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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: How to measure what motor I need.
30/07/2020 11:06:03

Florian - a few thoughts :-

I'm afraid I can't advise on the final power train combination (I'll leave that to the experts)...but, I would do the floatation /ballast test first.

Reason : you may need a 'double-hull' approach. This would be an extension 'downwards' ie to increase stability and to lower the centre-of-gravity of the whole model. This can then contain additional ballast if necessary.

I did this on my little fast launch quite successfully and it does give some extra protection to grounding on hidden rocks etc below the surface.

If you do go this route, you may have to alter the prop shaft thrust line and hull exit point....

Hence, I would do the float /stability test first and put in some extra ballast to represent motor and batteries. Then give it a good wobble !

For the superstructure windows, I drilled a small (say, 2mm) hole near each window's corner (assuming square or rectangular windows), then cut and file to join up the holes.

Dave

26/07/2020 16:34:14

30 Kg - wow, that's going to take some shifting and transporting...

I expect you are planning a purpose-made launching trolley /model slipway ? (Most probably you are in a different age bracket to me !).

I suppose the ballast could be added after the model is in the water ? Just thinking outside the box now.

Good luck with the project - let us see some photos please,

Dave C

Thread: MTB 49
24/07/2020 14:34:56

Just a note on scale deviations :

If making an exact (static) scale model from the boatyard's /designers drawings, then you could reduce every linear measurement exactly. It would be pretty tedious and I'll bet that most scale modellers will make a 'compromise' some where.

Even plastic kits aren't exactly to scale, as to reproduce many of the smaller components would simply make them too fragile to handle.

For a working model some compromise is inevitable. Mainly in the hull volume area, most of the ones I've seen make the hull deeper than scale to give it good flotation /performance etc. They may also be slightly more 'beamy' and perhaps length-over-all is stretched a little too.

Enjoy your build (and don't be afraid to compromise a little !).

Dave

Thread: 3 Motors RC Boat
16/07/2020 11:18:08

William - if it isn't a rude question, how big is your water ? Have a look on Youtube at some of the really fast racing boats. They cover an awful lot of water in a very short space of time...

I see you're into motorsport - how do you fancy jumping straight from a Formula SAE into an F1 car ! (I found it difficult enough going from FF2000 to F3).

Seriously, even though you're experienced in R/C cars, I would plan a more gradual progression and leave the really quick stuff for later.

Have fun,

Dave

Thread: Returning modeller
09/07/2020 10:52:32

Hi Jim

There seems like a lot to learn at the start ! The best advice I can give is to find what works for you.

Inevitably, you will make purchases which don't work out. Put these in the 'spares' box - they'll come in handy one day...

Two further bits of advice :-

1. Join a club - benefits too long to list !

2. Test on the bench first (especially battery life), then in the bath - leaks, power test, rudder and prop under load etc.

Most importantly - have fun !

Dave C

08/07/2020 22:04:24

Back-tracking the thread a little, and just a quick addendum on the NiCad thing....my latest information is that whilst they are illegal to sell, they are still legal to use. I use one in a RC slope soarer glider powering just the Rx and two control servos.

Having said that, they do suffer from the 'memory' and 'black-wire corrosion' problems and are not very planet-friendly !

I think they still have a use on the bench as a temporary power source for testing, but, one by one, my models (including the little RAF launch) are now converted to LiPo power.

Connectors: (Power) I suppose everyone has their favourite(s) - I am slowly standardising on the "XT60" type, but have gold-plated 'bullet' connectors in one model. Both work well. I find the bullets are easier if you need a quick change. (Radio) I'm slowly standardising on the Futaba colour code as I find this the least confusing...

Good luck with your project,

Dave C

Thread: Auxiliary Drive for Pride of Baltimore
25/06/2020 10:47:22

I'm just wondering what, exactly, is the purpose of the auxiliary motor(s) ?

Is it just to get the boat back to 'base' if the wind dies, or, is there is a scale application here - ie does it need to supplement sail power in order to achieve scale speed ?

Context: I'm learning about scale sailing and have a need for something auxiliary on Yacht Ardent (mine may well be a little electric outboard hung off the stern though...)

I'll follow the thread with interest !

Dave

Thread: Yacht Ardent
24/06/2020 23:57:47

Yes Ray - quite a lot of Permagrit tools of various sizes in almost constant use, but, I am a bit space limited at present.

I think though, moving things around a bit I could make space for a scroll or band saw if it had a small 'foot-print' on the bench ?

My trusty hand fret saw at the ready though with a selection of blades ! Plans to be ordered soon once one or two other projects further advanced...

Dave C

24/06/2020 15:38:58

Fair point Dave, and effectively concurs with what Eddie and Ray are saying.

I recently spent the best part of an afternoon doing a drawing in MS Paint for a local engineering firm to cut and drill a top for my welding bench. Quite honestly, I could have done it in half an hour on a drawing board !

For 'one-off' jobs, the wonders of CNC etc probably aren't worth it....as I'm saving up for a decent lathe at present, the specialist machining saws may have to wait for Father Christmas.

Cheers for now,

Dave C

24/06/2020 10:57:33

Thanks both,

I have quite a large amount of 3mm marine ply given to me as 'left-overs' from my next door neighbour who is just completing a rowing scull.

I was just wondering if this would do for the frames (or, anything else) on Ardent ?

Cheers,

Dave

23/06/2020 23:05:53

I tried both "Belair" and "SLEC" for a quote for a laser cut kit for yacht Ardent.

No reply from Belair (probably not their thing as they do mainly aircraft stuff)...

SLEC replied (eventually) but want to see the plans first, plus a list of required parts - I would have thought they could work that out from the plans !

As I'm just looking for an 'order of costs' at this stage I was wondering if anyone else has similar experience.

Eddie - looking at the plans on-line, there doesn't seem to be all that much fretting /cutting out to do ? Is that fair comment ? (I'll be doing it manually)...

Regards,

Dave

Thread: Wiring a boat for beginner
23/06/2020 11:08:20

Hello Harry and Rob,

Harry - I wasn't able to open Dave M's diagram, but, one thing to include in the wiring is an appropriate fuse to protect the circuit(s). This can be of the inexpensive 'car' type (blade or cartridge). I'm sure Dave will be able to advise further on this if he hasn't already done so...

Rob - There are quite a few Youtube videos on FrSky /Taranis and many models to choose from. A lot of our own club mates use something called "Open TX" for programming the transmitter. See if you can find someone who has done this as it's quite a learning curve.

By the sound of it, your motors are "brushed" (rather than "brushless", so you will need an appropriate ESC, or two, to go with them. If I were you, I would consult Dave M on this.

Hope this helps

Thread: Fairmile D - help needed
22/06/2020 10:56:25

Hi David

Could I suggest a few simple tests before "committing pond" :-

- Run it on the bench in your proposed configuration. If you have the electrical test kit, measure amps (and watts) at different throttle settings. Quickly touch the ESC - insulated part - and feel the temperature.

- Put the props under static load, finger on end of prop boss(es), or, simple scrap balsa wood 'snubbers'. Check ESC temp again.

- Bath test. Feel the pull at the stern with different throttle settings. Check ESC temps.

if you have to quickly withdraw your finger from the ESC in any of the above - it's running too hot ! You need to do something about it...

Battery life /power delivery etc - These days, for a high-speed launch (brushed or brushless motors), I would only really consider LiPo's, although NiMh's (or, equivalent) may also be ok. One way or another, you need to establish your battery life before going on the water. Most modern Tx's have a timer facility - set it to a conservative amount initially.

In short - test, test, test...good luck,

Dave C

16/06/2020 10:44:02

David, my Dad was a skipper on 70' recue launches in the war. They mainly used the two 'outer' throttles for manoeuvring in harbour (3 shaft boat). I imagine at speed it would just be helm steering...

For the cooling on my boat I made some air extraction vents. You can just see these on the album "Dave's RAF Launch", (currently on page 5 of Albums) - between the main mast and the gun turret.

I use an old-fashioned "Bob's Board" - resistive mat - type of speed controller. Very 'old-tech' now and was concerned about heat build-up in the hull. So far it has worked well.

The air vents work on a simple aerodynamic principle, any water spills over the top decking run down to the stern and there is an internal lip in the vents to prevent any 'backwash' (probably overkill !).

You may be able to fit /hide something similar on your boat - as long as they have a supply of reasonably undisturbed air they should work...

Let us know how you get on

15/06/2020 11:01:59

On my little RAF Rescue launch (1/48 scale). I made the main superstructure removable. Space is quite tight inside...

This gives access to Rx, motor, coupling, top end of shaft, speed controller and LiPo (battery pack). Rudder access and servo linkage was more difficult. I fitted a separate screw down hatch at the stern for this at a later date.

It was easier for me as, being an own design, I made a lot of it up a I went along....I wouldn't worry too much about deck joins etc showing as once it's out on the water you won't be able to see them !

Have fun,

Dave C

Thread: Yacht Ardent
13/06/2020 10:44:47

Thanks all for the info',

I knew a lathe would be useful somewhere along the line !

I found that machining carbon fibre needs a good dust collection system otherwise my shelves etc get covered in fine carbon dust...whereas, with good old-fashioned ali' and brass I can get away with a dust pan and brush.

Not tried silver soldering yet but, have just bought a new TIG machine to try out...maybe on very low amps ? Otherwise, a butane /propane torch and the right flux and solder ?

Regards,

Dave

11/06/2020 15:36:59

Thanks both. I guess the next stage is to buy the plan from Sarik.

Eddie - I'll come back to you at 'mast time' - I have quite a stock of aluminium tubing now as currently making the rear wing spars for my sportscar. Is the mast likely to be taller than 1 metre ? If so, I'll need to make a join somewhere...

Regards,

Dave

11/06/2020 10:54:46

Thanks Ray - that's reassuring. I'm probably being over-cautious !

Coming back to lathes, is yours an ML7 ? I don't think I'll have room for a floor-mounted model, but, I'm currently looking for a bench-top one. About 2-3 foot between centres and 7.5" swing over the bed....any recommendations ?

Cheers for now,

Dave

10/06/2020 21:40:03

Thanks Eddie - a few further queries if you don't mind...

I've asked SLEC to quote for a laser-cut kit, but, on looking at your build thread there doesn't seem to be all that much cutting out to do - at least for the hull frames ?

I'm a bit nervous about making the sails though. Is this covered on the plan /article ?

Also, I'd like to experiment with vane steering and Arduino control at some point. Others have commented that I'll probably need a 'Y' shaped backstay to achieve this. However, I'll probably start with conventional RC initially.

One other thing I'd like is to have a small motor with folding prop as a 'get-out-of-jail' option mid-lake. I think Dave M suggested (in another thread) that Graupner used to do an all-in-one motor /shaft /prop unit that seems ideal...

Any views /experiences here most helpful,

Cheers,

Dave C

10/06/2020 15:57:08

Just found it ! "Under Sailing Boats and Yachts" (155) - with your SKU. - Most bizzare !

I think they need to work on their database search facility...

Dave

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