Model Boat Mayhem

Mess Deck: General Section => Beginners start here...! => Topic started by: Oldjedimaster on April 12, 2019, 01:38:52 pm

Title: Over-spec'd & over-weight? Advice Needed.
Post by: Oldjedimaster on April 12, 2019, 01:38:52 pm

Hello all Mayhemers,


Normally I just read the posts and look at the pictures, however I recently bought a Precedent Perkasa and trawled through the posts for
motor & battery setup to which I found Lakeside Bob's recommendation of a Torpedo 850 motor and added a 12v 7ah SLA.


My problem is that Bob's boat was 49" & mine is a 37" (can you see where this is going..?) Yup, the weight of it all combined in the hull is almost certain to sink her.
So, could anyone recommend an alternative motor & battery setup?
I have everything to get her in the water, I'd just prefer if she stayed on top of it rather than under.
Thanks, Guy.

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: DaveM on April 12, 2019, 01:52:53 pm

Guy
Unless you want to go for a brushless motor - which would be much the best option for performance - then the 850 is just about OK. IMHO this would be a better brushed motor, not least because it weighs 250g less. http://www.gliders.uk.com/Graupner-SPEED-700-BB-Turbo-12-V/productinfo/G6317/ (http://www.gliders.uk.com/Graupner-SPEED-700-BB-Turbo-12-V/productinfo/G6317/)   Just dump that 12v lead brick and substitute either a 10-cell 5000maH NiMH or 3S LiPo pack. That'll save you about 1.9Kg alone and give you just as long run time.
DaveM

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: canabus on April 13, 2019, 12:07:25 pm

Hi Oldjedimaster
May the force be with ewe!!!
I have two 37" Precedent Perkasa's one with a 3639-1100Kv brushless motor and the other with a D3548/4-1100kv motor.
Both run 3S lipo 5800mah batteries, 60Amp ESC and 37mm 3blade props.
Both run in a straight line over scale speed so a 750 kv motor would be better.
I had these motors so I use them.
They are not the best on turning, more of a wide turning circle.
The bottom of the hulls have more bumps and lumps that a country road !!!
I filled and sanded both out to a passable standard.

Canabus

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: Oldjedimaster on July 24, 2019, 07:26:31 pm

Thanks for all your comments, here is a youtube link of my first "Sea" trials.


https://www.youtube.com/watch?v=PPsyZhu_JqA (https://www.youtube.com/watch?v=PPsyZhu_JqA)




While I'm still doing the fittings for this kit I decided to test her seaworthiness. This is the glassfibre hull version, single shaft, powered by a standard 540 motor with a 7.2 nicd. I was pleased to see that the single rudder was responsive and the boat was able to go from full-Ahead to Full-stop in two boat lengths. The decks were left clear of fittings for the test.

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: Oldjedimaster on July 24, 2019, 07:51:12 pm

Hi,
I want to do a "Build" with photos, where should I post it?
Thanks.
guy.

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: tica on July 25, 2019, 11:34:05 am

Hi if it is a  Perkasa I'll suggest that you place it in Dry Dock / Shipyard: Builds & Questions -> Navy - Military - Battleships

Quick link https://www.modelboatmayhem.co.uk/forum/index.php/board,93.0.html (https://www.modelboatmayhem.co.uk/forum/index.php/board,93.0.html)

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: RST on July 25, 2019, 10:36:35 pm

If it were me:

1: hold your phone the normal way doing vids please!

2: looks good but I personally would look at a 8.4v Ni-Mh set-up

3: please build the big trim tab on the transom.  It's such a big feature of the boat, I think it helps, but nothing to compare to without apart from the wash behind

Cheers,
Rich

Title: Re: Over-spec'd & over-weight? Advice Needed.
Post by: Oldjedimaster on July 26, 2019, 05:52:20 am

Quote from: RST on July 25, 2019, 10:36:35 pm

If it were me:

1: hold your phone the normal way doing vids please!

2: looks good but I personally would look at a 8.4v Ni-Mh set-up

3: please build the big trim tab on the transom.  It's such a big feature of the boat, I think it helps, but nothing to compare to without apart from the wash behind

Cheers,
Rich

Thanks Rich,
1) Duly noted, but the "Mrs" filmed it, however I've purchased a new camera so this can be avoided.
2) I started with 7.2 but 8.4 is on the cards.
3) The big trim tab is still to be fitted.


Cheers,
Guy