Raidboat Pacific Proa

Discussion in 'Multihulls' started by BCowan, Sep 2, 2020.

  1. rob denney
    Joined: Feb 2005
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    Likes: 123, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    If you want to know anything about Harryproas, either ask me (harryproa@gmail.com) or join the Harryproa chat group: HarryProa@groups.io | Topics https://groups.io/g/HarryProa/topics
    where Rick Willoughby recently analysed the Harryproa set up, explaining why "The two large rudders near the beam give very close to ideal balance",
    "Another thing that I find nice in operation is close proximity of the two helms so both rudders can be used simultaneously",
    "When a standard HP is lifting the ww hull, the drive and drag are essentially aligned but there will be leeway if only the back rudder is working. It needs both rudders working to negate leeway. When the windward hull is loaded, it is pulling the boat to weather so the aft rudder has to pull the aft end to weather thereby reducing or negating leeway. There is a position of perfect balance for any particular conditions. "
    and a bunch of other observations from sailing and analysing an 18m Harryproa

    The forward rudder is not locked in position, although it can be. I have found the easiest way to steer upwind is to lock the aft rudder and steer with the front one. Reaching, use the aft one and downwind, lift the front one and as much of the aft one as you need.

    A board will make it harder to shunt, as it cannot be aligned with the water flow, so stalls, creating drag. 2 large, liftable, kick up rudders is the best solution.

    Any other questions, let me know.
     
  2. BCowan
    Joined: Aug 2020
    Posts: 13
    Likes: 1, Points: 3
    Location: Colorado

    BCowan Junior Member

    Thank you Rob, this is hugely helpful. I have begun poking around the HarryProa discussion forum too, so thanks for the link. I wish I had the time and ambition for a larger project with IntelligentInfusion, but I currently dont even live next to a state that is next to the ocean......so for now I have to stick to my small boats and mountain climbing.

    I hadnt thought about steering with the forward rudder, and the idea that the drag from the windward hull makes some turning moment and weather helm is not something I had thought about either. Seems to me a multihull, and particularly a proa, has a more complicated dynamic of helm balance than a monohull heeled over. Figuring out when it is advantageous to lock a rudder, or leave it free, or steer with one or both rudders will be part of the sea trials and practice I need before committing to the Everglades Challenge. Learning to sail in a new way with my proa is going to be fun and interesting.

    For my proa, I have cannibalized a Hobie 16 rudder assembly, and the only challenge I see to this is the shallow water and frequent kicking up and needing to quickly and easily re-deploy. So the pressing question I have is about the placement of the rudders on the leeward hull.

    Do you think there is an ideal distance between the rudders as a percentage of the hull length? Certainly the HarryProa rudders are not mounted on the end of the bow/stern (100% of hull length), but your rudders look farther apart than dividing the hull into 3rds (33%). Im planning on a 21' (6.4m) leeward hull for my proa. I can conveniently place the hobie rudders about 12' (3.6m) apart, making the distance between the rudders about 55% of the hull length, though I can close the distance between the rudders with minor modification to the platform. Just wondering what your thoughts on rudder placement and helm balance.

    Right now my rig is looking like a pair of lugs, and I am absolutely sold on the schooner rig. Though Im sure many will scoff, my love for lug rigs has only grown with the 125sq ft mainsail I have for my yawl. A balanced lug rig to me looks like a lateen with part of the luff cut off, making it easier to reef. We'll see how it all comes together.....

    Thanks again for the ideas and passion. Were having a gnarly snowy day (slow) at work, so planning to really get to reading the HarryProa discussion forum.....
     

  3. rob denney
    Joined: Feb 2005
    Posts: 766
    Likes: 123, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Different rather than complicated. And less dynamic as the loads and directions stay pretty much the same unlike a heeling hull.
    Depends on the rig (schooner is more verstaile), windage, the load on and willingness to fly the windward hull, the rudder size and ease of lifting and the agility of the crew. 55% apart is as good a starting point as any. Helm balance should be a touch of weather helm.

     
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