The sponsoon sleeves, part two, and the pockets

After the banana shaped PVC I have to make the nylon parts. I make the nylon straight in stead of curved, the flexibility will allow the nylon to follow the curves.
Using permanent marker I set the distances between the lines I have to draw. I use a long and straight piece of wood as a ruler. It does not matter if it is slightly curved as long as you use the same part of the ruler for all lines. Main advantage of making straight nylon parts is that it is much less work when drawing.
I draw lines to cut the nylon, and lines to sew on. Make sure you draw the lines clearly so that they shine through the fabric, it is very practical when you are able to see the lines on both sides of the fabric.
The nylon I used was shorter than the sleeves, so I had to join two pieces:

After that I use pins to fix the nylon on the PVC. Start out with the two central lines, and after that the edges. When you start with the edges you have a problem with the centrelines: you wil not be able to check underneath the fabric if it is exactly in position. When pinning the edges, work from the middle towards the ends. Here the centreline and one edge are pinned.
I sew everything on my old and battered Vendomatic machine. My mother gave it to me years ago when she bought a shiny new one. But actually, for heavy type of work without fancy stitches this one is much better. It is very heavy, but cast iron stays forever. It is as old as I am (41), but still going strong.

The fabric I use is 64 gr/m2 Ripstop nylon for tents from ESVO, and the yarn is their polyester-cotton tent yarn. If you can get it, use a light colour for the nylon as it is easier to see the markes lines. Make sure you have sufficient yarn, I used a complete 125 meter bobbin only for he sleeves.

Sewing the sleeves done, it is now time to make the pockets for the ends of the side stringers. On the nylon the pockets can not be glued on, so I thought of a different solution.
First I stitch on an oversized rectangular piece of PVC near the end of the sleeves.
Then I cut this pattern:
Here the glue is on already, that causes the edges to come up. Now I put a piece of aluminium of 20 mm diameter on the PVC. I fold the lower flap over the aluminium, then two of the three little pieces around the end, then the big upper flap down and finally the last two small pieces. When you do this correctly you end up with this:
And seen from the backside:
No photograph of the completes sleeves yet, "Card full" said the camera.....

I put pockets on both bow and stern ends of the sleeves. Doing this I hope I can go without the straps that Tom uses on his boats. The staps are difficult to make as they have to be sewn onto the nylon.

The gluing of the pockets was the first real glueing I did. Before that I made a few test pieces. I use Helaplast glue, as I could not get HH-66 in the Netherlands. I tried various amounts of thinning and found out that with thinning the bond is better, probably because the layer of glue is thinner.
On flat surfaces it works very well to use a clothes iron in stead of a heat gun. The iron allows you to apply heat and pressure at the same moment.

The sponsoon sleeves, part one

I decided to use the new method of making sponsoon sleeves that Tom has developed for his new double. With this method the sleeves are for 1/3 made out of PVC, and for 2/3 out of ripstop nylon.
The method is lighter and might result in less wrinkles. Tom is ethousiastic about it, but his wife Rita does the sewing. As I am quite handy with the sewing machine I decided to give it a try.

Today I started out making the banana-shaped PVC parts for the sleeves. Here I use a different PVC, a quite supple grey version of about 500 gr/m2. Main advantage above the black stuff is that it is easy to mark. For sewing I need proper and clear lines to make the sleeves exactly the right dimensions.

The marked skin is put on table with the grey stuff on top of it. I tape both skin and grey PVC to the table to prevent any movement.
Then I carelfully roll back the grey PVC and put small marks at the locations of the tape markings on the skin. This way I copy both gunwhale and chine lines onto the grey PVC.

I add markings for the cutting and sewing lines.
Again the kids help, this time to connect the small marks with long black lines. Both want to help, and that usually results in conflicts or disaster. So I let them help in turns, and let the other one take photographs. Lots of them...


After cutting the banana looks like this:

A really nice fit.
Luckily the banashape proves to fit both left and right on the skin (or should I say port and star?). So I can use the first one as a template for the second one.
Some more drawing and cutting yield two nice antisymmetric sleeve bananas:


Ready for sewing. But first I have to make the nylon parts.

Starting the skin: the bottom part

A large roll of back PVC has been looking at me for weeks. Now it was time to unroll it.
Working with PVC requires a large flat table. And a large flat table requires a lot of space. So some serious ordening was necessary in the shed. All bicycles that are not used on a daily basis have been moved upstairs or hung from a wall. Four sawhorses together with two old hobby tables from our former house make a table of 0.8 x 4.3 meter. Five meter would have been better, but this should be OK.

First action is cutting a blank of approximately 5x1 meter, and marking the centerline with tape on both sides.
A disadvantage of the black material is that is is difficult to mark. The paper tape works nice, and a white pensil from the kids works somewhat. On light colours you can use permanent markers, on the black you hardly see those.

The blank is put onto the skinning frame, and clamped at bow and stern.

Using paper tape the gunwhales, chines, bow and stern are marked on the blank. Also the trim line is marked, 50 mm below the gunwhale.

Back on table the blank is trimmed to size.

For cutting I use Black and Decker elektrical scissors. That may seem lazy, but that is not the point. The elektrical scissors give you the possibility to cut the material hardly lifting it from the table and without any movement, so you can cut very precise. I started using these with carbon fibre, and for that it is a godsend as it prevents tearing out fibres. For PVC it works like a charm as well.

The final result.

The bottom tube

The bottom tube needs two bend an the ends. So I started looking for a half decent tube bender for 19 mm tubing. It proved nowhere to find. 15 mm was abtainable, for 40 euro's. And a 22 mm version for 100. Way to expensive to try.

So I dedided on a different approach. I delved into my scrap metal box and found a metal ring of about 100mm diameter. Using this and some wood I made a crude bending rig for use on the milling table.

It proved perfect on the first try. No kinking of the tube at all.

After that I had to turn down the inserts, as the tube sizes I work with do not have a sliding fit. I use 22x19mm, 19x16mm and 16x13mm for the frame. At the middle sleeve the 19 mm has to be turned down to about 18.7mm, and the inserts are turned from 16 mm to 15.7.
An insert.
Turning down the 19 mm tubing.
The middel connection, still without the sleeve.
The frame ready for skinning.

The skinning frame

Now I have got all materials the building really starts.
First the stations are drawn and sawed.Then the correct locations on the strongback get a block of pine.

The stations are screwed onto these blocks using small square pieces of wood. A piece of string and a buble level are used to align al stations correctly. I planned on using a laser, but the string was simpler.


Stringers (18x27 mm) are connected to obtain sufficient length. Gettings proper wood is difficult. The first wood I looked at was not nearly straight. The stringers I used now are straight, but two snapped wen bending the stringers.

Is stead of using HDPE snaps for the bottom tube I just changed the stations a little bit. I hope this will work OK.
Also I made the stations in such a way that the stringers fit in at the edges, this makes positioning of the stringers much easier, especially when working alone.

The strongback

The strongback is the basis for building the boat. On this a skinning frame will be setup that will be used to get the shape of the skin right. This frame will not be part of the boat later on.
I build the strongback exactly as designed by Thomas and put some effort in making it straight and level. The strongback is of course re-usable and can be used for lots of other boats.

In stead of long bolts I used m10 stud that I shortened using the lathe.


Bolting the strongback together:
I try to get the kids, Yentl (6) and Levia (4), a little bit involved in these projects. Even when that sometimes means that you have to do things over again.....

Obtaining materials

The first major hurdle is obtaining materials. For some reasons it gets difficult when you want something that goes outside the scope off the do-it-yourself-shop. And living in the Netherlands I have to find other suppliers than supplied on the yostwerks site.

The design calls for:
Aluminium 6063 or 6061 tube in various telescoping english sizes
PVC coated fabric in 10 and 18 oz weight
HH-66 PVC glue
Folbot sponsons (air tubes for the commercially made Folbot folding kayaks)

First the tubing:
I will have to use metric tubing, with the disadvantage that they will not telescope properly. Metric sizes have a zero tolerance fit, wheras with english sizes you can end with 0.2 mm clearance. But as I do own a lathe I will turn down the inserts slightly, no big deal.
The only material I can get is 6060 T6. Not as strong nor as corrosion resistant as the required materials, but I am happy that I can get any proper material. I will use the folowing sizes:
Keel / stringers: 19x1.5 mm
Inserts: 16x1.5 mm
Sleeves: 22x1.5 mm
Coaming: 13x1.5 mm
Total material cost for tubing is approximately 130 euro.

Second the PVC:
Yost uses 18 oz fabric for the hull, and 10 oz fabric for the deck.
18 oz is approximately 640 gr/m2, and 10 oz is approximately 340 gr /m2.
Luckily I found a company nearby (Pro-seal zeilmakerij) that makes lots of products out of PVC coated fabric. They were willing to sell me some PVC. Regretfully the lightest material they have is 500 gr/m2. So I ended up buying 680 gr/m2 PVC in black for the hull, and the same material in yellow for the deck. I also got some quite supple 500 gr/m2 material in grey that I might use for the sponson sleeves and the coaming. I could use it for the deck as well, but the yellow is much more beautiful.

Then the glue:
HH-66 is only available in the USA and canada. I found a shop in the UK as well, but they refuse to sell overseas. I probably will use another glue, Helaplast. A German builder has used this and it should work identical to HH-66. Another possibility is Tarpo-S, from Planenwelt.

And the sponsons:
The sponsons are sold in the Folbot webshop. But shipping from the USA is quit expensive unless I use the non-trackable USPS that I hear mixed reports about. I decided to order from the German Folbot dealer: Outtrade. Four sponsons including shipping will set me back about 178 euro. If I make a second boat I will probably try to make the sponsons myself.

Building an inflatable kayak

The start of a new building blog. I just have to make things and as I love bicycles and kayaks it is not surprising that I want to build them. Last project was a bicycle made for two, shown at tandembuilder.blogspot.com. From the road to the water: the new project will be a boat.

For long I have been fascinated by collapsible boats. We own a Feathercraft K2, and although a bit on the heavy side it is a dream to be able to take a kayak on a plane. A couple of years I ago I wanted to build a single folding kayak, but insufficient attic space blocked the effort. Recently I stumbled on the internet over the magnificent site www.yostwerks.com, by Thomas Yost. Thomas has been designing and building folding kayaks for years and is sharing all his designs and knowledge on his site. His latest efforts have been the development of a series of seaworthy inflatable seakayaks called "Sonnet". Those kayaks are way beyond anything that is currently on the market. The traditional image of a folding kayak is that of the large, wide, overly stable double kayak. And then come the Yost Sonnet designs: sleek, narrow, rugged greenland-style kayaks, capable of handling rough water, and that in a package with a weight below 10 kg that you even can transport on the back of a motorcycle. Amazing.


Here an beautifull Sonnet 16 example build by David Long. (courtesy www.yostwerks.com)

I have a trip planned to Australia to visit my brother who happens to be living aboard a boat near Sydney. Actually, his boat is the larges sailing Proa in existence that he designed and build himself, but that is another story found at www.pacificproa.nl.

With this:


as my temporary home, a seakayak would be a treat for an avid seakayaker like me. So I am going to build a Sonnet 16 and take it on the Plane to down under.

In this blog I will try to document the building process and share my experiences. The design details can be found at the inflatable kayak builders manual. This build wil be mine, but all credits for the design and the technology are for Thomas Yost, of course.