Tag Archives: moulds

Progress – reaching the bilge & stringer

We have been planking continuously now, if only work would stop getting in the way….

Reached a couple of milestones in the last week

  • Planking reached half-way up the stem and half-way round the transom (of course we are no-where near half way at the broadest point of the hull).
  • Planking got too high to reach – so installed some staging to stand on (slices of one of the trees that came down last winter and some old scaffold boards)..

At this point the planking has been going quite simply, as the hull shape means that at this point the planks are almost straight and level (in the horizontal plane)… I think I sense trouble ahead as we reach the forefoot…

Here are latest pictures; she is starting to show her lines, and they are more “tug/yacht” than “fine river launch”, but we like them, and she is meant to be sea-going so I guess this is to be expected. But it’s hard to get far enough away to get a proper picture.  (click for full-size images):

Planking reaches the Bilge Stringer

Planking reaches the Bilge Stringer

Planking half-way round transom

Planking half-way round transom

Making sense of the planking?

I think we are starting to get “into the flow” with the planking… Louise and I work like a (reasonably) well oiled machine now – as you can see from the pics below the hull is starting to take shape.

Continue reading

Carpentry 101

Well another milestone is reached, I have managed to start on the Hull for Befur. We cut the moulds out in the old house in Medstead, but this last week we have managed to rebuild the strongback (provided FOC by Graham in Shepperton from the Selway Fisher Yahoo Group, thank you Graham) and started erecting the moulds. Continue reading

Step one complete!

Here are half the moulds for Befur with louise providing scale

Here are half the moulds for Befur with Louise providing scale (Oh, I mean "elegance" - phew!)

Well, we passed the first milestone; all the formers/moulds/jigs are cut out, and I only made a complete hash of one of them! One needs a 14mm “outer” laminating around it due to my misunderstanding of the frames v ribs question and cutting it undersize – but that will serve as good practice for the rest of the laminating I have ahead of me.

Here are the rest showing the ones next to the Transom and Stem;  an elegant stern and prow designed to cope with open water…

Louise modeling the other half of moulds...
The other moulds showing the end ones (next to stem and transom

We are going to return to some metal work while we await the arrival of the Castings from France…. (end August) – I think I will fix the two bikes occupying the building space and turn them into wood funds…

 

First Mould astern of stem
First Mould astern of stem

As you can see the bows flaire to throw off spray when operating in rough water, and the transom has a significant tumblehome, so the moudls are made in two halves, so that they can be dismantled and removed once the stripping is complete.

The game plan is then to cut the floors, frames and bulkheads to shape using these moulds. Having spoken to Paul Fisher he has persuaded me that we should not try to fit floors etc. prior to sheathing the inside of the hull, so I am planning to just preinstall the Hog/Stem/Transom (of course) and the Bilge Stringers and Clamp.

Next up is sourcing the timber for the strongback of the building jig. I was thinking of building box sections from OSB (sterling board) to save weight and money, but “the community” has persuaded me that this is a bad plan, and I have come to agree. While I think the actual box sections should be a strong as the timbers, I concluded I could not attach the “risers” that hold the jigs in place firmly enough – It would be too hard to spread the load to acheive a stable solution… so 30+ meters of 8 by 3 – here we come!

So Far So Good

Well I  have turned the first 7 sheets of chipboard into moulds and am half way there…

Paul (from SFD) clarified my confusion, I was thinking that the frames marked on the drawings were like the ribs on some of the pictures of his designs, just square and laminated onto undersized moulds – but they are full bulkheads cut away as needed to fit under sole and behind seats and lockers – at least I figured this out before I cut more than one undersize 🙂

plastic batten providing a smooth curve from the marked offsets

plastic batten providing a smooth curve from the marked offsets

Using the plastic batten to produce a smooth curve round the offsets from the mould drawings really works well, and has highlighted 2 or 3 occasions where I had miss-measured or mis typed a dimension, so hopefully we are going to wind up with a fairly fair jig!

The game plan is to a few 3/4-inch panel pins into key marks, and then pull the batten round… normally 3 or 4 are enough, and the fact that the batten will normally then automatically align itself with the other poinst marked from the offsets  from the plan show wat a good job SFD’s computers do in fairing the design.

clamps hold the batten in place, and a few panel pins set the line of the curve

clamps hold the batten in place, and a few panel pins set the line of the curve

The ally clamps just hold the batten down and stop it jumping out. Then when it’s all in place you just draw round it, pop it out, pull out the pins and break out the jig saw!

…and tonight Paul from the Castle of Comfort (my local) came round to help move the next 8 sheets of chipboard in to cut the rest of the moulds…

 

Sawing Straight (not)

Having clamped a pair of mould-half panels together, I figured I could just cut them out with a jig saw….

The "Offending" Saw - as always it's the bad workman who blames his tools!

The "Offending" Saw - as always it's the bad workman who blames his tools!

So off I set, slowly and carefully sawing along the line – 2 inches in I  encounter the first problem – there is so much dust I can’t see the line… At this point I engage “smug-mode” and pick up the shop airline, and with the spare hand blow the dust clear as I saw…

… I reach the end and discover (horror) that the b*&^&^y saw has cut at an angle to the vertical – and (double horror) this mis-cut has resulted in the lower panel being significantly undersize (we are talking about a ~5mm undercut!) grrrrrr….

I check the saw and the blade is square to the foot, so I am mystified…

A number of posts to the Selway Fisher Builders Yahoo group follow… (this really is a great group of people) and a deal of suggestions emerge within a few hours. These range from observations that cutting 1.5inches of chipboard in one go is too ambitious, thru to real Zen-like encouragement to chill more, take up a pipe and cut them with a Japanese hand saw – excellent!

So, I take some of my scrap chipboard (I just made a nice new bit of this) and draw curved lines and practice my sawing (by hand and other approaches) – including sawing it an inch oversize and improving my planing and surforming technique.

In the end two key factors emerge 1 – you cannot saw two at a time (you were right Graham) and 2 – I was going too slow! By setting the variable speed JigSaw to “flat out” and keeping my feed rate slow the desired results emerge….

The first three moulds - halves bolted together, showing the marking out

The first three mould-halves bolted together, showing the marking out (Nos 1,12 and 16)

I leave the workshop with three assembled and very “boat shaped” moulds – life is good again!

 

Marking out the moulds

We progress. Having cut the first 7 sheets of chipboard into panels sized to provide the first half-moulds we set about marking them and cutting them out.the first few mould half panels cut...

Selway Fisher provide a set of mould shape drawings, these have a set of horizontal lines at fixed distances above and below the water line (like +50mm, +100mm etc.) and for each of

a stick cunningly modified to provide a ruler with markings corresponding to the verical mould shap offsets

a stick cunningly modified to provide a ruler with markings corresponding to the verical mould shape offsets

these a distance from the centerline of the boat to the edge of the mould. So the first step was to produce a “ruler” with these “vertical offsets” from the waterline marked.

Having first located the waterline on each sheet (by treating one edge of the sheet as the bottom of the hull and then measuring up to the waterline datum position), the ruler is then used to mark the positions (and then draw in) the horizontal lines on which the offsets will be measured.

Then measure and mark the offsets onto the boards. Once this is done I then nailed small panel pins into some of these locations and used them to locate and bend a batten (I used a bit of the plastic finishing strip from a laminate flooring project) to the shape of the edge of the mould. It soon became clear that the batten needed holding against the mould in a couple of places, so bent scraps of ally were srewed into the chipboard to hold everything in place.Moulds showing marking out and

This bit was VERY satisfying, as you could see how the batten automatically took up a smooth (fair?) curve that passed thru the other marked points. I had miss located acouple of points but these became immediatly visible (because the batten “missed” them by  a mile).

My plan is to laminate the frames/ribs onto the moulds before planking, so I chose a batten which was the same thickness as the frames (ribs), so for the moulds that were located where the frames were to be located I drew the cutting curve on the inside of the mould and for the moulds where the frames were not located I drew to the outside of the batten. (I am still a bit nervous about the actual thickness of the frames, as I can’t see this marked on the drawings, so I am awaiting an answer from Mr Fisher when he returns to his offices next week). Actually I spent most of a day computing a set of offsets for the moulds with ribs, but the math was pretty complex, and so in the end I adopted Louise’s suggestion of drawing the inner mould shape from the outer one, as described above!

Removing the batten left some very boat shaped lines on the moulds – then I marked on the hog and clamp cutouts ready for cutting (again these are fitted before the planks) … filled with positive vibes I clamped the mould halves in pairs and picked up the jig-saw and things to a turn for the worse!