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Member postings for Dave Cooper 6

Here is a list of all the postings Dave Cooper 6 has made in our forums. Click on a thread name to jump to the thread.

Thread: Bristol Channel Pilot Cutter
03/04/2021 12:36:20

Ten frames in. Starboard has better profiles than Port at present. Black dots indicate estimated static waterline. Frames 9 &10 are above the w/line. Motor thrust line probably between T1 and T2. Next step a trial 100% frame.

50% ten frames.jpg

Thread: Another stupid question, for those who know
02/04/2021 17:32:38

Forgot to mention the launch's superstructure (one-piece) is held on with two rubber bands and a paper clip....

Rudder /Linkage access is via a small screw down hatch.

I can post some photos if you're stuck...

02/04/2021 16:57:54

Carl - at some stage or another, you'll regret having no /limited internal access - it becomes a real pain...

I would say, Rx, Battery, Motor (if fitted) and shaft coupling plus, rudder linkage access of some sort is a must. If a yacht, then sail winch servo access is also desirable I'd have thought.

A little thought now can save a lot of grief later on ! Hatches /coamings held in place with small screws etc can do the trick (you'll hardly see them when the boat is on the water).

I sealed the inside bottom and sides of the RAF launch with sanding sealer, followed by a rub down, and two coats of model aircraft dope - thinned 50/50 with cellulose thinners. No doubt there are other methods too.



Thread: Rigging
30/03/2021 10:28:11

As Kev says, a local club will most likely be of great assistance.

Failing that, there's always good old 'trial and error' ! Many a design /construction problem solved this way...

I would also search out the websites of the specialist model boat suppliers. Much can be learned from their adverts and product descriptions etc.



29/03/2021 22:29:21


Perhaps, I can suggest an alternative way forward for you :-

Contact a local full-size sailing club and ask if you can "crew" for someone in their boat. By the term 'crew' it is generally taken that you will "assist" them to sail it. Explain that you are a beginner and they will understand.

Initially, you will help to launch the boat (perhaps a dinghy) and handle the fore sails (Jib or Genoa) under supervision. Someone else - usually the owner - will 'skipper' the craft and he/ she will make all the decisions.

You will learn more than I can write here, but, especially how the sails work in relation to the wind. Much of this will be directly transferable to model yachts (although there are some differences). As an engineer, you will no doubt be familiar with 'vectors'. So, you can use this knowledge to resolve the various forces involved in your mind.

As a bonus, you will learn all the specialist names of the various ropes and fittings etc. on board - and there are a lot !

Have fun,

Dave C

Thread: Prop Tube lubrication & sealing
27/03/2021 13:41:39

Hi Stephen

I was looking into this just the other day. On my little RAF launch (16" I just arranged things so that the motor end of the prop shaft was above the water-line. Then removing the nylon bush, put a little 'vaseline' at the top end and replaced the bush. No problems with any water in the hull so far...and, the shaft spins freely.

For my Pilot Cutter (42", the thrust line may be a little more awkward. So, I'll probably buy a purpose made shaft complete with lubrication kit (syringe, grease etc). I think "Model Boat Bits" do them.

Happy modelling,

Dave C

Thread: Bristol Channel Pilot Cutter
23/03/2021 14:47:06

Hi Ray

Yes, quite agree. No. 5 is also quite flimsy at present and needs a better section definitely.

Not tackled no. 6 yet as the stringer lines aren't flowing as I would like...more work to do ! (This may resolve itself when F5 is corrected).

What about the rudder ? Many full-size lines drawings show it going to (near) full keel depth - I'm inclined to follow suit.

Thrust line for the motor shaft is also a first attempt. I guess this is not so critical as it will be just a small 6v, 'get-you-home' motor.

Cheers for the feedback,


23/03/2021 11:25:48

Some extra frames and experiments with strength /stiffness and internal access. Rudder may need to be enlarged.

50% frame development.jpg

Thread: kms bismark
14/03/2021 22:23:19

Hi Chris

Just a few extra points on the Arduino front which may be useful :-

1. If the power supply side is getting messy, you can just use a PP9 battery as the 'chip' has it's own on-board voltage regulator.

2. You may find it easier to do a lot of the more complex control movements in the software. If you, or a friend, have any knowledge of the C++ language, it's mainly a question of calling the appropriate library and doing some tailoring.

3. I use the "Elegoo" R3 Uno starter kit for experimentation. It comes with a servo, stepper motor, jumper wires, breadboard etc etc. and is great for proving out theories before committing to the final solution.

4. If you need more inputs and outputs than the Arduino range can provide you can use the "Teensy" board instead. It will run the Arduino software ('Teensyduino' so no need to re-program.

Have fun,

Dave C

Thread: Beginner's kit - simple, not too dear
14/03/2021 15:49:46

Hi Henry

Like you, I also came from a 50's /60' s aeromodelling background. The fact is that modelling skills are generally transferable across different disciplines - model railways, cars, boats, planes etc.

With a recommended kit most of the difficult part is done for you - design, selection of materials and so on. Just take your time and follow the instructions carefully.

The radio side is also mostly fool-proof these days, so if you still have some basic tools, give it a go. The experts on this forum are always on hand to help (there are some very good guys here with tons of experience !).

Happy modelling,

Dave C

Thread: Bristol Channel Pilot Cutter
14/03/2021 13:41:23

Stringer lines photos to follow as soon as possible.


Edited By Dave Cooper 6 on 14/03/2021 13:44:28

Edited By Dave Cooper 6 on 14/03/2021 13:46:15

14/03/2021 13:39:02

Sighting shot along the frames. Next step will be to try a stringer or two to see how the lines flow. Slowly getting used to this upside-down way of working !

50% keel and frames.jpg

14/03/2021 13:34:44

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

Thread: kms bismark
13/03/2021 10:37:05

Quite an ambitious project Chris.

I should look out for RC Swordfish torpedo attacks and rudders jamming !

Computer-controlled gunnery ? (There's a fascinating technical description of this on the internet. Sorry, couldn't find a suitable link for you just now).

I'm planning to use an "Arduino" for the turret on my RAF launch. In the 'C' program code you can select a random number generator and then get the chip's output pins to drive a stepper motor - fun to play with...

Good luck with the project,

Dave C

Thread: Bristol Channel Pilot Cutter
08/03/2021 17:39:56

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

07/03/2021 19:12:19

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...


07/03/2021 16:06:40

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

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...

Thread: Newbie
04/03/2021 15:07:23

Hello David

Welcome to the forum.

I'm currently at the design /scratch build stage too although mine is for a working boat under sail.

I think the others may appreciate some extra details such as beam, estimated finished weight and draught etc if possible before venturing advice on motors.

If it were me, I would probably go for a brushed motor with a NiMh or gel-cell type battery. However, the experts may disagree - I would go with their advice primarily.

Happy modelling,

Dave C

Thread: Bristol Channel Pilot Cutter
03/03/2021 13:46:16

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

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