Crossbow fl

Discussion in 'Sailboats' started by Doug Lord, Jun 21, 2012.

  1. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Crossbow fl / Crossbow XPRO

    The Trapeze Movable Ballast System coupled with the Crossbow fl and it's DSS foils, rotating wing mast, square top main and square top jib stands an excellent chance to make relatively high performance planing dinghy sailing accessible to many more people than it is now. It is something I'm very much committed to trying to do because of the potential value to so many people that would miss out on a really cool part of small boat sailing otherwise. My system is a revolutionary system that offers very fast ballast/wing movement coupled with enough buoyancy to allow the wing to right the boat and/or prevent a capsize.
    If I go ahead with the Crossbow XPRO it will be to test the Trapeze Movable Ballast System and use those results to raise the money to build a production prototype of the Crossbow fl design described in detail earlier in the thread. See post 123 below.
    ----
    Pictures-L to R, #1-3=Crossbow fl showing the original sliding, buoyant wing with tip floats and DSS foils, #4-5=Rough mockup of the Crossbow XPRO(experimental prototype) showing the wing, sliding bucket seats and the recessed cockpit(will require an Elvstrom bailer or similar) :
     

    Attached Files:

  2. Baltic Bandit

    Baltic Bandit Previous Member

  3. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Crossbow XPRO

    ===================
    Just a bit of an update: if I go forward with the Crossbow XPRO I'll probably use the electric system and ,possibly, the actual Crossbow fl rig if the wing mast is still available.
    The electric system would be added after we test the system manually and it would give valuable information toward the production prototype. As I visualize it, any production version of this system would probably have an electric wing moving system which would make moving the wing(and righting the boat) as simple as moving a joystick on an RC boat.
     
  4. Baltic Bandit

    Baltic Bandit Previous Member

    So you are using an electric system. Here's an example video of a 5o5 gybing in big air Notice that at 35 seconds they go from crew weight on the wire all out to crew weight 75% of the way across the boat in 2 seconds http://www.youtube.com/watch?v=ClrGBB59sdI&feature=player_detailpage And this one shows Phillipe Kahn and crew going Wire to wire in roughly 3 seconds http://www.youtube.com/watch?v=7nfdQTGdfdA&feature=player_detailpage

    so is that the speed at which you are talking about your ballast being able to move across?

    If so, how are you going to prevent someone from getting injured? Are you planning on using the kinds of sensors they put in Elevator doors or something?
     
  5. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ---------------------
    No, the Crossbow fl system will move the ballast weight further and faster. Ricks initial design showed the capability to move 80 lbs 16' in 3-4 seconds, if desired.The ballast in(or on) a 10' wing(including wing tips) moves a total of 16'(ballast and wing moving simultaneously) in 3- 4 seconds at max speed, max outboard to max outboard. At that level, it would be able to do so all day every few seconds(for two 8 hour days w/o recharging)-way after a crew was tired. We're only talking about 3.6 mph(at 16' in 3 seconds-5.3' per second) at max speed in a nearly frictionless environment.
    The electric system is the only way to go for disabled sailing and probably for any use in a production system since I don't think the manual system will be fast enough-but I'm going to test it anyway. And of course the electrical version is controlled with a simple joystick just like the RC test boats were(except with a bit more sophisticated joy stick).
    ---------------
    Duration based on Rick's preliminary calculations(updated from his spreadsheet by me 11/5/13) :The system for the Crossbow moves 80lb(36kg)16' in 3-4 seconds and can do it for 8 hours moving the max distance once every 10 seconds for 8 hours. Practically, that would probably translate into 2+ days of sailing. A 20% grade is factored into the results as are 7660 start/stop cycles.
    --Peak power:369 watts
    --Battery required: 24 volt 10.2 AH
     
  6. Baltic Bandit

    Baltic Bandit Previous Member

    Hmm now i'm confused. 3-4 seconds puts the per second power consumption in the 540 watt range. Which over the course of an hour of sailing works out to be around 36,000 watt hours

    Using a 12 Volt system that requires a 3,000 amp hour battery system which weighs roughly 360#-400#. that basically makes it into a very slow boat as no skiff can handle that.

    While it is honorable that you are seeking to bring high performance to disabled sailing, this seems like the numbers just don't work the way you are suggesting.

    One of the things your calulations don't seem to include is that because high performance boat trim is very dynamic, the weight would be moving about every 1/2 second. Admittedly short distances, but that sort of "start stop" motion is what really drains batteries

    Also I'd be very concerned that you have built in zero safety margin. Since the 5oh in the videos is tacking at 3-4 seconds, and your Crossbow can only move at 3-4 seconds, you have zero safety margin.

    I don't know of any handicapped enablement system that does not run with a safety factor Can you point me to one?
     
  7. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ===================
    Unfortunately, your calculations appear to be way off base. Rick W did an excel spreadsheet showing exactly what the power requirements are, what the duration is and what the battery requirement is as per my last post. I have great confidence in Rick based on his work with electric power and his detailed analysis of my requirements. We'll know more when the system is assembled but for now I'll go with Rick's recommendations in post 125.
     
  8. Baltic Bandit

    Baltic Bandit Previous Member

    hmm can you point me to Rick W's spreadsheet? because I can't seem to find a link to it in post #125. I'm glad you have great confidence in that analysis. That would be a great tool for the rest of us to learn from. Is there a reason you cannot present the calculations?

    And I'm still concerned about the zero margin of safety. Did you miss my question on that?
     
    1 person likes this.
  9. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Crossbowfl

    =======
    1) yes, it's proprietary(for the time being).
    --
    2) Don't be concerned-your premise is incorrect. The 505 crew was maxout out to maxout in 6 seconds*, not 3-4. The Crossbow system is 3-4 seconds for moving the ballast 16' whereas the maxout CG to maxout CG of the crew is about 12.4'. So, as a comparison, the Crossbow system moves 1.3 times as far in about 2.5 seconds less time(about 42 % less). But the real kicker is that the Crossbow system could do that every 10 seconds for 8 hours! And do it again for a second day with no battery replacement or recharge. And the margin of safety: considerably more reserve power than would ever realistically be required-probably double or triple. And one more thing: this system is capable of faster speed and up to 12' more distance if we(the team) decide we need it. But I don't think we will.
    ---
    *This was done with a stopwatch starting when the guy first makes a move to come inboard and not ending until he is full out on the wire. Initially, I counted the seconds and came up with 5, but I started late. Just to double check I sent the video to a friend and asked her to come up with a time. She got 6 seconds as well.
     
  10. Baltic Bandit

    Baltic Bandit Previous Member

    ah so we have a set of calculations that you are asking us to "trust you" on. but thought this forum was for sharing actual information and educating people - I'm confused as to why then you would cite fairly straightforward data analysis as proprietary. Isn't it just F=MA, Ke=VM equations http://www.youtube.com/watch?feature=player_detailpage&v=gou6teYRyvY? http://www.youtube.com/watch?feature=player_detailpage&v=qwIUqtITHEE

    As for max out to max out doug. I linked to 2 videos, one which had 75% of the transition in 2 seconds and the other had Wire to wire tack in 3 seconds - so I'm very confused about your source of "maxout to maxout in 6 seconds".

    I've raced 5ohs in 15+ knots of breeze and can personal attest to the fact that 6-7 seconds means you are swimming in a gybe or a tack. Note you cannot time from the moment the person changes their trap adjust or foot position. you have to time it from the moment they move their weight inboards to the moment they are out on the trapeze - or in the case of the gybe, hiking the boat flat from the hiking straps.

    Its true that in the gybe you transition 75% - to get the boat moving and thus reduce loads on the sails - and then you actually come back in, finish gybing the kite and complete the transition over the next 5 seconds. but if you do not move 75% of your weight across in 2 seconds, you swim.

    I recommend you talk to some real world experienced sailors about this. I can give you some referrals if you would like. Folks from National Olympic squads.

    Now the way I was taught to design for safety by Cornell's School of Engineering, was to design for a speed or strength or robustness that was slightly above the targeted safety margin. that way the safety margin could actually be executed.

    Are you saying I misunderstood what my professors were teaching?
     
  11. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    =============
    I have confidence in Rick and his spreadsheet, thanks. I'm also convinced that the Crossbow system will be faster than any trapeze crew. Further, the system has been tested in RC models for many years and until we begin testing full size there is no need to re-design the system or discuss it any further since I have clearly described it's designed capabilities. The charactersistics of the system described in post 125 are satisfactory and achievable thanks to the help of Rick W and a couple of others. I'll go into the system more when testing has begun.
     
  12. Baltic Bandit

    Baltic Bandit Previous Member

    But doug I'm trying to learn from your expertise here. The physics videos I linked to are how I was taught to do this kind of analysis. So I'm wondering where my numbers are wrong. Can you please help with a more detailed explanation?
     
  13. Doug Lord
    Joined: May 2009
    Posts: 16,679
    Likes: 342, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Crossbow XPRO

    I've been able to do a lot of thinking about the Crossbow XPRO in the last few days, and I've been looking again at seeing if I could find a viable way to use the DSS foils. Generally, speaking the chine is too high on this boat-but there are solutions to that. The boat needs to sail at a 10 degree angle of heel upwind and if it does that with the current freeboard the side of the boat at the DSS foil would be underwater or very close and the foil is too close to the surface. There is a solution to that too ,but it's getting into real work and making mods that might only be beneficial on this use of the hull. For those who don't understand DSS, there are several threads in this forum that can explain it pretty well. Bears thinking about.......

    Rough mock up of the Crossbow XPRO with the current DSS foils:
    click for a larger picture-
     

    Attached Files:

  14. Baltic Bandit

    Baltic Bandit Previous Member

    hmm so if this is a solution for a disabled person, how does DSS fit into the safety issue? Doesn't DSS lose righting force the more heeled the boat is. so if you are relying on DSS and a gust hits and your heel increases, doesn't your righting moment go down?

    Isn't that the opposite of what you want in a safety focused boat?
     

  15. salglesser
    Joined: Apr 2012
    Posts: 58
    Likes: 3, Points: 8, Legacy Rep: 47
    Location: Colorado, USA

    salglesser Junior Member

    Hi Doug,

    When are you planning a full size model?

    sal
     
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.