Modifying a Whitehall

[Tom Hoffman]

I have started building a modified Whitehall. I have stretched it to approx. 21' Length at the waterline will be approx 18'6". I live in Iowa, and am building it to full fill several functions that I have wanted in a boat for years. I want to do some rowing for exercise, but I also would like to motor back up the rivers so I don't have to shift cars.

Now my Question: If I wanted to put a sail rig on it using a dagger board. How would I determine where to cut slot through the keel so the boat would be set up correctly to sail also where would I place the mast step?

I would build a dagger board box and seal it so no water came in during operation of course.

Any help would be greatly appreciated.

[Andrew Craig-Bennett]

Well, here are a few thoughts:

To locate the rig in relation to the dagger board box, draw the proposed sail plan and the hull profile with the daggerboard down (but ignore the rudder). Find the notional Centre of Effort (actually the centre of area) of the sail plan and the Centre of Lateral Resistance of the underwater profile.

The easiest ways to do this are by drawing, for the sails, and by cutting out a thin card silhoutte of the underwater profile and poising it on a knife edge.

Arrange things so that the CE is between 5% and 8% ahead of the CLR, but give yourself a margin of error by allowing some mast rake.

Actually I would not use a dagger board, on a boat of this size, for river use. If you clip a shoal with the board, which is highly likely, disagreeable consequences, ranging from capsize to ripping the centrecase out of the boat, may ensue. I would definitely go to the slight extra trouble of making a centreboard and case. And, by the same token, I would make a kick up rudder.

[Bob Smalser]

For a 500-hour project, that'd be too big of a stretch for me to not be consulting somebody who did this center-of-effort stuff every day. Same probably with the beam width on that boat with that kind of stretch. I'd rather spend the dough up front and then build with confidence rather that wonder if I was gonna have to change something later.

The only difference in manhours between a centerboard and a daggerboard is an easy pin and raising tackle.

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[ 04-18-2005, 11:01 AM: Message edited by: Bob Smalser ]

[Dean4140]

I agree with Andrew. The alignment of the CE of your sail with the centerboard in the down position is critical. If correct it gives you a nice neutral tiller that you don't have to fight. Some people put in a double or adjustable mast step to find the best mast position for their sailing conditions.

Once you've had a center board you'll rarely go back to a dagger board. I've had center boards suddenly start moving up when beaching or in shallow water and realizing I forgot to raise it. CB's have saved me a lot of potential damage. Go with Andrew's advice. CB. Dean

[Dean4140]

I dido Bob. Dean

[Bob Smalser]

I've a rather large folder on the "ideal" Whitehall I've been planning to build for 30 years.

Lovely boats. But they began life as a narrow, tippy, hard-to-turn pulling boat not well suited for sail.

Start making major changes to something already close to squirrelly, and it may be time for the intervention of a proven designer.

[Andrew Craig-Bennett]

A Whitehall is a pulling boat that can be sailed, which is not at all the same thing as a sailing boat that can be rowed! I would think any of the traditional pulling boat rigs, as seen on some Whitehalls and similar boats, like whaleboats, would work. Low C of E helps, so spritsails and such are indicated.

The difference, really, is that in a nice Whitehall you are going to row upwind, rather than tack under sail. Which, for a boat to be used on rivers, makes very good sense, to me.

Once we have decided that we will row upwind and sail downwind and across the wind, we don't need a high windward efficiency rig, so we can go with a low rig with short, easy to stow, spars, and moderate sail area.

[Tom Hoffman]

Thanks guys for the help. I had not ment that I was going to sail on rivers. Those mostly here in Iowa are less than 3 feet deep. I would just float down them and motor back up. The sail idea was for the small lakes around here that would have the depth and surface area. May be I will just keep this as a pulling boat, and my next boat will be for sail.

Tom.....

[Bruce Hooke]

How much are you stretching the length? If you are going from 19' to 21' there are not likely to be that many issues. If you are going from 15' to 21' without making other adjustments you are likely to be in for some very unpleasant surprises come launching day.

[grange]

You might try working with a really easy leeboard or two first. You could slap them on the gunnels, move them back and forth a few times under sail, find the sweet spot, and if you still decided you wanted to build a box in the center of your boat, you'd know where.

[Tonyr]

Grange, that's exactly what I did. Worked just fine. I used a pair of large clamps to hold the board in place.

Tony.

[Steve Lansdowne]

Having built a sail-rigged Whisp, I'll vouch for the fact that a narrow pulling boat is not an ideal sailer. I'd stick with the row/motor rig and build your second boat for the lakes.