Inflatable boat

I've tried to find out as well, all the scant info (youtube)

is about fabric/glue construction.

It seems to be a "black art".

I imagine they just to 'trial and error' to develop a pattern.

I was thinking of using foam "packing peanuts" to simulate 'air' while wrapping material and marking it.

Maybe a CAD sheetmetal program where you could design a shape and turn it into "sheetmetal" which the program can then 'flatten', and you add overlaps.

Maybe a good tailor could be useful.

 

At a certain level inflatables seem to be all cylinders, cones, and mitres. I'd try modeling with wood or foam pipe insulation and wrapping with paper for templates then scaling up. Pretty old school but seems doable until someone can enlighten us with a easier modern method. Seems like you're going to need some sewing type skills for a project like this.

 

I believe you can do all that pattern work with math.
Get hold of a Math teacher and you'll get more than you asked for.

There wasnt any stitching in any of the tubes on my Metzler, or my buddies who had several other kinds of RIB's.

 

If you are doing a one off, or just want to knock some ideas around, TollyWally has the right idea. Make your shape to scale in something easily formable, then cover every square inch of it with paper (masking tape works well). Use a marker and plan out your shapes right on the paper, trying to think about how they'll lay down flat. Then, take an sharp knife and cut each sheet out. Scale them up, add some seam allowance, and stitch it all back together again. This also works for copying a preexisting shape or object.

If you haven't made something that inflates before, even if you are comfortable making objects defined by their 'shell', it is worth doing some tests. The way seams and panels interact is not always intuitive once an object is finally pressurized. This can become especially pronounced where surfaces meet at hard angles, and where beams or long skinny prism shapes are desired.

Just remember that most of us are used to thinking in terms of linear surfaces (lines, planes, blocks, angles, etc.), but inflatables try to take on more organic shapes.

If you have access to the materials at low cost, I'd say go have fun with it. Inflatables are lots of fun!

 

This video shows you how the tubes are put together with adhesive and how they are cut out.
http://www.youtube.com/watch?v=WqbvaNfRl2Y&NR=1

 

Tolly,

Turns out it was quite rational and economic, he has access to cheap and

abundant building materials. He/she said this following my query.

-Tom

 

LOL Tom,
I was speaking of generalities not specifics.

 

What type of boat are you building, and what size? Raft, Kayak, pontoon? Also will you be using an inner tube with an outer casing? That might be easier for self made than having to do the commercial type without the PVC welding machinery.

Porta

 

At least a start

Silenthunter, you certainly have received some off topic advice here I have never built an inflatable but I used to repair them and there is nothing too complicated about it. (I was an Avon dealer) Several of the river runner boat manufacture's started out with very low tech designs, built by hand. Most all inflatables were formed and glued by hand through the 1990s and the technics still work. The fabric you have available will determine the type of glue. I saw plastic drums being used as the tube molds/forms at one small builder, and their boats looked good and worked well. I still use a 1988 avon that I rebuilt 17yrs ago- it holds air and gets used hard. bruce

 

Inflatables and hybrids (some mix of air filled flexible, foam filled rigid, aluminum, wood, etc) can offer great weight and portability. Ie, if you had to have something in the trunk of your car to get across the water, it would likely be a folding skin on frame boat or an inflatable. And they can be very tough and fast (try this in any equal size/weight boat: http://www.covertex.co.nz/site/covertex/images/items/Thundercat Boat.jpg.


It is typically glue for hypalon and heat for PVC?

Is there potential for significant weight savings with other materials - say something like a Spectra or Vectran fabric with a polyethylene bladder?

Some fabric info at:

http://www.inflatableboatfabrics.com/

Maybe it would be better if inflatables were thought of simply as foam core boats with ultralight .1 PCF foam and a more flexible resin .

 

Good to hear advice from guys like Bruce that actually are documented in the process.
I've always thought the only reliable place you could go for help in finding the right glue, was the Fabric manufacturer.

I miss my Metzler!

 

While i have not built an inflatable boat i used to make air bag presses for pressing snowboards and we originally made the bags out of 20oz PVC tarp material (the type used for semi trailers )glued together with a contact adhesive called HH66,we bought the fabric and adhesive from a local canvas shop,i have no doubt that this would be ok for a boat as they only run,what 3-5psi,we ran 100psi in these air bags and they were like a metal drum if you rapped on them,we used a simple 10" overlap seam but we needed clamps to close the ends machined out of 2" steel barstock to handle the pressure.
Steve.

 

So did you get anywhere with this?
I'm thinking of doing the same thing - I've got a source for some quality european Hypalon fabric at below cost. It's still kind of expensive though, ~ $400 - 500 (us$) for enough fabric for a 2.5m boat with 400mm diam tubes. 1st grade = $45 plm, 2nd = $35 plm all @ 1.5 wide 1mm thick. Ive worked out a stupid easy way to draw the patterns. Just have to sort out a source for the fittings etc.

Cheers Simon

 

I think the easy way to draw the patterns is to mock them up in paper tubes. They do not have to be 3d just joined and layed flat. The importat thing is to ensure the joint angles are the same so the tube sections match. I'm not real good at explaining things - but if you get a piece of paper and fold it in half then tape the edges to form a flat tube, then cut the joint angle required, you'll see what i'm getting at. The off cut when flipped 180 should be a perfect fit. - just a matter of staggering the seams so that they also match (if the section being joined raises off horizontal). If you try to join two different angles, then you have problems as the tube joint cross sections will be of different diameter.

Anyway i think the whole patten can be drawn in 2d,without actually drawing anything other than some angled lines, no need for any fancy cad or maths.

cheers Simon

 

http://www.inflatableboatfabrics.com/

has the parts. Might be worth asking them if they know where to get patterns. Or do a catamaran style where the inflatable part is simply two cylinders.