Crushed Lower Boom

M

MichFish

Member
After a two year search, finally found a nice used fish for my wife. It's put a smile on my face watching her take pride in cleaning her new toy. She has this grin when she reminds me that she is at the "ideal weight" for a sunfish ....... the race is on.

We found a problem. A prior owner over tightened the goose neck, denting the lower boom. I didn't take the time to inspect this area prior to purchase. The spars are nice and straight, but I'm concerned about the damage.

I'm going to move the goose neck slightly from the damaged area. I'm trying to decide the best direction for the move. Part of me feels that more force is applied to the rear of the lower boom, hence moving th goose neck slightly to stern, but I'm not sure. Any suggestions? We really don't want to purchase a replacement boom at this time.
 
MichFish said:
I'm going to move the goose neck slightly from the damaged area. I'm trying to decide the best direction for the move. Part of me feels that more force is applied to the rear of the lower boom, hence moving th goose neck slightly to stern, but I'm not sure. Any suggestions? We really don't want to purchase a replacement boom at this time.
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http://www.sunfishclass.org/frequent/sunfish__tuning_guide_for_racers.htm
Many or most competitive Sunfish sailors position (and adjust) their gooseneck depending on conditions.

Here is a link to a guide, on the class website (scan down to section VIII)
http://www.sunfishclass.org/frequent/sunfish__tuning_guide_for_racers.htm

Other sailors have their own nuanced preferences on these things -- their own scale that works for them -- however you can get the general idea from Scott Kyle's chart below, from that linked article:

VIII. GOOSENECK POSITION (INSET)
Wind strength Gooseneck Setting
Under 5 knots 17-18
5-8 knots 18-19
8-12 knots 19-20
12-15 knots 20-21
15-20 knots 21-22
20-25 knots 22-23
Over 25 knots
Jens Rig, 20-21
 
Our dent/damage is 21 inches from the tack, so I can go either way. What I'm trying to decide is what direction from the goose neck experiences the most stress. Aft of the goose neck has the load of the long end of the lower boom along with the sheet loads. Fore of the goose neck has the upper boom loads, but the upper boom appears to transfer a good portion of its load to the upper end of the mast.

The boat will only be used is reasonable wind conditions. I'm just attempting to extend the life of the lower boom, reducing the stress on the damaged area if possible.
 
MichFish said:
Our dent/damage is 21 inches from the tack, so I can go either way. What I'm trying to decide is what direction from the goose neck experiences the most stress. Aft of the goose neck has the load of the long end of the lower boom along with the sheet loads. Fore of the goose neck has the upper boom loads, but the upper boom appears to transfer a good portion of its load to the upper end of the mast.

The boat will only be used is reasonable wind conditions. I'm just attempting to extend the life of the lower boom, reducing the stress on the damaged area if possible.
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I've never seen a spar bend from stress in front of the gooseneck, so based on what you are saying you might move the gooseneck back just a bit. Depending on how ambitious you are and how bad the dent is, you might insert a reinforcing section of tubing or dowel - a couple of feet into that end of the spar. In an extreme case - again if you are ambitious - you could reverse the caps and the direction of the lower boom altogether, so the weak dent area is out on the end (towards the clew). That would require repositioning the two mainsheet blocks (you might through-bolt them). That would probably dramatically increase the useful life, though I have never tried that.

Jumping a bit, I've done that with masts - much simpler - that I was afraid might be weak (when masts break, it's usually at the deck) -- reversing the end caps so the suspect area is near the top rather than at deck level -- greatly extending the mast life of older masts (those from the pre-internal-reinforcement days). Maybe something like that would work on spars - reversing their direction.
 
There is not a lot of force at the front of the lower spar so moving the gooseneck either way should be fine. Moving it back would provide max protection for the boom. Swapping the boom end for end is a great fix. That would be best long term solution and will allow gooseneck adjustment to suit the conditions. BB
 
minifish2 already mentioned it - but I think the easiest solution would be to take the forward end cap off the lower boom, and insert a wooden dowel, or piece of pipe, with an outer diameter equal to the spar inside diameter (or close to it), as a reinforcing piece to keep the spar from deforming any more. maybe grease up a wooden dowel with some epoxy, and slide it in place, and then replace the end cap.

cheers,
tag
 
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