The Building Process for the Seil Skiff

Introduction

The St Ayles Skiff was designed by Iain Oughtred, an Australian of Scots descent now living at Bernisdale outside Portree. He has been designing lovely small boats for home building since the seventies, when he was one of very few promoting interest in historic boat shapes. Decades ago he was a successful racing dinghy helm and his sailing boats are deceptively fast. Our skiff comes with a good pedigree.

The prototype St Ayles Skiff - almost complete

The prototype St Ayles Skiff - almost complete

The basic building method for all of Iain’s boats, like those from many other modern designers, is clinker-planked, but using plywood instead of traditional boatskin larch and epoxy glue instead of copper nails and roves.

A traditional rowing skiff has dozens of thin ribs, usually called timbers or frames, made of green oak or similar, steamed and bent in after the hull has been constructed over temporary moulds, then quickly nailed in place. These are not necessary with a glued clinker boat, as the unframed hull is incredibly stiff and strong without them, but the St Ayles Skiff does in fact have four frames, to add more strength and support the rowers.

Scottish Coastal Rowing Association has agreed on certain principles to prevent members trying to get an unfair advantage. These include the requirement that one must use larch or wood of a greater density, disallowing the use of carbon fibre and banning metal pegs for the oars. One crew apparently uses ebony for these. At present there’s no minimum weight limit, but one may be introduced if required. The lightest skiffs come in at about 170kg, but apparently there is a professionally-built Rolls Royce skiff that weighs 250kg. To be competitive her crew take the floor boards etc out when racing.

What follows is based on my experience and looking at the Ullapool skiff photo-description for Ulla, accessible on their website here:- http://ullcoastrow.wordpress.com/our-build/

There are different ways of doing things and we may decide to depart from what follows. Where there is an obvious alternative I’ll mention it. We discussed these a bit at our meeting on 19 June and although no final decisions were made I’ll record what the mood seemed to be.

Step One – Preparation and setting up

The existing floor is concrete with a slope lengthways, which can be dangerous and disorienting. Ideally we would lay a temporary floor to support the building frame and provide a safe working area of about 30 feet long by 12 wide but considerations of the cost of doing this and the other uses of the building mean that we have looked for an alternative. After a very valuable input from Richard Pierce we have come up with a method which will work. It involves constructing a solid base for the construction by making three mdf or chipboard boxes, two of eight feet and one of two feet to get the required eighteen feet to support the moulds, fixed to the floor with legs of varying sizes to fit.

The hull is built upside down over ten moulds, with the four frames fastened to them where required. These are usually set up on a big ladder frame, which either has integral legs or rests on some heavy trestles. I note that the Ulla’s frame sat on just two of these and I suppose it depends on how strong they are. Our proposed method eliminates the need for a separate ladder frame and also provides a platform on which tools and materials can be placed. Further, only needing to be two feet wide it will enable us to get inside the upturned hull and scrape off surplus glue before it cures, saving a lot of time later in the process.

This is the most important part of the whole build, because we must get the set-up perfectly true and ensure that everything is strong enough not to shift during the build process, which will involve people having to climb on it from time to time, for example to plane bevels.

We also need some work-stations, for cutting the scarfs to join the hull planks together, mixing glue and doing carpentry work. We have Nick’s existing workbench, which has a vice, for small woodworking jobs and will construct a larger one for the other work.

Epoxy is horrid dirty stuff and has to be kept away from one’s skin, tools, everything. We will need some basic rules about handling it and plenty of items like nitrile gloves.

Step 2 – Making the stems, keelson and frames, setting them  up

Like most of the skiffs already done, Ulla has laminated stems and keelson. For this work they used a moisture-curing polyurethane glue, probably Balcotan, although I think many builder’s glues such as Gorilla are very similar, being rated for outdoor use and waterproof. These glues are not gap-filling but this doesn’t matter when you are laminating from thicknessed timber strips and using lots of clamps. The main advantages are that it’s convenient – you only squeeze out of the bottle what you need, less toxic and cheaper. Because we will probably use slightly green larch for these parts a glue which tolerates moisture is good.  Epoxy will have to be used later for the planking work.

The alternative method would be to make the stems from solid timber pieces cut out and joined together, then cutting in the rabbets (or rebates) but that begins to require real carpentry skills. The feeling at the meeting was that we should go with what the others have done, keep within our skill levels and improve the learning experience for those who will build their own boats later.

As the stems are made from thin strips that bend easily we don’t need to steam anything. My own experience has been to use more, thinner, strips rather than fewer, thicker ones, to minimise springback. It uses more wood and glue, but I feel you get a better result.

The Ulla team nailed wooden blocks onto a large board to bend the strips round, but they then needed very big clamps to get the distance. We can use some brackets made from angle iron that I got cut up and drilled to take bolts years ago. You make the inner pieces first, then laminate the outer stems on to them, so they fit later, as they don’t go on until after the hull is planked.

The four frames are glued together from plywood pieces included in the kit and I would use epoxy for this, as the plywood is made from something similar to it.

The stems, frames and moulds are then set up on the ladder frame and we laminate the hog or keelson, (that is the inner wood keel), over them.

Then we bevel the stems and keelson to take the planking and mark the plank landings where required. The positions are given in the kit.

 Step 3 – Planking up

The main benefit of building from the kit is finding all the planks precut, so that no marking out is required, nor any calculations, in short all the time-consuming things that boatbuilders normally do. I reckon this took 90% of the time building my yellow wherry and I’m annoyed that I didn’t get some of the plank lines quite right, as you can’t fix these things later. All of this is done for us, but we need to join the plank sections end to end by scarfing them together.

There’s a very helpful photo-sequence on the Jordan Boats website, here:- http://jordanboats.co.uk/JB/clinker_ply.htm

There’s also a video of him here:-


Scarfing involves planing long bevels on the ends of the pieces, lining them up carefully and gluing them with epoxy. There are a few ways to cut the bevels, best known are with a router on a special board made for the purpose or simply with a very sharp hand-plane.

We could leave the plank parts in their sheets until required, but it may be better to cut all the scarfs as one exercise. We cut the parts out with a Japanese pull-saw, then remove all trace of the little webs with sandpaper, then scarf the parts, line them up and join them.

To date most teams have scarfed the planks together on a flat table. Alec Jordan has made lining-up easy by drilling the parts for nails, over which strings can be stretched to ensure perfect alignment. The problem with this approach is that you then have to handle the extremely long planks with great care. The method is fine with boats up to, say, fifteen feet, but handling planks twenty two feet long is no joke. Fitting them accurately, when the gluing surfaces will be slippery, is also a problem.

Following a discussion with Alec Jordan, Richard and I think it will be better not to join the plank sections off the boat. It is relatively simple and safer to join them on the hull as the work progresses, provided steps are taken to avoid flat spots at the scarfs. To ensure fairness battens are clamped along the outer, unsupported edge, preventing the planks from sagging between the moulds. This sagging has been experienced even with some pre-joined planks and some teams have required to do emergency propping to save the day.

Each plank is fitted, using screws to the stems and keelson and epoxy. We will need to make a lot of big clothes-peg clamps from scrap ply to hold the plank laps together while the glue sets.

After each plank is on and the glue has cured it is bevelled to give a good fit to the next one. Minor errors will be filled with thickened epoxy.

A result of the box base method outlined above we should be able to avoid most of the messy glue drips and runs before they’ve cured, but some will be unavoidable.

It’s important to avoid any risk to health through exposure to uncured glue. Never allow solvents near your skin because  they dissolve its natural oils and allow the epoxy into your system. Wear a mask when sanding epoxy.

Step 4 – Finishing the Outside

This involves filling any nail-holes and scrapes, cleaning everything off, gently sanding the exterior, fitting the outer stems and keel. We should also get some coats of primer and undercoat on at this stage.

Then the hull is turned over and we should have a party.

Building teh prototype - Turnover Day

Building the prototype - Turnover Day

Step 5 – Fitting the Interior

In the cold daylight after the party we can start to clean up the interior. There will be some drips and runs of cured epoxy that will have to be carefully softened with hot air guns and scraped away, followed by very careful sanding, taking care that we don’t remove the outer veneer from the plywood.

In general cleaning up and sanding are the most time-consuming parts of the whole job.

What follows is fairly conventional joinery work. It will make the difference between a pretty or an ugly boat but not to her speed. The close-up detail photos of Ulla’s inwales and outwales, seats etc give an idea of what to aim for.

It seems that we have to learn some Shetland words too, fastibaands are the transverse supports for the seats, kabes the pins the oars bear on but rouths –any ideas? Maybe the Seil skiff should have Gaelic parts, to confuse the opposition.

Step 6 – Painting and maybe varnishing

We won’t epoxy coat anything. It’s unnecessary and can be deadly, because if the epoxy skin gets damaged and allows water into the veneers the boat will rot.

It’s good value to do a proper paint job, from primer through undercoat to a topcoat using the best quality paint we can afford, all oil-based.

It may seem a pity to cover fine carpentry with paint, but to put fine varnish on a competitive skiff asks for lots of work in future. On my wherry I’m glad to have everything well coated with paint, as minor scrapes can be fixed as they occur. For that reason we won’t be using posh treatments that need factory conditions.

 Step Seven – Meantime Jobs

We will need an awful lot of oars. Shorter, older and lighter rowers prefer short oars, beefy show-offs longer ones. Oars will sometimes get broken.

There isn’t a recommended style for the rudder assembly. Options are to have a fixed or hinged, lifting blade. And steered by a tiller or by a yoke?

Some boats have a flag-staff.

 Boat Name, Colours and Graphics

We need to pick a name, possibly by a competition with shareholders voting for the winner, (or we could auction the right to pick a name from an approved shortlist) a colour scheme and a design for a logo for fund-raising materials, flags and teeshirts.

 Appendix

 Things to be done now, following meeting on 19 June

 Step One –  Preparation and Setting up

  1. Build the base boxes as described in the text.
  2. Build work station for gluing and scarfing. I think this can stand away from the building set-up, across the end of the shed.
  3. Gloves, first aid kit.
  4. Housekeeping items – waste bins for wood, toxic waste, and general stuff. Bin bags. Pin board. Clock. An old bookcase for putting tools and clamps on.

Step 2 – Making the stems, keelson and frames, setting them all up

  1. Laminate the stem sections. Good PU glue required and clamps – we need as many as possible. Please paint or mark your own so that we don’t fight over returning them later.
  2. Larch or Douglas Fir strips, cut and if possible thicknessed. Not finely planed, or the glue doesn’t stick. Very fine, straight clear pieces needed for keelson (hog) and keel.
  3. Epoxy glue and additives – to be subject of separate note. EGK has supplied a bin of microfibres enough for a couple of skiffs.
  4. Basic hand tools, including block planes.

Further Steps to follow

Article written by Ewan Kennedy

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