loose footed mainsail is it safe?or to much stress at one point?

Re: Good point?

'Nearly all in-mast furlers have, IMHO, totally inadequate sections for their booms, but that can be countered by the observation that the load centre moves closer to the boom as you reef.'

Any sensible person would have taken a couple of turns of the sail a long time before these strains got too great ,one of the advantages of in-mast reefing.
 
I tried modifying a bolt-rope-foot mainsail

for use with full-length horizontal battens, and it was unsuccessful.

You need a far flatter-cut main for full-length battens - as to whether you can modify an existing bolt-rope main for just turning into a loose-foot main, you do need to replace the bolt-rope with something that will tension.

As to vertical battens, they allow a slightly larger roach, instead of the hollow-cut leech that an in-mast furler demands, but do nothing for aerofoil shape - which is the main reason for full-battening a mainsail.

Whilst a purist might decry a mast-furling main, they do save an awful lot of effort, for some sacrifice in performance.
 
Re: I tried modifying a bolt-rope-foot mainsail

A boom intended for roller reefing should be thicker at the outer end, to wind up more sail and prevent the boom drooping.
A boom intended for a loose-footed sail should have a wider middle section.
An ordinary boom can be of uniform section.
A disadvantage of a boomless sail is the sheet block flailing around. At least a boom is reasonably predictable and visible. A heavy block on a large sail suddenly gybing can go anywhere, and crew have been killed this way on large vessels in the past.
 
Re: I tried modifying a bolt-rope-foot mainsail

charles_reed
regul
Good point? [Re: trouville]

which has to be answered by a question: "Where is the main sheet attachment to the boom".
In fact it's the bending, not the compression, force which causes the problem.**********************************************************



Firstly thankyou william.H ive never used a loose footed main for me the reply is very helpful particularly since im now tempted to put a platimo (when i get it)roller reafing not on the forstay but up the mast with my main to try!!

Back to Charles question!

To me it was a compression load!
WHY:The boat was an old wreck the mast and boom were what you find on converted fishing boats to put things on and perhaps a stay sail!

We took galvanised rope for the stays (the old stuff had long ago rusted away)new bottle screws(galva) added chain plates on the outerside of the hull amd so on.(He wanted the mast as well as a stay sail being a good idea along there)

The sail was from an old raceing boat (a swan we were told!!)The boom was about 3 feet out from the clew.i loose lashed the clew to the boom and used line as out haul from clew makeing a 6:1 purchase which allowed us to tention the foot.

The old broze claw is just that a frame that slides onto the boom to attach the main sheet this we possioned under the clew end(not popular these days even on traditional boat as it can take your head off more effectivly than the boom when forgoten on a downwind run)

What i saw was the main pulling the clew and tack together.(the bow of the foot under load)
JUST AS
When i hoist the main i take a turn arount the cleat and pull OUT on the halyard its a huge force more effective than a slipery small winch!!and so seemed the main to tenion under sail.

(When i cut off the ripped part i doubled and glued then doubeled and glued the foot a one inch heam then sewed with zig zag it was quite a strong foot!!)

I think it was the center pull of the main that caused the compression? and a weakness/fault that caused it to bend??Wasent it???Or why would a compression load provoke a bend????????????????????????????????????????????????????????
And would the boom have broken by the clew if there had been a bolt rop and grove to stop the outward bow?? Or are the forces the same but in line??(little face with ??? above head if there was one to click on) /forums/images/graemlins/confused.gif
 
Re: I tried modifying a bolt-rope-foot mainsail

for what it's worth, i replaced my new main for a loose footed one, previous boat, and broke my boom a few months later - coincidence ???

the new boom has two attachment points to spread the load as the main sheet is not opposite the clew

if you main sheet is fixed oposite the clew i can't see a problem
 
Both the boats shown below have no main boom. They are each in their own way good examples of loose-footed mainsails.


barge1.jpg


RichardsBoat.jpg



The successful racing trimaran has an efficient full-battened mainsail - it could be argued that the battens perform the function of a boom - and the powerful mainsheet tackle has quite heavy upper multiple-sheave blocks, which have to be shifted when reefing. That's a difficult evolution, fraught with potential for accident in a lumpy sea, but there are solutions.

Sheave blocks that may cause expensive damage to boat or crew have traditionally been sheathed in 'split chrome leather' to lessen the blow. Have a glance aloft at any of the 'Fifes' along the quay at St Tropez or Antibes, or 'Valsheda', when next you're passing, and you'll see!

Given that there have been over a score of serious 'bent head' accidents on UK sailboats in recent years, perhaps we should be thinking of ways to soften such blows. The leather sheathing mentioned is quite expensive, but there is a cheap and effective alternative.....

Take a punctured PVC fender, and cut it open. The inside surface will be clean. Use this material in place of expensive leather, appropriately shaped, doubled, and sewn into place, to 'pad out' those hazardous blocks.



/forums/images/graemlins/wink.gif
 
Re: Good point?

[ QUOTE ]
My impression is that, fortunately, the owners of boats fitted with in-mast furling tend to avoid heavy weather.

[/ QUOTE ] I find it difficult to imagine what experience led you to say that. Many such vessels have circled the world; hardly 'avoiding heavy weather'.

It's so much easier to reef, in fact, that when short handed I make passages with far worse weather threats than I would with slab reefing, though I haven't tried fully battened sails.
 
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