Bristol Channel Pilot Cutter

[Dave Cooper 6Participant @davecooper6]

Just arrived in the post – an early Christmas package containing :-

Motor, ESC, shaft, U/J, couplings and a prop.

I will trial assembly this lot over the next few days together with rudder and dummy sail winch servos to check how it all fits in. The servos will (most probably) be standard Futaba 3003's for now until I have some better inspiration.

I'm fairly sure the propshaft alignment will be out so I expect some sleeving and jigging will be needed.

Photos to follow,

Dave

[Ray Wood 3Participant @raywood3]

Hi Dave,

It is a good idea putting the shaft, coupling and motor in at this stage as access will be tight after you have planked and the deck fitted

I wouldn't worry too much about alignment is only a get you home motor, not a fast electric !!

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Thanks Ray.

Yes, everything fits in nicely. The servos look rather puny though. My spares ones are Futaba S3001's and may just be OK for rudder (they're ex-model aircraft and have seen some service, but, they check out alright on the bench…).

I was planning on working all sails from one sail winch initially, and later, moving to separate servos for independent control of fore's and main's – any thoughts ?

Also, a recommended sail winch would be good – I've no prior experience here….Looks like the full-size has either a 4:1 or 6:1 purchase on the main. Just acquired a 2.4 GHz Tx and will be collecting a box of Rx's soon from a fellow clubmate.

Cheers for now,

Dave

[Ray Wood 3Participant @raywood3]

Hi Dave,

I can see no real advantage of having separate controls to the mainsail & foresails , I'm a fan of the bigger Hitec lever servo/winches about £30.00 I use them on my barges with a 2 to 1 pulley there is plenty of travel my only experience with a drum winch ended in a massive tangle below decks

Most for the time on the water is spent beating to windward with all the sails in tight, the foresails work just as well with a brass wire horse and being self tacking, so less to go wrong

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Hi Ray

Yes, the Hitec lever winch looks nice. I was on the verge of ordering it then I thought I'd pose the question first.

I'd spotted a Youtube video of a model of the Jolie Brise at around 1/15th scale. It was reaching nicely in light airs, on both tacks the sail settings looked the same. This seems to bear out your theory – I expect it applies to beating as well. In fact, I think the only advantage of independent sail control may be when going 'goose-winged' (I tried this once on a flotilla yacht in Greece ) or, possibly, when racing…

Cheers,

Dave

ps Spent most of this morning re-aligning the prop shaft. It's now within 1/2 a mil'. I think that'll do !

 

Edited By Dave Cooper 6 on 09/12/2021 16:06:29

[Malcolm FraryParticipant @malcolmfrary95515]

The usual cause of tangling with a drum is lack of tension. When it unwinds, tension is needed to keep the line tidy. With good wind, the pressure from the sail "might" do the job quite often. Any other time it is a certainty that the line will hop off the drum and make friends with almost anything.

There are several cures.

Easiest is an elastic line above deck that pulls the line out from below. Has the minor disadvantage that the elastic has to be regarded as an expendable spare part. Since all of the power generated by the sails goes through it and the arm develops quite a considerable twisting force, a really solid mount is advisable. As is ensuring the the arm does have room to swing. ( A club member ran one with a transmitter with not quite the right settings. When it got to the travel limit determined by a frame, it tried to mash through the frame, but managed to mash the splines instead..)

Next is the continuous loop. Most winch drums have two layers. The loop starts with windings on the lower spool, heads off to a turn point, goes over a straight run long enough for the required travel, turns and comes back to the upper spool. As it feeds out of one, the slack is taken up by the other. Zero chance of a tangle. The take-off for the sails happens on the straight run, which can be above or below deck, builders choice. A 6 turn drum winch needs about 17". The shroud that you get with some winches is helpful, but by no means totally foolproof with a single ended setup, but this might depend on the type of line used. Since the pull is linear and always in just one direction, mounting is vastly simplified.

It doesn't matter which system is used, you don't want potentially slack line below deck, while practically nobody can design a machine that can tie knots, mother nature does it for fun. I can vouch for this having had the slack line from an arm tie itself round the slide switch and turn it off when pulling the sails in. That was in a Victoria done as per the instruction book.

[Dave Cooper 6Participant @davecooper6]

Thanks for the explanation Malcolm. I've not yet got into detail planning of the sail operation but will bear in mind your advice…

The motor mount, rudder and sail winch servo mounts will be 'beefed-up' to cope with anticipated loads. I'll also do some line tension tests with the lever arm in different positions. Fortunately, I've got quite a lot of internal space to play with.

Is there any data regarding typical main sheet loads per sq. ft. of sail area. I was thinking in terms of a 2:1, or 4:1 purchase ?

Regards,

Dave

[Malcolm FraryParticipant @malcolmfrary95515]

There are such things, but the one that I looked at, while appearing useful. upon further reading, indicated that the author had little understanding of the real world that we live in, or general engineering principles.

While it is possible to calculate what loads the winch will undergo, there is no useful calculation that takes into account the wind forces that will be encountered. As a result, most of us go by the TLAR rule. (That Looks About Right). I suspect that even if his calculator was used, if you didn't de-rate heavily to account for the unexpected, the chosen winch would have a short life.

[Dave Cooper 6Participant @davecooper6]

Propshaft in and tested :

Following much work with rulers, protractors and the like, the motor mount starts to take shape :

Motor is MFA 919D with 2:1 reduction gearbox, driving a 40mm prop via a 4mm shaft. Hopefully, this will pull me out of the weeds and get me home !

Alignment is not 100% perfect but should be ok – some adjustability has been built into the mount just in case…

Edited By Dave Cooper 6 on 19/12/2021 16:53:13

[James HowgegoParticipant @jameshowgego39404]

Looking good.

Did the pilot cutters not have any shear? IE rise in the decks towards the stem?

Also are you putting noggins in between the frames each side of the keel to land the planks on?

Cheers James

[Dave Cooper 6Participant @davecooper6]

Hi James

Well spotted – shear not yet installed. The plan is to include some when the foredeck gunwales go in.

Some noggins already in at the topside. I expect to see more at keel level later (I'm currently planking from topsides UP to keel – ie inverted).

General comment : this my first own-design yacht, and, my second o/d boat. Actually, my second model boat ! As such, it's 'semi-scale'. There will probably be some features incorporated from "Apres Cours", "Jolie Brise" and "Kindly Light". Otherwise, there is no attempt to go 'exact scale' at any stage.

Regards,

Dave

[Ray Wood 3Participant @raywood3]

Hi Dave,

That set up should get you home ok

That shaft is at rather a steep angle but its fine and the prop will be good and deep in the water.

Good luck with the planking

All the best Ray

[Dave Cooper 6Participant @davecooper6]

Hi Ray

Yes, I could have gone with a double U/J set-up and effectively 'flattened' the the prop' thrust line. In the end though, I just went with the straight-forward approach. I also wanted easy access to the motor and coupling in case of any operating issues. (The motor is now just below deck /gunwale level).

Next up will be the mounts for the sail winch and rudder servos which will need to be quite 'beefy' I think. I may 'triangulate' these off the stern frames – we'll see, but again, I'll aim for good access to aid set-up etc.

First course of planking is in plus a few extra noggins here and there. I've gone with balsa for now, but I'll review it as work proceeds.

Have a Merry Christmas / New Year (such as we are able !),

Dave

[Dave Cooper 6Participant @davecooper6]

Mark 1 rudder for the Pilot Cutter. Made of 5 pieces, 3 pine plus 2 marine ply. Tongue-and-Groove jointed all round.

Only problem is the ugly glue line ! It's had one coat of Light Oak stain so far. The aft piece is getting rather thin in places to permit further rubbing down….should I re-make it, or, try something else ???

[Ray Wood 3Participant @raywood3]

Hi Dave,

Slightly brutal answer I'm afraid, but the real work boats would have been painted below the waterline with black pitch or tar, paint it ??

Regards Ray

[Dave Cooper 6Participant @davecooper6]

That saves my bacon Ray – estimated waterline will be somewhere between the top of the glue line and the top of the main hinging post.

Looks like paint it is !

Regards,

Dave

[Dave Cooper 6Participant @davecooper6]

Some experiments with rudder hinging. Using 'brass look-alike' flap-back hinges as a guide. If these stay, they will need to be recessed into the rudder and rudder post. (Just held in with self-tappers for now).

I have a feeling there may be a better solution…..perhaps, home-made or, commercial ? Thoughts ?

[Ray Wood 3Participant @raywood3]

Hi Dave,

Good to see your getting on with her, the hinges inset in the rudder stock & keel would certainly work if you can find a hinge with a central pin ? or it will be like an offset flap.

I prefer brass for anything getting wet and like using thin gauge tube in short lenght's soldered onto say a 6ba brass bolt or screw for each side with a continious brass pin through the whole lot as the attached shot of my barge Portlight.

That doubler beside your prop shaft looks a bit heavy duty !!

Regards Ray

Edited By Ray Wood 2 on 23/02/2022 16:55:08

[Andrew BiggsParticipant @andrewbiggs29914]

Hi Dave – your Pilot Cutter is looking good. I cheated and bought a hull from Sarik models – its called Katie. I used four 3mm eyebolts. Two on the rudder and two on the hull, then used a piece of 3mm dia stainless rod. This is removeable so the rudder can be taken off the boat.

Hope that makes sense – look forward to seeing your progress.

[Dave Cooper 6Participant @davecooper6]

Hi Ray /Andrew – yes both your solutions look very nice and professional I must say.

I think I'll keep mine (somewhat 'jury-rigged&#39 for now until I work out the steering servo mount and linkages…

Andrew : I particularly like your tiller – did you make it ?

Ray : Been so busy with the sportscar (oil and exhaust systems) lately, the boat's been up on the shelf for a while. I've now acquired a 2.4 Ghz Tx from a club auction, plus a box of free receivers to boot !

Very neat hinge solution if I may say. Yep, I'm thinking brass too (can't beat the real thing)…

You're quite right about the prop shaft doubler. I need to fair that in pronto – it somehow got missed last construction session !

Many thanks for the helpful comments both,

Regards,

Dave

[Andrew BiggsParticipant @andrewbiggs29914]

Hi dave

the tiller is made from several strips of wood laminated and clamped around a former, which was a piece of wood with a curved edge. Once dry the tiller can be tapered and sanded smooth. I made one for our full size boat in the same way.

it’s worth while making a card template first to get the curve right.

[Dave Cooper 6Participant @davecooper6]

Hi All,

Just wanted a quick 'heads up' on rudder linkages etc.

I'm just about to start a rudder servo mount and feel that a single push/pull rod and clevis might look rather ugly on a working boat.

Currently, I'm favouring a 'closed loop' (pull /pull) linkage. Another concern is that when the yacht is fully healed over it will ship water in through the linkage passages. I can go 'wire-in-tube' with a close fit /grease to mitigate this though…Alternatively, have a deck based system going via a working tiller ? However, this will probably mean a line and pulley system to actuate from below deck level to cockpit.

All comments /experience welcome.

Dave

ps I may be over-thinking this !

Edited By Dave Cooper 6 on 26/03/2022 11:19:46

Edited By Dave Cooper 6 on 26/03/2022 11:22:54

[Ray Wood 3Participant @raywood3]

Hi Dave,

Yes the closed loop system would work well I don't think you need to worry or over think the chances of water ingress as the holes can be quite high up on the transom and relativley close together, mount the horn as high as you can .

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Thanks Ray,

I think I'll mock something up, as you say with the horn as high as possible.

I've got about 30 deg's total rudder deflection (15 either side) at the moment which I don't think will be enough. So, I'll modify the transom to accommodate a bit more deflection, and make some clearance for a higher horn position at the same time.

Target will be about 60 degrees of rudder (30 each way) for now. I'll add more later if need be….

More photo's to follow,

Dave

[Dave Cooper 6Participant @davecooper6]

Part way through the rudder servo mountings when the dreaded C19 bug struck.

I've managed a 1/2 hour session in the workshop this week. It was enough to determine that if I put the closed-loop horn as high as possible (per Ray's suggestion) it should work.

The servo can then go just under the cockpit floor, probably with a removable hatch for access and adjustments.

I seem to remember from my model aircraft geometry, that the horn 'off-set' should match the servo actuator off-set. With a closed-loop, 'pull-pull' system, this means that the cords shouldn't go slack and /or solid rods shouldn't bind.

I'm sure a photo, or two, will make this clearer (in due course…),

Dave

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