Anybody into big scale - 1/48? Need help

arfabuck
25th January 2009, 06:39
Hello there,
I am having trouble getting a decent, ( as in appearance ) scale speed with the larger boat(s). 8 - 12' lengths.
Using the formula of the root of the actual speed does not appear realistic.
Electric motors scavenged from photo-copiers,geared down to 4" props.
I also hate that vibration type ripple on the water, yet cannot detect any on the bench. The shafts are running true and the props have been balanced.
Any ideas gentlemen?
TIA
Art

jg grant
25th January 2009, 08:03
hi I've built a two metre Grand banks schooner. I can't give you any advice but I'd love to see some pictures of your models Regards Ronnie

jg grant
25th January 2009, 08:05
Where abouts in NZ are you?

arfabuck
25th January 2009, 23:02
Where abouts in NZ are you?

Click on "my location" top right hand side in blue under "join Date".

I see you are in Auckland too, St Heliers way?

regards,

Arthur

Isoprenia
30th January 2009, 04:42
Hi Art

As you know Big scale with ships is a relative thing. a 1/48 scale fishing boat is rather dwarfed by a 1/96 scale aircraft carrier of 10 feet or so.
With as many miles between us , I can only offer a few suggestions to try. Vibration can come from many sources. Possibly even electronic speed controls . In order to maintain high torque at low speeds these devices supply full voltage in pulses of varying duration , this in turn causes a jerky revolution of the motor. the model train guys use flywheels to help smooth this out .try to find a controller with a high PWM frequency may be an option. Another option may be to mount the motor in rubber vibration mounts , also attaching lead weight to the motor can itself to increase the mass , thus requiring more energy to initiate vibration. This of course assumes it is one of the sources. Careful analysis and placement of ballast may too prevent transmission of the vibration to the hull. rather than building gear or belt drives yourself , you might try a precision gear motor , look for surplus , as they are quite pricey new. some of the new brush less out runner motors have a large enough armature to act as a flywheel, and planetary drives are available for some.

I like my boats to have a bit of headroom to take them above the desired scale speed in the event that something goes wrong, I can return quickly. one of our guys has a 1/96 scale Yamato with a water ballast , the boat partially sinks as the tanks flood , one of the tanks develops a leak over teh winter , and he began sinking ..for real!. the extra available power got him ashore and cheated me out of a dive trip.

in a nutshell

isolation : rubber or other absorbers

large mass : lead dense materials , require more energy to accelarate thus absorb vibration.

balancing: lessens the initiation

Concentricity:lessens the initiation

uniform prop pitch.lessens the initiation

hopefully this helps or gives you some ideas.

Cheers and good sailing

Brent

arfabuck
30th January 2009, 07:03
Hi Art

As you know Big scale with ships is a relative thing. a 1/48 scale fishing boat is rather dwarfed by a 1/96 scale aircraft carrier of 10 feet or so.

isolation : rubber or other absorbers

large mass : lead dense materials , require more energy to accelarate thus absorb vibration.

balancing: lessens the initiation

Concentricity:lessens the initiation

uniform prop pitch.lessens the initiation

hopefully this helps or gives you some ideas.

Cheers and good sailing

Brent

Thanks for that Brent.

There are a couple of things that you mention I have not looked at yet.

As for relative size, -I did mention the 8 -12' length but now I am venturing into the 'super-size', some would say it is no longer a model = 19'.

In fact it is bigger than most of the 1 : 1 boats I work on.

Fun and games!

Arthur

Arrow5
30th January 2009, 19:00
A newby to the forum ( joined today) and my first read reveals what I joined for , large models ! Arthur, is it going to be a manned model ?

NoMoss
30th January 2009, 19:37
I am not a model maker but there is a site about a 1/8th scale model on line at francois_zanella_s_boat. If that is not enough address I will try the whole thing which is very long.

arfabuck
31st January 2009, 04:36
I am not a model maker but there is a site about a 1/8th scale model on line at francois_zanella_s_boat. If that is not enough address I will try the whole thing which is very long.

http://pagesperso-orange.fr/bernard.joannes/bateau.htm

Wow! That is some houseboat!!

No, mine is not going to be manned - CV and I do not fancy having to lie down to drive - or get a crick in my neck by having to poke my head up through the S/S.

Prefer staying on terra firma with an R/C unit in my hand(s).

Part of an IJN fleet starting with the largest and working my way down.

Still looking for plans of a harbour tug - Eisen. Anybody know where I can obtain them? Any scale?

art