Jib only sail plan?

[stonedpirate]

Hello,

Does anyone know if having a bipod rear freestanding mast with jib only will sail upwind with the correct shaped hull and keel?

I am thinking off bolting on 2 masts at the stern that meet at the top with a stay from the stern.

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Those vertical sections are bolted onto the transom.

So its 2 bent aliminum poles as the mast.

Hope that explains it

Cheers

[alan white]

Come on, stonedpirate, think about it. Something's missing. What is it?
A clue: The missing part is a lot of BS.

[stonedpirate]

Bipod masts have been used since 4th century bc.

Jib only sails are normal for small craft.

2 examples:

[alan white]

They are not at all common. They are A frame rigs, but without a backstay they won't perform in any kind of breeze. What I was hinting at was that the backstay (BS) was missing from your description.
Jib-only sails are not so normal at all. For example, of the thousands of sailboats I've seen in person, I've never seen one.
There are threads here for you to read through with a lot of discussion of the rig. Use the search feature.

[stonedpirate]

Why would i need a backstay on a freestanding mast?

The forestay isnt really a stay, just a line to hang the jib from.

I know they are not common, but neither are 10 foot bluewater crusiers

[stonedpirate]

On such small craft, the hull speed is only 2-3 knots max, so a full blown rig is overkill.

Looking for a rig that is simple and bullet proof.

[tom28571]

Where loads are very small as in small craft. a jib only/aft mast can work ok.

I've seen a few like Gary Hoyt's and another seen at our town dock that intended to sail the Atlantic to reclaim the Greek Marbles. That one had already lost his marbles. Luckily for him he did not make the attempt as the rig appeared marginal in ordinary weather. There is nothing simple about an adequately strong aft rig to support the bognacious tension needed. Its a terrible idea on several fronts. Using different size or reefed jibs plays hobb with the balance. Sheet loads are also very heavy compared to split rigs. How do you rig for sailing downwind?

[stonedpirate]

Its a Ljungstrom rig.

Basically it is like 2 jibs stich together in a diamond shape.

Downwind both triangles are out so its like a double jib diamond. Upwind the sail folds in half to a normal jib.

[alan white]

Your original question was whether the rig you described could go to weather efficiently. No, it won't. The jib's luff has to maintain tension, and when the wind causes it to sag, it loses its shape and the drag increases relative to the lift. The boat then heels excessively while falling off to leeward when close-hauled.
Only some means of preventing the masts from arching forward could keep the luff reasonably straight. The obvious solution would be an aft-facing strut (boomkin) and a backstay. The problem is that you've just lost all of that simplicity that you thought made the rig so cute.
Just because you've found a picture of the rig without a backstay doesn't mean the boat in the picture can sail well.

[stonedpirate]

Ok, a lot of that was over my head

My requirements are 2-3 knots down wind and the ability to go even slightly upwind to avoid losing ground.

I am not aming for peak perfomance, racing potential or speed records.

Just to get a tub from point A to point B without sinking. Close enough is good enough for my tub.

And if this rig provides all that then i'll go with it.

Yes, there are superior rigs with superior perfomance, but i am going for simple and durable with the least breaking parts.

[alan white]

Even simpler, and to my mind, better by far, is a single mast without a jib having no stays (freestanding carbon fiber, e.g.). It's about as simple as can be. You see, because the jib has to be tensioned to be useful, it will be either complicated or slow on the wind. Downwind isn't a worry. The sail shape hardly matters. There are plenty of boats that have no stays whatsoever, and for ultra simlicity, that's where to look.

[messabout]

Bolger had a design that utilized the jib only system that was suspended by an A frame. It was an inspired idea but it came to pass that the idea did not work as well as hoped. You may seek to re-invent the wheel but this one has a flat tire.

On the one hand you say that it is a Ljungstrom rig but then you want simplicity. Can't have it both ways. Downwind you will still need poles for both sides of the unfolded sail. That is not only not simple but also a pain in the ass. If you want a simple, inexpensive, proven rig..then go for a sprit, or lug rig. We already know that those rigs work quite handily.

[tom28571]

Originally Posted by stonedpirate

Its a Ljungstrom rig.

Basically it is like 2 jibs stich together in a diamond shape.

Downwind both triangles are out so its like a double jib diamond. Upwind the sail folds in half to a normal jib.

This is frustrating. The above is nothing like your first question.

An aft bipod mast with jib alone is not a Ljungstrom rig.

[stonedpirate]

An aft bipod mast with jib alone is not a Ljungstrom rig.

Its not technically a jib, its a diamond that can fold into a jib. Dont know what they call it, but thats what jim betts called it when he designed the above boat "SoDoIt!".

Even simpler, and to my mind, better by far, is a single mast without a jib having no stays (freestanding carbon fiber, e.g.). It's about as simple as can be. You see, because the jib has to be tensioned to be useful, it will be either complicated or slow on the wind. Downwind isn't a worry. The sail shape hardly matters. There are plenty of boats that have no stays whatsoever, and for ultra simlicity, that's where to look.

Thanks Alan. Yeah, my original design had a single free standing mast up front. I just iked the idea of the bipod because it can be attached to the transom and free up space on the tiny dck and doesnt have to put a hole in the deck and run a pole through the front of the boat.

I'll figure something out. Decided not to risk the bipod rig because it got some bad reviews from the people that designed the boat in the first place.

Cheers

[alan white]

You can have a deck-stepped mast. It needs to be stayed, but it's very strong and an arching member can carry the load to the sides. Then there's no post or mast down below.