Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: stobby256 on October 08, 2008, 09:01:22 pm

Title: Prop size
Post by: stobby256 on October 08, 2008, 09:01:22 pm
Hi Guys,

Is there guide as to what prop size I should start with? It was easy with aircraft   :'(

So I'll run a 48" mono hull sports boat, twin 700BB Turbo motors, and a choice of props from 30 - 80mm!!!!  I know its suck it and see... What should I start with?  Im guessing these props will be submerged.
Title: Re: Prop size
Post by: Martin (Admin) on October 08, 2008, 11:08:57 pm
In plastic props, I would guess 40X - 55X..... metal props.... I have no idea!

A quick search finds:
http://www.fastelectrics.eu/props.php
http://www.fastelectrics.eu/list_props.php
http://members.tripod.com/psfastelectrics5/boat_setups_used_in_the_nationa.htm
http://www.murrellsmodels.co.uk/Boats/Blade.htm
Title: Re: Prop size
Post by: stobby256 on October 09, 2008, 01:33:32 pm
OK - so 40-50mm would be a great starting point.

Looking from the back, which way do the props turn...  LH goes cwise, RH goes anticwise....  does it matter? As they are not surface piercing props, Im aiming for them to protrude just below the hull. obviously as parallel to the hull as I can...  ::)

Many thanks!!!

Steve
Title: Re: Prop size
Post by: Martin (Admin) on October 09, 2008, 01:41:48 pm

Looking from the back (towards the front), usual rotation is Anti-Clockwise.
Title: Re: Prop size
Post by: Martin (Admin) on October 09, 2008, 01:43:29 pm

BTW: there are some nice propellers here....  http://www.seawear.com/jewelry/propellers.html
Title: Re: Prop size
Post by: stobby256 on October 09, 2008, 02:00:04 pm
Quote from: Martin   -   Forum Admin on October 09, 2008, 01:41:48 pm

Looking from the back (towards the front), usual rotation is Anti-Clockwise.


Great - what abpout a contra-rotating set up?
 :kiss:  Not sure about those props.....  The brecelets are more my thing  :kiss: :kiss:
Title: Re: Prop size
Post by: ronkh on October 09, 2008, 02:56:45 pm
Quote from: Martin   -   Forum Admin on October 09, 2008, 01:43:29 pm

BTW: there are some nice propellers here....  http://www.seawear.com/jewelry/propellers.html

Typical.  ::)
Title: Re: Prop size
Post by: Martin (Admin) on October 10, 2008, 05:58:00 pm

A good read about props (full size) here: http://www.boatfix.com/how/props.html
Title: Re: Prop size
Post by: BJ on October 11, 2008, 05:26:33 pm
Quote from: stobby256 on October 08, 2008, 09:01:22 pm
Hi Guys,

Is there guide as to what prop size I should start with? It was easy with aircraft   :'(

So I'll run a 48" mono hull sports boat, twin 700BB Turbo motors, and a choice of props from 30 - 80mm!!!!  I know its suck it and see... What should I start with?  Im guessing these props will be submerged.

Try the attached jpeg and take your pick.
Title: Re: Prop size
Post by: stobby256 on October 11, 2008, 08:22:11 pm
 :-))  WOW!   :-))

MANY THANKS!
Title: Re: Prop size
Post by: Shipmate60 on October 11, 2008, 09:12:31 pm
stobby256,
You could always give Simon at Propshop a ring (I believe he is still working for the company) and get advice from those who make them.
A good while ago I phoned him and asked, he made what I thought was a daft suggestion, so to prove him wrong I fitted his suggested props.
A big piece of humble pie was eaten, the model well exceeded my expectations and I am an experienced modeller.
We can all learn something.

Bob
Title: Re: Prop size
Post by: stobby256 on October 12, 2008, 06:47:25 pm
Cheers shipmate60!!

I'm on the case!
Title: Re: Prop size
Post by: PkBoo on November 28, 2008, 02:46:16 pm
Hi Stobby, Iīve found out that the only proper way to find the right prop is to test and test again. Water is barely compressible so you cannot scale it as with air. As you said itīs a lot easier with a plane. Lately Iīve been building (actually kitbashing {-) ) a speeder with a PT hull and found that with a 30mm prop I could fully exploit a BL motorīs speed at 4300Kv without any real issues with heat development. Mind you Iīm only using a 3s Lipo pack and that thing just flies. I hope to setup a vid coming weekend so I could show and tell. GL on the choice. Boo