Homemade Inflatable Boat

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Intro: Homemade Inflatable Boat

I'm starting this topic to both log my experiments and to petition contributions and ideas from others.

The basic premise, to build a strong, inexpensive inflatable boat. If you look at the Zodiacs, you'll see they run into the thousands of dollars. Even the lower cost (smaller) inflatables at WestMarine sell for over a thousand and go up. My basic plan is to use some heavy canvas, and impregnate it with something to make it air tight. The canvas should add plenty of strength allowing it to hold a little bit of pressure and stay rigid. Everyone I've spoken to about this project has responded either that I'm crazy (possible), this is impossible (I'll never believe it), or both.

Lets start with the base material. I am really thinking of using a heavy canvas, like the kind available at the hardware store as painter's drop cloth. Purchased like that, I can get large pieces of canvas that are very sturdy and inexpensive. I've used this material to make bags, covers, and cushoins for my sail boat. So, I think its a good starting point.

Next up, a low cost way to make the canvas air tight and durable. An early thought was to use latex because its cheap and readily available. The problem is latex will not last very long exposed to the sun and elements. I have experimented with "PlastiDip" stuff used to plastic coat tools, and "liquid electrical tape" but, these two substances are hard to the saturate fabric with. Probably just as well, as these would be pretty expensive in the quantity required.

I really think that a liquid vinyl or some kind of vulcanizing compound would be ideal. However, I have no idea where to find such things.

Step 1: Trival Math

This is trivial but, still something to consider.
The greater the airpressure in the inflated chambers, the stiffer the vessel will be. Determining the air pressure to use will come from a combination of material strength and size of the chamber. This will be modified downward with a consideration of material strength decline with age, consideration of forces from use (people sitting on it, waves, motor, etc) and a safety fudge factor.

Generally in the realm of inflatable boats, 5psi is considered high pressure.

So, for a 24 inch diameter tube, we get a circumference rounded up to 76 inches. So, 1 psi would equate to 76 pounds of force trying to tear it apart (2 would be 152). Since large tubes will be very hard to contain lots of pressure, a compromise could be to stack narrower tubes that could each have a higher pressure.
This asks for some pro/con cosideration.

Stacked Tubes:
  PRO                        |   CON• Higher pressuere (stiffer) | • Greater weight• More air chambers safer if | • More complex construction  there is a puncture        | • More material/expense
The single tube is basically, the opposite of the above. If material costs are kept low, the cost part may not be a big deal.

A quick and dirty method of measuring the strength of the material is to cut a one inch wide strip to a length equal to the desired circumference, plus a little bit for hangers. Hang it up and start suspending weights from it until it breaks. Do it a few times and pick the low value for the weight that causes it to break.

Step 2: Basic Design

My thoughts for the initial design are (loosely) based on using the RB-15 while in the Army.
So, the floor, will be made of several sections of wood planks, that can be made rigid with sliding bars (ok, this part is the only resemblance to the RB15). The transom, will be supported/anchored to the floor using 2 triangular pieces of wood.
Instead of a wrap-around inflatable tube, my first attempt will have two long tubes tapered at each end, with two short conecting tubes for seats. The boards will sit right down the middle.

Step 3: A Word About Materials

One of the objectives of this project is to create something that can be built with readily available (and low cost) materials. This is one of the reasons that some choices may appear to be kindof odd.
I've received some really great comments and suggestions (some of which I am going to try but, have to wait for materials to arrive).

The idea behind the canvas is more about providing strength than acting as a substrate for the airtight material.

Some more experimentation over the weekend has shown that RTV silicon is almost perfect. Its strong, and seals well. However, It needs to be thinned to saturate the fabric. A bonus for a boat, is the silicon could survive an accidental fuel spill. Negatives are, I have no idea where to buy it buy the galllon, and its expensive. Another problem, is fixing leaks would be near impossible as once cured, new silicon doesn't bond well.

I've been busy with other things lately and then sick for about a week so, I haven't been able to do to much.
I've just discovered this instructable:
https://www.instructables.com/id/EGF6OU1EIGEP4HCZUE/
I think they have found the perfect substance to coat the fabric with, rubberized roof paint. I'm going to try to pick some up on the way home and give it a try. On the surface, it looks like it could be perfect. Strong, flexible, resistant to the sun. I'm really motivated now
:-)

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45 Discussions

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CarlyD5

2 years ago

I am building an inflatable and I am not certain if the fabric I bought is air permeable or if I am losing air through the seams. I bought #1046 70D VINYL COATED NYLON from Quest outfitters. Is there a way to test if the fabric I bought is air permeable? Thanks!

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Starsword7

2 years ago

I found this great method for creating inflatable tubes, simple and cheap:

http://www.yostwerks.org/AllPVCA.html

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blockh34d

4 years ago on Introduction

hello i wanted to mention rabbit skin glue, an old school method of stretching canvases. It's tricky to apply but will pull canvas as tight as a drum, and may offer nice durability, it seems to age well with art canvases. To apply it you melt it down and squeegee it into the canvas. Traditionally you leave the canvas a little loose because the rabbit skin glue will shrink it down so tight it might warp the frame otherwise.

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BayouHazard

4 years ago on Introduction

You're all talking over my head, but, what about "slime" or "fix-a-flat"?

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jmccabe4

5 years ago on Step 3

I am trying to figure out how to cut out the material to make the cones on the front and back of each tube and seal them correctly. Not really sure of the correct technique here?

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rawhiderrr

5 years ago on Introduction

I have so much enjoyed reading all of the comments. I found this place while I was searching for a way to complete an idea. At first I didn't know what I wanted to do It was just a thought. Kinda like putting the cart before the horse idea. I am going back to fishing since retired and I want to get a little 10 ft jon boat, no bigger.I want to take my dog with me sometimes and plan on just getting away from shore in lakes and ponds. I need a small firm boat to paddle around etc. no motor.However I wanted to make something I could attach quickly to the side to help me and dog(big dog never been in boat) from tipping it over(I'm clumsy and getting old and infirmed) yet pack it away in the truck.An inflatable that is reasonably thick to protect from sticks and stuff in all these weird ponds I may get into. Having no idea what to do I was very happy to read and learn things along those lines. Even though I may be more confused I believe I can solve it now. I have used a inflatable fishing chair off the coast of Saudi Arabia in the red sea (not again) and did grow up in the intercoastal waterway in Fla, but not that fond of swimming.Anyway sorry to run off at the mouth but wanted to say thanks for the read.

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nzioki

5 years ago on Introduction

hi, can i use silicon glue in joining canvas, PVC and other materials used in making inflatable boats?

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PaulEjcpoczatek

Reply 12 years ago

I was hoping that whatever I saturate the canvas with would also prevent rot. The PVC sheets look pretty good. I need to see where I can find some. Maybe, bonding the PVC sheets to the canvas and then turn the whole thing inside out. I think the canvas would allow a higher pressure than the pvc alone. Any idea where I can find some?

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PaulEjcpoczatek

Reply 12 years ago

Thanks, I think I'm going to order a sample to conduct some tests with. A big thing with the canvas was to try to have something that could be built with a trip to a local hardware store. Its beginning to look like a hardware store version of this may be more difficult than planned.

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big lenPaulE

Reply 6 years ago on Introduction

PaulE

They often sell PVC tarps at home improvement stores as tarps. That is where i got mine.

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weldor

6 years ago on Introduction

Try using a coating material such as "Blue Max" from the AMES company. THey are located in Salem Oregon. This is only one of their products that will seal out water. It is a water based, water clean up liquid latex formula. I have seen it demonstrated and the stuff really works awesome! It comes in 1 gal and 5 gal cans. Check it out. There may be other brands that work as well.

Good luck and keep us posted.

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akagoldminer

7 years ago on Introduction

Why not impregnate the canvas with silicone caulking like the kind of stuff you would use around a bathtub or shower. could be applied with a drywall joint compound spreader. it dries pretty quickly and could be used on both sides if necessary. sewn seams could be sealed with it as well. I may try this myself because i dont like the standard inflatable rafts I see in stores. as fo a valve i think one of the one way valves like on air mattreses might work pretty good.
I am also considering making a surf board from the pink 2 inch thick foam insulation covered with fiberglass and attaching a trolling motor.

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germeten

7 years ago on Introduction

A couple years ago I priced epdm rubber roof coatings in bulk 5 gallon pails for around $150. Prices have gone up a bit. See:

http://www.fixallroofs.com/ssl/order/order.php

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vinylgraphix

8 years ago on Introduction

It's gonna take me a while to post the instructions online, but if you guys want the patterns write me an email at: vinylgraphix@gmail.com. I'm gonna make a better version for the tubes.

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artnsue23

8 years ago on Step 3

One thing I haven't seen anything about is the valve you are going to use to inflate you pontoon.  I have looked all over the net for a complete boston valve.  All I can find is the exterior portion that screws into the receiver built into an existing inflatable.

1 reply
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vinylgraphixartnsue23

Reply 8 years ago on Introduction

Boston Valve it's not a good valve. Look for Halkey Roberts, I purchase mine for $6 from www.westmarine.com. It's not the best valve on the market but it's pretty cheap and it's doing the job very well. Look here for more valves: http://www.nrsweb.com/shop/product_list.asp?deptid=1030

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vinylgraphix

8 years ago on Step 3

I made a pontoon boat using tarp material (180z. PVC coated material). The tubes are 12" diameter and 13' long. I used Vyna Bond glue and Halkey Roberts valves. I made the 3D design in Solidworks and then unfolded and cut the patterns. I think I spend $150 on everything, still I have to make another frame from 1/2" or 1" pipe and I'm gonna use Clamp-On Framing Fittings.