Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Help with a hull  (Read 1870 times)

AlanP

  • Guest
Help with a hull
« on: March 20, 2011, 09:00:38 PM »

Hi, I have been given this hull of a yacht that I would like to do. If anyone could give me an idea of the point of balance so that I can put a dropped keel on it, the position of the main mast and the height of it, or any other information that would help me I would be grateful.

Alan








Logged

tobyker

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,315
  • Location: Scotland - West Coast
Re: Help with a hull
« Reply #1 on: March 20, 2011, 10:50:02 PM »

In theory you want to get the centre of effort of the rig (wind pressure) over, or with a very slight lead over, the Centre of Lateral Resistance of the hull. To find the latter, you put the hull in the bath weighted down to the waterline and push it sideways with one finger. The point at which you push it so it moves sideways without slewing to bow or stern is the CLR. However, the rudder affords some lateral resistance so you need to dummy one up before trying the experiment. If you then want to fit a drop keel and keep the CLR the same, the centre of effort of the keel (dropped) will need to be in line with the CLR. Height of mast -say about 1.5 times overall length of hull?

That's just for starters - now the experts can have a go!
Logged

AlanP

  • Guest
Re: Help with a hull
« Reply #2 on: March 20, 2011, 11:09:23 PM »

That's a hell of a start, thanks very much for that tobyker  :-))

Alan
Logged

lancek

  • Shipmate
  • *
  • Offline Offline
  • Posts: 0
Re: Help with a hull
« Reply #3 on: June 08, 2011, 11:58:01 AM »

Looking at the shape that hull do you need to put in a drop keel?  It looks as though it will have good lateral resistance already. With regard to rigs look around and see what other people have done with boats of similar size and displacement. 
Logged

tigertiger

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 6,968
  • Location: Kunming, city of eternal springtime, SW China.
Re: Help with a hull
« Reply #4 on: June 08, 2011, 01:07:23 PM »

Looking at the shape that hull do you need to put in a drop keel?  It looks as though it will have good lateral resistance already. With regard to rigs look around and see what other people have done with boats of similar size and displacement. 

I tend to agree
Logged
The only stupid question is the one I didn't ask

AlanP

  • Guest
Re: Help with a hull
« Reply #5 on: June 08, 2011, 01:30:25 PM »

Since starting the post I have obtained some plans of the deck and rig, so if no dropped keel I presume I would use lead shot in the bottom of the hull to get it down to the water line.


Alan
Logged

tigertiger

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 6,968
  • Location: Kunming, city of eternal springtime, SW China.
Re: Help with a hull
« Reply #6 on: June 08, 2011, 01:37:14 PM »

You can set the lead shot in resin.

Alternatively you can use a food bag, place in the hull, and then put the shot and resin into this. That way you can remove it if you wish.
Logged
The only stupid question is the one I didn't ask

lancek

  • Shipmate
  • *
  • Offline Offline
  • Posts: 0
Re: Help with a hull
« Reply #7 on: June 09, 2011, 02:28:07 AM »

Because of the lead pollution of the waterways with lead shot it is becoming increasingly difficult to obtain in the Antipodes. I find a cheap source (ie free!) of ballast are wheel balance weights that my local tyre dealer is only too happy for me to take off his hands. The material isn't a 'pure' lead but a brittle Pb based alloy that melts easily. I cut the clips off the weights with side cutters. If you have to get the ballast through a small hole in the keel your options are limited. You can cut it into small slivers (which is tiresome) or melt it and make your own shot which is potentially dangerous. Otherwise you can use small fishing sinkers, which make a very expensive ballast or go to the scrap metal dealer and see if they have any 3mm/one eighth inch lead sheet which you can slice up with a Stanley knife/box cutter.
Logged

AlanP

  • Guest
Re: Help with a hull
« Reply #8 on: June 10, 2011, 06:41:53 PM »

Thanks for that Tony, I will be getting on with this as soon as I have finished the Shrimper, so stand by for more questions  %)

Alan
Logged
Pages: [1]   Go Up