Yrvind

Discussion in 'All Things Boats & Boating' started by Manie B, Aug 16, 2011.

  1. sharpii2
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    sharpii2 Senior Member

    Actually, my handicapped brother has something known as a "Spork" It has fat, triangular tines cut into the front edge of a spoon.

    Sven's would be better for dieting, however ;)
     
  2. Angélique
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    Angélique aka Angel (only by name)

    Congratulations on your birthday Sven . . :)

    Godspeed in life, with the build and with the voyage [​IMG]

    -- Sorry I'm a day late, I had no internet coverage yesterday. --
     
  3. Manie B
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    Manie B Senior Member

    Happy Birthday Sven

    Happy birthday Sven and may you have many years of happy sailing :D
     
  4. Angélique
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    Angélique aka Angel (only by name)

  5. sharpii2
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    sharpii2 Senior Member

    Interesting vessel. I wonder what is was used for. Was it a river boat?

    The reason I picked the pram hull form for FOOTBALL is so the ends would be very similar. The advantage to this is, when the boat is hard pressed and heeled over, it keeps its balance. Its fore and aft trim change very little.

    A boat with a wide stern and a pointed bow tends to pitch forward, when hard pressed under sail. This immerses the the bow further and moves the Center of Lateral Resistance (CLR) forward. This can cause the boat to want to round up into the wind, which is not all that desirable for a boat designed to sail primarily down wind.

    This is one of the reasons we see boats, designed and built in the days of working sail, with their maximum Beams Further forward, especially in Northern European waters, where blustery conditions are a fact of life.

    When designing a ten foot boat, of very heavy displacement, it is difficult to put the maximum Beam that far forward, as the bends will be quite sharp. Also, the bow will be quite blunt as well.

    John C. Hanna took the SPRAY hull form, reduced its Beam, but moved the Max Beam further forward. The result was a very blunt bow and a boat that had a reputation for being quite slow.

    Moving the Max beam further aft cures those ills, but creates the ones mentioned above.

    I actually drew a concept that was very similar to YANKEE GIRL. So similar, I named it the G.S.-10 in honor of the designer/builder of the original. I moved the Max Beam aft a bit and went with a wider stern, to make her a little easier to build.

    Other than that it looked a lot like YANKEE GIRL.

    But I soon realized I might have control problems when the boat was hard pressed.

    This didn't suit my plan to set sail without a self steering vane or engine.

    I figured such weight and complexity should be best left ashore.

    That's when I started thinking about helm balance and that's how the concept for FOOTBALL was born.



    This is one of the reasons we see boats built in the days of working sail with their maximum Beam
     
  6. MoeJoe
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    MoeJoe Junior Member

    What do you think of Yrvind's "next boat" design? I think it has a lot going for it, sure has plenty of redundancy with twin rudders, twin leeboard, twin masts and sails :)
    With all of those variable wind & water surfaces it should be easy enough to self-steer/hold a steady course. For me I'd probably need to scale it up a bit
     
  7. sharpii2
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    sharpii2 Senior Member

    I wonder about its high free board combined with very small sail area. Small sail area is a recurring theme in his designs, most of which have crossed open water.

    This new design is different in that it has a lot of topsides exposed to the wind. Based on the pictures, it appears that each sail has 6.5 to 7.5 sm of sail. The topside area (in profile) seems to be around 5.2 sm.

    In essence, the hull is like that of a cargo schooner sailing in ballast (no cargo)

    This combined with a very high Aspect ratio (AR) lee board might mean trouble in a blow.

    The lee board could stall and the boat could become unmanageable.

    As for self steering, the twin sails aught to work quite well, if they can be kept from fouling each other, but I'm skeptical of the idea that sailing dead down wind is the best course, when sailing down wind.

    The boat could have a strong tendency to roll, especially with its shallow, flatish bottom and no keel to dampen such roll. This roll could be both wind induced and wave induced.

    Mitigating that to some extend can be the shortness of the rig and a relatively low center of gravity.

    Balancing the boat to sail upwind or across the wind may be somewhat more difficult than it appears.

    Two reasons for this:

    One, there is only one sail and apparently only one place to step the mast.

    Two, the high AR lee board will likely stall long before the lateral area of the hull becomes effective, so, when it's deployed, only the lee board can be counted.

    The lee board also seems to be ahead of the Center of Area of the sail.

    This is another recurring design theme.

    In order to keep the bow from weather cocking into the wind, some weather helm must be used.

    No problem is the rudder area is up to the job.

    The only question is how much? And how much does that amount change with changing hull and wind speed?

    If it were my boat, I would set the two sails in tandem, always, and play them off each other by differential sheeting and differential reefing.

    The lee board would only be used for sailing up wind, and down wind sailing would be done in a series of down wind tacks.

    All the same, it is very heartening to see somebody doing sailboat design work that is not focused almost entirely on performance.

    Reading about the exploits of the original BRIS inspired me to do design thinking ow my own, on resilient, shallow draft sailboats that can handle blue water.

    Here is an example. (see attachment)
     

    Attached Files:

  8. sharpii2
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    sharpii2 Senior Member

    Ooops! Just look at the Yrvin site again. Noticed that the sail area was stamped on the sails in the drawings. They are only 4.6 sm each.

    This makes the boat, under a single sail even more under powered.
    with one sail, the boat has an S/D of only 5.31. An S/D of around 15 is considered about normal. An S/D of around 10 can still be called a sailboat. Sailboats with S/D's in the high single digits have made successful ocean passages.

    But a sailboat with an S/D of only 5.3? Especially on a boat with almost the same amount in topside profile area.

    I am a believer in small rigs, but even I have to wonder if this is below some absolute threshold between sailboats and sail assisted boats.
     
  9. Manie B
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    Manie B Senior Member

    sharpii2 - excellent posts and some very good analysis!
    thanks, I concur.
     
  10. sharpii2
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    sharpii2 Senior Member

    Memories of BRIS

    Just got done reading Sven's latest post on his web sight.

    He said the original BRIS had only 4.0 sm of sail.

    With all due respect, I think he is mistaken.

    IIRC, the original BRIS was built in a cellar in Sweden. She was about 6.1 m long and about 1.8 m wide. She had a flatish bottom with a well rounded turn of the bilge.

    From this point, my memory gets a bit foggy.

    I think she left Sweden with tandem lug sails and a centerboard.

    Once she reached the USA, my memory gets a little clearer.

    I think "Cruising" magazine did an article on her refit. This article had photos.

    She was refitted because she was found almost frighteningly tender.

    The refit went as follows: (IIRC)

    1.) The centerboard was removed and replaced with a ballast keel of about 270 kg.

    2.) The lug rig was replaced with a masthead sloop rig. The mast towered about one boat length above the deck.

    3.) A self steering vane was very cleverly attached to the back stay.

    I think the stated sail area was around 18.5 sm. This may have included a 120 jib, which was very customary at that time, for plain sail area.

    Except for her raised deck cabin, her double ended hull, and her lack of a cockpit, she looked very conventional.

    It is possible the mast looked taller than it really was, and I remembered the stated sail area wrong. But I would swear she had at least 14 sm. 4.0 sm would have meant a comically short mast.

    The masthead rig proved quite strong, IIRC.

    BRIS was turtled at least twice, on one of her voyages. Each time, she righted herself with little or no damage. The damage, IIRC, was a rip in the main sail and some water shipped on board due to a hatch left partially open. This impressed me a lot.

    The masthead rig was found difficult to balance, IIRC, and the boat was considered too tender to take on the Horn.

    A new BRIS was planned for this endeavor. She was slightly shorter but considerably wider. She had a long keel, deeper than the original BRIS.

    She was drawn with a mast that towered considerably taller than one boat length above her deck. She was to be fitted with a masthead cutter rig, with a long bowsprit. The cutter rig, IIRC had three jibs.

    The rig was found to be too tall and was cut down, with a considerable loss of sail area. But she was probably still in at least the low teens in S/D. She rounded the Horn twice, but problems were found with the aluminum alloy she was made of.

    IIRC, it was with BRIS IV, the small sail area trend started. She was made of some foam/plastic composite, which was quite resilient. She was to have tandem sprit sails, with a top sail on each.

    She was found too tender for the two sails (four, including top sails), so one mast was eliminated.

    She was approximately 4.5 m long and about 1.5 m wide.

    I don't remember her displacement but I do remember calculating her D/L to being around 7.5. She sailed across the Atlantic at least once, with two people on board.

    TANDEM vs BIPLANE

    During the early days of flight, the engines were not all that powerful for their weight. For this reason, some of the earliest pilots were women (they are generally lighter than men). The biplane configuration was then used almost exclusively. The reason for this was weight savings. A biplane can be built quite strong for its weight, because of the cable truss like structure made possible with the paired wings.

    For this reason, the actual wing spars could be made much lighter (with turn of the 20th century technology) than a single one for a monoplane.

    The price for this was less lift per total wing area. A lot less lift. I read that a biplane can have a wing span that is about 20% shorter than a mono with the same wing chord. This means the total wing area is producing only about 63% of what it could be, with a single wing.

    So increasing the wing area by 60% (with two wings at 80% of the original span) produces only a 20% more lift.

    With a tandem sail set up, the aft sail area is often discounted by about 50%. But this is usually when up wind sailing and running are taken into account. Reaching you get pretty much the full value.

    So, if this is true, the biplane rig gets you only about 63% of your total sail area, where the tandem will get you about 75% at least.

    The tandem rig has one other trick up its sleeve.

    Even if unstayed, it can fly a very light drifting sail from the top of the mizzen mast. It could be used only in very light winds, as it's luff will start to sag badly, with more wind.

    Why not compromise between the two?

    Why not have three steps for two masts?

    This way, the mizzen mast (which will be quite short and light) can be moved up front, to be paired with the fore mast, when running down wind.

    I see two advantages with this approach.

    1.) The two masts don't have to be off set so much on the hull. They need be only far enough apart, so the two luffs don't touch.

    2.) For this reason the mast steps can be much stronger.

    As they are, I worry about a wave induced capsize, while under sail.

    The swiveling mast steps would be quite vulnerable, as they are not true tabernacles. The boat could come upright without both masts.

    The masts, still attached to the yards, could be hauled back in, but re-stepping them could be a big problem.

    With my three step proposal, you could have three tabernacles. One for the main mast and two for the mizzen.

    The axle for the mizzen would simply be removed and installed in the new tabernacle, when the mizzen is moved.

    It is always a pleasure communicating with a life long hero, no matter how indirectly.
     
  11. Westel
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    Westel Senior Member

    Yrvindt says the he seldom sails dead downwind, he allways prefer some angle to sail by.
    He obviously likes the time spend on the ocean as he never made a "performance" boat to move "fast".
    On his last boat the sail was so small that it completely looked out of proportion.......but he allways make it !!!

    His last design resembles much the English narrow channel boats.....
    H. Lindeman crossed the Atlantic in a dugout canoe so a narrow long balasted hull is capable of doing it.......he also crossed the atlantic in a folding kayak.....which doesn't mean ofcourse that such a vessel is the "perfect" sea going solution LOL !!

    Yrvindt sure changes his mind a lot during his build, wether that's good or bad is a matter of opinion I guess.
     
  12. Angélique
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    Angélique aka Angel (only by name)


    Looks like you missed or misinterpreted this part . . . ‘‘ I could have put up more sail but chose to use only 4 square meters. ’’

    To me this means Sven writes here that the original BRIS had more sail area available of which he chose to use only 4 square meters during the described 1974 Doldrums passage, the further info about this passage is based on the 4 square meters of used sail area there.
     
  13. sharpii2
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    sharpii2 Senior Member

    I see.

    But I remember, or at least I think I do, him commenting in the account, he wrote back in the '70's, that he wished he could add more sail aft, instead of adding a bigger head sail.

    An average of 3.5 kts is not that shabby for a passage through the doldrums, for a 20 ft boat.

    It will be interesting to see how this ideal boat works out.

    It has a high Heft factor, Hf, which I think works well for a boat with a small rig.

    Heft factor is a term I invented that compares Beam, rather than Length, to Displacement.

    A boat can have a very high Hf, but still have a very low Displacement/Length ratio (D/L), as this proposed boat does, if it is very narrow for its Length.

    The Heft factor is calculated as follows:

    Volume * 20/((Length * (Beam^2))

    The Hf for this proposed boat is:

    0.806 * 20/ ((5.8 * (1.1 ^2)) = 2.30, which is a pretty high number

    An IOR influenced sailboat, by contrast would have a Hf of around 0.75.

    The D/L of this boat would be about 118, which is a pretty low number.

    A boat with a high Hf should have a great deal of momentum for its size and should perform better than expected with a small sail plan.

    A boat with a low Hf should be able to carry a much larger sail plan for its weight, but may be easily stopped by a head sea chop.
     
  14. sharpii2
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    sharpii2 Senior Member

    Just read Sven's latest post about his Yervin 10 boat.

    I see his reasoning for the biplane rig.

    Down wind, it will certainly be superior to a tandem one.

    Weather raking one mast forward and another one aft will actually get more effectiveness out of the rig, when reaching, remains to be seen.

    At the very least, he will have a spare mast, if he finds the second sail doesn't help very much, when reaching.
     

  15. sharpii2
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    sharpii2 Senior Member

    Having studied Swen's latest web site posting, I feel I should make some comments.

    He has a model with two masts, that are side by side, that are actually stepped on the extreme edges of the deck.

    Apparently, each is on an axle, so it can be pivoted fore and aft.

    The yards of both balanced lug sails are attached to the masts with only the halyards. The booms apparently are to be tethered to the deck, in the usual balanced lug fashion.

    But here it gets interesting.

    To set one sail further aft, the model shows one mast canted pretty far aft, with its sail having its boom tethered to the deck there.

    The problem I see with this is that the mast is acting more like a crane boom than a support column.

    This will not only put a lot of bending stress on the mast, but will also put tremendous stress on the pivoting axle and the locking pin.

    This mast, if it isn't massively strong and stiff, will certainly bend like an archery bow, just as it would if it had a jib and no back stay or back drifted shrouds. Such bending will likely cause the sail to sag and bag, if it has any three dimensional shape to it.

    My biggest concern is that the axle and locking pin may not be up to the job. There is also the chance that the mast could bend too far and snap.

    Since Sven does not want a hatch in the aft portion of his boat, nor does he seem seem to wish to come on deck, I think it is probably best that he revert to his original plan of having his twin masts in standard style tabernacles, side by side.

    Set up as such, each can be lowered independently from the other, and he will be free to set his sail from either the leeward or windward mast, or set one sail on each, while sailing down wind.

    Another option would be to put the tabernacle for the 2nd mast just aft the hatch and to the Port side. This way it will be very easy to work from that hatch, as Sven's right hand will be on that side when he stands in it, facing aft.

    This will make it possible to set both sails on a reach or a tack, but will not allow enough clearance for the boom and yard of the forward sail to pass the aft mast.

    This would definitely not be a good set up for short tacking. :)

    It will probably only work well on a Port tack or Port reach. On a Starboard tack or reach, the Port stepped aft sail and mast will only be in the way of the Starboard stepped mast and sail. This is especially true when sailing on a Starboard tack. On a Starboard reach, the fore sail could be dropped, ported around, and reset so its boom and yard are to the lee of the Port stepped aft mast.

    This sounds and probably is too clumsy to be worth considering. So the side by side masts, with sturdy tabernacles are probably still the best system.
     
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