Mast Rake

[santeana]

As a newcomer to the forum I've contributed to one or two threads (to gain confidence!) but until now have been a virgin poster. So here goes.

Routinely my boat is wintered ashore and the mast unstepped. On launching in the spring the mast is restepped and rig adjusted to set mast rake. I've only owned a boat for 3 years and in year 2 (05) watched DIY owners and hired marina riggers doing this work. I joined the DIY club. That year, when hard pressed, the boat sailed with considerable weather helm compared to the previous season, occasionally needing two crew (on tiller) to keep on track.

This year (06)we launched the boat; loaded gear and provisions; filled fuel and water tanks; pushpit sprouting; Aries hanging; sails bent; crew lounging.... trim checked and only THEN did we set mast rake. Handling was transformed never needing more than one hand on the tiller even when hard pressed.

It seems logical that the true datum is with the boat trimmed to the Loaded Water Line even though rake is measured at the mast base. However, I've not observed owners, or riggers, giving this much regard, if at all - launch, step, rake seems to be how it's done. Maybe I'm missing something.

Am I just unlucky? Do most yachts float trimmed unloaded, as launched? Mine certainly doesn't. Is there a better way of measuring rake? How do you go about it?

 

[sailorman]

Rival 34 i would suggest about 9" rake aft

 

[abbott013]

I wrote this for another forum, when i had my old boat. the general rules are still the same.. I looked right into this when setting up my mast, in the end i bought a Haynes book called Sailing Rigs and Spars, ISBN 0-85429-753-7. In the book they say a Masthead Rig boat should have a rake of 1%-2% and a Fractional Rig 2%-3%, so for a 10m (32ft) fractional mast the distance between the aft face of the mast and the line at gooseneck height would be between 200-300mm (7.9-11.8in).
I worked out that for a 5182mm (17ft) masthead rig boat you would need a distance of 51-103mm. I used the mainsail halyard with a 5kg weight suspended from it, hanging in the cabin.
The distance between the mast and the halyard pulley must also be endered into the amount of rake required for the final figure. It should also be carried out with the boat in the water, on a very calm day (no wind).
I hope this is of some help to you, good luck.

 

[macd]

Hope Teine is treating you well, Ron. You won't be surprised that the R32 can get horrible weather helm if not set up correctly, too.
I think the problem is sometime compounded on boats like the Rival by the pronounced sheer at the bow. Even when raked back a degree or two, this gives the optical illusion of making the mast looks as though it is actually raked forward. I've had a sailmaker tell me my mast was all wrong when in fact it wasn't, as sighting on a convenient lampost clearly showed. Maybe what we need is a banana-shaped spirit level /forums/images/graemlins/smile.gif

 

[macd]

Incidentally, if you dangle the weight in a bucket of water, it damps out the swinging, making the job far easier.

 

[santeana]

Thanks guys. I don't have a problem with knowing the rake - it's 12 inches - or measuring it. In '05 due to my ignorance I set up the rake on launchining the boat. In trim condition the stern sinks 4 inches with payload which sets the mast back another 6 inches or so. Thus I had a rake of 18 inches! Hence weather helm. It strikes me in observing how others set up rigs, even riggers, this could be a common but latent issue.

Mac - TEINE is a delight! Thank you.