Cookies used in this website are gluten free, wheat free and dairy free. By using this website you agree to our use of cookies. More Info
Guest
Login Below
Join Us On Social Media!
   
Get The Model Boats App!
Apple App Store
Android app on Google Play


Help Support This Website
£
or enter custom amount

(Non Contributor)

Help support this free
website and donate.



£285 a year is needed to keep the website and apps online. Please consider donating £5 or more to help towards these fees.
All donations are securely managed through PayPal. Amounts donated are not published online.

Many thanks for your kind support.

Model Boats Website Team


Donation History
December 2018: 4 people
November 2018: 11 people
October 2018: 9 people
September 2018: 13 people
August 2018: 5 people
July 2018: 8 people
June 2018: 8 people
May 2018: 7 people
April 2018: 24 people
March 2018: 11 people


Unique Visitors This Month

Website Members

Terms and Conditions
Privacy Policy
Advertising
Contact


Model Boats Website
Active Users (9)
Login or Register
To Remove This Ad

Login or Register
To Remove This Ad
>> Home > Forum > Any Other Questions! > 47" Fireboat power question
47" Fireboat power question
(830 views)
Author Message
rolfman2000
(Fleet Admiral!)





Forum Posts: 126
29th Apr 2018 11:06  
>> Permalink
mdlbt.com/41395

I have a 47" classic Fireboat which I would like to use my G-60 500kv electric motor with a 6s Lipo battery and a 120 amp watercooled esc. I wondered if anyone could give me anyone idea of what prop size to start with experimenting to give best power anyone and endurance ? I am told the G-60 is the electric equivalent of a 10cc glow engine, so what size would go on that might be a start. Thanks in anticipation, Dave W 😊

Flack
(Fleet Admiral!)





Forum Posts: 171
29th Apr 2018 18:57  
>> Permalink
mdlbt.com/41404

Just a word of caution - I fitted my 47 inch fireboat with a JP Energ I.C. 60 O/R 670 (C50-20) Brushless Motor which is similar to the one you are considering fitting. I use it with a Fusion hawk 120 amp electronic speed controller and it is powered by two 4s LiPo batteries. The performance is exciting to say the least and I find that once it is on the plane it becomes unstable and prone to capsizing.

Shaun.

rolfman2000
(Fleet Admiral!)





Forum Posts: 126
29th Apr 2018 19:11  
>> Permalink
mdlbt.com/41405

Thanks Shaun, I intend being careful with it. The boats were originally fitted with 10cc glow engines, so an equivalent electric motor should be ok. But I can always reign it in on the throttle side of the esc curve. Are your 2 LiPo's in series of parallel ? I expect parallel, as series would give 8s which would be crazy. You still didn't say what size prop you were using.
Best wishes, and good sailing, Dave W 😊

Flack
(Fleet Admiral!)





Forum Posts: 171
29th Apr 2018 22:57  
>> Permalink
mdlbt.com/41409

Hi Dave,
Definitely in parallel to give the duration. I have just moved home and all my boats are in storage so unfortunately I can't give you the prop size at the moment.
Cheers Shaun

ronrees
(Sub-Lieutenant)





Forum Posts: 9
30th Apr 2018 09:28  
>> Permalink
mdlbt.com/41416

Hi Shaun,
This design of hull forces the craft higher and higher the faster it goes. When it is high on the plane and almost hanging on the last few inches of propshaft it can fall off the plane either way, usually to the right (Starboard) side because of engine torque. The full size boats were fitted with 2 or 3 engines to help counteract this.

The British Powerboat Company, who originally designed the hull that Vospers copied back in the 1930s/40s also noticed this which led to double skinning the hull with 1 inch thick mahogany for extra strength against pounding and falling on the waves. Lowering the drive angle of the propellor shafts and adding more weight from the C of G back to near the stern.

We build this 3 screwed designed hull with one mainshaft usually so do not have the benefit of shaft rotation to stabilise the boat at speed.
It was in the 1960's that Fairey engineers had the same problems (Swordsman,Huntsman etc) They came up with large transom mounted powered Trim Tabs. Their boats had similar problems and only one shaft in the main.

I suggest you try fitting 2 x 2 inch wide by 1 inch deep trim tabs at the very bottom of your transom midway between the keel and the chine as well as move your battery packs forward a bit initially. Try some fast tests with this, you only need 2 to 4 degrees of down on the tabs initially. Add removeable weights near the CG as needed, a bit at a time but don't stop the bow lifting up onto the plane.

Have fun, best of luck.

Ron Rees


Ron Rees
ronrees
(Sub-Lieutenant)





Forum Posts: 9
30th Apr 2018 09:44  
>> Permalink
mdlbt.com/41418

Hi Rolfman,

This one is for you.....I wouldn't fit a 6 cell Li-Po to run your 47 inch fireboat!..It would be uncontrollable almost, even if you throttled back. That relates to an output speed in excess of 11,000 rpm at the prop. Safer to try a 5 cell (9,250rpm) or even a 4 cell (7,400) initially. Also see my message to Shaun. I use a G60 in mine with 4 cells which is ample, the extra battery pack in Shauns will double the running time. I only use 1 cell. I use a 50mm two blade Hydro Graupner prop (From Gliders UK), it could handle a bigger one but everything starts to get a bit warm!!

Cheers......Ron.


Ron Rees
rolfman2000
(Fleet Admiral!)





Forum Posts: 126
30th Apr 2018 10:12  
>> Permalink
mdlbt.com/41420

Thanks Ron. I always though the I'v times the voltage gave the prop revs. As my G-60 is only a 500kv, then my 4s at 14volts should be sufficient, but a 3s might be a bit short at 11.1v. But I will give the Graupner 50mm hydro a try, which at the least is a place to start from. Once again, thanks for the advice Ron. Happy sailing, Dave W😊