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Block on boom placement

wjejr

Active Member
Hello fellow Sunfishers. My 1971 Sunfish redo is nearly complete, and this past weekend I rigged the boat and put up the sail. I noticed that the block on the boom is quite a bit aft from the main sheet hook in the cockpit. Is there a reason for this? Every boat I have ever sailed without a head-knocker has the had the block on the boom directly overhead of the main-sheet ratchet. As it is, it seems to cut down the available cockpit space. Should I move it forward?

Thanks for your help.
 

wjejr

Active Member
No, I have two blocks. The aft one is more or less over the bridle. The front one is the one I am wondering about. It seems to me that it should be farther forward and over the front of the cockpit area.
 

beldar boathead

Well-Known Member
You can move it although very few people do. It always is a bit out of alignment. Moving the gooseneck to 17 or so will help, but if you are rigged with the sail up fairly high for headroom you will need the gooseneck at 20 or so. BB
 

signal charlie

Well-Known Member
Staff member
First, what Beldar said.

Moving gooseneck to around 22 inches and tying halyard around 60 inches from outhaul sets up a nice recreational rig, that might move block forward a bit.

How far back is the mast step from the bow, maybe it is in the wrong place?......Just kidding :)

Other reason may be that someone busted the boom, bought a top spar (cheaper) and converted it to a boom but missed the mark a bit on block placement.

Good luck!

k
 

Amory Klein

New Member
Does anyone have an actual answer to the question of "block on boom placement"? I'm assembling a brand new pair of undrilled spars and a new sail, and today I bought a new non-swiveling block for the front and a swiveling block for the rear. I'm ready to drill the holes in the lower spar and finish the job but I need to know exactly where the blocks belong.

I'll keep searching and I'll probably find the answer elsewhere, but for a moment I thought I might have lucked out and found what I wanted right here in one of the most recent threads.
 

signal charlie

Well-Known Member
Staff member
Does anyone have an actual answer to the question of "block on boom placement"? I'm assembling a brand new pair of undrilled spars and a new sail, and today I bought a new non-swiveling block for the front and a swiveling block for the rear. I'm ready to drill the holes in the lower spar and finish the job but I need to know exactly where the blocks belong.

I'll keep searching and I'll probably find the answer elsewhere, but for a moment I thought I might have lucked out and found what I wanted right here in one of the most recent threads.
If you are just rec sailing, here's an idea. Put the gooseneck on the boom, around 21 inches back or wherever you normally set it. Put the boom on the boat with the mast like you are rigging it. Put the forward block over the hook/cleat and the aft block over the eyestraps.

Tomorrow I'll try to measure one of our spars.

Tip: put an outhaul cap on the forward end of the boom, tab turned downwards. That will keep interlocking bolt from gouging deck.

Good luck
Kent
 

sailthefish

New Member
I had 2 sets of spars handy to measure.

1st goes to a pre AMF, fiberglass Sailfish.
From interlocking eyebolt to center of block eyestrap is 74.5", and 60" between centers to the block eyestrap on the tail end.

2nd set goes to a 74 Sunfish.
67.5 to the first block, and 58.5 between centers to the 2nd.

Don't know if the Sailfish spars are the the same as a similar vintage Sunfish.
 

kmac17

New Member
Measure from the forward end of the spar, not the end cap. Forward block at 62", aft block at 126".

126" for the aft block is a pretty position. With a loose outhaul a sail grommet will be right over the eye strap rivet. White electrical tape one that is prudent.

62" for the forward block is a little closer to the tack than standard. With the gooseneck at about 17" from the tack this aligned the forward block with the forward edge of the cockpit, where your hook or ratchet block are.

Spars have not changed much. Older ones may have cork in them, my 76 does, for floatations that may or may not be effective. Sealing end caps is a better method to get some flotation in the rig.
 

Amory Klein

New Member
Thanks for the responses so far, guys!

I already have the sail mounted on the spars so all I have left to do is install the boom blocks. At this point I'm thinking that maybe I should rig the boat and find the point where the forward boom block lines up with the ratchet block, with the gooseneck in an intermediate position. I also gather that I should make sure the blocks won't interfere with the sail grommets at any outhaul adjustment.

I'm curious about the rear block position. In post #3, "wjejr" said that his rear block is "more or less over the bridle." Does that sound right? It seems to me that it belongs a bit forward of that position. What would the effect be of moving the rear block to different positions along the boom?

I expect to finish the job this coming Wednesday (June 11, 2014) so there's plenty of time for any more suggestions you guys might have before I do this.
 

kmac17

New Member
Because the gooseneck can be adjusted. And because adjusting it is desirable to effect the balance of the boat for different conditions and crew weight. There is no "exact point" where the blocks are directly over the bridle or the rachet block or hook (depending on what you have installed). You basically want to mount the blocks where they won't interfere with sail ties as the outhaul is adjusted. There is no standard rule on placement. And there are a some good sailors who have shared the numbers they use if you want to go looking. I posted previously numbers from a multi-world champion and so far have found them to work well on my recently re-rigged 1976 boat.

Cheers, Kevin
 

Amory Klein

New Member
Kevin, I'm not sure what you're saying here:

126" for the aft block is a pretty position. With a loose outhaul a sail grommet will be right over the eye strap rivet. White electrical tape one that is prudent.
What does "pretty" mean in this context? Is it good or bad? What does "White electrical tape one that is prudent" mean?
 

kmac17

New Member
Sorry, iPhone typing while being too tired didn't work out so well.

Aft block. 126" up is a pretty GOOD position. This is as far aft as you can go on the boom without interfering with the sail tie when the outhaul is at maximum easy. Since there is 4+ inches of range in the outhaul, to go on the other side of the sail tie you would need to go out to 131" or so. And that would put you beyond the bridle more often than not so best to stay forward of it.

The white electrical tape would be prudent around the aft pop rivet on your eye strap for the aft block. The tape will keep the sail tie from chafing on the rivet head. White tape is recommended instead of black because black electrical tape heats up in the sun and the adhesive gets gooey and messy.

You can use the same white tape at your halyard location on the gaff spar to keep the clove hitch from sliding. 106" from the forward end of the gaff spar is the maximum position for the halyard. Any higher on the gaff spar and the rig will basically be on the deck and smacking your forehead. Every inch you move the halyard down the gaff spar is another inch between the tack of the sail and the deck. If your sail doesn't have a window, then you'll probably be happy at 96" as your starting point for the halyard.

Moving the gooseneck pivots the sail giving more headroom the farther forward it is. This also effects the balance of the boat for the conditions you are sailing in.

Cheers, Kevin.
 

sailorlem

Member
I have had many sunfish over the years and all of them I feel had the forward boom block too far rearward by at least 12 inches.
Causes the sheet difficult to pull when sheeted in close. Will be moving the current one soon. Don't race so no rules infraction.
 

wjejr

Active Member
Hi everyone,

Well I finally got around to measuring the distance. The distance from the front of the boom, not end-cap is about 74 3/4". So that seems quite a bit further back than the 62" - 67 1/2" mentioned in the comments above. The measurement I got more closely corresponds to what "sailthefish" measured for the Sailfish.

I am tempted to move the block forward, but I think I will go sailing first and see how it goes. Thanks for all of the comments!
 
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