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Bristol Channel Pilot Cutter

Possible next project

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Dave Cooper 603/03/2021 10:44:08
290 forum posts
29 photos

Research has thrown up some line drawings of hulls. This one could be "Kindly Light" or, a near approximation.

kindly light hull drawings.jpg

Armed with a pair of proportional dividers, I could do with some advice on how to work towards a set of working plans. Sail, Rigging and deck details still under research...

Thanks,

Dave C

Kev.W03/03/2021 11:06:39
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316 forum posts
38 photos

Haven't seen anyone mention a model owned by one of our club members, not sure if it is still available, but someone may have a copy of plans they would share.

'Cariad', found this when I googled it ... Cariad

Ray Wood 203/03/2021 13:01:18
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2418 forum posts
849 photos

Hi Dave,

Have you that drawing as a paper version ? if so what size is it ? When the copy shops open again you could get it enlarged, It rather depends on how big you want your model to be ??

Or the harder way is to enlarge your drawing by hand with a compass, flexi curve rule & pencil

Regards Ray

Dave Cooper 603/03/2021 13:46:16
290 forum posts
29 photos

Hi Kev and Ray,

Kev: "Cariad" looks very close to what I'm looking for. I'll certainly put it on the short-list.

Ray: Sadly, I only have a small electronic drawing version at present. Attempts to enlarge it have lead to blurry outlines and fudged figures !

A rough plan at the moment is to make a 'half-size' hull in card /balsa. I think I'm aiming for a finished model size of around 40", so the mock-up would be approx. 20" hull length. If this turns out OK, I'll convert the card frames to wood (probably 3mm marine ply).

Photos to follow as soon as the mock-up is under way.

Cheers both

Dave Cooper 604/03/2021 23:26:53
290 forum posts
29 photos

Just pondering main mast positions as most line drawings don't show it. I want to get this right as I think the deck-supporting frames in this area will need to be quite close in to carry the longitudinal and lateral sail loads.

From various photos I've studied, a figure of 5/13ths of deck length back from the stem head seems about right ?

I think this will mean frames at around the 4/13th and 6/13th 'datums' thus enclosing a fairly stout keel box for the mast step. This may be over-kill as the standing rigging will probably take most of the loads in tension (my usual tendency to over-engineer here !). Anyway, I'll try it out on the mock-up and see how it looks.

Any thoughts welcome...

Dave Cooper 607/03/2021 16:06:40
290 forum posts
29 photos

Hi All

A brief update : Have decided on 40" Hull length, around 11" beam and 9-10" draught. There will be plenty of space for interior lead /steel /epoxy ballast and for the RC gear plus a small auxiliary motor.

To begin with all sails will operate from one servo. Later, the main(s) will be on one servo with the jibs on another.

Half-size mock-up to begin as soon as I can lay my hands on some good quality card for the frames. 10 stations, 1 frame per station (over-kill ?). Mast at frame 4. Stem post, keel and transom in balsa - these to be transformed to 3mm marine ply on the finished model.

The model will be 'semi-scale' as I won't be slavishly following any existing lines drawings. (Mainly for reasons of hull volume). It will also feature an 'overscale' rudder to assist with tacking.

Hope to lay out the 50% frame plan next week with some photos.

That's it for now

Malcolm Frary07/03/2021 16:59:58
1010 forum posts
Posted by Dave Cooper 6 on 04/03/2021 23:26:53:

Just pondering main mast positions as most line drawings don't show it. I want to get this right as I think the deck-supporting frames in this area will need to be quite close in to carry the longitudinal and lateral sail loads.

From various photos I've studied, a figure of 5/13ths of deck length back from the stem head seems about right ?

I think this will mean frames at around the 4/13th and 6/13th 'datums' thus enclosing a fairly stout keel box for the mast step. This may be over-kill as the standing rigging will probably take most of the loads in tension (my usual tendency to over-engineer here !). Anyway, I'll try it out on the mock-up and see how it looks.

Any thoughts welcome...

A very rough and ready way is to draw your sail plan on card, and see where it balances. Do the same for the side profile of the submerged part of the hull. The first indicates the probable centre of effort, the other the probable centre of lateral resistance. On a 40" boat, having the sail plan centre about 1" or so forward of the hull centre seems to work.

If going for internal ballast, lead. Anything else lets the centre of gravity rise too much, and in a scale hull, there just isn't the space available low down for anything much lighter than lead. Cast ingots if that can be managed, a wide variation of shot sizes if not.

Dave Cooper 607/03/2021 19:12:19
290 forum posts
29 photos

Thanks Malcolm

I'll certainly plot the C of E and the CLR as you suggest. On the pilot cutter, the bowsprit will be adjustable in length, so this should allow some movement of the C of E to, hopefully, achieve balance. Failing this, I think I can also build in some 'range' to the mast step position.

In the past, I have used lead shot from shotgun cartridges for ballast (model gliders mainly) encased in epoxy. I have also got some lead blocks left over from my son's karting days - so these could be pressed into service as well...

Dave

Dave Cooper 608/03/2021 17:39:56
290 forum posts
29 photos

Following some basic research started work today on a half-size hull mock-up. Frame positions and trial fitting of stem and transom post to get a feel for things :

50% hull mock up.jpg

Dave Cooper 614/03/2021 13:34:44
290 forum posts
29 photos

A bit more progress: Keel and frames 1, 5 and 9 in position. (The eagle-eyed will have spotted the stern post being reversed in the previous photo - oops !)

50% keel side view.jpg

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