Gaff Rig Design

I'm in the design process for a Steel 45ft boat. I bought a set of stock plans for the Vickers 45 AC designed by Dudley Dix. The design comes with a bermudan rig, but I would prefer to have a Gaff Rig with topsail and Bowsprit. Could you either point me in the direction where I might be able to get a sailplan for reference to design the rig for this boat. I.e. A sailplan for a dsingle masted gaff rigged 45ft boat.

Any help would be apprecited.

Regards
Steven Prince

steven_prince@lycos.co.uk

[osteoderm]

There may be far more to such a conversion than you assume. Try contacting the designer directly; they will already have all the information about centers of effort/resistance, ideal lead, etc., so they should be best able to make the changes at this, the design stage, rather than later on, halfway through building. It's not just as simple as swapping one stock sailplan onto another stock hullform. Placing a low-aspect rig with a bowsprit onto a hull designed for a high-aspect inboard rig may require signifigant changes to mast position, chainplate position, which in turn may be reflected by much change to the boat's internal structure. Gaff rig is very adaptable, but it's still true that some hulls take more kindly to gaff or bermudan rig.
Having said that, get a copy of John Leather's excellent Gaff Rig Handbook; more pertinant information there than any of us could write down here, including much discussion of hullform-sailplan relationships.

I wasn't planning on just swopping one plan for another. I was going to use it to gain idea's. I'm designing the new rig with the help and support of the boat designer. I've allready got John Leather's book and Hand Reef And Steer. I was just after some designs for inspiration.

[Ian McColgin]

Ahoy Steven,

Dix's style is so very modern that I have trouble seeing a gaff on this. I assume that as he is involved he's thought about the weights aloft and all that but I must say that your aesthetic daring leaves me breathless.

Anyway, one thought not always shared: The topmast is a great place for that safety feature known as progressive failure. That is, make it light and lightly stayed so that it will break off harmlessly if you are so inprudent as to carry sail too long into a breeze. I think you can find good references to this in Phil Bolger's remarks about his design work on the replica of HMS Rose.

If you make a sliding or retracting bow sprit - ala Thames barges - you will save much money in dock fees as they must charge by the liniar feet you actually take up, not LOD or LWL.

Regretably, all the really handsome gaff cutters I know are for such different hull types and are US NA's so you'd have a hard time getting access to the drawings anyway. But if by odd chance the posthumous collection called "Pete Culler's Boats" is in a library near you, look to the husky and very yachty looking cutter near the end of the sloops and cutters section.

Er - - maybe not such a grand thought. Culler and most traditional gaff rig designers within my ken matched their rigs with hulls of quite noticable drag (draft well aft, not drag like resistance) and such a rig would likely overpower the steering dynamics of Dix's design.

Is Dix indulging you in this as a way to get you to fully accept the design as he made it, or is he really this openminded? Are you making aesthetic changes to the above water hull lines to harmonize better with the gaff rig?

G'luck

Ian

[steven prince]

Ian,

The design actually looks really good with the Gaff rig. I've had a few people say the Gaff rig looks far better than the Bermudan cutter.

I've got a few pics of my proposed design on the link below.

http://www.metalboatsociety.org/phpb...pic.php?t=1721

If you would like to see some pics I can email them to you.

Regards
Steven

[H/V Vega]

Hi Mate,

Look there is much more to rigging a hull with the best rig than getting a few pictures and what worked on another boat. The right rig must be designed for your hull and her specific center of lateral resistance. What looks great superimposed on the hull as she would float may not work at all under way. The center (s) of lateral force from the sail plan must work in careful harmony with the hulls center of lateral resistance or you get a dud. One quick and easy way to get the hulls center of resistance is to make a photograph taken exactly from off the beam and about half way from the keel to the waterline (use a normal lens no wide angles here please) when she is out of the water then cut carefully around the underwater body and along the water line. Balance that on the edge of a knife blade and you will have a very good idea of where the hull center of resistance is. Make your sail plan lead that center ever so slightly and you have a good chance of getting a boat that sails well. Hope this helps a bit.

[steven prince]

H/V Vega,

I do understand that you have to keep the rig balanced or you will upset thebalance of the boat. My boat isn't actually built yet. I'm in the process of designing it and then building it. I have the great advantage that I have created the design on a C.A.D program that will give me the two centers. The rig center is on roughly the same position on the X axis as the original rig (it's about 200mm further aft) but it is now lower than the original rig, but a gaff rig generally has a lower center.

I have been getting advice of several people to help with the design of the rig to ensure that it sails ok.

Regards
Steven