Bristol Channel Pilot Cutter

[Dave Cooper 6Participant @davecooper6]

A quick calculation reveals that a 3mm error in a hull of 42" LoA is rather insignificant. In fact, the Windows calculator jumped straight into 'Scientific' notation…

OK, I'll stop berating myself now !

Photos soon…

Dave

[Dave Cooper 6Participant @davecooper6]

Little and Large – the 50% mock up (left of main structure) is still providing a useful reference…

[Ray Wood 3Participant @raywood3]

Hi Dave,

Wow that's put it in context !! She's going to be BIG

Good luck & keep us posted.

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Hi Ray,

Yes, even with a removable keel I think it will weigh a bit – I'm already planning the launching trolley !

Regards,

Dave

[Dave Cooper 6Participant @davecooper6]

Think I'll be attempting some planking soon. I'll probably take Ray's advice and use Balsa strips as an initial step.

[Dave Cooper 6Participant @davecooper6]

[Dave Cooper 6Participant @davecooper6]

I have some 'gunwale' blocks in place – bow and stern at present to give the structure more stability. Thinking of continuing this all the way around 'top-sides'.

I'm feeling my way into planking and will probably start top-sides (with carvel) and then move "up" towards the keel whilst still inverted…

Shortly, I'll need to decide on mast step, steering and motor positioning.

Edited By Dave Cooper 6 on 12/06/2021 11:22:05

[Dave Cooper 6Participant @davecooper6]

Adding in the gunwales /inwales has produced some reflex curvature (plan view) into the topsides. It's all still very rough at present but I'm not sure whether to remove it now, or, wait until the frames are faired in ? Any thoughts welcome…

[Tim RoweParticipant @timrowe83142]

Hello Dave

In my experience it is always best to correct errors as soon as you find them. This helps to stop them compounding. Sod's Law means later errors never cancel out but double!

I am having to do quite a bit of fairing up on the Thames Barge Kimberley I am build to the Veronica plan. I was very careful to cute the frames out accurately. The deck line and the chine lines came out clean but there was a nasty hollow in the aft sections where the curves of the section transition into the chines.

Unwanted hollows are bad news for two reasons:

The first is that you cannot sand the hollow out. You have to sand down the high areas all around and very soon you will run out of hull thickness. Slightly high spots are easy to deal with as they can be sanded down. They often occur where the planks are bent around the frames and do not take a fair curve. Clearly there is always a limit to how much material you can remove.

The second is that when painted, hollows (concave) surfaces stand out like a sore thumb from the light reflections whereas slight variations in convexity are hardly likely to be noticeable.

My planking is balsa starting with 2 layers of 1.5mm balsa which gets around the curves very well. Some high spots have been taken off the first layer but the hollows were filled with a lightweight filler. The first layer is probably about 80% fair and the remaining 20% I can get by sanding the second layer. The final external planking is 1mm mahogany.

It is worth taking the time to get the fairing correct. The shipwrights of old would never let anything pass through that was wonky!

You will probably end up doing planking in your sleep.

Tim R

[Ray Wood 3Participant @raywood3]

Hi Dave,

I agree with Tim on correct bulkhead shape's, but as I think you are building by eye, it's very difficult to get the shape right by trial and error and not from a drawing

But in my experience all is not lost, The planks won't follow your hollow sections they will curve nicely round the bulkheads that are correct and while planking packing pieces can be added to give the plank a fixing/gluing point.

If you plank up from your building board to the turn of the bilge, you should get nice topsides

Only thing is to remember is how you get her off the board ? when the hull is complete.

Regards Ray

[Tim RoweParticipant @timrowe83142]

Hi Dave

Ray is perfectly correct. You may however find that a frame is high in which case you can shave a bit off so it could be a combination of the two processes. Trial and error it will be but you will get there. Just remember to do the same both sides!

Tim R

[Dave Cooper 6Participant @davecooper6]

Hi Both – thanks for the advice – yes, I think action now is the answer….running some bent card strips around the hull it seems she is 90% fair – a small hollow at the bows and another at the stern, but otherwise looks OK.

I think I'm looking at 3/16 by 3/8 balsa planking as a 'starter-for-ten', I'll run a couple of planks up from the gunwales, checking both sides are the same, and see how it shapes up.

Ray: the structure is secured to building board by masking tape which I've drawn the layout dimensions on (see last photo). The tape will come up with the hull (I hope !) and be sanded off together with any surplus packing pieces I put in to get the deck 'rocker' right.

Dave

[Dave Cooper 6Participant @davecooper6]

Just finished running a rubbing strip from frame 5 (mid-ships) to the stern blocks and the curve looks quite nice. I'll do the same from F5 forward to the bows and then post a photo or two.

Looks like a little fairing-in will be needed here and there but nothing too dramatic…

Dave

[Mike Waterhouse 1Participant @mikewaterhouse1]

I'd fasten the bulwarks to a strip of wood about 1/2 X 1/2 inch. Attach each one to a building board before you start planking. This is to keep it all in place & will reduce stress to a minimum. Use lime instead of balsa, it bends quite well & is better than balsa. You can also steam it for awkward pieces.

When I built my Cariad 39 inches long excluding the bow sprit, the ballast was 15 Lbs. Consider putting a motor inside, I used a 555 with a 25 mm 2 bladed prop, it helps if you're becalmed to get back to the bank.

I did think about making a detachable lead keel to give more stability in higher winds but not got round to that yet, it sails very well. I'm sure you'll get a lot of pleasure from it as I have mine.

Safe sailing Mike.

[Malcolm FraryParticipant @malcolmfrary95515]

On the real thing, if an auxiliary motor was fitted, there was no requirement to have the prop on the center line. Fitting was considerably easier if not trying to arrange a hole up the backbone of the vessel.

That snippet from "Topsail and Battle Axe" – a good read for anybody interested in Bristol Channel cutters, if it can be got. I had mine from my local library, back when local libraries were still around.

[Dave Cooper 6Participant @davecooper6]

Hi Mike and Malcolm

Mike : Yes, the transverse x-members were used on the 50% mock-up to good effect, Surprisingly, at 100% I can't budge the frames except for a little fore and aft flex . This is probably due to the multi-laminations used on the gunwales I suspect. However, I'll review it when there are a few planks in place either side. A motor on-board is part of the plan. I'd not thought of using lime but I'll try and source some strip wood and do a few experiments…

Malcolm : Tom Cunliffe says in his book on Pilot Cutters that he had an engine on board "Hirta" when he owned her. This has since been re-named "Cornubia" (see photo at the beginning of the thread) her original name post- restoration. Mine is loosely based on "Kindly Light" from Barry, South Wales and built by Coopers near Bristol.

I'll look out for the book you mention (not sure if my local library is back in service yet !).

Regards both,

Dave

[Dave Cooper 6Participant @davecooper6]

Following on from work on the gunwale laminations, it looks like one of the frames nearest the bow needs correcting.

There is an 'inset' of about 3mm which will lead to some concavity of the profile. I'm thinking of packing this out as the planking rises up from the gunwale (hull inverted). I suppose filler could be used but I'd rather stick with 3mm marine ply which the rest of the frames are made from.

Don't really know how this error has crept in as port and starboard frames were cut and sanded as one !? (Possibly incorrect placement either side of the keel, or, a simple measurement mistake from the hull centreline to the outboard position).

Still, better to correct it now I think. I'll take some photos when the first few planks are in place showing the packing pieces.

[Dave Cooper 6Participant @davecooper6]

[Dave Cooper 6Participant @davecooper6]

Off the building board for now. Just a small repair to one gunwale rubbing strip as it was lifted. Work continues strengthening the transom, bow and adding further gunwale in-fill pieces. Then it'll be back on the building board for planking to begin

.

[Dave Cooper 6Participant @davecooper6]

Some experiments with mast, bowsprit and boom positioning. The bowsprit will be shorter (over the hull), the mast taller and the boom longer (just overhanging the stern). All spars likely to be hardwood dowel – not really decided on the wood type yet but, open to ideas ?

[Ray Wood 3Participant @raywood3]

Hello Dave,

The cutter is looking in good shape now, have you decided what materials to plank with ?? I would use block balsa at the bow and stern , which is a lot less stress full trying the cut the planks to the exact length to fit the stem.

How's the sports car progressing ??

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Hi Ray

I like the idea of using block balsa for bow and stern – that makes a lot of sense, and gives a nice interface for the planks to key into.

I'm currently thinking of 2-later planking. First 'skin' will be balsa – not sure about the outer skin yet – lime or mahogany maybe ?

I've now got someone to assist with the engine on the sportscar (hasn't been run for c.10 years !). Just working on the construction of the rear wing elements in between work on the cutter…

Cheers for now,

Dave

[Ray Wood 3Participant @raywood3]

Hi Dave,

If your thinking of 2 layers of planking, I would put the harder wood on first so you can pin the balsa to it ? I think Lime, Bass or Obeche would be best material, I find Mahogany is very brittle & splits easily when pinned to the frames.

I have turned up various parts over the years for my friends replica Ford GT40 unfortunatley he can't drive it any more as the 4.2 litre engine ignition system plays havoc with his pace maker

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Interesting thought Ray. I'm thinking of maybe using some "L" shaped pieces either side of the frames to attach the first layer of planking to.

Also, current plans are to install the prop' shaft, motor mount and maybe winch /rudder servo mounts too. Just measuring up for these now as, once planking has begun, it will be more fiddly to get inside the hull with 70+ year-old fingers !

Dave

[Dave Cooper 6Participant @davecooper6]

A right old patchwork of balsa blocking. First the bow, then the stern. Much of it from the scrap box.

The basic idea is to add strength to the structure and to provide a basis for the planking to attach to.

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