3 Steps
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.
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## 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.
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vinylgraphix says: Aug 12, 2010. 2:19 PM
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.
dshandy in reply to vinylgraphixMar 23, 2013. 7:16 PM
Did you glue the seams on the outside?
artnsue23 in reply to vinylgraphixAug 15, 2010. 7:07 AM
That's awesome! Thank you for the info. Are the seems sewn as well as glued or just glued? Is the tarp material canvas or some other coated material? Where did you buy it?. Sorry about all the questions but I've had almost that same boat running around in my head with no ability to make it a reality. Thanks a lot for the info you've already given.
vinylgraphix in reply to artnsue23Aug 15, 2010. 9:43 AM
The seams are glued with 1 inch overlap and another 2 inch strip over the seam. The material is Polyester coated with PVC. I used 18oz material, its good for lakes or big waters but if you want to go whitewater I recommend 35oz or 40 oz. If you want something cheap go with 22oz and make the bottom double. Here are some links were you can buy the material: (This guys have good deal on material but the sell only black for 22oz and big roll 50 yards to 70 yards. Don't use black cause pressure it's gonna build up from the heat, use light colors. Mine it's working good on 99 degrees but if I'm in the water, on land I have to release the pressure) http://www.myteeproducts.com/tarp-fabric-c-4.html (I bought from this guys) http://www.perfectfit.com/12905/154103/Boat-Toppings/VINYL--TEX-18-oz-Vinyl-Coated-Fabric.html
useraaaaa in reply to vinylgraphixJan 11, 2012. 10:19 AM
i wana buy 2 pontons like that
\$120
artnsue23 in reply to useraaaaaJan 11, 2012. 12:57 PM
Here is my home made inflatable. The pontoons are a little simpler one piece design. 14" diameter 12' long.
dshandy in reply to artnsue23Mar 23, 2013. 7:26 PM
Did you glue the a 2in. strip on outside of the seam?
artnsue23 in reply to dshandyMar 24, 2013. 5:12 AM
Yes I did. to strengthen the seam.
vinylgraphix in reply to artnsue23Jan 11, 2012. 7:48 PM
That's nice. Can you show me the patterns? I am curios how it looks unfolded. I've tried to do the same thing in Solideworks but I couldn't.
artnsue23 in reply to vinylgraphixJan 12, 2012. 6:28 AM
Here is the basic pontoon layout.
artnsue23 in reply to vinylgraphixJan 12, 2012. 6:11 AM
I'm trying to figure out how to post an image from Sketchup here, but so far I'm unsuccessful. If you want to give me an email address I can send you the files.
artnsue23 in reply to vinylgraphixAug 15, 2010. 11:59 AM
Thanks a lot. I appreciate all of the info.
Crankitup in reply to vinylgraphixAug 14, 2010. 4:17 AM
Great work! I've been wanting to do something similar for a while. I first got the idea after seeing this nifty commercially available inflatable cat and deciding it would be too expensive to purchase and have shipped to Australia where I live. You should post up an Instructable, even if only a quick one. I'm sure you'll inspire many to follow your idea.
vinylgraphix in reply to CrankitupAug 14, 2010. 9:24 AM
Thanks Crankitup! Before I build mine I made a lot of research over the internet but I never saw the Soar Cat. I like the idea with the grommets along the tube. I'm thinking to do on mine the same thing and lose the frame. It's light weight this way and much cheaper. :) May be I will post my idea but it's gonna take me a while to prepare the materials and may be to change the design a little bit. I want to make the back of the tube the same like the front with the nose up.
Crankitup in reply to vinylgraphixAug 14, 2010. 7:55 PM
Thanks for replying. Good luck with it all and I look forward to your instructable if you decide to post one. Cheers, Neil (Crankitup)
rawhiderrr says: Feb 19, 2013. 1:29 PM
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.
nzioki says: Dec 15, 2012. 4:46 AM
hi, can i use silicon glue in joining canvas, PVC and other materials used in making inflatable boats?
jcpoczatek says: Sep 3, 2006. 4:09 PM
Canvas might rot? This guy made an inflateable kayak, look at the folding ones too good info.

http://yostwerks.com/Inflatable1.html
PaulE (author) in reply to jcpoczatekSep 3, 2006. 4:29 PM
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?
jcpoczatek in reply to PaulESep 3, 2006. 6:04 PM
I think the canvas is unnecessary, since the PVC is a polyester fabric that's coated.

This is the place the kayak guy recomends, but you might need to place a large order. They have hypalon fabric too, which is what whitewater rafts are made of.
http://www.mauritzononline.com/vinylcoat.html

Seattle Fabrics has a good selection too. And they have a \$2 sample pack.
http://www.seattlefabrics.com/vinyl.html
PaulE (author) in reply to jcpoczatekSep 5, 2006. 7:42 AM
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.
big len in reply to PaulEMay 17, 2012. 8:26 AM
PaulE

They often sell PVC tarps at home improvement stores as tarps. That is where i got mine.
weldor says: Oct 5, 2011. 1:15 PM
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.
akagoldminer says: Mar 29, 2011. 6:55 PM
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.
germeten says: Mar 20, 2011. 12:24 PM
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
vinylgraphix says: Aug 15, 2010. 9:51 AM
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.
artnsue23 says: Mar 12, 2010. 10:14 AM
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.
vinylgraphix in reply to artnsue23Aug 14, 2010. 8:51 AM
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
vinylgraphix says: Aug 12, 2010. 2:21 PM
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.
mr.dr.prof.joel says: May 17, 2008. 2:48 PM
ya/know Mythbusters did something like this
squidstew in reply to mr.dr.prof.joelAug 5, 2010. 3:36 PM
Yes, the myth was a prison break from Alcatraz (the Clint Eastwood movie, "Escape From Alcatraz"), they used rain jackets that would have been issued to the prisoners in those days and some sort of home made glue. The boat was very flimsy, but it did hold together. I think the author of this article is looking for something a little more rigid, as would I.
DaveB13 says: Jun 16, 2010. 3:53 PM
If the main negative factor of the low buck little inflatables is sturdyness, why not just make a strong material cover to go over one you have, maybe have long patch of tear proof material built onto the outside of the cover, and be sure to rely on the strong areas when you have to board on some nasty bank. If you need speed / portabliity/ low cost then I've never seen anything that competes with that yostwerks page above. If you need capacity / power there are long foldable wood boat plans around that work like the www.porta-bote.com which is about the most commonly in use tender I've seen in my wanderings, and I think you need for/aft strength for any engine use at all.
doront says: May 20, 2010. 7:39 PM
I have a very old Avon Redcrest inflatable that I am in the process of restoring.  I got everything I needed from Inland Marine.  They have a product called liquid rubber that adds a 4-6 mil rubber coating on an existing boat.  Maybe something like that and their sealant products and glues might be a good place to start with the canvas idea.  I bought their complete restoration kit for about \$220 but starting from scratch you may need more.  I've used the hyplon glue to reattach all its pieces and the tube sealant to stop the pinhole leaks.  So far I am very pleased.  I also plan on making a wood floor and using it as a means to give the soft bottom some shape more like a RHIB.  I hope this gives you some ideas.  Good luck!
skaar says: May 8, 2008. 7:58 AM
tarp as the fabric, liner of plastic, cheap, and maybe castoff abs or pvc pipe for some parts, as another idea. it may be possible to make a tube of the cloth, wet coated, temporarily clamp it together and fill it with air to force the coating through the cloth, trim it to shape after it's cured into a tube. there's one feller on the web that builds skinboats from uncoated tarp and willows, you might be able to get by without any coating if you do things right. maybe build the pontoons as skinboats, abs stringers and cheap wood frames, sealed bleach jugs as floatation.
ScottZwanenbeek says: Mar 12, 2008. 1:35 AM
Hi Paul, Why reinvent the wheel? :-) Besides 'Hypalon', many 'zodiac' style boats are made with a material often used for tarps and is made from a PVC laminate on a polyester or cotton fabric core. Polyester is better for boats as it doesn't suck water into the core. While the tarp material resellers will tell you to use a heat gun, etc, you can make life easier using specific glues. For an example of usage, check out 'yostwerks.com'. Happy boating!
joren says: Jan 22, 2008. 1:59 PM
I've been thinking of making an inflatable boat too--a sailing catamaran. Something similar to:Ducky, Easy Sail and the half dozen smaller sized sailing inflatables out there.

I'm having trouble finding info on the web of people who have created their own inflatable boats. Tom Yost has a small kayak on his website he made with vinyl-reinforced poly tarp material gluing the seams with hh66 glue. He references a south american gentleman that made one too, but that's about it.

I was either thinking of using 18 oz tarp material like Tom, or use that for the outer hulls and make inner tubes with 20 mil pvc pond liner (a stretchy vinyl). My thought was the stretchy pond liner expands and pushes against the reinforced vinyl to create a more rigid structure. 18 oz vinyl tarp material can be had for \$3 /yard (62" wide) and 20 mil pond liner is about \$3 a sq yard.