New Jib Design Idea

Hello! I came up with this idea to minimize the air influence from single mast on the main sail.

the idea mainly came from reading this paper. I came up with an idea of an A-type that is basically the best of most worlds, in which its still as convenient as the standart and as performative as a foil-sail. Given that i recently found a guy who can work with carbon fibre at a high level, the goal is to make it in the same weight category as a standart single big mast.

What do you guys think, will it work?

 

This has been done many times. The usual layout is a triangle with a pointed, not rounded top. Yes it works well enough. The luff of the main can misbehave because is has no support from a conventional mast. The downside of this kind of rig is that it involves extra weight aloft as well as twice the aero drag caused by the twin masts.

With a pointed tip triangle the masts can more easily be unstepped.

Others will surely weigh in here. One of the variations of this idea was worked on by the constantly innovating Phil Bolger. In his case he used only one sail that amounted to one giant jib. He was not particularly impressed with the practical outcome.

 

The idea won't work because it's based on false claims that masts create unfavourable drag. A search on this forum will show that is an old idea that has been killed off by modern CFD and science.

The mast is actually a major creator of drive. Many of the old claims that masts created harmful drag seem to have come from the tests of Marchaj, but he used disproportionately massively over-sized masts that are far larger than those seen in any actual sailing craft.

Do a search here for "mast" and look at the posts of tspeer (the late Tom Speer, a wing section designer for Boeing and America's Cup wingsails) and Mikko Brummer, a sailmaker who does CFD work. They point out that masts do NOT cause the harmful drag that has been alleged.

Theory apart, anyone with a decent knowledge of practical sailing craft performance will note that the devices that claim to reduce the mast's (alleged) major drag just don't work as well as old-style theory claims. They have been tried for well over a century, and repeatedly failed. And if the mast was such a major cause of drag, why did people move away from old-style masthead rigs with massive genoas?

On top of that, consider what happens to the luff of the mainsail in your rig. As the sail pressure increases, the luff will sag inward and the sail will become fuller and fuller as the wind increases (as a jib does) instead of flatter (as can happen with a good conventional mainsail on a fractional rig). The load will also cause major compression loads, all of which (I understand) are taken by the leeward of your masts. Designers I knew who worked out the loads found that these bipod rigs had to be much heavier than a conventional mast to stay in column and avoid breaking under compression.

 

I think the thread has a slightly misleading title in that the innovation relates to the mast and not really the jib.A frame or bipod masts crop up from time to time and just like windmill rigs,they cause more losses than gains in performance.The extra weight and windage outweigh any theoretical gains and were it not so there would be lots of them in regular use.There is a paper at https://apps.dtic.mil/sti/tr/pdf/ADA395503.pdf with a great deal of interesting and verified data relating to drag.

 

Fabio Fossati, Pressure Measurements of Yacht Sails

Chesapeake Sailing Yacht Symposium, march 2016

The mast is innocent and not problematic as we see here in passing because it was not the objective of these measurements

and ... compare Jib leading edge with MainSail (mast) leading edge

 

Wings, Sails and Parachutes

With an angle of attack of around 30 degrees (25 - 35 AWA) a sailboat builds 1 wing with 2 elements, it is something like a 1914 plane landing with a high angle of attack

Close reaching sails are sails

Running Downwind sails are parachutes as we see for example in a spinnaker

 

The intriguing question is if we can build 1 wing with 3 elements: Jib, StaySail, MainSail

My impression is yes with maybe 35 degrees or 40 degrees angle of attack, but it is not a crucial question because it is a reaching configuration, but it would be nice if it worked well upwind in the 7-10 knots wind zone and 10-12

 

America 'schooner'

1 Wing built with 3 elements

 

My lightweight Plywood Epoxy WindSurfBoard for an old fogey could work Upwind as 1 wing built with 3 elements ?

I don't know, in fact I'll keep quiet and not even mention it when i order the sails because why argue with the inertia of preconceived ideas

 

I have plans for a Robert Tucker plywood boat from the late 60s with a bi-pod mast and 2 roller reefing systems. Nothing new here.

 

Please stop hijacking threads with your childish rectangle that is supposed to be the fastest boat in the world.

 

This is pretty much the refrain that all of us who've experimented with radical rigs join in with. The theory we had in the 70s and 80s predicted there were big gains to be made from radical rigs, and I was just one of many who experimented one way or another. Heck, I still have a Bethwaite wing mast hanging from my garage ceiling. But they always disappointed. Occasionally there might be a flash of performance that looked to have potential, but I never managed to capture it. It wasn't until Messrs Speer and Brummer brought CFD analysis into the mix that the theory started to match what we were reluctantly experiencing on the water. The reason I am now pretty conventional in my thinking about rigs (but not completely, I built a fairly radical pole mast not that long ago) is not that I'm an unimaginative plodding conservative (at least I don't think so). Its because I've been there, done that, tried it in full scale, spent the money and it didn't ********g work!

 

So much slower than a sloop that the Americans didn't race the two together, and the Europeans gave the schooner a rating reduction of about 20% compared to a sloop.

 

Incorrect. There is no such inertia. Many of us are very experienced and very aware of the use of staysails at various angles so there is NO "inertia of preconceived ideas" ideas here.

What we have, which you appear to lack, is actual experience, knowledge and research. The cutter rig and the related double headsail rig etc are old ones and if you stopped insulting people and making false claims you would be able to learn what we know about about how they work.

 

Could work Upwind as 1 wing built with 3 elements ?

Sabes que sí