Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: g4yvm on August 26, 2010, 11:56:55 am

Title: Effect of sail trim on steering
Post by: g4yvm on August 26, 2010, 11:56:55 am
Guys, after your advice on keel position on my 'footy' I have made changes
I noted after today's testing that the set of the sails (main and jib) has a huge huge huge effect on steering ability of the rudder and really, to control the boat, I have to use tiller and mainsheet together. I don't mind this, but wonder whether it is usual for model yachts of this type

David
Title: Re: Effect of sail trim on steering
Post by: pugwash on August 26, 2010, 12:18:28 pm
David I know zilch about model boats but what you have said relates to real yachts - if you have the main or the
jib oversheeted you are going to alter the attitude of the boat to the wind as you will be pivoting the yacht around
the "centre of effect(or effort - never can remember which it is) which is usually somewhere in the region of the mast.
If thejib is oversheeted the boat will fall off the wind and if it is the main the yacht will come up to windward.
the old full keel yachts with their sails correctly set will almost run in a straight line - not so easy with a modern
fin keel yacht - more work for the helmsman -  just set you rudder to midships and keep experimenting with the
main and jib sheet until you get it reasonably well balanced.

Geoff
Title: Re: Effect of sail trim on steering
Post by: g4yvm on August 26, 2010, 12:40:22 pm
Geoff, thanks.. Yes I was trying to relate it to full size yatchs.  My footy has some serious isues I think -  firstly as the sails fill in gusts she turns to windward on one tack but to leeward on the other.  I cant fathom that one.  She also digs her nose in sharply and yaws badly on either helm (one tack to wind, one to lee if you follow me).


She also heels far too much, more than other modelyachts I have seen.


I note that the jib fills and rises, I probably ought to run the sheet through an eye closer to the clew and hold it to the deck, I think that might help.
I think she's just badly designed (be me!) and I'm not sure whether I ought to simply start again. Or possibly buy a known working boat and see how they work first.  Its all very well being a full size sailor, but knowing how things work doesnt mean I know WHY!

Its fun this innit?

David
Title: Re: Effect of sail trim on steering
Post by: malcolmfrary on August 26, 2010, 12:57:21 pm
Quote
My footy has some serious isues I think -  firstly as the sails fill in gusts she turns to windward on one tack but to leeward on the other.
Something asymmetrical, either the lean of the mast side to side, a bias on the rig, the way the sails were made giving a different shap one way as opposed to the other.
Quote
I note that the jib fills and rises, I probably ought to run the sheet through an eye closer to the clew and hold it to the deck, I think that might help.
A "horse and rider" will help - a sort of sliding trunnion running on a bar crossing the deck.
Once the sails are sorted, and the wind force is converted into forward motion, the excess leaning may well be cured.
Title: Re: Effect of sail trim on steering
Post by: Jimmy James on September 06, 2010, 08:52:45 pm
Start with the keel
1. Is it in line (an offset of 1 or 2 deg. can make all the difference) also is the keel symmetrical (the same on both sides)
2, Check the mast is on the centerline and is not canted to port or stb'd...  the rake of the mast can be adjusted to allow the vessel to tack quicker or get closer to the wind.
3, Gripping is a sign that the vessel is out of balance, the usual problem is the the ships head is forced down by the wind and the rudder is partly lifted out of the water (It's a common problem on modern yachts  (And square riggers ) modern yachts tend to be much finer forward than the older craft which were much broader in the shoulders and had more lift (( A, put some ballast down aft ,B make a larger rudder ,C try moving your keel slightly aft or adding an extention on the after end of the keel...any or all of these suggestions should help.
4, As a rule of thumb, your main sail when it is hauled in hard should not be midships but just over the quarter (6 or 8 deg. off the centre line.)..hauling it in any more only heels the vessel over ..slows it down and can lead to a capsize... the jib should be hauled in slightly less than the main on a fore and aft rig
Try these and you should get some improvment
JIMMY 
De Freebooter