4.75m Trimaran Project

Discussion in 'Multihulls' started by kaymaran, Jan 2, 2016.

Thread Status:
Not open for further replies.
  1. gonzo
    Joined: Aug 2002
    Posts: 14,449
    Likes: 640, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    A tri will simply have more weight with no more righting moment than a monohull with hiking boards.
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ===========
    Absolutely not- if its designed properly. That means over-square with foils and small amas. It means using a wand controlled lifting foil on the main hull and a single uptip foil on each ama with a rudder t-foil on the main hull.
    12' tri 17' wide with two crew sitting 2' to windward of center compared to 12' monohull 5' wide with two crew on trapezes(total crew weight the same for both boats) :
    A) 12',5'wide,carbon, 90lb mono two crew on trapezes, max RM 2320ft.lb.
    B) 12',17' wide,carbon, 140lb tri max rm with crew sitting 2' to windward of center:
    4620ft.lb.

    The tri would have a minimum of 1.99 times the RM of the mono!!! And thats with the crew sitting 2' to windward of center and with no downforce
    from the main foil. Needless to say the tri still has lots of room to be powered up substantially further, if desired.

    12' concept model,mainfoil wand controlled or surface piercing T foil(with manual or automatic downforce), ama foil wand controlled t-foil or uptip foil-beam varied depending on type of foil. Rudder T-foil on adjustable gantry:
     

    Attached Files:

  3. TANSL
    Joined: Sep 2011
    Posts: 6,151
    Likes: 280, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I seem to understand that both are engaged in a discussion on a topic that you do not understand well. In my opinion the maximum righting moment (RM), to a certain displacement, depends on the hull forms and its appendages, not the position of the crew.
    I think not to be wrong but if you show that I am, I will not hesitate to recognize this and will have learned a little more.
     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Rm

    On a small boat like either of the two in my example the crew weight(350lb total for two) is way more than the weight of either boat. On these types of boat the position of the crew is critical to a correct total RM(righting moment).
    A) Roughly,the crew(350lb) CG on the mono is 3+3.5=6.5' from the CB(center of buoyancy) producing 2275ft.lb of RM, while the hull(90lb) is about .5' to weather of the CB producing about 45ft.lb. of RM for a total RM of 2320ft.lb..
    --
    B) on the tri the crew(350lb) CG is about 10' from the center of lift of the lee hydrofoil when flying the main hull which produces 3500ft.lb of RM. The hull(140lb) CG is about 8' from the lee hull center of lift when flying the main hull and produces 1120ft.lb of RM for a total RM of 4620 ft.lbs.or 1.99 times the RM of the mono.

    ===================
    The point is that in each case the RM due to crew weight is way higher than the RM due to hull weight. Hope this was helpful.
     
  5. TANSL
    Joined: Sep 2011
    Posts: 6,151
    Likes: 280, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I insist that the righting moment does not depend on the position of the crew but the hull shapes and appendages.
    The crew weight exerts a heeling moment which can be contrary, or not, to the one due to wind.
    But I guess it is a matter of nuances.
     
  6. Gary Baigent
    Joined: Jul 2005
    Posts: 2,992
    Likes: 114, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Really Doug, no s**t! Well, put your money where your mouth is and you design and build a 12 x 12 foot (okay make it supremely powerful a la your smoke head dreamy renderings and make it 12 x 14 foot beam, no, make it 17 foot, lets not be conservative) - a way over square trimaran that can carry your weight, put on the necessary huge rig to actually get the contraption to move ... and we wait with held breath to see this lightweight? avian with you aboard levitating with ease over the sea.
    I mean just double or triple the size of your latest red toy boat contraptions ... and there you are ... and then you can prove all the doubters and rude ANZACs wrong?
     
  7. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    The concept is a long way toward being proven already ,Gary. Way oversquare, three foils in the water,mainfoil unloads just before developing downforce which adds RM, planing amas, planing main hull, two different altitude control systems-both automatic, flys in a 5mph breeze, a bit more testing and shes ready to go fullsize:

    [​IMG]

    [​IMG]
     
  8. Gary Baigent
    Joined: Jul 2005
    Posts: 2,992
    Likes: 114, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    How many times have you posted these way overblown, polluting images, Doug? - 50 maybe even 100 times?
    Even you must be getting bored with the repetition?
    But probably not?
     
  9. gonzo
    Joined: Aug 2002
    Posts: 14,449
    Likes: 640, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    TANSL: The righting moment in a dinghy is mainly the weight of the crew times the distance from the center (F*d). Many of them have little stability.
    Doug: Are you saying that a tri is lighter than a monohull with hiking boards and no amas attached to them? That would mean the amas have negative weight. It is hard for me to see how that can be.
     
  10. TANSL
    Joined: Sep 2011
    Posts: 6,151
    Likes: 280, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I am sure that the RM has another component that you're forgetting. Study a little more, and when you understand it, try to explain it to me. Thanks in advance.
    "distance from the center": what is the center of which you speak?. Tank you again.
     
  11. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ==========
    Gonzo, in my examples above the tri(17' wide) was 140lb and the mono 90lb. I didn't know what you were referring to when you said "hiking boards"* so I used a 5' beam on a 12' dinghy with two guys standing on the gunnel on trapezes. Both examples were the same length with the same crew weight.

    * the only boat with two crew that I know of with anything like a "hiking board" is the Skate(LOA 14')-is that what you meant? For my example both boats were the same length with the same crew weight.
     
  12. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Mono RM

    TANSL, maybe this illustration from Frank Bethwaite will help you understand how to calculate RM for a high performance dinghy. Note that most high performance dinghies are sailed upright* so the hull shape, angle of heel(which is zero) and hull/rig weight does not affect RM:
    *in my example, I allowed the mono to have a small angle of heel


    [​IMG]
     
  13. Doug Lord
    Joined: May 2009
    Posts: 16,653
    Likes: 322, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Trimaran RM

    ======================
    In diagram below:NOTE: the tremendous advantages of an oversquare platform plus the Fire Arrow foil system(with mainfoil downforce) can be configured to be way more than double the RM of this configuration!No way any monohull could even come close to the maximum possible Righting Moment!)
    A) Boat CG to center of lift of lee ama foil=8'. Boat weight(140lb) times 8'=
    1120ft.lb.
    ---
    B) Crew CG to center of lift of lee ama foil = 10'. Crew weight(350lb) times 10' =3500ft.lb.
    ---
    TOTAL TRIMARAN RM= 4620ft.lb


    [​IMG]

    ======================

    Concept Test Model(Fire Arrow)--illustrates foil layout:

    [​IMG]
     
  14. Gary Baigent
    Joined: Jul 2005
    Posts: 2,992
    Likes: 114, Points: 63, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Doug spews his silly defecation yet again.
    Build a real world 4.75 metre trimaran that can actually carry your overweight posterior - then maybe we'll genuflect to your nautical superiority? But not holding breath.
    But you do realize that once more, you've wrecked another interesting thread with your inane fixations.
     

  15. OzFred
    Joined: Nov 2015
    Posts: 503
    Likes: 53, Points: 28, Legacy Rep: 16
    Location: Earth

    OzFred Senior Member

    Doug, you've had your own thread for that boat going for over 5 years. Reference it if you like, but don't turn this thread in to a proxy of your thread.
     
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.
Thread Status:
Not open for further replies.