Crossbow fl

The only way I can make sense of the beam motion is that the trap lines to the mast and the lines to the transom are fixed length and the beam is an arc that swings around an axis approximately where a backstay would be if there was one. The ballast must move in proportion to the beam movement because they move at the same time from the same motor. If this is right it's not so hard, but the ballast positions are limited to one arc about the backstay, not fore aft up down. If you don't seal the ballast inside the beam it will be greatly simplified. The only benefit of sealing it in is the buoyancy of the ballast path -but you can just add buoyancy outside.

I don't see any reason the hull couldn't be built in wood. I don't think you need any carbon fiber except for mounting the DSS foils. I don't even think you need anything special for the mast if it's only 18ft. Just make a special buoyant masthead with the trap lines you need.

If you give up the flashy materials this boat is not that hard or expensive to build.

 

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The wing always pivots at the center of the boat regardless of how much it is extended outboard. When the weight and wing are centered the shockcord(attached to the trapeze wires and wing)) is supporting the wing ends. But as soon as the weight moves the wing tilts by amount the skipper allows it to-with the load then taken by the wire instead of the shockcord. The amount of tilt may be adjustable from the cockpit but I haven't decided yet. On the models it worked fine to just have a preset tilt that was only adjustable on shore. One thing to keep in mind is that if the wing wasn't allowed to tilt as it was extended the outboard end would rise. At the very least the system will keep the wing level at a 10 degree angle of heel.
The transom lines will be set up so that they don't require adjustment whether the wing is centered or max out unless the skipper wants the weight aft.
There is no backstay. The only limit on the movement of the ballast is the movement of the wing.
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PS- whats being considered is something like 1/8th" Okume carbonated.

Trapeze wires with bungy cords on model system:

 

Well if you run the calcs as I did earlier, you need about 15 liters of buoyancy at the mast tip to be safe with the weights involved. that's a fair amount of volume being carried up there.

You actually don't need carbon for the DSS foils either. it just makes them a bit lighter - but Laser's and other dinghies have been building such foils out of foam and glass for decades. consider that when I was 235# I could stand on the end of a Laser II foil to right the boat with no harm to the foil.

But the expense is not in the materials but the labor of a hand build of a custom hull. The thing is that these are all experiments in unproven approaches, which suggests that a custom hull build is largely a wasted effort since not only does it add expense, it also adds a design variable.

A much more affordable way to go would be to buy an old Laser II hull. this has the advantage of being designed as a two person trapeze boat that does plane upwind. so then you scale down the "Trapwing" for the corresponding righting moment, convert the jib to self tacking, and you now have a hull platform that cost you all of $1000 instead of $25,0000. (that $25k price comes from the build cost of a Swift Solo).

Now you then buy a cheap used PLC (they are on eBay for a couple of hundred bucks or you can start with an Arduino device) and a used actuator motor from eBay as well. In fact the right way to do this would be to build the "trapwing" and the whole roller/bearing mechanism as a "bolt on" independent unit. That way you can develop and refine the "trapwing" and its mechanisms long before you bolt them to a hull.

So for roughly $2k you can build, prove out on dry land and refine the Trapwing. One of the big advantages of this approach is that you can have a steady power supply as you tinker with the mechanism of the trapwing and getting the speeds of transfer and accel/decell curves of the weight right (remember you are going to actually have to apply breaking current as the weight approaches its ideal position, otherwise the shockload of the weight stopping motion will essentially cause the flow over the sails and foils to be disrupted). And it also lets you precisely instrument the power consumption of the system so that you can figure out what size batteries you are going to need

THEN once the trapwing itself is refined as a unit. you buy the Laser II and bolt it to the deck of the Laser II. and then go sailing with that.

This gives you a platform of known behavior that you know has the performance you desire. So if it fails to perform, you know is not the hull and the rig, but rather something in the way the Trapwing interacts with it.

and then once you have this PoC done. THEN and only then, do you have something that is viable for startup funding.


I've been involved in half a dozen startups - 2 are currently active. One of which has gone for crowd funding http://www.indiegogo.com/projects/t...st-powerful-pocketable-gameable-officeable-pc the other we have chosen to avoid crowd funding because the product isn't as clearly pre-salable. So trust me on this Doug, what you have as a wish list will not get you the $$ you desire because you are not taking a sufficiently iterative engineering approach

 

Doug,
are the trap lines adjustable length underway or is there just elastic taking up slack? If the trap lines are adjustable how is it done?

The inclusion of shock cord in the models makes me 10X more concerned about scale up problems and emphasize the value of test mule. For $100 you could have a full size manual mule that would demonstrate the actual power and forces needed.

I still think this boat could be built with 4 and 6mm ply and little or no carbon. The ballast shift could be proven on many existing small hulls. Disabled sailors might have a preference.

 

BB,
nice looking project. I am far more interested in your involvement/experience with these crowd funding projects than anything we are talking/arguing about here.

I don't know if Doug wants the discussion here but I have lots of questions about your experience with crowdfunding startups.

 

Well this would be the approach to take using fundamental engineering principles. And since it avoids the funding issue as well, its pretty clearly the right way to go

Happy to contribute what I know of crowd funding. the thing to recognize about crowd funding is that because you are dealing with crowds - pretty much anything can happen, and will, so anything I say will be broad generalities.


but the keys are that you have to have
a) broad enough appeal to attract the funding
b) offer sufficient bona fides that the crowd believes you can execute

Generally crowd funding will only be available for things that COULD get funds in other ways, but which don't want the hassles of that (ie giving up ownership of the company)

 

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Skyak, this thread should remain about the Crossbow fl only-it is not about crowd funding which, due to some recent developments, may not even be necessary.
Start another thread if you want to discuss crowd funding-in fact there may already be several in the forums.
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And, Skyak,one more item-it's just nonsense to talk about 15 liters of masthead buoyancy if you understand the design of the boat and the role the buoyant wing plays. Because of the extensive model testing we have already learned a lot about the Trapeze Movavble Ballast System. What we need to do now is build a boat that is designed from scratch to take advantage of the technologies that make up the Crossbow fl concept which include the Trapeze Movable Ballast System, DSS, wing mast and a unique seating system for a singlehander. Anything less would be a waste of time and money since some of the most important elements have already been proven on other boats and in model testing. Only a complete working system proves the viability of the whole concept.
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Skyak, unless you find it indispensable to do so, please don't quote "bb" in your responses. It is the moderators intention that we ignore each others posts. I have no interest in reading those posts and it contravenes the moderators plan. Thanks.

 

Well crowd funding is part of what you have been discussing Doug, so its well within the discussion of the Crossbow FL project

 

BB,
I will PM you and we can go from there. It seems as relevant here as anywhere but the thread is very long and it's Doug's call.

 

Crossbowfl

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Skyak, as I said previously, crowd funding should not be part of this thread. And, as I said in my last post, if possible please don't quote "bb" in your responses.

 

I dunno - seems like a bait and switch on Doug's part. He raises the issue of crowd funding and then says that if BB is knowledgable about it, its not allowed for discussion.

 

One day, I hope, I would like to sail this boat in the EC or let someone else do it. I think the boat is ideal for that Challenge as a singlehander,albeit a small one. And at about $375 a person the advantages this thing has would allow one to experience one of the greatest sailing challenges around without a crew whereas a "normal" boat this size with this power would require two.
The boat would undergo extensive testing including long trips in the intercoastal and maybe a trip over the Challenge course itself.
Whether I do it or somebody else does it someone could have a real blast and an extraordinary experience!
Here is the 2014 EC thread in "Multihulls": http://www.boatdesign.net/forums/multihulls/2014-everglades-challenge-48607.html

 

Crossbow fl--rotating seat

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The rotating seat, if it can be effectively worked out, will add RM to the boat based on a crew weight of 250lb. Crews weighing less than this for racing would have to carry lead ballast under the seat to keep the total weight and RM the same for everybody.
The rotating seat has to be safe, particularly, when something odd happens.
With the wing in the center the boat can only roll 17-20 degrees. With it extended to weather ,if the boat rolled to weather it would be less than this.
If it got knocked down with the wing to weather, the wing would automatically drop to approximately the center position-or further if the crew wanted it to. With no input from the skipper this would bring the boat to a 17-20 degree angle of heel. With the Trapwing on the boat it can't physically capsize-it could be knocked down but would instantly pop up as if it had a weighted keel. Of course, the skipper could level the boat with the joystick or manually at any time. What has to be determined in testing is how does the seat react, how easy is it to move the seat(+ballast, if any) from a downside position etc.
I'm relatively confident that it can be done safely but we'll find out with the extensive testing of every system on the boat.

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TECHNICAL: (corrected 2/22/14)
The additional RM from the crew is about twice that from the same weight(250lb) in the tilting seat and so would allow a minimum of 30 sq.ft. more sail area.
Sail area would go from 120sq.ft. to 161.8 sq.ft(including wing mast-150+11.8) in a slightly taller(+2') rig making the boat significantly higher in performance.
This seems like an excellent way to go so it will be incorporated into the prototype at least for testing.
SA/D is significantly improved and Bethwaites SCP/Boat weight* is improved to .30 from .2. Bethwaite gives .3 as the begining of upwind planing.
(SCP= RM/distance CE to CLR= 1603/11.25=1/// SCP/Boat weight=142.48/473=.30)
So from a previous ratio of .2(post 177) the increases in RM and Sail Area due to the rotating seat have increased the Bethwaite ratio to the point of allowing us to expect upwind planing on the Crossbow fl. Note that the effect of the DSS foils upwind were not considered above. Since the DSS foil will add about 12% to upwind RM(1603 X1.12=1795;1795/ 11.25= 159.58/// SCP/Boat weight=159.58/473= .34), the likelyhood of upwind planing with the additional sail area is even greater. To improve the boat with the additional SA I have tentatively increased length to 15.6' from 14.6' and slightly increased freeboard.
This lends even more credance to the rotating seat as an important improvement to the whole concept! (provided it passes exhaustive testing)
* The formula to calculate this is published in "High Performance Sailing" by Frank Bethwaite on page 181(an 18' skiff has a ratio of around .61).

 

Doug you do realize that the 49er class tried weight equalization and it did not work.

And your "technical" calculations on RM do not seem to be based on anything connected to actual real world implementations. Particularly in light of you not including the weight of the batteries and the motor for the trapwing and the significant additional hull weight due to reinforcement that those will require.

You seem to forget that a 3mm Glass/Foam/Glass sandwich might be able to hold the weight of a body falling on it during a captsize but the weight of a sharp cornered battery going from 15knots to 0 in 1 meter places much higher point loads that need significant reinforcement structures.

 

Below, I've done a sketch of the new rig on a hull one foot longer. There seem to be tremendous advantages to these modifications including the potential to plane upwind.

Sail Plan -modified version of Crossbow fl:
This shows the greater sail area, slightly higher freeboard and one foot longer length. The extra length means that the Trapeze wing may be able to move fore and aft without pivoting about a vertical axis. The wing will still be able to pivot about a horizontal, fore and aft axis thru the use of the trapeze wires and shock cord/springs that allow the angle to be adjusted . See next page for comparative shots of the old version and new version and a summary of whats changed.