Bowsprit questions

[MNagy]

I'm trying to figure out how to add a bowsprit to my MacGregor 21, and I'm considering using that carbon fiber mast kit on BoatBuilderCentral.com.

I need it to be removable or retractable for trailering, but the simpler, the better. I was thinking of making some sort of bracket for it that would be fixed to the deck and then have two through-bolts, maybe a foot apart, holding the pole in the bracket.

Are there any detailed instructions anywhere on the Web describing how to retrofit a retractable pole through the hull of a boat?

Some details:
The boat is 21' overall, displacement with crew etc is around 1800 lbs.
The sprit needs to extend 3' past the bow to clear the bow pulpit.
It will have a removable stay going down from the end of the sprit to the bow eyelet.
I will be flying a 240 sq ft asymmetric spinnaker from the end of the pole.

What length and diameter of pole do I need? If the standard carbon mast kit isn't strong enough, what about getting two kits of the same length and doubling up the layers? (I'm assuming I could get a custom-length kit in the 6-8 foot range)

Are there any alternatives that would suit my needs better? Please chime in if you have any advice at all.

[Evan_Gatehouse]

Whatever you decide make sure the deck mounted bracket is wide enough that you don't point load the bowsprit on it's side. In other words it has to be (a) wide and (b) a snug fit all along the length of the bracket.

Local reinforcement of the pole at the bracket wouldn't hurt either.

[Cracker Larry]

I will be flying a 240 sq ft asymmetric spinnaker from the end of the pole.

Hmmm. I've never seen a spinaker flown from a bowsprit. How would you gybe it? Are you referring to something more like a drifter where the tack is secured at the bow? This may be hard to gybe also as the forestay may interfere. What you are proposing in effect makes the boat a cutter, rather than a sloop. Cutters typically use a small headsail to accelerate the air flow over the jib. The mast is usually set farther aft than on a sloop, so the boat will balance.

A 240 ft. sail that far forward would have a lot of leverage and lifting force. It may unbalance the boat to the point of being uncontrollable.

I would fly the spinaker in the conventional fashion, off a spinaker pole attached to the mast. Otherwise you may get poor handling, or worse, bust something.

Just my thoughts, I might be wrong.

[MNagy]

Larry, it's odd that you've never seen a spinnaker flown from a bowsprit...it seems like every performance boat nowadays has a retractable bowsprit from which to fly an asymmetric or "cruising" spinnaker. For example, check out these photos of the J/80.

Whatever you decide make sure the deck mounted bracket is wide enough that you don't point load the bowsprit on it's side.

Huh? Do you mean the thickness of the bracket material? Or the overall width? If I need a snug fit on the pole, then doesn't that pretty much mean that the bracket's width has to be = pole diameter + 2 * bracket material thickness?

Here's a quick drawing of what I had in mind:

Are you saying that the edges of the bracket shouldn't touch the pole, so as not to take all the load if the pole bends sideways? If so, could I just flare the edges of the bracket outward?

[Evan_Gatehouse]

Ok. the picture helped. I was picturing a circular clamp type bracket.

How about an aluminum pole? No offense, but the Macgregor 21 is hardly a sportboat where every lb. matters.

[MNagy]

If I could find a suitable aluminum pole to use, I would, believe me. I just have a hard time believing that some random aluminum tube that I find would be strong enough. Maybe if I cannibalized an old boom....

Or do you know of somewhere I could get something that would work for my purposes?

Are there any opinions out there about using the carbon fiber kits? Would I need to double-up material, or will one layer be enough?

[Cracker Larry]

Larry, it's odd that you've never seen a spinnaker flown from a bowsprit...it seems like every performance boat nowadays has a retractable bowsprit from which to fly an asymmetric or "cruising" spinnaker. For example, check out these photos of the J/80.

Sorry, I guess it is a matter of terminology. I would not call that sail a spinnaker, I would call it a drifter. I haven't been on the big boat sailing scene lately. New marketing terms are out I suppose.

How about using an adjustable spinnaker pole? I've flown drifters like that. You could mount a pole eye fitting on the bow deck to clip the pole on, secure it at the head stay fitting, then run it out until the bobstay (is that what you call that?) is taught.

[PJPiercey]

MNagy,

Check out onlinemetals.com.

I would recomend looking at this product:

http://www.onlinemetals.com/merchant.cf ... its=inches

I used this material for the center sections of the three piece masts on the CK17 I built.



I used this material for the lower sections:

http://www.onlinemetals.com/merchant.cf ... its=inches

This three inch tube was a bit of overkill. I could have gone with 2.5" diameter with a .125 wall thickness.

Aluminum is very easy to work with, you can use your wood working tools to cut and smooth it.

Paul

[MNagy]

Larry,

I should have picked up on your use of "drifter". I know what it means, but I guess I didn't read your post carefully enough to remind myself. For some reason I always think a drifter is like a really big and light symmetric spinnaker.

Anyway, your idea about the adjustable pole sounds super easy to implement. But how would I secure it to the forestay? Maybe I could use my bracket method for this.

Paul,

Thanks, that is just what I'm looking for. If only they anodized the aluminum as well...

[PJPiercey]

If only they anodized the aluminum as well...

I painted the aluminum with the S3 primer and paint. Looks great! and I think it is tougher than anodized masts that I have had.



Paul