Aka attachments to Nacra 5.2 hulls as amas

Discussion in 'Multihulls' started by nwguy, Oct 28, 2019.

  1. revintage
    Joined: Nov 2016
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    Location: Sweden

    revintage Senior Member

    Nwguy,
    Don´t worry about buckling etc. As you have a force from the rear going part of the shroud bridle, the force from the crew will be counteracting it. The more wind, the more upward force. If you worry, begin with calculating the force from the shroud. Hard to see, but you could maybe shorten the forward bridle wire and lengthen the rear going to get less force on the rear. If you have clearance from the sail and wishbone boom you could also move the rear inwards to make things easier on the rear beam waterstays. Not so much as on the Hydroptere prototype though ;-) .

    Waiting for pics from the maiden voayage!
     

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  2. nwguy
    Joined: Feb 2010
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    Location: Poulsbo, WA

    nwguy Junior Member

    Well, I took the trimaran out for its first sea trial a couple of days ago. Launched at about 4:00 pm on an incoming tide in north winds initially ranging from maybe 8 to 13 knots. I had the jib sheets routed incorrectly through their cleats, but soon got that sorted out. Did some reaches, tacking and jibing, making sure I had adequate steerage and the ability to return to my launch spot. No problems there. Then sailed downwind for 5 or 10 minutes to the port marina for my town of Poulsbo, WA. The wind was stronger than I thought it would be. That with the low/mid 50s air temp and gray skies made me think I should head back and do a longer trial in nicer conditions. I sailed upwind back to my beach quickly. The boat points really well with its 5' long carbon daggerboard. Then I thought, what the heck, I'll sail downwind a couple of miles to my friends house and back. Did some running almost directly downwind, then some broad reaches. Reached my friends house, did some beam reaches, then headed back upwind home. Was out for maybe an hour and a half. Got pretty cold. My findings and impressions:

    The amas could be a bit higher, but I think they're going to be fine the way they are. When I got to my most downwind point, the wind was gusting to maybe 16 or 17 knots at times. There were whitecaps. While heading upwind home I had the windward ama typically about a foot or a foot and a half out of the water. Easy to modulate the height off the water by shifting weight around on the giant tramps (they're 8x9' each). So in light wind, both amas will probably be in the water unless the crew intentionally puts weight on the leeward ama. Still very fast though. In heavier air, the windward ama flies naturally.

    The boat tacks pretty well. On the latter part of the trial I was making every tack without going into irons or backwinding the main. Jibing is pretty exciting.

    The boat has tremendous speed potential. I should have reefed the main given the gusts. I was sheeted out to shed wind most of the time so as to not scare myself. I didn't have an app or device to gauge my speed, but it seemed very fast. Probably over 15 knots at times. Acceleration is alarming. I almost went off the back of the boat one time after jibing and getting the main sheet set.

    I sailed sitting down at first, but then stood up like I used to when it was a foil boat. That was the right thing to do. Much better control over weight shifting. One hand on the tiller and main sheet, the other hand on either the boom or the shrouds. Will probably put a piece of garden hose on the shrouds where it's convenient to hold on to to form a comfy handhold.

    It's a pretty dry ride. On slower speed reaches and when sailing downwind, I didn't get wet at all, even when sitting down. Then when sailing fast and/or upwind, the spray wasn't bad at all. I'd say it's a comfortable boat. I like the giant tramps a lot.

    The helm is pretty light. No extraordinary effort to keep going on a reach of any direction. With hands off the tiller, the boat tends to turn downwind. I may try to cant the mast back a bit to fix that.

    Nothing broke! It didn't make any funny humming or whistling noises, even at higher speeds.

    When viewing the boat at its mooring ball, I could see the the amas were pitched upward at their bows, too high of an angle of attack. I made the rear attachment points adjustable and have since raised the rear of the amas by about 4". Looks about right now (see pic below). Next time I haul it out of the water on its dolly, I'll cut off excess metal on the adjustable ama/aka attachment plates.

    I ditched the struts supporting the rear aka and made water stays from 1x19 stainless cable instead. I didn't notice any weird flexing while I was standing back and towards the amas during the strong gusts.

    It's super fun to sail. My being able to sail it solo in such strong gusts on its first run is really encouraging. I can't wait to sail it with a friend so we can sheet in properly and explore its speed potential. Pic of the mainsail below.

    amas.jpg main.jpg
     
    Corley likes this.
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Can you take a pic of the water stays for my curiosity?

    glad to hear things went well

    The reason asking about the water stays is you could put a lifeline atop the rear aka for any falling off concern.
     
  4. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Congratulations, that's the best "first time" report I've heard in a long time.
     
  5. nwguy
    Joined: Feb 2010
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    Location: Poulsbo, WA

    nwguy Junior Member

    I took the boat out a second time. Gopro video here:



    Similar conditions to the first time. In the end, a bolt rope on one of my tramps pulled out of its track on the vaka. I've since ordered more slug slides from sailrite to fit into the tracks and have re-sewn my tramps to use a sleeve and pole to lace onto the slug slides. The slides are on back order till 4/30, so no sailing until I get them. I downloaded a free, cheesy speedometer app for this trial, but it said my max speed was 82 mph. Any suggestions on a good accurate app for checking speeds? Not looking for a full-featured sailing app.

    Fallguy, here's a picture of my new, rear waterstays:

    waterstays2.jpg

    With just me on the boat the lower waterstay attachment points are about 3" above the waterline. I've read that life lines are useless at speeds over 6 knots. Even in light air this boat will typically be sailing faster than that.

    I did cut unneeded metal off the rear aka-ama attachments. Probably saved a pound and a half of weight. Metal won't be dragging in the water either. Here's a pic for comparison:

    akas.jpg
     
  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    It looks like fun, but a bit scary. Hope you are vested; cheap insurance against a fall.

    I think the only thing I didn't like was the underducking, but that is sailing; not sure if there is any way around it. My smartphone has a good gps app. You didn't hit 82, but she goes!
     
  7. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Forget the lifelines. They will just be something to trip over. That boat will sail right out from under you or the crew if they don't pay attention. Just like 50K hobies.
    Looks like a really good second sail.
    I'll bet you would not have to backwind the jib to tack. Just start the tack, pop the jib, settle on the other tack, then sheet in the jib. You will recover your speed better.
    Third sail you are going to fly the main hull? On the video!?

    Do you know how much the boat weights?

    Congrats again.
     
  8. nwguy
    Joined: Feb 2010
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    Location: Poulsbo, WA

    nwguy Junior Member

    Good advice on tacking. Will try it next time I'm out. I really don't intend to fly the main hull. Too scary for me. Don't know what the boat weighs, but a Supercat 20 weighs 45o lbs. and a Nacra 5.2 weighs 350 lbs. Probably close to 450. Looking forward to sailing it with a friend who can handle the jib.
     

  9. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Flying the main is easy.
    Just don't let it get very high. 1' is plenty.
    And don't cleat the main and jib.
    Hand hold them so they can be released easy.

    It's fun. You will probably notice the water noise get quieter and not much else.
    And watch to be sure the lee ama doesn't dive below the water.
    Move back on the tramp.
     
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