Converting a Jib-head Sloop to a Gaff rig

[RobertZ]

All,

I am beginning construction of the hull on a Glen-L Minuet. (15' LOD Jib-Headed ply-on-frame sloop). It is a fairly "traditional" looking boat. With that said, it shows on the plans a jib-head rig, and I was considering how to convert it to a gaff rig. I want to do this for several reasons.
1.) I believe I could store the boat in my garage lengthwise with the mast/boom within the length of the boat with the shorter gaff rig. Otherwise, the jib-head mast is 18 ft, which pushes the limits in my garage lengthwise.

2.) I believe the gaff rig is nice looking, and it is what I want on this small boat.

Here is my question...Is there an authoritative source that I could read to understand the standing rigging changes and mast/boom scantlings/dimensions I would need to create a gaff rig for this boat.

Thank you to anyone with any insight. I ordered the plans for the Stevenson Weekender, and was going to try to copy its sail plan for the smaller Minuet but I do not know where to begin. I was going to build the Weekender, but I wanted a boat with ballast or a centerboard.

Thanks again,
Robert

[ 08-02-2005, 12:17 PM: Message edited by: RobertZ ]

[JimD]

You might want to look at Venchka's thread 'Give me every reason'. Atkin drew two boats, virtually identical hulls, one with a fractional marconi sloop rig such as the Minuet has, and one with a gaff rig. The rigs are interchangable. I can't think of any reason it wouldn't work on a Minuet. In fact I had the same idea and ordered a gaff main kit from Sailrite where the sail (for another boat) was very close to the same size in square feet with the Center of Effort in very near the same location. I may one day finish the conversion.

As for scantlings I would think that if you just kept with Glen-L's scantlings for Minuet you couldn't go far wrong. If you want more authoritative info on gaff spars and rigging then John Leather's The Gaff Rig Handbook is a good source.

[RobertZ]

Jim,

Thanks again for the information. I will order the Gaff Rig Handbook for a little reading before I get too far into the build.

Just so I understand, are you basically saying you believe the mast might be left in the same position if I keep the total sail area approximately the same? I am still trying to learn the "technical" sailboat terminology like CE. Barry at Glen-L explained it as the place the wind puts its finger to propel the boat. From what I have seen, the mast for a gaff rig is usually shorter for the same sail area.

RZ

[JimD]

Robert, the CE is more or less the geometric center of the sail. Very easy to find on a square or rectangle just by drawing two corner to corner diagonals and the CE is where they intersect. It is also very easy to find on any right angle triangle, but a little trickier to calculate on a gaff or most actual jibs because of the odd shapes. The jib will have it's own CE. Sail plans have an overall CE which is the combined CE of the main and jib which will be somewhere between the two separate CEs and this is designed to be at a certain point along the hull. In making the conversion you want to keep that combined CE very close to where Glen-L designed it. Without quibling you can make almost any change you want as long as the combined CE doesn't move more than a couple inches and the total amount of sail square footage also stays around the same. The sail I was going to use was from Charles Wittholz caboat dinghy because it is quite high peaked and has a CE quite close to the CE on Minuet's bermuda main. A Weekender main might have the CE too far aft and that would require restepping the mast a bit forward to compensate. This would also mean new placement of the jib and a longer bowsprit so you have to play around with things to make the least amount of work for yourself. The height of the mast would have to be at least high enough to accomodate the jib which fortunately on Minuet is just about where you'd want it for a gaff rig. You'd also likely be reduced to the lower shrouds.