planing pods/skis/amas

Discussion in 'Multihulls' started by sigurd, Dec 12, 2004.

  1. Doug Lord

    Doug Lord Guest

    Aoa

    If I were you I'd get a copy of this artcle and the other Professional Boatbuilder articles on stepped hulls and/or contact Mr. Clement, the author, at Eclement5@aol.com
    In the article Clement points out that the ideal running angle for the cambered hull surfaces used by Plum was 2-3 degrees modified to a higher AOA in folowing seas or rougher weather. Fascinating stuff!
     
  2. tspeer
    Joined: Feb 2002
    Posts: 2,201
    Likes: 170, Points: 63, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    I like the deep foils, but I wonder about the step. Especially since the vast majority of my sailing has been done at sub-planing speeds. I think I'd be tempted to put in a flap that was flush with the hull but could be deployed to form a step when the winds made it worthwhile.
     
  3. Phil Locker
    Joined: Oct 2004
    Posts: 95
    Likes: 4, Points: 0, Legacy Rep: 49
    Location: Ottawa, ON, Canada

    Phil Locker Junior Member

    I don't know how you'd accomplish that without quite a steep approach to the step / planing pad. Easier to have an actual hydrofoil that nests flush with the bottom of the hull and can be cantilevered down (carbon or G10 supports on each end of it). But then you're back into full foiling territory.
     
  4. Doug Lord

    Doug Lord Guest

    retractable step

    Phil, if you get the article you'll see that a wedge shaped step would be fine. On a 14 footer it could be 3" in the F & A direction and made so the aft end pops up more or less 3/32"(2.4m)when it is deployed. There is an important sweep angle(outboard end aft of center)that would have to be used but the beauty is that it would be 100% retractable!
    So you've got a pretty good idea and it seems to me that it could have applications on planing sailboat hulls in earlier planing and faster top end.
    But I don't think it could beat a foiler but I'll never say never.....
     
  5. Skippy
    Joined: Nov 2004
    Posts: 568
    Likes: 1, Points: 0, Legacy Rep: 12
    Location: cornfields

    Skippy Senior Member

    If you had a low AR foil with highly swept leading edges, that should solve two common foil problems: deeper draft and structural weakness. And even if it's not adjustable, it does have more wetted surface, but wouldn't it still have a higher AR than the planing surface, and wouldn't the flow lines be cleaner?
     
  6. Phil Locker
    Joined: Oct 2004
    Posts: 95
    Likes: 4, Points: 0, Legacy Rep: 49
    Location: Ottawa, ON, Canada

    Phil Locker Junior Member

    Okay, so I'm building it

    What the heck, this is my slow season. The hull is under way. No planing pad until I get it on the water, pin down the exact daggerboard placement, and then will fabricate a few alternative "pads" of different heights and shapes to see what they do to performance in a breeze.

    http://www.philsfoils.com/11ftr/11ftr.html
     

    Attached Files:

  7. Doug Lord

    Doug Lord Guest

    11

    Way to go , Phil! How much do you think it will weigh ready to sail?
     
  8. sigurd
    Joined: Jun 2004
    Posts: 827
    Likes: 8, Points: 18, Legacy Rep: 65
    Location: norway

    sigurd Pompuous Pangolin

    The problem as I have heard it, with adapting sailboard rigs, is that they are made for much less power than your skiff. A 10m board rig will be made for light wind, and designed to flex out the force from gusts/harder wind. so you may be a bit underpowered with all your RM, otherwise I think efficiency of the rigs are ok?

    Maybe it would be a super solution with a stiffer mast than what the sailmaker intended?
     
  9. Phil Locker
    Joined: Oct 2004
    Posts: 95
    Likes: 4, Points: 0, Legacy Rep: 49
    Location: Ottawa, ON, Canada

    Phil Locker Junior Member

    weighty question

    Way too early to tell. I'm trying to build it light, without being fanatical about a bit of extra epoxy here & there (build speed takes priority at this point). And I know I could have got away with a thinner core, especially in the wings (but thick foam in the wings is a subst. for aft floatation tanks).

    It'll weight what it weighs... I'll report when its done.
     
  10. Phil Locker
    Joined: Oct 2004
    Posts: 95
    Likes: 4, Points: 0, Legacy Rep: 49
    Location: Ottawa, ON, Canada

    Phil Locker Junior Member

    I'm trying to solicite educated opinions on how to make it work, but it seems most people trying it haven't had much success. But as they say, cheap is a virtue overcoming many faults. Dropping in a modified sailboard mast & sail bought "off the shelf" is going to cost considerably less than a one-off solution. Shroud position, spreaders, prodder, are all under consideration.
     
  11. grob
    Joined: Oct 2002
    Posts: 216
    Likes: 5, Points: 18, Legacy Rep: 53
    Location: Cotswolds Waterpark, UK

    grob www.windknife.com

    Phil,

    If you take a look at our boat www.fourhulls.com, you will see that we use two 7m windsurfing rigs. Although I have heard that opinion many times I haven't encountered the problems that sigurd talks about. Yes the top will twist off, its designed to do that. But the rest of the sail still seems to hold its shape well.

    I am still of the opinion that using windsurfing rigs is a good option. I am yet to find a more cost effective lightweight solution.

    All the best

    Gareth
    Warob Marine
     
  12. alyne
    Joined: Aug 2003
    Posts: 55
    Likes: 1, Points: 0, Legacy Rep: 38
    Location: Somerset UK

    alyne Junior Member

    Windsurfer rig

    Phil,

    I can also confirm that windsurfer rigs have potential. I have used an 8.1 m windsurfer rig on my beach cat, and have had a few fast sails on it. See link:

    Pink Onion

    OK, I have learnt alot about rigging windsurf rigs since these initial pics (needed another foot of downhaul :D ) but I have generated plenty of power to get up on the plane. With this boat I just reinforced the botton 1 metre section of mast with fibreglass tape and had it free standing, this gave a little extra strength at the foot without distorting the sailshape

    A much better solution I shall be using in my next boat is to attach shrouds directly under the boom, I believe this is what Gareth does. The rig is designed in a way to be stayed at this point.
    I would recommend: By a sail, mast and boom off ebay...plenty to choose from, and devise a simple system to stay the mast below the boom.

    Your build pics look great.
    Hi there Gareth... have been following your design with interest

    Andy
     
  13. grob
    Joined: Oct 2002
    Posts: 216
    Likes: 5, Points: 18, Legacy Rep: 53
    Location: Cotswolds Waterpark, UK

    grob www.windknife.com

    Hi andy,

    Thanks for the complement, we use a "sub mast" which is attached to the boat with stays, this is basicaly a strut that takes all the compression loads.

    This sub mast can be seen clearly in this picture

    [​IMG]

    The windsurfing boom is then attached to the casting at the top of the sub mast via a clevis pin joint. The advantage of this system is that the mast is supported at the base and the boom, this allows the windsurfing mast to behave and bend as it was designed to.

    Well done on your design, I have nothing but admiration for those that attempt these projects.

    All the best

    Gareth
     
  14. gggGuest
    Joined: Feb 2005
    Posts: 794
    Likes: 15, Points: 18, Legacy Rep: 76
    Location: UK

    gggGuest ...

    This is of course an argument for using a Moth sail - the top Australian "sailmaker" gets batches made at a Far Eastern outfit to keep costs down.
     

  15. Doug Lord

    Doug Lord Guest

    Phil's boat

    Phil, did you see the latest Prof. Boatbuilder with the article by Clement on stepped planing hulls? It would sure be cool if you could incorporate that shape(similar to the underside of a 63412 section) into your hull in some removable way. Then you could sail with and without it and see what happens. It seems to me that if the aft portion of the swept planing surface could be hinged or something it could allow use in every condition.
    So how's the boat coming?
     
Loading...
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.