Albin 27 - Mast Thread

[Jay Knoll]

Joe

Why so small a main? It looks to me that you could drop the boom down a bit and gain some sail area. I think Don makes some good points especially taking the shrouds to the rail but I think that you could just go to the outside of the toe rail and avoid the complications of piercing the deck with the chainplates. Probably take a little metal bending to go around the rubrail but shouldn't be a big deal. We had external chainplates on our Crealock 27, owned her for 24 years and never had a problem.

Jay

Jay

[JT48348]

I'm thinking. The size of the main doesn't need to be big because the main won't be used for driving the boat. The main is a steadying sail. The jib will be a teacher on a roller fueling so it doesn't have to be doused and can be adjusted as need be. I plan to put a dingy on the roof so the boom is high.

Since the original rig went on a Catalina 22 I'm trying to keep the shrouds similar and at a similar width. Hence the idea of putting them to the cabin top.

Dons solution for the stem head is a good one. And I did think about the rub rail using exterior chain plates. Jay I like the simplicity. I'm just thinking the shrouds will be at quite an angle. But it could be a good solution.

[Jay Knoll]

Joe

I can't remember, but does that mast have spreaders? If so, you should be able to get the shrouds at 90 degrees or so from the deck. You could take the uppers to the rail and mount the chainplates for the lowers on the cabin trunk. Then you'd have the angled shrouds going over the top of the cabin and the uppers outboard so you could still go forward without climbing over the shrouds

Jay

[JT48348]

Possible stem fitting for back stay fittings. I located found this fitting for a few bucks at a local marine salvage yard. They have several others. 316 stainless. I think it might work well for the stem fitting because there's already a slot in the bowsprit where this thing could stick up through.

[don123]

That would put all the load on the bowsprit and none on the hull. I think a 12" piece of stainless 1" X 1/4" thru-bolted into the anchor locker and sticking up through the bowsprit would be a better choice - Probably cheaper too. You could use two more similar pieces bolted through the aft wall of the aft cabin for the backstays . . . . and two more similar pieces for the mast chainplates through bolted to the hull

http://www.ebay.com/itm/1-4-x-1-x-12-Lo ... 233b5d68bf

Drill a few holes in those and you're all set - A little wet sanding and polishing and they'll look like chrome

Don

[JT48348]

This piece is to be bolted to the deck at the fore peak. Not to the bowsprit. It sticks up through the bowsprit and is not attached to said bowsprit.

Back stays are bolted to aft cabin room or side deck with backing plate.

[don123]

I don't know Joe - The deck is cored and relatively flimsy compared to the hull and the hull to deck joint is nothing more than a few widely spaced pop rivets - No glue, no bolts. I can't think of a single sailboat that transfers rigging loads to the deck and not the hull . . . . but your sail rig is relatively tiny, so maybe you'll get away with it

Don

[JT48348]

I will be double checking this...

[don123]

Random thoughts

Looking at your avatar with the largish jib, the smallish main and the mast placed so far forward and then looking at the underbody of the hull, where the directional stability afforded by the keel doesn't really come into play until aft of your proposed mast placement, I *think* you're going to find this pretty off balance when the wind fills the sails - I think the boat will be hard to keep on course, especially if the winds are at all flakey

An easy change to make might be to step your mast on the cockpit roof directly over the double bulkhead between the engine room and the forward cabin. Mount a compression post between the aft edge of the 'dash' to support the cockpit roof. This would be an even stronger set-up than where you have it placed now. It would also make it much easier to raise and lower the mast aft, as opposed to having to raise and lower it forward from your proposed location

Given your restriction on the main size caused by your desire to have the boom clear the dink on the roof, I think I'd also consider using a forestay which meets the mast at the spreader location rather than the masthead - A fractional rig. This would help get the ratio of main to jib back in balance and add to directional stability

Don

[smacksman]

How about a small gaff main. Gaff works better off the wind than bermudan/marconi mains. You can also drop a gaff main downwind without having to come into the wind. And for a quick slowdown then scandalise the main by dropping the peak of the gaff. And the real eyecatcher would be flying your ensign from the peak - real nautical!

The main downside is needing to have running backstays to keep the luff of your jib furler tight or it won't furl.

[JT48348]

'Been doing some computations for the mast experiment. I was able to take the A27 line drawings we got and compute the approximately Center of Lateral Resistance (CLR). This is one of the computations necessary for trying to determine where to step the mast. Not sure I undersatand all of the process, but near as I can tell, the CLR and the Center of Effort (COE) which is computed from the sails and their cut, helps predict how the boat will handle under sail and where the mast might need to stepped to get a "balanced helm."

In addition there's a computation for determining "the lead", which tells you how much the mast and COE can be forward of the CLR. Lead, depending on who's giving the advise, can be anywhere from 5%-20% depending on the type of boat.

I was currious where the lead would be knowing the approximate CLR and estimating the mast step. My concern is: does the mast really need to be aft of the pilothouse in order to get any type of balanced helm. Can't say I still know the answer to that. But by my calculations if the mast is stepped aft of the forward hatch and in front of the pilothouse. the lead should be no more than 15%. Thats high, but might be ok.

My mast step would be on the forward cabin top, since I have a great support under the deck from the new bulkhead for the bathroom project, and since I can't mount the mast aft becuase of the proposed hardtop.

I've determined my mast will be a simple afair. Approximately 20-22' long, with two lower shrouds on each side and a fore stay. No back stay, no spreaders. This is a very simple rig and easy to raise and lower. I got the idea from the pilothouse sailboat I just completed and the rig is basically the same thing. Very simple. Because the mast is so squat, the shrouds are aft of the step, and the sails will be smaller (except for the jib), and becuase the boat is designed to be used an auxilary sailer, I'm going this route as an initial experiment. I can always add the spreaders, and backstay (which I already have). But why make it more complicated than necessary.

This is the same rig as whats used on Briney Bug

[sail149]

JT
I think you CLR is about 10% to far FWD. Also the lead can be a lot less for a boat that does not heel much. Even zero is ok , espically as your not making a rig to go to windward!

Have you thought of forgetting the main and just go with a large roller genny?
Years ago I helped build in one day a sailboat with a jib only rig ( from a jet 14) and sailed upwind and down!
And yes that's me helming on a cold october day!

[JT48348]

The CLR was computed from taking the below waterline profile and balancing it on a point between fore and aft which I believe is one method of doing it. I was surprised it was that far forward but that's what it was. Don't know how effective method is but that's what was done.

My sail rig will sail almost exclusively by jib. The main will be tiny

[sail149]

Some interesting experimenting and comments were just posted about putting a sailing rig back on a A25 on the Yahoo Albin group.
Do you get the emails?

[sail149]

image.jpeg

Hi , re the CLR location. Did you include the rudder? You should include at least half.
Yes a cut out of the underwater profile balanced on a knife edge is the classic way to find the CLR.
I measured from the CLR the the bow at wl and CLR aft the distance 1/2" shorter on your sketch , but clearly there is greater lateral plane aft of the CLR. Hence why I think it looks odd.
So I tried the balance just for fun haven't had to do this for years.! Hard to balance but this is what I got.
Did I include too much rudder?
Thanks letting me have some fun this morning!