Model Boat Mayhem - Forum

Dry Dock / Shipyard: Builds & Questions => Working vessels R&D: => Topic started by: turner on August 10, 2014, 12:49:27 PM

Title: Loyal Class - Prop Choice
Post by: turner on August 10, 2014, 12:49:27 PM
Hi

I've not been on here for a very long time, my last post showed progress with my 1:25 Burutu - still got that and making very slow progress will post some updates soon.

While I've been away I bought an immaculate Loyal Mediator (approx. 1.00m long) It has a home made "scale" 3 blade prop measuring 50mm dia on an M5 shaft

It performs ok ahead but hardly anything astern  - I have read that fitting a coarse two blade prop will improve this (done this on my Waveney lifeboat)  but was wondering what the current thinking is - would one of the 5 blade Rivabo Brass 5 Bladed Propeller LH (A-Type Blades) offer any improvement ?  I guess there will be others on the market also.

regards

David
Title: Re: Loyal Class - Prop Choice
Post by: Shipmate60 on August 10, 2014, 02:00:18 PM
Any decent scale prop will be good on her.
I have had one of these and used the geared motor and a scale 3 blade prop, handled fine.
One thing to remember if ballasted deep and slightly bow high she will handle almost any sea but she is still a heavy model so will not stop in half her length.


Bob
Title: Re: Loyal Class - Prop Choice
Post by: hmsantrim on August 10, 2014, 07:14:58 PM
Hi David.
 I have a plastic three bladed prop on a model forward is ok but very poor going astern.  In your case having a metal prop I recon the blades just needs a little tweak with the pliers to slightly increase the pitch.   This is old skool engineering O0
 
Frank   
Title: Re: Loyal Class - Prop Choice
Post by: mudway on August 11, 2014, 01:58:02 AM
They carried a 3 blade prop.
Title: Re: Loyal Class - Prop Choice
Post by: turner on August 11, 2014, 10:35:12 AM
Thank you Gents
 
Like the sound of old school - its cheap !  :-))
 
I am not looking to enter this into any scale comps - (principally as I didnt make it)  just want to sail it.
 
I would imagine that an owner of a full size vessel  might consider a prop upgrade to a four / five blade item if it gives them an increase in performance or manouverability or economy accepting of course any limitations due to engine size / speed
 
regards
 
David
 
 
Title: Re: Loyal Class - Prop Choice
Post by: Shipmate60 on August 11, 2014, 12:51:21 PM
Check to see if the blades are concave ahead.
If so just flatten them with a pair of pliers.


Bob
Title: Re: Loyal Class - Prop Choice
Post by: dodes on August 11, 2014, 04:35:21 PM
Remember on a full scale vessel, it is estimated on average that the astern power is 65% of the ahead power, this is due to hull resistance and a prop is designed to give max efficiency ahead not astern.
Title: Re: Loyal Class - Prop Choice
Post by: merseyferry on August 11, 2014, 11:31:36 PM
hiya dave  my loyal class is slighly smaller then yours but she has a 3 blade prop  handles quite well regards pad ]www.youtube.com/watch?v=4TzMFInD5C8&index=1&list=WL (http://www.youtube.com/watch?v=4TzMFInD5C8&index=1&list=WL)
Title: Re: Loyal Class - Prop Choice
Post by: turner on August 12, 2014, 07:42:17 AM
Thanks gents
 
I appreciate that a boat is not going to go astern as well as it goes ahead - I would guess with the current prop I get about 10% performance astern.
 
Looked carefully at the prop last night - one blade is slightly larger than the others and all three are only slightly dished.
 
Took the plunge and ordered a couple to have a play with - will start filling the bath tonite !
 
David
 
Title: Re: Loyal Class - Prop Choice
Post by: mudway on August 12, 2014, 09:41:23 AM
Just a thought, what speeed controller are you using? The "blue" ones are noted for giving a lot less power astern than ahead.
Title: Re: Loyal Class - Prop Choice
Post by: turner on August 13, 2014, 07:20:33 AM
Had another look inside last night - the units are "Action Electronics"
 
Title: Re: Loyal Class - Prop Choice
Post by: turner on August 18, 2014, 02:41:09 PM
New props arrived - went for fitting the three blade first.
 
Sunday morning in the water (millhouses) significantly better performance in reverse
 
Thanks all
 
David