Fore vs Aft Headboard Holes:- Overlooked Sail Trim Feature?

[rardiH36]

Just wondering if using the forward vs aft headboard hole for halyard attachment is a not often mentioned main sail trim feature. I don't ever seeing anything about it in my speed reads of various sail trim books, or on this forum. An internet search yields some results in sailing forums, but answers seem somewhat conjectured rather than definitive.

I am asking now because ever since I got my boat, I have had two halyard shackles on the halyard loop at the top of my halyard. One I attach to the fore hole. The other to the aft. (I've done this because I thought it made no real difference and using both holes served to spread the load 50/50.)

Yesterday, for no real reason, I decided to just use the forward hole. First indication of difference is that the sail hoisted easier as the head neared the top. (I hoist the sail by hand generally to the last few inches before tensioning with the cabin top winch.) So maybe more vertical rather than tangent pull up?

The second difference is that when I slackened my topping lift, the boom dropped down several inches lower than before. It was now at my head crown height when standing in the cockpit rather than a few inches above. Maybe it was my imagination, but I thought the sail shape did appear less cupped and flatter along the aft/leach area in the brisk winds yesterday on San Francisco bay.

It seems that tensioning the sail with the headboard's 2" further out aft hole gives much more tension to the leach section of the sail than using the forward hole instead? Intuitively I wouldn't have thought it would make much of a difference.

Any insights?

 

[Don Guillette]

Re: Fore vs Aft Headboard Holes:- Overlooked Sail Trim Featu

I think the holes have to do with way a mast is set up. The forward hole is used if the halyard goes through a sheave on top of the mast and that hole, because of the pulling angle, allows the sail to be hoisted easily with no binding. The aft holes is used for some other setup but I don't know what that setup is.

 

[Jackdaw]

I think the holes have to do with way a mast is set up. The forward hole is used if the halyard goes through a sheave on top of the mast and that hole, because of the pulling angle, allows the sail to be hoisted easily with no binding. The aft holes is used for some other setup but I don't know what that setup is.

Exactly.

If the mainsail sheave is forward in the mast like in this diagram, so the halyard wants to run down the back face of the mast, then the forward hole will give a better run and bind less.

Once the sheave starts moving aft (like on a crane), the aft hole often works better.

 

[Sprega]

Headboard halyard hole

Thanks Jackdaw. That's one of the things I love about sailing. The more you know, the more you realize you don't know. After close to fifty years of sailing, you just pointed out a simple thing to me that I had never thought about.

 

[rardiH36]

So, all recognize the two holes can aid ease of sail hoisting and halyard tensioning depending on the format of the masthead sheave placement.

But what about my sail trim question/observation? Yes, we have the leach cord to play with to minimize leach flutter. In my case, the masthead sheave is close in to the sail slide track. Using the outside hole seems to tension more of the leach section of the sail than only the leach cord. I am thinking that for the last several years, my using the aft most hole has has done to the leach sort of what a shrunken bolt (luff) rope does to the front section of the sail. Negatively distorts the sail shape.

 

[Jackdaw]

But what about my sail trim question/observation? Yes, we have the leach cord to play with to minimize leach flutter. In my case, the masthead sheave is close in to the sail slide track. Using the outside hole seems to tension more of the leach section of the sail than only the leach cord. I am thinking that for the last several years, my using the aft most hole has has done to the leach sort of what a shrunken bolt (luff) rope does to the front section of the sail. Negatively distorts the sail shape.

It might, to a very slight degree.

The effect on sail shape is probably minimal. Putting the halyard in the aft hole might 'cock' the mainsail headboard forward a few degrees, which in turn might try and pull the leach/roach of the sail slightly tighter by raising it 1/2 inch more in relation to the luff. But on a mid-30s boat with a dacron main, I would not expect the effect to be noticed at all. And the tension on the bottom of the headboard tends to even out.

But, as sails age they tend to blow out and 'hook' more. Extra tension directly on the leach might make that worse. So play, experiment, and make observations!

 

[Pat]

Re: Fore vs Aft Headboard Holes:- Overlooked Sail Trim Featu

It seems to make a noticeable difference on our 272 w/the Z-Spar mast....the sail never binds vs. nearly always binding otherwise.

 

[Joe]

Re: Fore vs Aft Headboard Holes:- Overlooked Sail Trim Featu

I think Jackdaw's illustration with the crane would indicated that the back hole would help bend the mast when the mainsheet is tensioned. A little more leverage perhaps.... but hey, why don't we ask a sail loft? Any sailmaker folks out there?

 

[RichH]

Re: Fore vs Aft Headboard Holes:- Overlooked Sail Trim Featu

The difference of 'hole' location of the headboard is to accommodate how much 'overhang' there is on the masthead sheaves. The goal should be: is to have the middle of the hole directly 'below' the aft edge of the sheave - to prevent/minimize binding of the slugs or luff boltrope; and, such becomes more important when using 'batt-cars' instead of slugs, etc.

Mast bending is accomplished by a completely different mechanism - backstay or backstay moment arm, etc.