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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: Throttle Stick not working
15/08/2019 14:27:46

Hmmm, yes, you could have something there...

I think I'll give it one last go before consigning it to that big spares box in the sky !

Dave C

14/08/2019 21:16:55

Hi both - thanks for the replies. The test set up is Tx /Rx /and 2 servos known to be good. (I swapped the servos over and got the same result)...

Throttle stick advanced - servo does not move. Same stick retracted - servo does not move. Servo reverse switch activated throttle servo goes to extreme position in one direction only. Yes, Dave I did not make this clear !! No ESC in the circuit at all, just conventional Futaba S3003 servos.

Thinking back over my moves to fit the ratchet, I think I may have accidentally 'tweaked' the spindle - this tends to lean toward a mechanical problem - well spotted Dave, if that's the case ! Presumably, the servo reverse is purely electrical, so, if the pot is 'parked' on zero before the switch is thrown then throwing it would give travel to the other extreme.

Now to the remedy :

1. Try and reattach spindle to pot - full strip down ?

2. Fit new pot and try and get it to mate with existing stick unit (plenty of "B5k's" available with different shaft spec's)

3. Source new stick unit complete - there must be some out there, but, they seem to have eluded me so far.

Update : one of the battery springs has just let go and is resisting solder manfully ! The set is fighting back ! I think a LiPo / NiMh uprade is also on the cards...

What 'fun'


13/08/2019 21:08:52

Hi all

A little electronics 'teaser' problem on a 27 MHz Futaba Attack II Tx :

After fitting a throttle ratchet to the left-hand stick, the unit ceases to function with the exception of servo reverse - which works as expected...

Meter readings from the pot' are similar, but not exactly the same, as the right-hand unit. Just wondering if I should change the pot, or, try and source a complete new stick unit. As the set is now approx. 15 years old this could be tricky !!!

I'm tempted to junk it and go 2.4, but, don't like being beaten by a niggle such as this. Any ideas gratefully received,


Thread: Help - 48 inch Fairey Huntsman 31
08/08/2019 15:55:50

Hi Andrew,

I wouldn't automatically exclude brushed motors as there some advantages for marine use. However, that is a big model !

I'm sure the experts will be along soon to give you all the advice you need...

Good luck with your project,


Thread: Motor /Controller /Prop upgrade
08/08/2019 10:46:02

Thanks Ashley - that makes sense. Just finishing off a bit of bow shaping /rudder hatch access at present. As soon as I've got this in primer I'll post a few pic's for all to comment on...


07/08/2019 20:23:49

Hi Ashley, Chris, Ray.

Thanks also for your contribution. Current thinking is to change one thing at a time on the launch - that way I can see what's having what effect. I still don't know if the hull design is sound yet !

I'm staying 'brushed' for the time being even though a brushless set-up would, ultimately, "add lightness" (an old Colin Chapman aim for making racing cars quick).

Looking at the trim of the boat in the kitchen sink, I could do with shifting some weight aft. I've had to shorten the shaft by 12mm in order to fit the Huco coupling (1st job), only the receiver will be in the bows. The 1500 Mah Lipo fits nicely in front of the rudder servo ie well aft.

Has anyone had to resort to using ballast to get a model to plane, or, is all this in the hull design ?

Regards, Dave

05/08/2019 18:58:50

Hi Folks,

Thanks once again for all the techie advice. I think the 'must haves' are: larger diam. shaft, new speed controller, fuse, and a selection of props to play with (including 2-bladers).

Looking through my son's buggy stock, I've found a small collection of motors going from 280(ish) up to a 540 can-size, so, can afford to burn out a few in the bath on a trial and error basis !

Been thinking about the stepped hull. This is a shallow 'v' stationed at about 1/4 to 1/3 back from the bow. At mid-ships it is 8mm deep and tapers to 3mm outboard. If it doesn't work, and /or makes the model unstable, I can convert it from the shallow 'v' tapering aft to a flat bottom stern without too much bother ie by adding some extra sheeting (whilst watching the dreaded weight gain).


05/08/2019 14:10:41

Thanks for the very comprehensive replies everyone - obviously a wealth of experience here... some more data on the model and equipment currently available :-

Length = 16" , Beam = 4.5", Empty hull weight (with rudder and steering servo /linkage) = 236 gms.

Motor label says "380 /385S" and is 280mm diam. 6 volt (runs quite nicely both ways and is now suppressed).

Shaft diameter = 2mm (I think this was why I couldn't get a two-blade racing one originally ?).

Props = '40' and '30' both 3-blader's.

Controller = "Bob's Board" , Type PB2, rated at up to 2.5 amps - servo mounted.

Available LiPo's (from my aircraft stock) :-

2s 7.4 v 450 Mah 20c weight 31gms

2s 7.4 v 1500 Mah 25-35c weight 83gms*

2s 7.4 v 2200 Mah 20c weight 123gms

* Size for 1500 Mah is 70 x 35 x 18 mm

Yes, not sure about the stepped hull either. Maybe worth a try along with one of the above LiPo's and the existing motor as a first test ? The 'step' was installed a few years ago so would require 'surgery' to remove !

Going to a generic model show on Sunday so may be able to source a better shaft /prop etc. to experiment with...



04/08/2019 23:02:11

Hi Folks,

A few years ago my son and I built a small (16" RAF launch just for fun /experience of our own design. It had a 6v brushed motor and heavy dry cell batteries and a '40' prop. Performance was disappointing - ie it didn't plane !

Got it down from the shelf yesterday and decided to do a refurb' /upgrade...I've fitted a secondary 'stepped' fore hull (like a hydroplane), and now wish to go brushless as I've been very impressed with my brushless electric glider's performance..

A few questions :- what motor /controller combination to fit ? (even though it's a fast electric - hopefully - I'd like reverse as well).

What prop to fit. The Graupner rep was in the model shop when I bought the 40 and suggested a 2-blade racing prop. They didn't have one, so, I got a 30 3-blader instead. BTW do these numbers refer to Pitch ?

As a young lad I had an RAF fire tender fitted with a "Mighty Midget" motor. This was also slow !!! However, the motor pulley drove a twin prop system via a rubber belt and 2 further pulleys on each prop shaft. Quite neat and I wonder if this would be less trouble than a twin motor set-up ? Maybe belt slip is a potential problem with a fast electric.

Sorry, I seem to have gone on a bit here...


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