H 376 Mainsail Reefing

[Don12364]

Hi Glenn,
I have an H 376 and am in process of ordering a new mainsail.

The current sail is fully battened but it only has two reefs and is hopelessly flat below the first reef. It has the footrope in the boom groove but on the new one I shall specify it to be loose footed.
When we pull in the first reef at 18kts true it is rather overkill and the boat seems lifeless so I intend to specify three reefs on the new sail and have the first reef a little lower.
At present the luff is 49' 1"(P) and the foot is 15'3" (E) with, of course, the huge roach which distinguishes Hunter from the others.
The first reef is 9' up and the second is 19' up from the boom.
The Z-Spars boom (Z 480 section) has 4 sheaves at each end to cater for three reefs and an outhaul.

My question is:-
On my new sail how much luff do I need to specify to the sailmaker for the third reef?
I would like it to handle 40kts true as the top end because above that I tend to loose interest in the finer points of sailing and just want to get the hell out of it so would probably take the sail down altogether. Nonetheless I need the boat to still handle safely up to that windspeed.
I have done the calculations using C.A. Marchaj's several formulae but would much appreciate the advice of a boat designer.
I appreciate the 376 was probably done by Lars Bergstrom but your input would help to keep me on track - and avoid the waste of much hard earned cash!
Regards,
Don Alexander.

 

[sailingdog]

A better question is how much mainsail area do you want to have up when you're sailing under the third reef and figure out where to put the third reef based on that. Is it your intent to have the third reef replace a dedicated storm trysail? If so, size it appropriately.

I'd also point out that two-line reefing systems are far better at keeping the reefed sail shape flat than single line reefing systems. A good read on why this is the case is on Pineapple Sail's website.

 

[Don12364]

Dog

Yes thank you I know all that.
What I want to know is what are the parameters Hunter use in their designs so I can adapt them if necessary
- which I why I specifically asked Glenn

 

[ghen]

At 40 knots true I would prefer a trysail because it saves the mainsail from a destructive beating. The draft of a normal mainsail would also be too deep and create too much power. My experience in sailing in wind like that has proven to me that the sail suffers too much shape damage for my taste. Unfortunately, reef point position much of the time gets determined or adjusted due to batten position, headboard location and such. You have to consider where spreaders are in proximity to battens. Good sailmakers are in tune with these things. The stability of the boat is a determining factor. A stiffer boat needs less reefing. I try to set up the first reef for 16 knots true. That parameter is mathematical because the actual limit is effected by air temperature (cold air is much denser) how the sail is set and more. I think what I am trying to say it that it is not necesarily an absolute number. Experience with the boat and knowing what you want can fine tune it better than calculations.

 

[Don12364]

Thanks Glenn,
A simpler question:- What is the design wind velocity max for the fully reefed mainsail as supplied with the H376 please? It measures 219 sq ft. I could stick to this for the new sail.
I do not intend to sail in winds of 40knots true. As I said I would take the sail off by then.

 

[ghen]

Donalex,

I did not design that boat and I have not studied the stability data so I just don't know.