CNC Plans not Included

Well it's beautiful but I like all boats so I'll just trust you guys )) I'm not sure I want the classic look, I think I am headed more into the future theme with all electric. As for resale, I think that is largely influenced by warranties, support etc ... and low maintenance which is why I am looking to electric, micanti anti-foul, no holes below waterline, kickup rudders and board, unstayed mast. That is what I would want This boat shouldn't need to be hauled for 5 years maybe 10 barring any accidents.

Added safety rail and rod holders.

 

There is no way your proposed electric setup will increase resale value. It will have the opposite effect.

 

That is an unprofitable comment in so many ways lol

 

I am positive that an Unstayed rig fits this boat but what innovations can be leveraged to boost upwind performance. A Biplane rig adds shade and expense but seems to get the job done. RD suggest a taller rig but Groper says that adds weight and Brian confirms that with his write up on the Dynarig ( DynaRig MotorSailer http://www.runningtideyachts.com/dynarig) saying that on the maltese falcon - The Royals - top segment of sails account for 40% of the loads.

a simple unstayed rig


a biplane


But what if the unstayed mast was engineered to -for example- 70 feet and then you added another 10+ feet where that top segment was configured to be self furling sail.

The idea being that while in heavy winds a lighter unstayed mast might be too bendy and just stay de-powered. With the top segment furlable, the mast would encounter it's normal engineered load. Conversely, in light winds, adding the top let's say 15 sq. meters of sail would boost performance without overly bending the mast. 15 sq meters doesn't sound like much but when you consider the example of the Maltese Falcon (40% of the load) I think it's plenty.

It's not for setting speed records, just for being speedier in light conditions without having a tremendously huge mast.

EDIT ... Actually I didn't think that through very well. All I need to do is build the extra length of mast and make the extra length the first sail reef.

 

Okay double backtake ... what if this could be a fairly fast boat, it might be a mistake to penalize the design. It's light, the hulls are lean 1:14, I just need more rig so I was thinking a hybrid rig with as few stays as possible while keeping the safety benefits of an unstayed rig.

And I would keep the Dynarig because it's way up there for those low wind days and because that extended part of the mast can be used to offset the back stays so they completely clear the boom and work nicely to bend the mast to tension the forestay. And I would go easy on tension and use shock cords because you have the bury so you aren't going to demast.

To compensate for the compression loads the mast would have a bearing which sits on top of the socket. It wouldn't require any extra beefing up in my design, all the structure is there be it for lateral or compression forces. I get to fly a lot more sail and improve overall performance while keeping safety aspects of an unstayed mast, reducing maintenance to some extent, reducing weight compared to a fully unstayed mast and I am sure there are more pros and cons but I see mostly pros.

 

Jorge - your design is getting very complicated - lots of systems that require heaps of debugging as you build-its the type of stuff that sinks projects due to huge budget blowouts and time delays as your building. KISS unless you have huge money and time to burn working it all out...

classic lines version with bimini roof held up by stainless pipe work and roll down clears - looks like a perfect charter boat to me

 

And i found some pics of the boat online - its called "prime mover" designed by scott jutson.

 

Interesting interior... Will see if I can find more pics on it. The Maine Cat is very similar in sheer with the same idea for Bimini. By the way have you considered a soft bimini for yours.. I don't think it would be hard to rig and I think it suits your racing design better.


I'm really liking my cat a lot, I guess different strokes for different folks but I'm not stuck on any idea, just exploring the possibilities. Maybe a curved mast top section and forget the dynarig... Anyway I will run it by the engineers and see what they say.

 

What the engineers will say is "How deep are your pockets?"

 

Yeah I just wanted to see if Groper was still checking in on me )) ... No but seriously I think the solution is simpler. If the top 1/4 of the sail accounts for 40% of the loads then that should be the only part that is extra bendy. The forestay should hit the mast (fractional rig) below the bendy spot. I think this is more along the lines of a possible solution.

I am doing a drawing now with soft bimini. I saw an example of flex solar panels attached to canvas and it was nice. That would shed about 700KG from my design... maybe I could come in at 8 tons!

 

Soft Top
Well it would be lighter and cheaper and cheaper looking too. Could be an option

 

A taller unstayed mast adds weight, but much less than a taller stayed rig. The unstayed rig is set up to resist the righting moment. It is big at the deck and small at the head. A stayed rig is the same all the way up to the hounds, and the taller it is, the heavier it has to be to take the increased shroud loads.
The unstayed rig is stiffness dependant, the stayed one compression dependant. Stiffness of the added section is not required if it will be reefed in comparatively low winds. The compression loads will always be present.
Adding 10% to a stayed mast will increase the weight by considerably more than 10% as the section and/or the walls will be larger all the way up. The top 10% of an unstayed rig weighs about 2% of the total 30% of the diameter and 7% of the material.
There is more wind up high, a lot more in less than 6 knots.
"The royals account for 40% of the loads" is meaningless as they are removed long before the masts reach their limits. Cutting off the mast so they were not flown would destroy light air performance and reduce mast weight by less than 5%.

A back stay will make very little difference, the main sheet controls the aft bend. A set of diamonds pr temporary light air shrouds are 2 ways to increase the stiffness without losing the benefits of the unstayed mast. Another is to reduce the taper ratio (not so small at the top), either as a wing mast or rotating the mast so the sail is on the leeward side, giving a similar cross section to a leading edge inflatable kite. We have just designed a mast section which is an interesting combination of these, yet does not require rotation. It provides a parabolic leading edge at 30 degrees to the apparent wind for a good foil without the area of a wing.

Adding headsails for light air puts sail area where it does the least good, at the most cost, hassle and inconvenience.

 

Rob, I'm really surprised at that, from racing cats with and without a small jib in light airs, the boat with the jib will win hands down every time. I used to be a Uni sail convert but now having sailed both on the same platform, then I have to say actual experiance over computer design is telling me that a small blade jib in light air is a good design in real world conditions.

Jorge have you considered the rig that is free standing but has a boom fore and aft for the main and jib ( sorry forgotten what its called ) that a few multi's had back in the 90's, it has a lot of benefits of Robs designs but a few extra benefits of places to easily store and reef sails into when at harbour or in a blow and being able to totally de-power the sails at will. The problems at the time these style of masts were being built was the expense of build, with recent knowledge of infusion build systems, then that cost factor may need to be re looked at.

The other thing you will have to consider is that your design is no light weight racer, getting up to speed is going to be a slow process, for that the jib is really what you need, just look at most mono's and look how they favour large over lapping jibs just for that very purpose.

 

Thanks RD, I will contact you guys to talk more about this when I am ready.

Wayne, that would be the Balestron rig or some call it the Aero rig after the brand. We discussed that a bit on here and sort of ruled it out as being the heaviest solution and it kind of dwarfed the boat. I read only good things about that rig however.

 

If they were that good- or if anything is that good- ask yourself why it is not the standard by which all others are measured. By default- the free market sorts the chaff from the weeds...