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Mast Step and Centerboard Trunk placement


fstauss

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I am currently building a Core Sound 17 and have a few questions concerning the mast step and centerboard trunk. If anyone could offer advice it would be greatly appreciated.

Mast step

1. I am unsure how far down from the prowl of the boat to place the mast step. If someone could give me a total # of inches from say a straight edge laid across the the inwales it would be of great help.

2. The forward mast must be set at a 3 degree rake to the stern of the boat. How do I accomplish this. Should the mast step be put on a slight angle? If so how do I determine 3 degrees? Or should I place the step level and cock the mast to the rear 3 degrees?

These questions have been driving me crazy!

Centerboard Trunk.

1. I can't seem to locate a measurement on the plans that indicates exactly where to place the trunk. Either a distance from the forward bulkhead or a distance from the rear bulkhead.

Once again any help would be very appreciated.

Frank

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Frank, tangent of 3 deg works out to hair over 5" rise on 96" run. Or about 2.5" on 48" run or about 5/8" on 12" run. Your main mast step will be about foot long so tilting it is the better thing to do. My mast tube is exactly 23" to the top of the plywood deck ( which is 1/4" ). The aft end of the center board case is 54 1/2"  from the aft bulkhead. I have to warn you though - my boat is sail No 14 but built from probably the original set of plans. Graham has done some tweaking since then. So I don't know how applicable these are any more. Best way for you would be to get an architect ruler and read your measurements off the plans. Those things aren't much at office supply stores.Good luck PeterP

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Peter:

Thanks for your help. I have never used the architectural scale before. I picked one up and figured how to read it. Works great. What will they think of next. Still trying to decide how I will do the mast rake but if I look at it long enough it will come to me. Thanks again.

Frank

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Frank, you'll need a GOOD 4' level. Check it against a plumb bob to make sure it is bang on. Fasten a 2.5 in piece of ply to one end of it so that when you measure something 3 deg out of vertical your level will read plumb. Save the other side for true vertical as you will need both. Presuming your boat is perfectly level both fore aft and athwart. Make your mast step where it fits in at the right depth. Make it large enough to allow some room for movement of the mast heel. Put it in using dry wall screws - check to make sure it has the correct slope. If you have your mast section set it on top of the step and clamp it against the king plank -and put your 3 deg level to work. Naturally, your stick/mast will lean along both axis but you only need to worry about fore and aft. Find the center of the mast hole. Drill out using a hole saw. Save the round. Run your mast section in and plumb it along both axis. Don't forget the mast goes through the center line at deck level. You plumb by moving the heel. Once you have it in there just right outline the mast step against the hull with pencil in case it moves when you take the screws out and then proceed to epoxy it in. Think how you will put it in and how you will do the fillets. If you worked carefully everything should be within say 1/4" max.  If you messed up -you can epoxy the round back in and start over. Good luck PeterP

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