Still waiting for my kit to arrive. It should have been here by the latest Monday 12th June from Amazon. Then it was supposed to arrive Weds, then Fri which is today. I've received a message from them saying 'sorry for the delay' but stating if it doesn't arrive by Monday (19th) I can get a full refund! It is supposed to be coming Royal Mail but recently I have had some Amazon packages delivered by Evri. The wait and anti-climaxes has killed my excitement. Ugh!

Hi Duncan have you looked at Gupi's build log? He shows photos of his keel, no dimensions. It is not a method I would use too much engineering on show. However the area of the keel looks to be about 6" x 2" with about a pound of lead underneath, so that is useful to know.
Bearing in mind the internals are 10+ years old things have changed a bit now.

Gupi suggests 2 sail winches, yes but only 10 years ago, I think one internal winch will work. Howes do them, called Kingmax sail winch, need careful setting up I have one operating at least the same sail area in a yacht. The winch line is all inside the servo drum so no need for an out and back system. The ESC would have to have the red wire removed from going into the receiver. I use a short servo lead extension for this and simply cut the red wire, so no damage done.

The battery is a bit powerful for this boat but depends what you have to hand. I reckon the receiver and winch can operate off a 4.8 v 2900mAh AA battery. The motor drive also AA but 6 cells. Makes the disposition of weights and balance easier to adjust.
Could go for a 6 cell NiMh for everything, but they are bulky to decide where they will fit.

With the removeable keel I would rather create a small box in the hull and a slot in the keel to enter and then a close fitting pin to hold it in place. Only needs to be 2 inches inside the hull and waterproof, so only a minute to fix or remove.

I have in the past used old boxwood ruler as my keel wood source for a small yacht. It is very stiff and maybe glued edge to edge and some 1/16th. ply each side and sand to an aerofoil section. A stick of old fashion solder might be enough for the keel,
cut in 2 and screwed in place on the bottom of the keel, filing to shape as well.

Lots to think about, it is worth stream-lining everything under water as it is 800 times denser than air. (Purists would say 784).

I am thinking about disabling the drive motors when sailing, not sure how but depends how many channels I decide to use. This way the rudder can operate without bringing in the drive motors.

I find things evolve as you do them so this would be a start for me. I like things simple as my memory is a bit dodgy now! I write it all down in a note book which helps if there is an interruption in the building.

Regards
Roy

Gosh- yes the Action P94 is expensive at £75+ compared to the basic ESC's at 2 for £8!

Hi Duncan I did a big search on the Internet and found the dual mixer esc with the single wire to the rudder control.
I could not find any separate mixers apart from the Action P94 which may be out of stock and quite expensive.
Aliexpress is a good site but there were mixers which for some reason they could not send to my address?

Sometimes it is finding the right wording for the search. Differential and speed regulator were used in some descriptions. Also Vee tail mixer is the same kind of unit.
Is there anyone out there who has found any small cheap mixers? I bought my one second hand and it referred to a web site no longer available.

Regards
Roy

Hiya,
Thank you for your research on this topic. Being a novice especially on the electrics side, the 2nd method sounds easier for myself with a mixer unit. The idea of having a switch to stop the motors working when sailing also sounds a good idea. I haven't come across a mixer unit yet - what should I search for please?
I really appreciate all your help and suggestions - thanks.
Have a good weekend

Cheers
Duncan

Hi Duncan, I found the intended esc's etc for the Bruma. Well I put them to one side a while ago. I have options-:

First is a dual esc which works off a single receiver channel. This has another wire with a pin connection which will plug into the signal socket on your receiver rudder control.

The servo connector wires working from the outside of the case of the receiver are black-red signal.
This would give 'Tank' drive i.e. but rudder not operating.
If you want the rudder to work then you will need to make up an extension lead with an interruption in the signal lead to connect to the yellow single lead then to a servo working the rudder.

Secondly I also have a mixer unit which has 2 connections to the receiver like the tank drive above. There is an i/p for the receiver rudder channel and an o/p going to the rudder.

So this has rudder moving and then you fit 2 separate esc's like you found, which then power the drive motors with port and starboard marked on the esc..

The throttle control on the transmitter controls forward and reverse and speed. The rudder control will also deliver a change of balance of the power supplied to the motors. It will slow down the inner motor on the turn and speed up the outer motor so that changes the boat's direction.

I have not tested yet but with the boat in the water and the throttle at neutral then operating the rudder will start one motor forward and the other in reverse, the boat revolving where it is. This worked on a previous model boat, spinning the model in either direction.

I have not decided which set up to use but there also has to be another channel for the sail servo or winch.
I am not sure I want the motors to come on when sailing only and using the rudder. This could be a switch on the boat to disable rudder i/p to the motors.

Remember the esc has to be on as it is supplying the current to operate the receiver electronics.

But another option with a spare on/off channel is to operate the power/sail choice from the transmitter.

So the little grey cells are cogitating what to do as the sailing keel is also an on/off option.

Any thoughts on the matter Duncan?

Regards

Roy

That is abdolutely brilliant Roy. Really looking forward to seeing how he did the sailing conversion. Thanks also for the building instructions. My kit should arrive next week. Cheers Duncan 😊

Hi Duncan these are the build instructions for Bruma I printed off. All 13 pages.

https://www.astramodel.cz/manualy/mantua/kr-800736_bruma_man.pdf

Hi Duncan I have had a response from Gupi. He will take photos next week and post them on to his build log.
He did say that he extended the rudder with an appendage for sailng.
regards
Roy

I've found on another website a blog of someone who has added a sail conversion but unfortunately there isn't quite enough info for a relative novice like myself! I thought some other members maybe interested in looking at these links. The first link below shows quite a few photos of the conversion and the boat sailing whereas my second link is the build of the actual boat as it comes without the sails. I've also emailed mantuamodel.co.uk to see if they might produce a sail conversion kit with a removeable keel. If others show an interest they may consider looking into producing an additional accessory package!😊

Sail conversion link:-

https://www.rcgroups.com/forums/showthread.php?2314493-Mantua-Bruma-my-first-sai

https://www.rcgroups.com/forums/showthread.php?2314493-Mantua-Bruma-my-first-sai