Biplane AeroRig Cat?

I'm not quite sure how I stumbled on this, the Hoyt offset rig:
Yeah, I'm checking out all my options .....

 

I'd be concerned about the increased sail area making the cat more likely to capsize. There needs to be a very wide beam and relatively heavy hulls for this to work.

 

They got to be light hulls for my application so I can portage this boat by bicycle 40 miles or more. I do plan on stretching the beam to 10' . The sails will be low aspect ratio vs what is normally used on other racing cats. It's my plan anyway. I'll be sailing this boat when I'm extremely tired during the Ultimate Florida Challenge, day or night and both usually. While Randy Smyth went for all out speed with his "Sizzors" I want to stay more on the safe side. I told him before he started that you got to finish to win!

 

Attached is a finite element animation of the unstayed wing masts for the 12m/40' biplane catamarans under sideways bending load.

It shows maximum stresses of <200 MPa in the carbon with enough heeling moment to tip half the boat (ie. tip the whole boat with both rigs working). Even hand laid-up carbon is good for 800+ MPa, so plenty of safety margin there.

It also shows the mast deflecting a little under 1800mm at the tip under this extreme load. This is about right for a freestanding mast this size.

An unstayed mast that is stiff enough will be way over strength.

rob

 

Rob,
that was an interesting little .avi file ...... and peaks my curiosity. I hadn't considered building my own mast before ..... am I getting in over my head with such a notion? I was going to try adapting windsurfing gear for this, or maybe a hobie TI rig, but now that I also have the proa concept growing as well, then maybe I should look into mast fabrication as well? and then there's custom sail sizes and ...... ....... and I'm just glad I got my kayak in expedition order and at the ready!

 

Building a mast is pretty simple, if you can use a jigsaw, string line and vacuum pump. It will not be quite as light as an autoclaved mast, but will be a lot lighter and stiffer than an alloy one. And cheaper than both.

I sell plans for $500. They contain everything you need to know, including materials supplies but excluding engineering. If you have a good idea of the loads and it is only a small mast, we can get round that. Happy to take the 500 bucks off the price of the proa plans, and include it in the race refund.

Won't be as cheap as a windsurfer mast, but this will need a lot of beefing up for a cat with you sitting 8' away.

If you want to progress further, let me know the weight and width of the boat, your weight and the height of the mast and I will see what it will weigh and cost for materials. Weights of similar masts are also handy.

 

Good baseline info here on DIY carbon masts.

http://www.aes.net.nz/comment19.html

Cheers,
RR

 

RR, thanks for that link!

Rob,
yeah, the engineering part, CE,CLR, rig, sails and boards, weight, all stuff I don't yet have figured out. I need to find a rig that I want to use, and the whole reason I started this thread about the aerorig.

I like the windsurfing sails because of it's great shape and wind range, but they don't reef, and I hadn't found a way around that yet.

The hobie TI rig is roller furling but I don't like the shape when it's reefed.

Matt Layden's Engima that he used in the UFC had roller furling in the boom, cool.

I need enough sail area for light winds, twist and spill as it fils in, and reefs for when it's blowin'. Yeah, so what else is new? Same ol' story, except it's freestanding and have to be light enough for me to remove, lay on the deck, stow for portage or the river paddling/pedaling , and to top it off I need two of them. ....... all a tall order in a short package.

 

Windsurfer masts will be too soft for the boat. Even beefed up they will still be too flexible due to their diameter. Pocket luff sails are hard work to reef, but worse than this is that they fill with water when you capsize and make righting the boat much more difficult.

THis is a great way to keep the sail under control. With the unstayed rig, the boom and sail can stay on the boat when the mast is removed, which makes rigging/unrigging a bit quicker and tidier.

2 of them on a 16-18' cat will be hard work to sail as you cannot see the lee sail when you sit to windward and the ww one will be in the way when hiking. I would think about one big unstayed rig and store gear in the other hull to balance the weight. This will still be a pain to get around, but only half the time!

Freestanding makes the twist/spilling automatic and you can get much more height for less weight than with a stayed rig. Reefing is simpler as you can ease the sail all the way out until it is pointing into the wind. Not only easier to pull the sail down, but the boat will be stopped, so your attention is not diverted by where you are heading, or potential capsizing.

Use a gin pole and freestanding is easier to rig/unrig than a stayed mast and a lot easier to stow. Especially at night and/or when you are knackered as there is less to go wrong.

On the proa, the booms could be permanently attached to the stub masts, which speeds up the rigging/unrigging considerably and makes the masts shorter than stayed masts. Point the booms towards the ends to keep the cockpit area clear for paddling. For portage, lay the masts on top of the booms and the ww hull between them.

 

The topic is Bi-Plane aero rig.

The modern airplane is a monoplane.
Time was when airplanes were Bi-planes.
The monoplane proved to be more efficient.
The bi-plane died out.

Simplified, a yacht is just a monoplane with one wing missing and lying on it's side on the water with the other wing sticking up.

Go Figure.

 

it's ok, we can drift some. It's about the pros and cons of the biplane rig. and as rob was saying, on a small cat it could be difficult to move around and see and be out of the way of the sails.

I think I'll have to build up a full scale mock up just to see everything a bit better. My models got me this far and I can see some piloting problems, time to see this in the proper scale.

Watching the ufc presently, and they are still on the move almost all the time, I can see having the easy of handling the boat could be of supreme importance at the later stages of the race when you're beyond worn out. I hope that by sailing vs paddling the 1200 miles (like mosquito magnet) that I can stay fresh by just getting enough sleep so I can finish the race without much of a problem.

In the cat configuration I figure I can sail in the proa style and only use one sail at a time when things get tough for me. I can also motor sail with my pedal prop during these conditions.

For the proa though a single stick would be much easier to control I'm thinking. Less there is, less to go wrong? or is it less options in case the crap hits the fan?

biplane cat, schooner rig proa or single stick? I can see much advantage to both, but I hadn't yet thought out all the details and problems of the proa in the ufc, like reducing beam at small bridges, portage mode and a cart, bike storage, etc....... Maybe I need to start up a ufc proa thread?

 

don't you just hate when you state a fact then something like this happens?

http://www.gizmag.com/boomless-biplane/21871/

and before this, the biplane had it's use, it just wasn't wide spread, but for certain situations like stunt planes two wings are still used. My reason for a biplane is to keep the CE low as possible. Besides, there's other VERY fast boats out there biplane rigged, you're just not gonna find this used in a monohull! but they do use multiple sails right?

 

There's a very big difference between multiple sails and a bi-plane rig.
Regarding the pic of the (proposed) boomless biplane, the last guy who built and flew a small version of that crashed and killed himself.

Of course there are still lots of biplanes flying. Restored Tiger Moths for example. But military bi-plane aircraft went out with the end of WW2.
The Fokker D8 of WW1 was not the first, but that and the Schneider Trophy seaplanes pushed the trend to the more efficient monoplanes.

Rob spells out the disadvantages for multihull use very clearly.

And the old toilet paper saying applies, "Why use two when one will do".
It's the KISS principle.

Take it from me. The use of a bi-plane rig on a Catamaran is a discredited idea.

 

What i got going "Isn't your father's day sailer". This isn't just any cat , it's meant to complete the 1200 mile Ultimate Florida Challenge, and there's certain design elements involved to perform all the tasks required. Rob's idea of only using one sail in one hull is an interesting option, basically it's sailing it like a proa .

And not to mean any disrespect but it's hard to just take your word. If I did that (and also listened to the general population) I'd be forced into a mono hull and what a dreadful life that would be! Besides, I've seen too many other fast boats out there and sure there's compromises with any boat but so far no boat has proved itself the ultimate design for this challenge.

...... but as you may have noticed, rob does have some good points regarding the proa, but I still have many details to work out on that and it might take awhile. I'll be spending lots of time in the proa forums .....

what i'd really like to hear about is someone that's actually built and sailed a biplane rig, I'd be listening quite closely then.