Monday, 28 November 2016

launch 2


The design brief
The original brief, for a customer who was looking for a kayak to enable him to improve his skills, was to build a copy of Brian Schultz’s F1. When it was clear that this was not possible, my proposal to design and build a “british” version of the Mariner Coaster (on which the F1 is based) was accepted. Only 13’ 6’’ in length, the Coaster was the first sea going “playboat”, a kayak for surfing, rock dodging, tide races, light camping and touring; essentially a day boat.
This 14 ft “british” version was designed with a lower profile for a windier environment with smaller waves than the Western US coastline from where the Coaster originated. The name Lowen – Cornish for “joyful” seemed right.

Looking back on the first trial paddle
Much of the feedback from the first day showed that the Lowen performed to these specifications: slightly tippy with good secondary stability that enabled effective steering through secure edging, no weather-cocking tendencies – this was important for a kayak without a skeg, good tracking, acceptable cruising speed, good enough steerage downwind and promising surfing performance.
The main problem was the tendency to pitch and bounce into a chop. This besides being uncomfortable and slowing the boat, also allowed the bow to drift off to leeward when paddling close to the wind F4 upwards. 
It was clear that the seat could go forward by about an inch, this would not only improve upwind performance but also assist the fit of a shorter person (less than 6’ 1/2’’) under the thigh brace. This done the second trial was conducted in the Carrick Roads, a deep water estuary, launching about five miles inland for the entrance into the Western Approaches.

Launching a second time

The wind, blowing NW f4 was channelled straight down the Estuary towards the sea; so that on launching - from the west side of the estuary, there was no sign of the wind. As can be seen from the photograph taken as it was starting to rain, this time I was using a short pair (200cm) of conventional paddles rather than greenland as on the previous trip. Normally used for surfing, I am able to roll confidently with them and I wanted to see how the boat would perform with a more powerful motor.
I made a circular paddle of the roads first up towards the Fal and then across and down feeling the increasing wind on the exposed side to just short of St Mawes. Paddling back upwind, crossing to Windy ridge to the south of the Mylor harbour approach (which as usual lived up to it's name) and then up the West side back to Loe beach, I mostly paddled through the slack of low water.
Steerage through edging was again good on all points with the exception of wind and waves on the quarter. I was not particularly concerned as I have found this to be a problematic in most of the boats I have paddled without a rudder. The kayak either wants to point fully downwind or across the wind and the paddler has persuade the boat to stay between the two through reacting to the waves as they come through. The main thing is to keep the boat moving even if off course a little. 
What happened was that I had good sections where the boat kept course - and even gave me a few diagonal surfs, and then sooner or later the control would start to go and the boat would move around somewhat until back in the groove. A stern rudder was rarely used; always a last resort, particularly a forceful one for it always slows the boat. Downwind I have consistently found that it is both quicker and more enjoyable to focus on keeping the kayak moving with an overview rather than a narrow focus on direction.
Into the wind and chop the there was less tendency to pitch with the seat moved forward, and the tendency to drift off with the wind just off the bow hardly noticeable (although the wind did not go much above f4), however the ride was a little more wet. I was pushing the boat much harder this time with the more powerful paddles and also when I realized that I was likely to be late getting home yet again. A most enjoyable paddle.
I think this boat goes at its best when pushed hard. It really brings out the liveliness - that slight spring that comes from the wooden frame allied with fabric. That is what skin on frame boats are about: they are aesthetically satisfying.

Wednesday, 23 November 2016


Launch 1 - Penzance
The forecast was F4-6 W to NW and my wife suggested I launch on a calmer day as she had heard that it was going to blow gale force; so I had a look at at what all the local weather stations were recording. They gave a different story, something like 8 - 11  mph; so off I went to Mounts Bay where I knew there would be some shelter should it blow after all
When I got to Penzance it was all quite calm. I like paddling here where my canoe club is based. On the West Quay where there being a really nice clubhouse, and there is not much of a carry even at low tide.
Despite the ocean cockpit getting in was easy, no wriggle necessary. My knees were about right on the thigh braces but I though the seat could go forward, particularly for a shorter person (I am just over 6ft).
Primary stability was not as good as expected but secondary was good: you can lean as much as you want with confidence, and steered well this way. Tracking was good and I was surprised how little the bow moved from side to side with the paddle strokes and seemed to cruise happily at 3.7 kn.
Outside the harbour it was blowing F2-3 from my right as I paddled due south to the Gear Pole an isolated rock about a statute mile out. No sign of weather cocking.
Once round the pole I paddled north easterly (towards Long Rock) to see how the boat performed with the wind and chop well behind on the left quarter and a long swell of about 1ft on the other. As expected it yawed quite a bit when the swells came through but this was surprisingly manageable through leaned steering so that I was able to keep the boat moving; the GPS was now recording 4 - 4.2kn.
Turning east toward St Micheal's Mount the swell, which was wrapping around from the Atlantic (13.5 ft at the Seven Stones light ship) had increased to about 2 ft on the bigger sets by the time I reached Marazion.
This has the potential to be a good surf boat, tracking well on the spilling waves, fast maneuverable and secure. With a good stern rudder broaching was not a problem. It would be harder to surf I am sure on steeper waves but I was impressed.
The boat was comfortable in the clapotis off St Michaels Mount - which was framed in a rainbow. I turned a little way past so that I would have a good 2 NM paddle straight into the chop and breeze which had by now freshened to F4. Into this I was doing about 3.2 kn, but as the wind freshened over the next 40-50 minutes to F5 gusting 6 my speed progressively dropped to 2 kn in the gusts.
Although this was a dry boat which did cut through the waves it was prone to pitching into the chop, particularly when it would steepen as a swell came through. The main problem was the lack of control once the bow started oscillating, and would tend to drift off to leeward. In controlling this I could feel the inside of my thumb catching something sharp on the right gunwale - which I could not locate, and this kept happening.
On the way back I turned right for a while to see how the boat would handle perpendicular to the the stronger wind - still no weather cocking or the bow blowing off to leeward. On reaching the harbour I thought I could hear an ice cream van and then realized it was my phone, but the touch screen would not work. I do not know whether this was due to my cold salty hands or the blood which was issuing from my thumb. When I got through after landing and drying everything off, it was my wife wondering where I was.
On the whole I felt positive about the performance of the boat, but it was clear that I needed to look at the problem of control into a chop - Next Post.
With regard to the change of the weather it turned out that the forecast was right. If you look at the chart of wind-speed at Lands End you can see that I launched in a lull at about 11am; the wind was still rising when I landed at about 1pm.

Sunday, 20 November 2016

Deck fittings on a skin on frame kayak

One other thing first - wear strips
Prior to this boat I had made wear strips of wood screwed in through the fabric into the keel, and then in the later boats finished the wood with a glass/epoxy strip on top. This time I dispensed with the wood and laminated a glass epoxy strip straight onto the keel and also the two chines at their lowest point where they are likely to take the ground. The strip on the chine is easiest to see.
The strips are simply a double layer of 6oz glass. The hull was protected with masking tape when they were laminated in place.
Deck fittings
 All of my early boats leaked. This was because I fitted deck lines the traditional way of drilling a hole through the gunwale, securing the line with a stop knot on the inside and taking the line through a hole in the skin. Sooner or later the seal on this hole would fail and small amounts of water would enter through them each time they were immersed: i.e. frequently when paddling through waves. Although the eight holes or more through the skin were unlikely to be all leaking at once, just one or two would be sufficient to give an uncomfortable slop round the seat.
These days I secure deck lines to webbing loops secured by plates screwed through the skin into the gunwale with gauge 8 machine screws of a length just short of the width of the gunwale plus the thickness of whatever you are screwing through. You can just see the sealant oozing out from behind

the plate, excess is cleaned with iso-propanol. The holes that took the screws had been drilled a touch too large and then their interiors coated with thickened epoxy the day before. Although you can buy plastic or stainless steel webbing plates from chandlers I laminated mine up with chopped strand mat, cloth and polyester resin in the form of long strips which were then cut to size and drilled etc.
The were loops sewn to size according to function etc.
They can be mounted at an angle to take the perimeter line across the foredeck near the bow. This crossover has the dual function of providing a paddle park, the raised fabric seam at the centre giving a little height under which the end of a greenland paddle can be pushed.
As shown below (if you click and blow up the picture - apologies)

You can also sew lines to the webbing as I have for the bow and stern toggle fittings:
and together:
Greenland paddles can be secured to the boat with the lines and toggles shown in the following picture. These are taken through webbing loops instead of the traditional method of a hole through the gunwale.
There will be some modifications in this area, following feedback from the launch which is dealt with in the next post.

Thursday, 17 November 2016

Coating the fabric

Tidying up a seam before starting the coating
Although mainly cosmetic, trimming excess material from the seam at the stern, and then folding what's left over once more with another row of stitching, made a big difference:
This is the third boat I will have coated in epoxy. Prior to that I had used moisture curing polyurethane, which although tough and easy to apply slackened off the fabric too much. Then I tried standard marine enamel straight on to the fabric, again with mixed results.
The down side was that I lost count of the number of coats I had to put on to seal the fabric which was expensive, added a lot of weight and seemed to take for ever. The first time I used the boat it was slightly porous as there was insufficient paint impregnated into the fabric - so I needed to apply more paint; but the surface needed abrading as I was way over the time limit for over-coating without doing this.
The useful thing that came out of this was that I understood that you cannot abrade coatings on a fabric, as doing so pulls bits of fibre onto the surface to create a very rough surface when the next coat goes on - a bit of a disaster really.
On a repair job at about the same time I found that the same thing applies to Kevlar for it is also a fabric: the same thing happened. The way round it was to laminate the kevlar with a layer of 6oz glass cloth over the top. This gave a smoother finish which could be abraded as the glass fibres, unlike those of kevlar which is incredibly tough, could shear off.
I do not think this would work on a skin on frame boat for the stretch characteristics of the fabric and glass might be different resulting on surface cracking (although it might be OK for making a plug). Marine enamel, however works really well as a top coat on top of fabric which has been already sealed with epoxy. This is what I did with the first boat I finished with epoxy.
I had resisted using epoxy for a while for I was concerned about cracking, but was persuaded to give it a go by the fact that its use is built into the building of Geodesic Airolite boats by Platt Montford, and I found it worked out fine. Although an irritant it is less of a health hazard than polyurethane, strong, flexible, easy to work with and economical.
As for this boat and the previous, the customers preferred a semi translucent finish. Thus after primer and filler coats, the kayak was finished with a marine quality varnish instead of marine enamel.
This picture shows the set up for coating. Far left is the face mask; the 3M 4251 Vapour respirator, which also gives particulate protection, then the rollers to use with the tray to get the coating onto the fabric. You need epoxy proof ones which is better than seeing your roller start to come apart and merge with the coating. Gloves are worn two at a time so that the skin is not exposed if you need to replace the outer pair; these are vinyl, but nitrile are best.
The mixing tub is on top of scales which measures down to one gram, which is OK for mixing more than 100 gm at a time. The resin itself is the standard pack from Reactive Resins; this is a Cornish company which manufactures all sorts of coating products including those for marine applications, about twenty five miles east in Bodmin. They specify measurement of resin (2:1 ratio) by weight. This more accurate and convenient than by volume - hence the scales. I have found their resins to work really well on fabric as they are quite flexible.
In the foreground to the right of the rolling tray is the pigment and a spatula onto which it will be added 0.7 grams at a time, to give a concentration of  just under 0.5% when added to the batch size of 150 grams. Although a polyester resin pigment, it is known to work equally well with epoxy at low concentrations. The amount I used was well under the threshold.
The scales supporting the spatula measure down to 0.1 grams which is great for measuring small quantities of epoxy - for example when glueing, and of course for additives like pigment. They only cost me about £10 on ebay. The other, for larger quantities came from Reactive Resins for about the same price.
This shows the hull after the initial priming coat and before the filler coat. There are few pictures as I find coating rather stressful - you do not want to make any mistakes. For the reasons explained earlier, you cannot sand down and start again.
I was coating something like 4.2 square metres of 440 gm/sq metre fabric. The priming coat for the hull weighed something like 650 gm and the deck 400gm. Filler coat amounted to something like 450 gm for the whole boat, so I used just over 1.5 kg to coat the boat in epoxy. The boat would be fully usable like this but would darken over time from the UV.
The varnish added about another 300 grams weight. I used Timberseal EV epoxy based varnish, again by Reactive Resins. Although the instructions recommended painting to give a nice thick coat, I found that rolling on and then smoothing off with a paintbrush to work better. I could have used this as a filler coat and saved some weight.
The photograph below shows the sealed and varnished boat with markings for screw points of the deck fittings. The final fitting out will be covered in the next post.

Saturday, 5 November 2016

Finishing the seam, fitting the cockpit and then some ironing.

Re-doing the seams
After having done the seams the cockpit was given the initial fit using spring clamps.

 In order to do this the excess fabric was trimmed. It is easy to take too much off - you need a good inch from above the cockpit rim to begin with. Then the tension was taken up by inserting nails through the fabric into the sewing holes of the rim. So as not to pull holes in the fabric I prime the areas where I will be making the holes with some polyurethane varnish.

However by the time I have completed the process of putting all of the nails through, I was not convinced that wrinkles which remained in the hull would disappear when I shrank the fabric through ironing later.

I also had one or two iffy areas in the first and rear thirds of the boat, therefore I decided to redo the seams of the middle two thirds of the boat both fore and aft of the cockpit. If careful it is easier to cut than undo the thread.

The boat looked much better when redone, having focused on removing some fabric from the centre section of the boat, partly by re-doing the seams in the opposite direction, i.e. away from the cockpit, the ends being pinned where the cockpit base would sit. This is actually the direction in which I normally stitch seams. Trying to stitch in from the ends does not seem particularly successful with this fabric and a rolled seam. Unfortunately if you don't try something different, you do not find out.
Then the cockpit was re-fitted, the photograph shows the fabric being folded over on itself to give better support for the stitching.

As there were now more wrinkles on the deck, particularly around the cockpit, a couple of pleats were sewn in, one each side. The photo shows the gathering of the pleat in the foreground before stitching.

Although lighter fabrics seem to shrink more, ironing test samples of this fabric on an ironing board have given me approx 2% reduction in dimensions. On the boat where there is no backing it is difficult to heat the fabric sufficiently to get the full shrinkage, so I am at pains to keep wrinkles to a minimum on the hull particularly before ironing.
This photo shows before:

and this after:

The post finishes with two views of the fully skinned hull:

The hull is wrinkle free, but a number remain on the deck which is acceptable. The completed pleat is visible in the first of the two photos. Please note that the techniques referrred to above are applicable the heavy polyester fabric that I use.

Friday, 4 November 2016

Sewing the seams

Sewing the seams
I use a common brand of Sewing Awl - the "Speedy Stitcher"; it is made in the USA and readily available in the UK, particularly in Mail order Chandlers - there are many other types readily available on ebay for example. The seam consists of two halves, each rolled around a rope core sewn together under tension with the speedy stitcher.
Rolling the seam
There is an overlap of approximately one inch of fabric at the seam. Making the seam on top of a stringer, preferably raised to give "V" in the deck is easiest. If there is no stringer it is necessary to insert a temporary batten as the two halves of the seam need to be pinned in place before sewing. I deliberately make my stringers extra wide and of cedar to give a better platform, and easier to pin in to.
I have found a soft plaited rope core to work best, something like 5mm. Although a little more expensive I use polyester as I figure it will not rot and unlike nylon, bond properly when the coating is added. For many years I used household upholstery piping chord and that worked fine. The seam is started by simply rolling the rope core at the start of the seam. There is a knack to this, something you just need to start doing and you learn as you go along.

The two pictures show the start of a seam from the bow stern-wards. The excess fabric remaining at the bow was tidied up once I had established the seam by a foot or two towards the stern.
I big issue is which way to sew the seam. I started in the way shown as I had already sewn a bow pocket, which can be seen just above the clamp in place, however; as you will see in the next post, by working towards the centre from the ends, you can draw wrinkles into the centre of the hull. Some wrinkles are unavoidable, my aim is to have them all on the deck and none in the hull.
Another issue is which way to pull the fabric. Pulling perpendicular to the gunwales will tend to focus any slack into the centre of the boat - which you don't want. Therefore I try to keep pulling perpendicular to the centre seam, which sometimes does not seem natural.
I find it works best to pin the seam about one foot at a time, sew and catch up, and repeat the process.
The sewing process starts by pushing the stitcher through the centre of the rolled seam- as is shown above, pulling through a good length of thread which will be threaded through the loop on that side of the seam. The needle is pulled out and reinserted 1cm or less along the seam; pushed right through as far as it will go and then pulled back slightly. You will then find it possible to pull a little slack from above (BUT NOT BELOW) the needle. The free end you have on that side is then inserted through the gap between the slack and the needle, so that it loops round the thread when the needle is withdrawn. When all is pulled tight you will have successfully have made a stitch.

This picture shows the seam being held firm as the needle is pushed through. Previous stitches through the centre of the seam are clearly visible.

This picture shows the thread being pulled from above the needle

This picture shows the thread from the far side being fed through the loop created above the needle. It is doubled over as it then takes half the time to thread through the six foot or so of thread on the other side.
With regard to my comment earlier that you must not thread below the needle. My awl has a groove cut in the lower side of needle and it takes the thread from a spool inside the handle up to the eye at the end of the needle. If you thread underneath, you short circut the whole process and jam the stitching.
It is a good idea to make sure that the fabric is securely pinned at the beginning of the seam.
The finished seam ended up looking like this, but I was not happy with the wrinkles that remained in the centre of the hull - next post.