Large sharpie for the Adriatic

Discussion in 'Sailboats' started by Igor, Jul 1, 2022.

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  1. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    I think what's being missed here is "yacht quality" as opposed to "work boat" quality.

    A good kit can get you pretty close to the former. But this comes at a price. The 10 ft scow I'm building, is being built of lumber yard matterials. I limimiting myself to just three quarts of epoxy, to make up for not so perfect glue joints, in vital structural areas of the boat.

    The sides are vertical, so I didn't have to bevel them.

    But I did have to bevel the frame bottoms, for the two inner frames and the bottom of the stern transom. I had to bevel the top bow transom log too.

    I did this with a sureform plane and a home-made sanding block. And I got them all reasonably close.

    The boat has just four cleats and four 1/4 inch blocks. It has next to no metal fasteners. I used homemade bamboo pegs instead.

    I think the total cost of this project is going to be around $400 US. I suspect a kit would cost me one and a half times as much, if not two.

    Anyone looking at my boat, who has even decent skills, would laugh. But I learned a lot from it.

    A lot of times, good enough beats really good.
     
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  2. Igor
    Joined: Jul 2022
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    Igor Junior Member

    It looks like a great boat and I like it a lot.
    The pluses:
    -all parts can be cut on CNC and quickly assembled
    - to keep the cost down an used mast, sails and rigging could be used

    The minuses (as I see it):
    -The long high aspect rudder could shear in broaching at the pivot point, maybe the casette rudder would be better?
    -the site says it has got 300kg of ballast but it does not say where.
    If that long dagger board/centreboard is ballasted it would require some sort od winch and bulletproof box, pin and accompaniyng structure to keep it where it belongs.

    On the other hand the boats like Parker's Egret 28 are rough & though while still being elegant. Less parts to go wrong. Big unballasted centreboard even if it fails and falls off it will not cause the boat to turtle.
    The rudder even though it is not the most efficent type it can be made virtually indestructible quite simply.
    The rig is low and and in the worst case scenario there is a chance that at least one mast will remain aloft.

    Regarding the motoring speed I have found one more account on woodenboat forum, the replica of Munroe's Egret (cross planked) does 6.5 knots with 5hp outboard, 4.5 knots into 30mph headwind and chop.
    Guess that the Parker's version with flatter run and smooth bottom could hit those 8 knots indeed.
     
  3. tane
    Joined: Apr 2015
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    tane Senior Member

    Looking at the Egret 28 I see, that it & the Birvidic cannot be compared at all, two vastly different types of boat.
    As to keel, ballast & winch for the Birvidics keel I attach some pics.
    Regarding the safety of the rudder: I think here we can trust F. Lucas, he has many designs to his name, red hot racers, cruisers,...
     

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  4. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    Looks to me like it wouldn't be hard to beef up the rudder and centerboard with some carbon fiber, or even metal, if that was a serious concern. But any metal would have to be kept from contacting the carbon. There may be other corrosion concerns, I'm no expert. The board or the rudder could also be made very strong in some combination of uni glass and cloth, with no concerns about corrosion. They'd be a bit heavier. Are they pouring lead into that centerboard? If it was going to be made out of fiberglass, a bit less lead could be used for the same overall weight. It would be important to make sure the centerboard trunk and the area where the rudder gudgeons are bolted in were strong enough, because that might be harder to revise later.

    If the boat will be doing 12 knots* at times, the board is 6 feet deep, and 1.5 feet wide, and the foil is a NACA 0012, then the force on the board might be on the order of 3,000 to 3,500 lbs just before it stalls. This doesn't mean the design is wrong. It may well be quite strong and have an appropriate safety factor.

    If there's a cable to pull up the centerboard, and it's in the water when the centerboard is lowered, it could make an annoying hum. I've been on at least a couple of boats where this was a problem. It could be ameliorated by a spiral wrap of a single wire, so that it doesn't shed vortices along the whole length at the same time. I don't know if the spiral wrap would be vulnerable, but, since oceanographers use cables like that, they may have a good solution for the problem. BTW, for anyone who carries a boat on top of their car, the spiral wrap also works on ropes and straps that tie down the boat. Also, I bet, on those round Thule bars.

    *The displacement quoted is relatively light, unless that's for the bare boat with no one on board. Let's say it gets up to 1,200 kg. the D/L (in imperial units) might be 110 or less, which I'm guessing means it will sometimes plane. Comparable to a mini-Transat. I suppose that means, if everything is as optimized for speed as a Mini-Transat is, that 15 or 20 knots might be possible in some conditions, with a skilled, aggressive skipper. But maybe the centerboard wouldn't be all the way down in those conditions?
    ----------------
    With either of these boats, I wonder if they won't trim down at the stern if you have many people on board.
    -----------------
    I wonder how far over the Egret can go before it doesn't want to come back up? If I was building one, I'd probably investigate this fairly carefully. I seem to recall a number of designs that have steel bottoms or maybe just steel sheets attached to their bottoms. If it could somehow be kept from rusting, this might be a way of keeping the ballast as low as possible, and making the boat more resistant to nasty obstacles.

    I wonder if Parker sells more complete plans? From those, one might be able to work out files for NC cutting, though it would take some work. Relatively straightforward, I should think, with a CAD system that can unfold sheet metal (which would also apply to plywood).

    If you wade through this link, you will find quite a few sharpies, almost all by Bolger, but there is also some version of the Egret.
    p https://www.flickr.com/photos/hallman/albums/72157613767421231
    My apologies if I've posted the link earlier in this thread.

    I've seen drawings for a sort of lens shaped plywood bump that's meant to attach to the forward part of the bottom on at least one of the Bolger Advanced Sharpie designs. I don't recall how much it's to quiet the boat down at anchor, and how much to reduce slamming underway. I haven't found the right search terms to locate it yet, but I'm pretty sure it was in Messing About in boats at one time. I have this impression that it may have been an idea from Susanne Altenberger. As drawn, I imagine it could deliver a concussion to a whale without much damage to the boat. ;-)
     
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  5. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    BTW, looking at the rig on Parker's version of the Egret, vs. the rig on the Birvidic, I'd guess it can be made for a small fraction of the cost.

    I imagine that, for the overall cost of the Birvidic, one could make a sharpie so much longer that it could be just as fast. Especially if allowed a ballasted board that was just as deep. An extreme example of that kind of thinking is the Insolent 60, though I suspect it would cost a little more than the Birvidic!

    Insolent 60 in 3D https://futabachan.livejournal.com/146688.html
    Note that it has the bump under the bow that I was talking about. I hope someone builds one someday, though I'm guessing it won't be futabachan.
     
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  6. tane
    Joined: Apr 2015
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    tane Senior Member

    nocable in the water: on the 1st pic("relevage...) you see, that the keel is raised with acable to thefat rod, that is integral to it.raised: rod up against compression post, lowered: rod down against top of keel case. There it can be secured with a lashing to guard against the keel coming up when the boat is knocked down.
    in the short vid she seems to move quite well.
    (for me personally the "retro" cabin is ugly, & category C insufficient, so the Birvidic was out)
     

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  7. Igor
    Joined: Jul 2022
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    Igor Junior Member

    Thank you for the photos!
    Birvidic is obviously a lot more sophisticated design capable of greater speeds, the Egret is geared towards laid back sailing and occasional cruising with spartan accomodations, more like camping really. It also looks like much simpler build. Btw I like the idea of lashing the CB rod to prevent it from folding back, simple and effective.
    On the other hand the centreboard looks quite complex to build
     
  8. Igor
    Joined: Jul 2022
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    Igor Junior Member

    This is rather a guesstimate but the Egret should pop back up from 90° knockdown, the plans call for 1000lbs of lead pigs centered around CB and bridge deck, its wooden mast and pointy stern *should* prevent it from turtling or at least from not being stable in upside down position as long as the hatches do not leak too much water inside.

    Parker does sell separate plans for Egret but these are nothing more than enlarged drawings from the Sharpie book.
     
  9. Igor
    Joined: Jul 2022
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    Igor Junior Member

    Parker sells plans for 46ft version of the New Haven sharpie with unstayed cat ketch or schooner rig, ballasted swing keel/foil cb and split cabins.
    This would be fairly large project though!
    IMG_20220808_022151.jpg IMG_20220808_022202.jpg
     
  10. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    Probably best to build a boat that is just big enough, and just complicated enough, to do the job you want it to do.

    ----------------------
    tane,
    I didn't parse that picture at first, but with your description it makes sense.

    I suspect that a good board shape helps a lot upwind, but I don't know what an ideal shape for a half delta wing shaped board like the Egret's is. I'm sure there's something better than a flat plate.
     
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  11. Igor
    Joined: Jul 2022
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    Igor Junior Member

    Maybe keeping the part of the board that remains in the trunk square but shaping the underwater portion like delta aircraft wing? large.jpg
     
  12. rnlock
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    rnlock Senior Member

    The thing about most delta wing aircraft is that they're meant for transonic or supersonic flight, mostly right side up, so they have different compromises. The Egret drawing shows much more sweep, and, if I recall, a completely triangular side view for the part of the board below the hull. I don't know if it would be worthwhile to make a sharp leading edge, to encourage vortex lift, or to use a shape similar to what you show in that picture. Presumably, vortex lift would make for better handling in extreme circumstances, but vortex lift is draggy, and I imagine the sharp leading edge is draggier, too. Plus, a sharp leading edge would be more prone to ventilation. One thing we can be sure of, at such a low aspect ratio, is that the flow won't be just 2D.

    I think if it was mine, I'd just use a conventional airfoil shape and hope for the best.
     
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  13. Igor
    Joined: Jul 2022
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    Igor Junior Member

    Iain Oughtred used twin hi aspect bilge boards in his version of Egret.
    Not sure whether they are deployed in tandem or one by one and would deploying two boards at the same time cause some sort of interference.

    Upside of such arrangement is obvious, it frees up a lot of useable space and should boost upwind performance some but the focus is on removing that bih a** CB trunk out of the middle of the boat that is already cramped inside.
    Downside is building two foils and trunks vs one. IMG_20220809_012813.jpg
     

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  14. rnlock
    Joined: Aug 2016
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    rnlock Senior Member

    I have to stop looking at that Oughtred Haiku/Egret. I'm supposed to be thinking about other things! Plus I don't think my wife would be comfortable in it. Maybe if you gave us both rejuvenation treatments...
     
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  15. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    A craftsman up here is planning an Oughtred Haiku and has built a first-class model. He has created articulating, to-scale models of himself and his wife to determine final accommodations dimensions.
     
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