyle section and other area whitewater, so I should be able to keep everything dry on the gentle waters of the bottom.

Better start a new paragraph, it's to early in the am to deal with the wrath of Poida!

Take care.

Tim

 

Nice design... however I am wondering the cost on this... or if it would be cheaper to buy a 8' pelican pontoon bass boat when everything is said and done... building it would not be a problem just the cost...

Brandon

 

Update On Pontoon

Little update hear. I got to see how my pontoon floats in my pool. The first thing I noticed when adding weight was the pontoon wants to roll VERY EASY. I will need to secure the pontoon to the deck with this in mind.

I added 185 lbs. to one pontoon and the draft was 5". I was hoping for a better draft, but I checked the numbers first and just needed to be sure.

Good news was that although I new the pontoon was going to leak, it didn't. But I will still add the foam inside the pontoon.

The total weight of the pontoon with the 12" sheeting is 35 1/2 lbs. A 3/4 sheet of plywood is about 60 lbs. Finished boat should weigh about 130 to 140 lbs.

Thanks to all that have given their two cents, but I might need a nickle.

 

One single pontoons stability will have no influence on the finished boat because by its self it is top heavy and will obvioulsy roll but with the deck and another pontoon this wont happen...just think of pontoons that are like tubes if you put weight on top it would roll over but does not stop the pontoon from making a good boat... as well I am glad to hear it did not leak...

Brandon

 

post more pictures

 

With that very thin gauge metal the foam may oil-can or pillow it out from internal pressure caused by the foam installtion.

Then again, if you don't fill with foam, water pressure at speed or in a turn may collapse the pontoon walls in.

Perhaps some sort of external plywood bracing in place during foam curing/installation will be required.

I've not seen or heard of this being done before, but I've never seen this aircraft like pontoon construction either.

 

Take a piece of 1”x12” sheeting and cut it so it will cover 2 bulkheads. Place the cut piece on the top of 2 bulkheads. Drill a 3/8” hole in the 4 corners of the sheeting to let the foam expand out. Drill a hole in the center of the sheeting to fill the area with foam. Continue to do this until all the bulkheads are filled.
Place a 12”x8’ sheeting board on top of the bulkheads. I am placing a 12”x8’ aluminum piece on top of the sheeting to finish the pontoon.
Using aluminum angle, cover the top edges of the pontoon. From about ½” down, from the top of the angle on the side, drill and install screws threw the angle, aluminum, and into the sheeting to hold everything together.
I am using a 4’x8’ sheet of ¾” plywood for the deck. Place the plywood 8’ wide on the pontoons. This will give you an 8’x8’ pontoon. The deck will be removable so I can take it apart quickly and slide the pontoons into my Explorer, then the deck slides on top of the pontoons so I don’t have to use a trailer.
jimith

 

were can u get the best foam to fill the pontoons?

 

I don't remember what I searched under. Look for expanding foam, or boat foam. There are different densities. The harder the foam, the more you need. It is quite expensive, and VERY difficult to use. That is why I am filling the compartments between the bulkheads with the blue foam sheet insulation at Lowes. Then to fill the voids I use the foam insulation in a can. I know it's not what should be used but it's cheeper, easier, and I am experimenting. The foam will not be exposed, and I just need to displace any water that is going to leak in. You could use ping pong balls, plastic bottles, anything to displace water then fill in the voids.