Hogfish Maximus - 44ish sailing sharpie?

Discussion in 'Sailboats' started by DennisRB, Sep 23, 2010.

  1. Sailor Alan
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    Sailor Alan Senior Member

    Chris et-al,

    Thank you for replying, I am honored by your advice.

    I hope today your WIFI is better than mine, up here in the foothills of Mt Baker.

    Whilst I agree with your statements, I was imagining the forward mast on the raked mast Ketch to be ON or THROUGH the forward bulkhead, and therefore not interrupting the forward V berth. I also imagined the after mast being stepped on a structural element in the galley, a galley return pole support, galley sink hand hold pole, or similar, and therefore relatively innocuous as far as interior incursion is concerned. I will have to check force (load) vectors with a raked mast and vertical support pole. I agree the 'foredeck' is going to be very cramped, but see#

    I agree about needing boom preventers, but racing we tend to use them unless beating anyway. Clearly my experience 'cruising' is counting against me.

    As far as double stick rigs are concerned. I notice several of the precursors to HFM were yawls or Ketches of different sorts. I am particularly enamored of your 'lightweight' cartoon, as it combines virtually all the features in the hull and deck works I have been dreaming about for some time. However I would consider a different rig, more 'Beowulf' or 'Red Herring' than a raked cat ketch.

    Now about rigs. I agree the longest possible leading edge on the tallest possible mast gives the best possible power to windward. We do after all do this on airplanes, use the longest practical wing for lift, the small horizontal empennage lifts DOWNWARD to provide dynamic stability. We also use LE slats, slightly analogous to a jib, and area increasing flaps, slightly analogous to a mizzen.##

    However. When racing with a single stick, reefing is easy enough, with one on the wheel, and two or three putting in a slab reef. When cruising, and basically single handing as far as crew is concerned, reefing can be difficult. A wind powered self steering system needs to work against something, usually the lateral force of the sail(s), and dynamically against the keel, and as the halyard is slacked off, the mainsail looses power, and the boat starts to loose way, rounds up, and possibly falls off on the other tack. None of this is fun whilst single handedly tying in a reef, even with 'jiffy' slab reefing. I assume an electric self steering system would hold a course better, but again, as the halyard is slacked off, the main does loose drive, the boat looses way, and suddenly directional stability is an issue. Yes, I know power winches hauling in the reef simultaneously is practiced, but all my experience thus far whilst trying to do so alone has led to burned lines, and a stuck, half in reef.

    Now, my assumption is that a double stick rig, though with less overall efficacy, can be reefed one sail at a time, so the mizzen and jib still draw whilst the main is reefed, etc. and the boat is still 'sailing' during the whole maneuver. I would welcome people's comments on this assumption, or fallacy.

    # For a while now I have practiced anchoring from the stern. The anchor is tossed out astern, and the forward momentum of the boat used to 'set' the anchor. Then a bite of anchor line is rove through an eyelet on a springy piece of nylon line running from the forward anchor lead, around the outside of the lifelines to the cockpit, and cast overboard. Now the boat lies anchored to its bow, with a slack piece of anchor line from the eyelet in the 'spring' to the stern.

    In retrieval, I simply start winding in the anchor line using a sheet winch in the cockpit, unsliping the 'spring' as it comes aboard, and the boat starts sailing immediately the anchor is 'aweigh'. This assumes room to leeward, but all activity was done single handed from the cockpit, using winches already there. Later, with the boat sailing, I can add sail, retrieve the 'spring' or etc as necessary.

    ## There is a sudden fashion for 'blended wing body' airframes, Boeing, Airbus, and now LocMar having all proposed such configurations in the last year or so. These are EXACTLY analogous to the older keel boats (like a 12M) with a blended hull and keel. Now we sailors KNOW that a separate blade type keel, dagger board, etc, just like HFM, is far more efficient than the older blended hulls. I ask why would aerodynamicist's want to go backwards?
     
  2. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Another blog from Chris Morejohn, in which he explains his experience and understanding of bows and rudders.

    Rudders, bows, Bolger, Culler, Parker, Chappelle,Martin,Kirby, Monroe....my thoughts
     
  3. sharpii2
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    sharpii2 Senior Member

    Three reasons:

    1.) Frictional drag. Airplanes are not sailboats. Though there is a strong similarity between a sailboat's under body and an airplane's plan form, the difference is that only the under body of the sailboat goes through the water. This is especially true on more modern designs, since the IOR era. With an airplane the whole air-frame must go through the air, so the the outer skin of the entire fuselage counts as frictional drag. This difference is also true in rough weather, when the topsides of the sailboat must go through the water too. The reason for this is there is usually a lot more power for the sailboat (wind) when the weather is rough. Not so for the airplane. As engines became more powerful and efficient, it was possible to carry more and more weight. This means more passengers. To do this, the fuselage was made either longer or wider. This produced more frictional area without contributing anything to lift. The blended body promises to change that.

    2.) Structural reasons. Though a cylinder with dome ends is an excellent shape to store compressed air in, it puts a point load on the wing, especially when landing, very much like a deep, short keel puts on the hull of a sailboat. The blended body promises to distribute these stresses at least somewhat, like the old faired in keels of the pre-IOR days did. The big hope is to get some weight savings this way.

    3.) Pitch stability. A conventional airplane has just one flying surface-the wings. The horizontal stabilizers usually create negative lift, to keep the airplane from pitching down. Since these structures contribute no lift and a considerable amount of drag, friction and otherwise, the practice is to make them as small as possible. This has reached the point where what was once static pitch control has now become dynamic, meaning control imputes, need to be administered just to keep the airplane flying. This is something that was never needed in the past-and was considered bad design practice then. What the blended body promises is static pitch dampening, like yaw dampening on a sailboat, somewhat like the deep chines of HFM probably deliver. This is probably the reason it is able to get away with a sloop rig. Yaw stability used to be quite a design issue in sailboat design, for voyaging sailboats, before wind vane steerers and electric autopilots. The Spray was able to get away with a sloop rig (later changed to a yawl one)

    Attached is a scaled sketch of my idea of an extreme blended body sailboat. Go ahead and laugh, but it might just work.
     

    Attached Files:

  4. PAR
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    PAR Yacht Designer/Builder

    The fairing seen on aircraft roots started with the development of the Douglas DC-1. It's wing was different, with a swept leading edge, but attached to the fuselage as typical for the era, just butted right in. This was found unsatisfactory at specific speeds and testing showed a fairing would ease the turbulence considerably. It worked so well that it became standard fair, until the P-51 wing was being developed and again turbulence was an issue at certain speeds. To delay high speed stall an additional fairing was placed in the entry of the root, easing flow and reducing turbulence.

    Many of these features were "co-pollinated" by yacht designers of the era as well, but working with considerably different speeds, not as satisfactory results. In fact many of the LFH designs, as well as most of the slack bilge "plank on edge" designs from the Brits, skidded off the leeward like a hooker avoiding her pimp. Once real testing started up in earnest after the second world war, things changed rapidly. Interestingly enough, the very fairing used on the entry to the P-51 root seems to be a new innovation on sailboats, for the same reasons.

    [​IMG]

    You can see the modest root fairing in this DC-2 image, but note the entry of the fairing is tight.

    The DC-3 below was the culmination of this development and the root is clearly seen and well faired.

    [​IMG]

    The B-24 was one of the first (if not the first) laminar flow wings, like the P-51, but check out the root. This was typical for the era.

    [​IMG]

    Now look at the root of the P-51, particularly the leading edge entry at the root.

    [​IMG]

    A bob Perry keel, look familiar? This is a cruising boat's keel, so penetration and high speed turbulence issues don't need to be addressed.

    [​IMG]

    A keel with root entry considerations taken seriously.

    This is a pretty complex subject and I've glossed over the history and evolution a disrespectful amount, but pictures can tell much.
     
  5. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

  6. PAR
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    PAR Yacht Designer/Builder

    A single chine boats present a V shape when heeled. That's not what would be considered a Scheel keel. A scheel keel is simply an end plate, incorporated/faired into the fin or appendage. It generates more drag than is justifiable, but some like them, for sentimental reasons. Henry theorized that you could reduce draft with his faired end plate idea, but after testing, you don't gain anything and you pick up a good bit of drag.
     
  7. Sailor Alan
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    Sailor Alan Senior Member

    Chris. I read yesterday that the rig on Hogfish Maximus is a repurposed second hand rig, complete with sails and spars. As such it is the perfect rig, and clearly fitted with great skill to get such balance. I am more Impressed than you can imagine.

    Thank you Angelique for the enhanced images from Chris's website. I am now even more enamored of Hogfish Light, or H-37 as it is labeled.

    Just thinking aloud here! The water ballast might be supplemented by more tanks at the bilge under the settees. Gilberj suggested rebar in concrete, and simple lead blocks as per Hogfish Maximus is also an option. Canned food is also an option, though less dense. I might consider filling the hollow CB with diesel fuel as an option too. It should still have very slight positive buoyancy.

    One reason for me wittering on about Ketches is my thoughts about using a used Dragon rig complete on the front bulkhead where the current mast is stepped, and a used Soling rig, mostly complete, on a bridge deck 8' from the transom. Each mast would be trimmed at the base to suit, and be deck stepped so it can be lowered. Booms would attach to the tabernacle so no punch loads on the mast proper. Main and Mizzen would be loose footed.

    I would also substitute a narrow cockpit for the current wide one, probably including stowage, or a berth in the quarters. I might work in a shallow "V" at the transom, or more probably a shallow radius to the bottom as it approaches the transom, just to smooth water flow.
     
  8. Angélique
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    Angélique aka Angel (only by name)

    According to the website we have to thank Lilly Morejohn for uploading the drawings and Chris for drawing them and making them public, so thank you Lilly and Chris [​IMG]

    Couldn't find the H-37 among the post #285 links though, perhaps you meant the H-38 Light - Light (LOA 37' 10") ?

    If not, please post a link to the H-37 . . . :)
     
    Last edited: Sep 16, 2015
  9. Sailor Alan
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    Sailor Alan Senior Member

    Thank you Algelique, and thank you Chris and Lilly too. Very fine work.

    It was the H-38 Light-light to which I was referring, my bad for not checking the drawing number correctly.

    My intention is merely to use Chris's cartoon as inspiration, as the design needs to be 'finished' anyway. I am nevertheless mightily impressed by its utility, structure, and practicality.

    I am currently building a 14' racing dinghy to my own design, for the 'Hardware Class' when it materializes. My build has been badly delayed by my passing my right thumb through my router. Bad wood and poor technique, but it is getting better, and could have been much worse, I might have damaged the router!

    Once this is finished, I wanted a larger project, within parameters. Permanent bunk for wife, or grandkids, to rest, enclosed head, headroom, little or no cooking facilities, and full length couches in the cabin. I assumed simple ply construction, ~30' and 8' beam for trailering, and simple, possibly split, de-mountable rig. The water ballast was a direct result of the trailering, and done well, I see no reason why a suitable boat cannot be so built. Incidentally, my 14' design has provision for water ballast, though I suspect the righting moment could be too much for the rig.

    This led me to The Commodores Sharpies, Meadowlark, and Bolger's 'Economy Cruisers' et-al. Gilberj nearly talked me into a Meadowlark, then suggested a ~30' Paradox, a very good suggestion.

    As a follow on to this 30' boat, I was considering other options, and became captivated by the possibilities of something like the H-38 Light-light.
     
  10. Sailor Alan
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    Sailor Alan Senior Member

    An incredibly complex subject, lots of books and papers, and still not as well understood as we might like.

    First let me state i am not an aerodynamicist, but a physicist, though i have assisted in the design and development of many aircraft.

    Interference from the wing/body joint, particularly creating turbulence on the tailplane, was understood quite early on, resulting in some interesting solutions. Both NACA (1915) and Farnborough (1912) in the UK were very early into this science, and at least some of the scientists at Farnborough were involved in sailing, or had friends who were designers. I assume the same was true at NACA. One of the first tasks they worked on were 'near field' effects, as they are called today, and interference drag. The famous NACA and RAF series of aerofoil cross sections came from this early research.

    Very early on, it was understood, correctly, that an aerodynamic protuberance (fin, wing, etc) exiting 'normal' to an aerodynamic surface generated the lowest practical drag with the least fairing. There was, and still is, serious issues when attaching, say, wings, at the lower 'chine' as exemplified by the P-51 and Spitfire as mentioned earlier. The solution in these cases, and as exemplified by most modern low wing airliners, is a long complex fairing at the training edge joint. Though leading edge filets do play a role, they are less important for this specific purpose. Famous examples using this principle of having wing surfaces exiting the fuselage at right angles are; the F4U Corsair, the MiG-15, and the Ted Smith (Piper) Aerostar. In the case of the Corsair, the 'cranked' wing allowed a beneficial aerodynamic wing attachment, a very short (and therefore light) MLG, and a lower than usual hinge line so the folded width was lower given a fixed hanger height.

    Leading edge 'gloves' or fillets, are often used to modify slow speed, and often high speed stall performance. Like a delta wing, this Leading Edge Extension, as it is called in extreme cases, maintains stable flow, lift, over a far larger angle of attack, again like older blended keel bodies.
    Note: delta wings, like heavily raked keel LE's, provide lift over a much greater angle of attack than, say, a straight wing, but at roughly twice the needed surface area. Hence they are more 'forgiving' but less efficient.

    This means, a hydrodynamic foil exiting normal to a boats lower surface, like a classic fin keel, is quite low drag without much fairing at all.

    One issue, presumably demonstrated by Hogfish Maximus, and most other such vertically deployed Dagger Boards, is aeration of the upper foil. The water accelerating around the foil shape naturally creates a lower pressure (partial vacuum), and this can be relieved by water being sucked down the Dagger Board slot. Partially due to general wave motion, partially due to proximity, air will be included in this water. Air, being compressible, whilst the water is not, will cause disturbances in flow around the upper area of the foil, in particular the foil to hull interface. This disturbance will cause significant drag in its own right, and also distribute this aeration back the the rudder in turn. Transom hung rudders also suck air down their sides, at the point of maximum water flow acceleration, about 30-50% chord, and cause their own drag and loss of performance. Frankly none of this matters much unless one is designing for maximum performance within artificial rules. The only consequence might be an annoying slurping sound in the Dagger Board case whilst sailing fast.
     
  11. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Alan,
    Do you have an opinion on the theoretical effectiveness of what Matt Layden calls 'chine runners' (and here), and what Chis Morejohn apparently calls a 'Schell keel'
     
  12. gilberj
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    gilberj Junior Member

    As far as I know no-one has done quantitative tank testing on "Chine Runners" WE know they work, as quite a few of these Paradox/Enigma boats have been built and sailed, including to windward. How efficiently is another question. Drag vs lift?
    Chris can answer whether he was inspired by the Schell Keel principal, or Matt Laydens Chine Runners.
    An opinion in this case is nearly worthless
     
  13. PAR
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    PAR Yacht Designer/Builder

    There is a fair bit of information on the Scheel keel, which has ultimately been proven to not do what Henry suggested it would. He theorized an end plate effect, but in testing it produced more drag than actual benefit.

    I don't know of any real testing other than empirical on chine runners, but those with experience will tell you they work, but only on certain hull forms and not as effectively as other appendage arrangements. Really shallow hull forms don't do well with them, so the boat needs to have some rocker and/or belly to it, to get the runner deep enough to be out of the turbulent surface layers. You can go up wind, but the same hull with more refined appendages, will go upwind much better. They do help hold off leeward skid, but again, with more conventional appendages, you'll experience better efficiency. The only advantage runners offer is marginal upwind abilities, without the inconvenience of an appendage case inside a shoal draft hull. This discounts leeboards. Offset cases can eliminate much of this issue, but if you're looking for a cruiser with unfettered shoal capabilities, given their limitations, runners are an option. As to the question "drag vs. lift" well I think it's best to think of runners as decreased bleed off vs. drag, as there's no appreciable lift.
     
  14. sharpii2
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    sharpii2 Senior Member

    Matt Layden's chine runners work on a different principle than the Scheel keel.

    The Scheel keel is supposed to provide all or most of the upwind lift.

    Keel runners, on the other hand, are supposed to produce a minor portion of the upwind lift, maybe 30 to 40%, with the rudder producing the rest.

    If you look closer at Matt's creations you'll see they had relatively large, deep rudders.

    The same effect can be produed with a deep cutwater, as with the Brittish coble.

    Even my Siren-17 sailed upwind with the board fully retracted and the rudder blade pivoted aft. It didn't do it very well, but it did it quite reliably.

    I had th jib furled and the full main up.
     

  15. Sailor Alan
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    Sailor Alan Senior Member

    Imaginary number, Gilberj, Et-al

    I agree speculation is probably pointless, but I can comment on similar aerodynamic research from the 50's. The keels have anticendant, the bilge keels that predated active stabilizers. Originally, these bilge keels were added diagonally along the bilge to warships and fast ocean liners on the assumption they would resist the lateral, or rolling, movement of the hull in water. They did reduce rolling, but primarily because they trapped stream wise water either side of the bilge keel, and the inertia of this volume effectively increased the damping moment. These 'bilge keels' needed very careful placement to limit drag.

    The rough aerodynamic equivalent would be the 'fence' used to limit span-wise airflow on a swept wing. Most famously used on the Mig-17, which had 3 on each wing. You will also often see them on the sides of 737, 767, A-320 et-al engine cowls where they control, or direct, local airflow around the engine cowling. The most relevant research was that done in the 50's which led to controlling airflow around the sharp corners of lower chines (F-15, Panavia Tornado, et-al), sometimes these are 'disguised' as missile rails.

    The idea is to reduce, or control, airflow around these 'sharp' corners regardless of AOA.

    On this application, we are interested in limiting the water flow from the boat side, to the boat bottom, so preventing, or at least limiting, skidding sideways. To be most effective, these 'fences' should be fairly 'sharp', i.e. limited rounding of the outer edges, and limited fillets at the sides as well. You may know of, and I have seen, reports of Paradox examples having poor windward performance, and I suspect all of these did too good a job fairing and rounding their bilge extensions.
     
    Last edited: Oct 5, 2015
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