Crossbow fl

Thanks sharpii2. Both considerations-moving weight aft and being able to pivot the wing for transport are integral to the design-as well as having the skipper slide fore and aft.( see # 8 in post 100)
The wing will be attached to the boat(at least for testing) with a stainless steel seat swivel of the type used to retain powerboat seats. The design parameters of such a swivel exceed the requirements for the mounting of the wing in the investigation I've done. I'll be sure they do by the time it would be used. The seat swivel would be attached to a strong structure on the deck tied into the hull. And it would attach to a carbon structure thru which the wing slides containing one main ball bearing roller and four smaller rollers to allow the wing to move thru it with the least friction. Inside the wing, a small carbon cart will carry the 80lb of lead with either rollers or sliding on a low friction surface.
The wing is supported, additionally, by two trapeze wires and fore and aft adjustable lines to allow some pivot while underway.
What do you think?

stainless wing swivel mount: ( as I understand it this seat swivel has to be able to take all sorts of accelerations found when a 200+lb person is riding in a fast powerboat. I know a company that does marine testing and will probably be able to get the specific design details there-and what the maximum forces the the thing was tested to.)

 

Doug.

I still think pivoting it while underway is a bad idea.

If you're going to go that route, I suppose the fore and aft control lines are a good way to go. I would suggest you make them a pair of bow lines.

As for the seat swivel. I don't think it's near strong enough. And pivoting the wing, while underway complicates using a trap line to support the wing. Remember, we are talking nearly 1100 ft/lbs static loads, here, with the wing extended. In any kind of a sea way, these loads will most certainly be multiplied.

A simple trap line support would work best (IMHO), if it supports the sub assembly, rather than the wing itself (so they can stay the same length). These trap lines would go out four feet from the CL to the ends of the sub assembly there.

The sub assembly would have three top retainer rollers: one in its center and one at each end. These would transmit the loads from the wing to the trap lines.

There are two negatives to this plan:

One, there would be a substantial upward, tension load on the swivel, once the wing is extended. This would be about 200 lbs, static load.

Two, once the wing is swiveled, the trap lines would shorten on both sides, tending to bend the sub assembly upward on each end ('ends' being side to side).

Better than having a seat swivel, to hold the sub assembly to the boat, would be to have a short mast.

The center of the sub assembly could then have a flange that fits over the top of it, leaving about two inches between the top of the 'mast' and the top of the flange, to account for the sup assembly rising, as it's pivoted.
At the very top of this mast would be a pair of large washers and a substantial pin (of maybe 0.50 inch dia. SS)

 

I'll think about your ideas, sharpii2. You realize, that when the wing+ ballast is full extended, that the load is on the windward trapeze wire and on the line that moves the wing outboard. Virtually no load on the center carbon structure. In a dynamic situation there would be intermittent loads on the pivot lines. The highest load on the seat swivel is when the wing + ballast is centered and is well under what I've been told the swivel is rated for. This will be further looked at, with Eric making the final decision.

 

I have thought of a second set of trap lines which would connect to the tips of the wing.

They will only give support when the wing is fully extended and would be slack otherwise.

This is the problem with trap lines.

You can, of course, have a block and tackle at either end of it, so its length can be adjusted, but this just adds more motors and more work for your sailor, not to mention more weight.

Your hull will experience compression loads at the mast step. These loads are roughly equal to the righting moment divided by the distance between the center line of the mast and the lower attachment point of your shroud/trap line.

 

sharpii2, I've posted this before-I think. But is the Trapeze Power Ballast System used on my Melges 24 model illustrating that the thing is designed to pivot about a fore and aft axis. The idea is that as the wing and ballast move outboard the wing can pivot. It is set up so that when the wing is centered, shock cord or similar is holding the ends up and as the thing moves the shock cord stretches it is stopped by the wire or very strong line-worked well on the model. This will work like this to some degree on the Crossbow. On the model the whole rack slid fore and aft as well. There isn't enough room on the Crossbow for the wing to side fore and aft.

 

Just a little status update. I'm close to being finished with my test model project ( http://www.boatdesign.net/forums/mu...lf-righting-trimaran-test-model-36058-42.html ).
Testing will continue on and on for some time. Pictures and videos will be posted as testing begins. May start a separate "test results" thread.
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So finish of the building on the MPX will make this project the number one building priority-probably around the first of the year. I've discussed this boat with a lot of people I respect and every one thinks that it is worth a shot. The idea of a movable ballast system that can allow a disabled or physically restricted singlehander to sail a fast, planing boat is still a rush to me.
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There is a possibility of doing a prototype of the Crossbow prototype. What I mean by that is that I have a hull here that served as the basis of the test model(above) but to use that hull for the full size version of the tri is out of the question for at least two years regardless of the test results. Similarly, getting the Crossbowfl built in the next year is highly unlikely due to financial constaints that will ease up in a couple of years.
But, the hull may be able to be used to put together a working example of the Crossbowfl sliding on deck Trapeze movable ballast system. And it could probably be done very inexpensively since the only things required are to modify the bow, build the "wing", install seats, find a mast tube and cut out a "sunfish-like" cockpit. I have the daggerboard, seats, rudder, and a couple of potential sails.
This working example may help raise the money to do the Crossbowfl by illustrating that the sliding ballast will work. It would probably not use the DSS foils that I have because the hull isn't designed for it. It may use an asy spin.
Here are some pictures of the unmodified 16' hull that is lighter than a sunfish . It's sitting in the garage now wondering what it's fate will be....
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The boat was experimented with by a friend using a very small sail. It is 16' and 110lb.:
click for larger view--

 

Crossbow XPRO( experimental prototype)

I had a little time and used it to mock up what the modifications I proposed in the last post would look like. The Trapeze wing would move fore and aft(or pivot like the Crossbow fl system) and side to side. Inside the sealed wing, the lead ballast would move as the wing does. The bucket seats don't adjust side to side but will slide fore and aft.
It ain't pretty but it gives a close approximation to the concept:

click--

 

Crossbow XPRO(experimental prototype)

In the last couple of weeks since I've finished most of the details of the Test Model trimaran(see link above) I've worked on for some time, I've come up with a new "wing" design for the Trapeze Movable Ballast System. Until now the wing design incorporated a sealed shape with sliding ballast inside the wing. One particular aspect of that design has always bugged me: it required a sort of "thru-hull" device at the outboard end of the wing for the line from the moving ballast tray to the boat. That line causes the ballast to move inside the wing when the wing itself is moved. The "thru hull" gizmo consisted of a sheave on the inboard end of the shaft going from inside the wing to a sheave on the outside. It would have been under a lot of load and the winding of line on the inboard and outboard sheaves was problematic.
So yesterday I came up with an entirely new design that has most of the bouyancy of the sealed wing and 100% of the tip buoyancy, while allowing a sliding cart with the lead ballast inside to slide on the upper ,outer surface of the wing. In addition, the portion of the wing between the two tips is split all the way across allowing a line to pass thru directly from the sliding cart to the boat, vastly simplifying the working of the whole system. At this point, the wing would be cut out of styrofoam and be carbonated-though that could change. Viewed from forward or aft the wing will be curved similarly to the mock up pictures above.
I have devised a very simple new addition to the wing system, even before this new design, which is the use of a shock cord that would tend to pull the weight to the centerline, making manual control much easier. I want to experiment with manual control of the wing and save the electric system for the actual Crossbow fl.

 

Crossbow XPRO---New version of the seat system

These pictures of the rough mock-up illustrate the "rear seat(thwart)" which works(at this point) as an assembly with the two side seats in that they slide fore and aft together.
The whole assembly is designed for a single person to use and the "back seat" allows the crew to slide sideways across the boat as well as allowing a fine adjustment to fore and aft crew weight. A major goal of the seating is comfort while providing ease of sailing. You can go a few pages back and look at the first illustration of this concept in the actual Crossbow fl design.
I've reached the conclusion that I don't like the seating in a 2.4 meter or Rave-I want to be able to sit sideways so it's easy to hold the extention tiller in my aft hand. This won't work for some disabled people and they'll have to use a single seat in the center.

Pictures,L to R : 1) new seat, 2) bucket seats only, 3&4) new seat.
click for larger picture--

 

Doug,

This has all been done before - International Canoe - so nothing new here all old news

 

Crossbow XPRO

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Thanks for your comments Basil. Unfortunately, you don't understand the concept if you think it has been done before on a full size boat in the same way as it is done on the Crossbow fl or Crossbow XPRO. However, you are right that it has been done before in more or less the same way by me on a series of RC models over the last 10 plus years. That's one of the reasons I know the system works. You are also right that on-deck movable ballast has been used before on boats like sandbaggers and also by one of the Herreshoffs using a sliding tray on deck on several boats that won races. On-deck movable ballast has a long history but in that whole history there has never been a system like this that combines trapeze wire support of a "wing" that allows lead ballast to slide side to side in or on a moving "wing" where the buoyancy of the wing is greater than the ballast on the wing.
Lead ballast is in a tray that slides on the "wing" when the wing moves, moving way to windward. It can be moved manually and/or electrically and it can be moved much faster than a crew can move.
The wing has much more buoyancy than what is required to float the lead ballast in the wing and therefore acts to right the boat if it is ever immersed.
So, no matter what happens the wing can work to right the boat and/or prevent a capsize regardless of the position of the lead in/on the wing.
My system is specifically designed to allow physically restricted and/or disabled people to be able to sail a high performance planing boat.
The only thing my system has in common with an International Canoe is that both use (entirely different) systems to get ballast outboard.
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The pictures below shows the closest things that have been done in the last 50 years to my system as best I can tell: 1) First, a bucket of water suspended outboard on a dinghy and 2) Second, Julian Bethwaites "tilting" seat on the SKUD 18. An illustration of a system that is similar, if I correctly understand Julians system, can be found in post 9 of this thread. Expanding opportunity for high performance monohull "dinghy" sailing is what it's all about:

 

Here is a little bit on the "original" on-deck movable ballast system from another thread:

 

Crossbow XPRO

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One of the potential problems in using this hull as a test boat for the Crossbow fl is the low freeboard aft. Back in the early 80's I used to race the US1-a sort of rip off of the Clark Mills designed Windmill that I raced for years.
The differences were that the US1 was an unstayed main only design and the US1 freeboard-particularly aft- was much lower than on the Windmill. In wind and waves it was relatively easy to flood the US1 because during a tack the aft lee side would go under water-something that never happened on the 'Mill. This could be really slow and annoying.
If I use the hull I have for the Crossbow XPRO, the problem may resurface except that the boat can't flood. The freeboard on the old hull is very, very low-mainly because the original hull(aeroSKIFF) was designed to fly and not be in the water in any wind!
I'll try it as is and see what happens.

 

But Doug, it looks like your "aeroskiff" has no actual cockpit, so how would it flood?

Also, I thought you were using this hull for the MPX trimaran. After all that's why you said your model was built overweight. Are you planning on reusing this hull in multiple projects? won't that be problematic with all the patching and repatching necessary?

 

that's still confusing to me. even if you spend 2 years testing your MPX, if you use up the hull building the Crossbow - why not have made your MPX a more efficient hull shape since you will need to build a new hull anyway?