Roller furling main

[andrewp100]

Hi all'
New to this forum.

I am fitting an experimental behind the mast furler, on an old masthead 30 footer and have been looking at a lot of alternatives and comments.

I have seen a lot of talk about the different approaches to the batten problem for furling mains (in mast or behind mast) and the solution seems to fall into 2 categories.

Go without battens and lose the roach / hollow the leach

or

Have vertical battens which give back some roach but don't hold the leach back in quite the same way as normal battens.

If the concern is about losing sail area (I know there are some other points to consider as well) why do I never see the suggestion to have a longer boom? This would give the roughly same sail area in the head of the sail even with a straight leech.
If we are trying to get as much sail area as possible, and it has to fit in the triangle between the mast, boom and backstay, what is the sense in designing the system with a short boom as though it were a racing boat with a restricted 'E' measurement.
I'd be interested to hear any comments particularly from those who might have tried this.

Regards
Andrew

[psk125]

Lengthening the boom is going to change the center of effort of the sail and mess up the balance of the boat in regards to its center of lateral resistance. You might then need to move the mast aft to keep the boat balanced, which would mean shortening the boom. Naval architects spend a lot of time working to keep the relationships of these forces where they want them so that the boat performs properly.
We raced to Bermuda once with an in-mast r/f main. Over then entire 635 miles, we ended up being pleased with the set of the sail for about 20 minutes. R/f booms might be preferable. They allow you to have battens and also to reach snags and smooth lumps when you need to without having to climb up to the spreaders first.

[andrewp100]

Thanks for the quick reply psk125. I was thinking that since cutting off the roach moves the center of effort forward, adding a bit back by lengthening the boom might help restore the balance.

[Rucksta]

Originally Posted by andrewp100

I was thinking that since cutting off the roach moves the center of effort forward, adding a bit back by lengthening the boom might help restore the balance.

Is an external furler (adapted headsail furler?) going to move the luff aft about 6-8"?
That would move the centre of effort -aft.
Any effect similar to headstay falloff would move the draft aft also effecting the CoE.

Is it possible to easily extend the boom even temporarily?

You could install the furler, try the main as is - no battens - and get a feel for the change in balance. Roll it in and out find the sweet spots.

Then make your decision to adjust the roach, install sunstrip &batten pockets at the foot length you chose.

Reengineer the boom for permanent fix; this may be as simple as removing the temp fix.

Have you considered luff foam?

[andrewp100]

It should move it back about 4 inches the way I have it set up. I also have a main that came with the boat that has no battens and just a pretty straight leech. Not sure why the PO had that made but it doesn't have much shape so I thought I would try that first. I really probably don't need the extra sail area because I don't race it.
I originally noticed that myself and most other people sailing single handed or just going for a mid week sail seemed to mostly only use the headsail so I figured I should try to make something as easy as a headsail furler.
Yes I will probably try foam in the luff once I have it working.
The furler I got for the foil was only $50 so if the whole thing doesn't work too well I'll probably just go back to slab reefing.
As you suggest, I'll probably just try a few temporary things and see what works.
At this stage I haven't destroyed or thrown out any of the original bits so it can always be put back how it was.

[Dockhead]

Some data points for you:


1. I have used behind the mast roller furling and on that particular boat it was awful both mechanically and aerodynamically.


2. I have used in-mast furling on several boats and all were mechanically excellent.


3. Hollow leech battenless furling main is pretty hard to get a good shape in, and give up large amounts of power.



4. Straight leech with vertical battens is vastly better, and actually quite satisfactory, not dramatically worse than a normal full batten main. Noticeably less power than a roachy performance full batten main, but not compared to a moderate roach cruising sail.



YMMV.