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
July 2018: 5 people
June 2018: 8 people
May 2018: 7 people
April 2018: 24 people
March 2018: 13 people
February 2018: 8 people
January 2018: 25 people
December 2017: 7 people
November 2017: 3 people


Unique Visitors This Month

Website Members

Terms and Conditions
Privacy Policy
Advertising
Contact


Model Boats Website
Active Users (13)
Login or Register
To Remove This Ad

Login or Register
To Remove This Ad
>> Home > Forum > Any Other Questions! > Props
Props
(681 views)
Author Message
ChrisG
(Chief Petty Officer)





Forum Posts: 15
1st Jan 2018 13:37  
>> Permalink
mdlbt.com/37031

I have two beautiful brass props for my new model under construction but I am unable to determine the r/h prop from the l/h prop. And which one is on starboard and portside.
Can any builder shed any light on this to assist me and stop me from scratching my head as it is starting to hurt.😡
It might be worth mentioning the markings on the props are unreadable even with my Sherlock glass.
Thanks and Happy New Year to all Chris G.

jarvo
(Fleet Admiral!)





Forum Posts: 550
1st Jan 2018 20:13  
>> Permalink
mdlbt.com/37048

Hi Chris, this is a problem i have had, once the props are out of there bags which is which? basically suck it and see, if you want them turning inwards look at the leading edge of the prop, if the edge looks left, its left hand etc.

Mark


Etherow Model Boat Club
RNinMunich
(Fleet Admiral!)





Forum Posts: 1831
1st Jan 2018 20:20  
>> Permalink
mdlbt.com/37049

Hi Chris,
here is the graphic answer from the Raboesch website. Makers of some of the finest brass props and shafts around. 😊
http://raboeschmodels.com/index.php/en/
As you can see from the pic the leading edge is actually the curved edge.
General opinion is that for best rudder effect (esp. if a single rudder between two shafts) is to have the props turning inward at the top. I.e. when going ahead port prop turns clockwise (R in the pic) and the starboard prop anticlockwise (L in the pic) seen from the rear.
Cheers Doug 😎


Attached Files - Click To View Large


Young at heart - slightly older in other places 😉 cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
Trillium
(Captain)





Forum Posts: 72
2nd Jan 2018 00:23  
>> Permalink
mdlbt.com/37052

This rotation question seems to pop up regularly.
Probably for a model, rotation direction doesn't really matter, but one authoritative answer can be found here: http://modeltugforum.com/index.php?topic=5947.0, which quotes from the Ship Handler's Guide.
To summarise the comments:
Outward-turning propellers means the blades of the propellers are outward turning in the upper half of their circle of rotation, and, when viewed from astern, the propeller with the right-hand blades is on the starboard (right) side and again, when viewed from astern to drive the boat forward, it must rotate in a clockwise direction.
This is the preferred arrangement on full-size ships because when using the props to assist a turn, i.e one prop pushing ahead and one pushing astern, the side thrust from the two propellers assists the turn.
The attached image from www.slideshare.net may help.
Roy


Attached Files - Click To View Large

ChrisG
(Chief Petty Officer)





Forum Posts: 15
2nd Jan 2018 09:53  
>> Permalink
mdlbt.com/37063

Many thanks to Mark, Doug and Roy for the information on prop rotation.
I will now be confidant that each prop is on the correct side of the boat, wiring the motors and connecting the ESC correctly is a task for the future to say nothing of connecting the R.C.
Thanks again👍

RNinMunich
(Fleet Admiral!)





Forum Posts: 1831
2nd Jan 2018 10:02  
>> Permalink
mdlbt.com/37064

Hi Roy, Happy New Year 😉
Twin screw rotation is case of 'Horses for courses'!
It's a Black Art and much depends on the hull shape, especially at the stern and the orientation of the rudders to the shaft lines.
What you write is correct for slow, short fat displacement hulls, like tugs and rig supply ships etc needing good slow speed manoeuvrability. Especially those with one rudder per shaft.
For long thin hulls (naval ships) and deep V and planing hulls (Fast launches and power boats etc) inboard turning screws are preferred to concentrate the thrust behind the centreline of the hull instead of dissipating it out into the open water. It also concentrates the thrust onto the rudder when only one rudder is fitted on the centreline.
Outboard turning screws tend to push the stern up and bow down. Inboard turning tends to suck the stern down and raise the bow. So making planing easier.
You only made one mistake in your description: "when using the props to assist a turn, i.e one prop turning clockwise and the other anti-clockwise".
The props turn in opposite directions when both are running ahead, or both astern. When turning, one ahead and one astern they then both turn the same way thus producing the combined side thrust.
I was advised to use inboard turning props on my H class destroyer (twin screws single rudder) by an ex RN Captain I met at the local lake here in Munich about 30 years ago!
@ Chris: What type of boat / ship are you building?
Cheers Doug 😎


Young at heart - slightly older in other places 😉 cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
ChrisG
(Chief Petty Officer)





Forum Posts: 15
3rd Jan 2018 11:34  
>> Permalink
mdlbt.com/37096

Hello Doug
Thanks for all of the useful information and yes it is a 'Black Art' and I have been party to some heated debates regarding props on large passenger carrying boats.
I was highly amused by the link to 'Raboesh' which if it wasn't a Chinese company should have been.
The model I am building is a Rother class lifeboat which will have twin props and a single rudder and I have read that due to the limited swing of the rudder the turning circle of the boat is much improved by having independently powered motors. Not at that stage yet still early days of the build.
Thanks again and best regards Chris G

RNinMunich
(Fleet Admiral!)





Forum Posts: 1831
3rd Jan 2018 11:57  
>> Permalink
mdlbt.com/37097

Hi Chris, glad to have helped, having already been down that road and learning the hard way! 😉
Actually Raboesch is a Dutch company. Not quite Double Dutch but in the case of 'Left - Right' props close to 🤔

Your boat: Rother class, OK so it's a slow (10knots) displacement hull.
With bilge keels which make turning more difficult.
I would probably use two brushed motors cos you don't need the Oomph of brushless. With brushed you can then use the Action Electronics Dual ESC and rudder mixer, P94Lite. From Component Shop. See pic.
https://www.componentshop.co.uk/action-electronics/esc.html
Good for 10A continuous to each motor - brushed ONLY!
I'm about to fit one to my 5 foot Graf Spee.
With the hull form of the Rother only sea trials will confirm which is best outward or inward. have fun with the build and trials, looking forward to updates / pics / vids 👍 BTW: will yours also be Self Righting??? 😉
Cheers Doug 😎


Attached Files - Click To View Large


Young at heart - slightly older in other places 😉 cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
ChrisG
(Chief Petty Officer)





Forum Posts: 15
3rd Jan 2018 14:23  
>> Permalink
mdlbt.com/37098

Hello Doug
I very rarely get my boats wet so the self righting will hopefully not be an issue and as I have had the bath taken out of my house the model when complete will not even get the old bath test. I have twin 540's linked to the 40mm three bladed props and as you rightly say experimenting with thee boat on the water will give me the most acceptable set up.
Your recommendation of the Component Shop P94 would seem ideal and reading the spec. it answers several other questions, I am not particularly electrically or technically savvy you will have noticed.
I must admit I prefer building with wood to plastic and P38, old fashioned, me, of course.😉
Regards Chris G


Attached Files - Click To View Large

RNinMunich
(Fleet Admiral!)





Forum Posts: 1831
3rd Jan 2018 14:48  
>> Permalink
mdlbt.com/37099

Go for it 👍😉 Look forward to seeing the results. Cheers Doug 😎


Young at heart - slightly older in other places 😉 cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!