A question about the Bolger Brick

Discussion in 'Boat Design' started by clmanges, Apr 4, 2021.

Tags:
  1. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    When I saw the drawings for this boat I was surprised that the mast was located as far to the starboard side as possible. The reason given was to free up as much interior space as possible in the boat (the leeboard is on the outside of the hull for the same reason, I assume, and also on the starboard side).

    I just have to wonder if there's any other significant advantage or disadvantage to this arrangement. I've only been able to think of one advantage: that when running direct downwind, the boom can be swung off to the port side, and if everything was put together just so, the sail's center of effort could wind up pretty close to the boat's longitudinal centerline, giving a level ride, and, I assume, unbiased rudder.

    I think tacking and reaching might be weird, though; I'm guessing that the boat might heel more to one side than the other.

    What say ye?
     
    bajansailor likes this.
  2. bajansailor
    Joined: Oct 2007
    Posts: 3,599
    Likes: 1,561, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Some info about the Brick for reference -
    Brick https://www.duckworksmagazine.com/03/r/excerpts/bwaom/01/brick.htm

    Bolger Brick.jpg

    I was trying to find a photo of one sailing on starboard tack, as I was thinking that the sail would become more in the way of the crew then, but maybe not, especially with such a high boom (less chance of bashing your noggin).

    This photo illustrates nicely how the rig is offset -

    Bolger Brick sailing.jpg
     
    Will Gilmore likes this.
  3. cluttonfred
    Joined: Mar 2014
    Posts: 64
    Likes: 15, Points: 8, Legacy Rep: 15
    Location: United States

    cluttonfred Junior Member

    Hehe, while the link goes to Duckworks, I recognize the blue-tinged drawings and photo as pics from my old site, still visible though incomplete here: brick - molepages. I am not much of a sailor, but my general recollection is that it made little difference what tack you were on in a boat so dominated by crew weight. On either tack, the leverage of the crew is enormous (you can see we're actually heeled the "wrong" way at the moment the photo was taken). I sold the boat when we went overseas and it soldiered on for quite a few years in the hands of Lincoln Ross, who sent me a pic of a bunch of little kids in it with him at one point. Here are a couple more pics:

    brick16_lightair.jpg brick18_boatbabe.jpg

    For getting a couple or young family out on the water at the local pond, lake, gentle river, or sheltered cove, I think it's a fantastic design and a great way to get your feet wet in boatbuilding. It's simple, cheap, fun, and easy to cartop (I transported mine on two cross bars clamped to the gutters of an old Peugeot 505 sedan). The exact same sail is used on several other Bolger/Payson designs (Cartopper, Elegant Punt, Gypsy, June Bug, Rubens Nymph, Surf, Sweet Pea, Teal, maybe more) so you could start with Brick and then build something a little more complex later on using the same rig.
     
    Last edited: Apr 5, 2021
    Will Gilmore and bajansailor like this.
  4. Will Gilmore
    Joined: Aug 2017
    Posts: 939
    Likes: 434, Points: 63
    Location: Littleton, nh

    Will Gilmore Senior Member

    It's so basic, it's highly innovative. I love the idea of it.
     
  5. cluttonfred
    Joined: Mar 2014
    Posts: 64
    Likes: 15, Points: 8, Legacy Rep: 15
    Location: United States

    cluttonfred Junior Member

    bajansailor likes this.
  6. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    The disadvantages are:
    1.) The Center of Area (CA) of the sail rises as the boat heels on a starboard tack (it sinks on a port one). This is because the mast is stepped far from the boat's lateral center of gravity.
    2.) the boat may handle different on one tack than another. On the port tack, for instance, the boat may experience more weather helm than on the starboard one. This is because, on the port tack, the horizontal CA of the sail is far from the centerline of the boat, where, on a starboard tack it is much closer to it.

    This effect will be far less pronounced on a scow or a catamaran than it would be on a nonohul with a pointed bow. This is because, when a scow or catamaran heels, it's lateral center of drag moves to leeward much more than it does on a pointed bow boat. This is especially true if the scow uses Lee boards, and the catamoran has its keels or center boards mounted on its hulls.

    The designer has to be careful not to Lee helm on the starboard tack.
     
  7. Will Gilmore
    Joined: Aug 2017
    Posts: 939
    Likes: 434, Points: 63
    Location: Littleton, nh

    Will Gilmore Senior Member

    Very nice and well reasoned explanation, sharpii2.

    Do you thing you could fix that with asymmetrical leeboards?
     
  8. cluttonfred
    Joined: Mar 2014
    Posts: 64
    Likes: 15, Points: 8, Legacy Rep: 15
    Location: United States

    cluttonfred Junior Member

    There is nothing to fix, Brick serves its purpose just fine. You guys are trying to put spoilers and a whale tale on a golf cart. :-/
     
    clmanges and Will Gilmore like this.
  9. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Probably not.

    What would likely work better is having just one 'board, and having it on the starboard side.

    This is because the board produces most of the drag, while it is trying to create lift.

    The 10ft scow I'm building will have a single Lee board that gets shifted to the Lee side with every tack. It is set up so, that when the boat is on a starboard tack, it ends up further forward than when the boat is on a port tack.
     
  10. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    What's your reason for doing this? Is there some asymmetry elsewhere in the hull or rig?
     
  11. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Yep.

    Looks like I forgot to mention that my 10 ft scow will also have a offset mast. It will be stepped in the starboard side deck.

    I chose this arrangement, because my scow will have no fore deck, so I can step on board over the bow.

    I intend to use it as a fishing boat on small lakes.
     
  12. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Regarding your asymmetrical placement of the leeboards, could you elaborate further? Some simple sketches would be nice, showing wind direction and reaction. Also, there's this solution (scroll down to "Paxton ..."):
    Types of Daggerboard leeboard centerboard etc https://pdracer.com/keel/

    I wonder if you aren't simplifying your design at the expense of extra operating labor by having only one leeboard and switching it from side to side. I like being lazy--and being able to react quickly--so I'd favor one on each side, independently controllable. Having only one also seems to work satisfactorily, as witness the Brick itself, and a lot of PDR builds.

    Finally, I wonder how much you'd even notice the effect, as cluttonfred commented about crew weight in post #3. I suppose that might be mostly a function of your hull shape.

    I'm just guessing and trying to learn here; I have no sailing experience at all; I just paddle.
     
  13. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Some pretty good questions.

    One of my design goals was to make the boat, including the board and rudder, out of 3 sheets of plywood.

    I know this is somewhat arbitrary, but I wanted as simple construction as possible, with no holes in the boat (at least none intentional).

    I thought of making two boards, but that would consume a lot of plywood. Then, I thought of having one large board, which would stay on the starboard side, but mean old Mr. Math capsized that idea. This is because, to get the most effective area, it's better to go deep than wide. But the deeper board would have to be thicker to endure the bending loads.

    I found that the smaller board would theoretically work if it was always on the Lee side.

    I thought of a staple on each side (made of timber, so it doesn't count), but rejected the idea for worries about mean old Mr. Stump/rock.

    I the had to consider how I was to secure this single board to the boat, while being able to switch it to the other side quickly. I decided to secure it at the top only. To do this. I needed 2 lines. One to hold the top of the board against the hull. And this one had to be automatically released, in the event of a bottom strike. The other had to keep the board in its fore and aft position. The only convenient place to attach this line was at the bow. The problem was, that if I ran the line past the starboard side of the mast, the board would further forward on the port side.

    I thought of making the length of this line adjustable. But this would add more steps to every tack. But then it occurred to me, when I looked at where the Center of Area of the sail was going to be, that this might actually help me, due to the center of hull drag being so far out from the mast on a starboard tack. So this line will be a set length.

    So, that's my story. And I'm sticking to it.
     
    Will Gilmore likes this.
  14. clmanges
    Joined: Jul 2008
    Posts: 576
    Likes: 144, Points: 43, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Are you talking about a fixed board of some sort? The supply of unfamiliar boating jargon seems endless to me.

    I'm unable to picture this arrangement in my shriveled old brain, but I'm very curious about it. Can you provide a photo or sketch?

    I'd love to see some kind of force diagram for this, even if it's a crude one. Also, is the sail's center of area different from its center of effort? And, is the center of hull drag fixed or variable, and how is it calculated?

    snip
     

  15. sharpii2
    Joined: May 2004
    Posts: 2,246
    Likes: 329, Points: 83, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Good questions.

    A 'staple' is a board or rod that goes across the outside of the board to hold it against the hull. This is so the board will stay down and can be used on both tacks. This was an innovation on US working scows which enabled using just one board which could pivot like a centerboard.
    A shorter staple can be used if the board is inserted down through it like a dagger board.

    A sail's Center of Effort (CE) is always different from its Center of Area (CA). The problem is that it changes constantly. So too does a boat's Center of Lateral Resistance (CLR) For this reason, designers use the relationship between the sail's CA and the boat's Center of Lateral Area (CLA) as a reference point when calculating a boat's balance*. These two never change.

    The Hull's center of drag is yet another factor that constantly changes (on a monohull sailboat). This is so hard to calculate, because it changes with each degree of heel, that it's often not even considered. For general purposes, it can be considered to be near the boat's heeled, lateral center of buoyancy. As it moves to leeward, as the boat heels, so too does the center of hull drag. But, as a monohull sailboat heels, a center line installed board or keel has its center of drag move to windward. And, because it's doing almost all the work lifting the boat to windward, it is also creating most of the drag. So the boat will tend to round up into the wind.

    I'd like to send you a few sketches, but I'm operating on a smart phone at this time. I will send you one soon.

    * A condition in which the sailboat will have an almost neutral helm no matter how far it's heeled over. Monohulls which achieve this magical condition are often seen as legendary. This is because, with any significant amount of helm needed to keep the boat going straight, there is a significantly added amount of drag.
     
    Will Gilmore likes this.
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.