Preventing Multihull Pitchpoling

Discussion in 'Projects & Proposals' started by Fanie, Sep 30, 2018.

  1. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    I've been watching video's on fast catamarans sailing and saw quite a few pitchpoling when the leeward hull sticks it's bow in the water.

    If one attaches a horizontal plate or fin on the bow that will force the bow to swim upwards then it could prevent these inconveniences.

    Well ?
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    Cat DSS: (better yet get a trimaran with the Fire Arrow Foil System!)
    How are you Fanie?
    DSS for multihulls.jpg
     
  3. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi Doug, from the shoulders on downwards I'm ok ! Thanks.
    Your image looks promising. Like to see it work on a cat in real life.

    I found your Youtube channel and the model tri. Nice. Even has an arrow on it so you know which direction to sail to :D

    Amazing how if one goes sailing there is never wind. We have that worked out more or less here. You go fishing with a sailboat. If there is wind, you sail, if there is no wind, you fish. Most of the time the wind doesn't know if it is going to blow. Or not :rolleyes: But fun we are going to have either way !

    Soooo... when do we see the real life hands on model ?

    As for the Fire Arrow Foil I'd like to see it on the bow, if you go into the surf for instance the bow should lift and prevent the water rushing over the boat. And instead of pitch poling it should slow you down just enough to recover.
     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    Fanie, take a look at the last few pages of this thread-this is the last page: High Performance MPX Foil/Self-righting Trimaran-The Test Model https://www.boatdesign.net/threads/high-performance-mpx-foil-self-righting-trimaran-the-test-model.36058/page-187
    I've 95% finished the design of a 14' trimaran using the Fire Arrow Foil System called "WOLF" .You can see a concept model in the thread and, of course, the original "Fire Arrow". You can also see pictures of the three "Ultim" trimarans that are using their own version of the Fire Arrow Foil System-Gitana 17, Macif and Banque Pop.
    My original Test Model flew perfectly on July 24th ,2014 and these big tri's just started flying in the last three years. The foil system they use is almost identical to the system I developed for the original Test Model and that will be used on WOLF.
    I'm hoping I can raise the money to get WOLF built-it will be tough to do but I might be able to make it work out.......
    =======================
    Check out this video of Gitana 17 about 41 seconds in where the port hull buries up to the crossarm but instead of pitchpoling she just slows down a bit and then keeps on flying. Keep in mind that the key to my foil system and the one Gitana uses is an adjustable foil on the daggerboard, an uptip foil on each ama(one used at a time) and a rudder t-foil on each ama and on the main hull.*
    *rudder t-foil only on main hull of Fire Arrow and WOLF.
     
  5. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Now if the wings on the rudders and the hydrofoils could adjust, and you have a little computer doing that for you, it could optimize the hull remaining flat without heeling and that is where the sails make most power. In a high wind when you're tearing down the stretch your biggest fear will be that a wing is going to hit air, it's going to be like a car tire blowing out at high speed, and you can then also make those slow motion back flips the racing boats make when they get too much wind under the hull.
     
  6. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    On my boats mainhull altitude-and angle of heel of the whole boat-is controlled automatically with a mechanical surface sensor(wand)-and manually on the big boats. On my boats and all the big boats the flight altitude of the ama is controlled automatically with UptiP foils. Ama foil attitude is controlled automatically* on my boats and manually on the big boats(for now) since electronic foil control is illegal in the "class rules".
    * by the combination of the wand controlled mainfoil on the daggerboard working together with the rudder t-foil that automatically "follows" the main foil.
    Gitana 17 flying like a bat out of hell:
    Gitana Foiling!.jpg
     
  7. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Ah yes you see the wimps ! The moment you do something that will advance something they make "class rules" and no advancements exist.

    Those boats are unpractical. Who can afford something like that ? It serves only one purpose and it is not so pretty if you want to be honest.
     
  8. JamesG123
    Joined: Mar 2015
    Posts: 611
    Likes: 73, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    Speed brings risk. Even with electronic (or even analog mechanical) control, there will always be some combination of wave, airflow, and oscillation between the two that won't be accounted for by the system or that overcomes it, especially if you out on the edge of its performance envelope.

    If you are going to exceed stable hull speed, you are going to have to accept the risks of the lack of static stability.
     
  9. BlueBell
    Joined: May 2017
    Posts: 616
    Likes: 57, Points: 28
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Not in the video I watched.
    At 41 seconds, the port bow digs in, followed by the vaka while the boat comes off foil and slows, considerably.
    That's where the clip ends.
    "Just slows down a bit and keeps on flying..."
    What visions you have doug, you're delusional.
     
  10. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    I can only guess that you weren't paying attention: the clip clearly showed the port bow re-emerge so she would have continued flying. Further, if she had pitchpoled it would have been disastrous as she was in the middle of a race-she didn't pitchpole because the foils prevented it. And she won the race!
     
    Last edited: Oct 1, 2018
  11. BlueBell
    Joined: May 2017
    Posts: 616
    Likes: 57, Points: 28
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Clearly not on the video I watched.
     
  12. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    You should watch it again carefully. This tri has wave piercing amas and they worked perfectly. Had the thing pitchpoled, it would have stopped dead-that didn't happen-and again, a pitchpole with a boat like that would easily have been a race ending nightmare-instead she won the race. Keep in mind, that in addition to the wave piercing amas the ama foil is designed to be able to lift the whole boat+ and clearly it was exerting tremendous force on the ama and in combination with the ama shape and rudder t-foils prevented a pitchpole. Port bow re-emerged at :46 in.......

    This is what a pitchpoled trimaran looks like:

    Trimaran Pitchpole.jpg
     
    Last edited: Oct 1, 2018
  13. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    That is what every one wants - exceeding stable hull speed, because this is how new crafts are born. If not for that we would still be rowing hollow tree stumps. The intention with all racing boats is to push the limits, and if possible at all, exceed it as much as possible.

    Right now I'm tempted to start a thread called planing displacement hulls, because displacement alone does not cut it (pun intended), most of these newer hulls plane. The displacement only happens at low speeds or when you sail into a wave. I'm not a fan of foilers, it is for competition only because it is a specialized field, I'm more for recreation and fun sailing on very fast planing displacement hulls. The limiting component on sail boats imo is the sails.
     
  14. JamesG123
    Joined: Mar 2015
    Posts: 611
    Likes: 73, Points: 28, Legacy Rep: 10
    Location: Columbus, GA

    JamesG123 Senior Member

    A planing hull can be just as squirrelly as a foil.
     

  15. Doug Lord
    Joined: May 2009
    Posts: 16,380
    Likes: 281, Points: 93, Legacy Rep: 1362
    Location: Melbourne, Florida

    Doug Lord Flight Ready

    Well designed foilers aren't "squirrelly"--same with well designed planing hulls.
    Fanie, foiling and or foil assist has permeated almost every aspect of sailing from windsurfers to kiteboards, dinghies, catamarans and trimarans up to 100'+, keelboats to 100'+, cruising or racing and growing every year. Not so specialized......

    Fanie, here is a thread about the DNA cruiser/racer cat with an automated foil control system designed to prevent pitchpole or capsize......
    Automatic Foil Control Systems https://www.boatdesign.net/threads/automatic-foil-control-systems.57923/#post-826047
     
    Last edited: Oct 1, 2018
Loading...
Similar Threads
  1. sailsocal
    Replies:
    2
    Views:
    2,446
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.