Biplane rigs

Discussion in 'Multihulls' started by cutawaycafe, May 15, 2013.

  1. T0x1c
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    T0x1c Junior Member

    I gave the link for the three suppliers, you will find all specs/inertia on their websites.

    Where do you get that 25% figure?
    The Wilderness 1250x is 6.35 T x 5.1 mcc / 2 x 0.99 = 16 T.m, and the profile can take the compression with 100%RM and SF 3. What does Schionning specify, a mast profile, xy inertias or RM?
    The design of the rig is the responsibility of the mast supplier. Each brand has its particular profiles. If you follow the yacht designer choice, the you are limited to the brand/profile he picked-up.

    ??? Where the hell did you see such recommendation? Are the joins glassed over on the Schionning drawings you have? I have never seen any Duflex construction with the joins glassed, could you please provide some links?
     
  2. groper
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    groper Senior Member

    Toxic, first google I tried turned up this, in Germany or Switzerland? .... I can't read German but it appears to have the details you requested on flat panel catamaran build, a good collection of photos in the gallery too... Check it out...

    http://www.ecocatamaran.ch/Willkommen.html
     
  3. groper
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    groper Senior Member

  4. rob denney
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    rob denney Senior Member

    The rig quote you sent me had the supplier and the date whited out. It had no details of what was included. There was no sail spec.

    The mast in the spec you sent me is NF710 (240 mm x 144 x 7.4 kg/ML). The mast on the plans is 241 x 152, 9.4 kgs per m. 1.27 times heavier.
    You are willing to undercut the designer's rig spec, but won't consider changing his hull materials and build methods?

    The join is only 80% of the panel strength. Therefore you either glass it, or the panel is heavier than necessary to make up for the below strength join.
    The drawings have an extra 1-2 layers to 100mm above the waterline, an extra layer spread over 20% of the topsides (presumably including the joins), and a substantial full length keelson glassed to the floor. There is also a note that "all joins have 2 extra layers of cloth inside and out". Presumably this applies to the lengthwise joins, but if one layer (plus fillets) is not enough for these, then why would it be for the athwartship joins?
     
  5. Corley
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    Corley epoxy coated

  6. groper
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    groper Senior Member

    Looks very simlar to Rob Dennys ballestron setups... roller furling headsail on the foreboom and main on the aft boom, the whole thing rotates... Theres a Cat getting around OZ at the moment with 2 of these on top, one stepped on each hull. I only have pics from before it was rigged;

    [​IMG]

    [​IMG]
     
  7. rob denney
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    rob denney Senior Member

    Update on Michael Oneill's Schionning 12m (post #28):

    The boat was launched and was a handful with the unstayed masts. However, it's performance was impressive enough that Mike chopped 3.75m off each mast (originally 15.8m high, presumably with the sail area equal to the conventionally rigged, stayed mast). The boat is now much easier to handle at anchor and on the mooring, but still goes very well. Attached photos are of the apparent windspeed and angle and the boat speed. Not bad for a well loaded cruising cat.

    It has also been sailed in 20-25 knots when it did an easy 18 knots and tacked without problems.

    I will post more information as it becomes available.

    Work progresses on the unstayed folding wing masts for the other 2 x 12m cats.

    rob
     

    Attached Files:

  8. pogo
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    pogo ingenious dilletante

    Decades ago

    German/swedish Designer Heinz-Jürgen Sass buit several cats with biplane-rigs.
    Short description:
    Freestanding rotating mast , profiles were round to oval for flattining the sails while reefing, varying wallthickness for feathering in gusts, wishbone booms.

    in a letter Sass described his solutions and gave all his knowledge , especially how to trim such a rig and it' s possibilities ( please use a mashine for translation):





    Das Parellel-Rigg
    Heinz-Jürgen Sass, Schweden
    Mit 25 Jahren Erfahrung mit Mehrrumpfbooten arbeite ich jetzt die letzten Jahre am Doppelrigg für Katamarane. Ich segle selbst mit einem kleinen Kreuzerkat von 6,5 m Länge und einer Breite von 4 m und zwei Segelflächen von zusammen 33 qm. Diese stehen an zwei unverstagten Masten aus GFK. Sie sind über zwei Alurohre gesteckt, die fest und dicht in den Rümpfen sitzen, so daß es keine Undichtigkeiten im Rumpf gibt, da alle drehbaren Teile über Deck liegen.

    Die Segel haben Taschen an der Vorderkante die über die Masten gestülpt werden. Hierdurch entsteht eine profilierte Vorderkante des Segels. Das Reffen und Bergen des Segels geschieht durch Aufrollen am drehbaren Mast. Das Schothorn ist an einem diagonal geführten Baum fest, der mit einem speziellen Haken um den Mast greift und heruntergezogen wird, wodurch ich den Bauch und Stand des Segels kontrollieren kann.



    Zur Zeit arbeite ich mit der 3. Generation Masten und der 2. Generation Segel, d.h. die ersten Masten hatten Kreisquerschnitt, während die heutigen nur unten noch Kreis-, oben aber ovale Querschnitte aufweisen. Die Wanddstärke variiert von unten 6 mm auf oben 2 mm. Das Gewicht der Masten ist ungefähr das gleiche eines voll verstagten Mastes.

    Der Schnitt der Segel muß, insbesondere im vorderen Bereich, sehr exakt der Mastkurve angepaßt werden. Hierbei kommt mir meine Erfahrung mit dem FinnDinghy zu Gute. Beim Kat treten jedoch ganz andere Kräfte auf, da das Vorliek 9,3 m lang ist und der Kat eine weit größere Stabilität hat.

    Das Unterliek des Segels darf bei diesem Rigg nicht länger sein, als der Abstand zwischen den Masten, da ein Vorteil dieses Riggs darin besteht, daß die Segel bei raumem Wind nach vorn durchschwenken können. Die Segelfläche entspricht etwa der von Groß und Genua eines normalen Riggs. Da es leicht zu reffen ist, kann man ungerefft lieber etwas mehr Segel vorsehen. Dieser kleine Kat läuft sehr hoch am Wind. Es sind mehrere Komponenten, die dazu beitragen:
    1 die Tasche um den drehbaren Mast, wodurch das Segel profiliert wird, 2. die fehlende Verstagung, die den Widerstand verringert, 3. zwei Segel, die einen Teil des Rumpfes als Segeifläche nutzen.

    Bei stetigem gleichmäßigen Wind habe ich einen Kreuzwinkel von 65° ermittelt, gegenüber einem ,, normalen" Boot, das 90° Kreuzwinkel hat. Dieser günstige Wert ist natürlich nur erreichbar bei ruhiger See und großer Aufmerksamkeit des Rudergängers. Die Idee des Doppelriggs beruht auf der Doppeldeckertheorie. Dabei stehen die beiden Segelflächen auf Abstand mit verschiedenen Schotwinkeln. Die Zirkulationsströmung überlagert sich, und das ,,Leesegel" muß immer dichter geschotet werden.

    Hart am Wind ist dieser Schotwinkel an beiden Segeln nicht unterschiedlich, sie stehen so weit auseinander, daß sie sich nicht merklich beeinflußen, d.h. man kann sehr schnelle kurze Schläge machen, ohne die Schotung zu ändern. Bei raumen Kursen läßt man dann das Luvsegel etwas loser als das Leesegel. Wenn der scheinbare Wind etwa quer zum Boot einfällt, muß das Leesegel viel dichter gefahren werden als das Luvsegel d.h das Luvsegel steht etwas quer zum Boot.


    Wird der scheinbare Wind noch raumer, läßt man das Luvsegel etwas nach vorn und das Leesegel quer geschotet. Bei achterlichem Wind werden beide Segel nach vorn rausgelassen, eines nach jeder Seite. Dadurch verhindert man auch das Risiko einer unfreiwilligen Halse. Das Segel schlägt nicht rüber, wenn es etwas nach nach vorn rausgelassen wird. Zusätzlich läßt es sich bei längeren Vormwindstrecken durch eine dünne Leine nach vorn zum Bug sichern. Bei leichtem Wind kann diese Stellung auch bei etwas raumerem Einfall beibehalten werden, nur wird dann das Leesegel etwas dichter gefahren, während das Achterliek des Luvsegels zur Eintrittskante eines ,, Vorsegels" wird.
    Hierbei erreicht man, was beim Segeln am wichtigsten ist. Es handelt sich darum, einen maximalen Luftstrom so auszunutzen, daß die Strömung nicht abreißt.

    Um diesen großen Luftquerschnitt auszunützen, macht man üblicherweise die Masten immer höher und höher, in unserem Fall nutzen wir die Breite des Bootes aus mit dem gleichen Seitenverhältnis der Segel. Wir können also mehr Segel tragen ohne die Segelfläche zu vermindern. Mit den Erfahrungen dieses und anderer Boote würde ich sagen, man sollte die Segelfläche nicht noch mehr unterteilen. Bei jeder weiteren Unterteilung mindert sich die Möglichkeit hoch an den Wind zu gehen. Jedes Segel muß individuell geschotet werden. Es geht leider nicht, wie beim Pyramidenrigg, nur eine Schot zu fahren.

    Der unverstagte Mast hat besondere Vorteile für den Tourensegler: Die Form und Wandstärke geben solche Eigenschaften, ohne daß die Kraft im unteren Teil des Segels verschwindet. D.h. bei böigem Wind reguliert sich die Kraft des Segels automatisch. Durch die Dimensionierung des Mastes kann man dann die gewünschte Eigenschaft für eine bestimmte Windstärke festlegen. Dieser Mast hat auch den Vorteil, daß sehr kleine Kräfte auf den Rumpf ausgeübt werden.

    Das ganze Boot braucht nicht so schwer gebaut zu werden, wie es eine normale Hochtakelung verlangen würde. Diese benötigt ein sehr steifes Vorstag, daß große Belastung ins Boot bringt, um hoch an den Wind zu gehen. Gerade diese Eigenschaft ist mangelhaft an vielen Katamaranen, die selten hoch an den Wind gehen können, weil die Boote, und damit das Vorstag zu weich sind. Gerade diese Eigenschaft hat den Ruf der Kats als schlechte Kreuzer bewirkt.

    Ich würde das Doppelrigg für Familiew und Tourensegler empfehlen. Es ist leicht zu handhaben und hat sehr großen Effekt. Da man nur 2 Segel braucht, ist der Preis auch verhältnismäßig günstig.

    Heinz-Jürgen Sass, Hainngatan 8, 18500 Vaxholm den 29.4.1988

    Source w. pic:
    http://www.multihull.de/technik/t-Sass.htm




    Mister Sass is an active member of this forum, unfortunately i forgot his nickname.

    pogo


    P.S.
    Perhaps i gonna translate the letter this weekend....
     
  9. Manfred.pech
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    Manfred.pech Senior Member

  10. rob denney
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    rob denney Senior Member

    A little more from Mike

    Yes I think I finally have the bugs sorted out now but we're still on the learning curve and frustratingly not getting enough sailing time. The boat goes like a rocket so I can't complain about performance. I ended up cutting a total of about 4 m off each mast which has made a big difference to the windage and handling and manoeuvring under power. Anchoring is not a problem once the anchor grabs and pulls the bow into the wind.. With the masts pointed in opposite directions ,I tie the trailing edges inboard, the boat sits stably at anchor. The problem is before the anchor is set or retrieving the anchor the boat tends to sail away even with the masts feathering into the wind. The masts rotate easily by themselves except in very light wind when there is not enough wind pressure to push them across when tacking.

    I think the masts could have been shortened even more than the 4m without losing too much performance. I settled on the amount I did because it coincided with the sail reefing point and minimised alterations to the sails.
     
  11. Barra
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    Barra Junior Member

    A little more from mike

    Whilst the concept is interesting let's stick to the facts.
    Mike also states from DIY forum that " it's not simpler to sail than a standard rig.... More complex to gybe, set sail etc ".

    By reducing the mast height by approximately 4 meters the sail area must have been cropped by around 40 sq m total? (5.5 m boom length?). This leaves a ridiculously small area
    For this boat.

    The apparent wind speed direction , boat speed details you show are unbelievable. Both give a true wind direction approx beam on or even aft of the beam and the left hand instrument shot shows the boat Sailing at almost twice true wind speed.

    For those that have difficulty with the maths, try google for apparent/true wind converters.

    Interesting concept though, still asking the question , why? Surely by reducing the mast height one is just delaying the inevitable regarding the forward stepped wings causing the boat to sail its ground tackle out of the sea bed. Having anchored behind a cape cod cat boat ( extreme example of fwd stepped mast) near Wilson's prom during a late winter storm, and watching it sail through 180 degrees before breaking free and reeking havock , I'm not sure how one overcomes this problem.
     
  12. groper
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    groper Senior Member

    As to the apparent wind figures - they seem ok. The first is a little hard to believe, as the true wind speed is calculated as 2.6kts from perfect beam reach. This means the boat is doing nearly twice the wind speed- which is the part which is hard to believe. However some error in the anemometer reading could be to blame for this, although nothing about these numbers suggest its impossible. Racing multihulls exceed these numbers all the time.

    The second set of data is more believable, as theyre on a broad reach 109degrees the true wind speed is now 6kts - they are doing 5.2kts boat speed which seems about right for a decent cruising multihull regardless of its rig type. so whats the problem???

    Second point of contention, is the quote from michael - youve deliberately left out information he provided which clarifies his statement about the rig ease of handling. That is - he was comparing it to a roller furling headsail and the ease of which they are unrolled and rolled away. Now you need to compare apples to apples here - theres no reason he couldnt have used 2 roller furling booms for his biplane sails - which eliminates his gripe about packing up and unpacking the sails from the lazy jack stowage and boom covers, and also having to hoist the sails by hand via halyards everytime you wish to set sail. So its not about sail handling once underway and the ease of which the sails can be tacked, gybed, run upwind or downwind etc... In fact, he specifically mentions how easily he can tack back and forth climbing upwind without having to touch anything to do with the sails - the whole rig is self tacking. Now you cant do that with a roller furling genoa, a little self tacking jib maybe, but then you dont have the sail area your concerned about... not to mention the hassle of hardware and ropes across the foredeck that goes with them.

    So theres several reasons why the biplane rig is appealing in the above regards.

    As to sail area - your also ignoring what he said about this also, and that is the boat always felt overpowered with the original mast height and he chopped them down by nearly 4m to the first reefing point to avoid alterations to the sails. Clearly he would have been sailing around reefed all the time, so why carry the full mast height when your not using it? He also says that the boat still sails very well with plenty of power with the lower masts - its just that now anchoring and mooring is not so stressful with such huge wingmasts making life difficult.

    Its his boat, and im sure he would have considered very carefully before chopping down his very expensive carbon masts... The original mast length was 125% of the LWL - now 100% LWL, seems alot more reasonable to me...
     
  13. Barra
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    Barra Junior Member


    Ok, a couple of points. Its a cruiser not a racer so sailing at close to twice wind speed with not much more sail than a seaslug caravan aint going to happen. So if one instrument shot is BS then surely the other is in doubt to.

    Maybe the engine was still in gear?

    Secondly there is no headsail so slashing the mast to way less than the standard stayed mast design is a little unusual to say the least. As the saying goes "there is no substitute for sail area". Your 125% to 100% appears to ignore this. Compare sail area to displacement at least, for the standard design, or even height of centre of effort. Does the bi rig carry kites down wind?

    As for consideration before acting, the article in the Aus multihulls seemed to indicate he had very little sailing experience on large cats , so I'm not sure all the facts have been considered. Based on a few jollys around the bay?

    How does one handle this beast in a marina with two wings aloft in a stiff breeze. Interesting times ahead I fear.
     
  14. Richard Woods
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    Richard Woods Woods Designs

    These last two posts made me go back through this thread. I see once again Rob is putting words in my mouth

    I assume he is refering to this thread

    http://www.boatdesign.net/forums/multihulls/carbon-masts-lightning-26861.html where I quote from Lat38 of the effects of a real strike (on a Freedom 40 monohull, so nothing to do with me). No axe to grind - I don't sell carbon masts, but I have been hit by lightning. It is also interesting to read the posts further down the same page. For example, this one - again not by me

    "In the early 1980s, hobie switched the top of their masts (about 8') to carbon/glass composite for safety from overhead power lines. The halyard was changed to rope, so there is no electrical path on the mast. After the change over, boats seemed to be struck by lightning while sitting on the beach or moored to a dock. (I never was aware of one being struck while in use) The composite section usually exploded, with minimal damage below it. Just an observation, but the damage was impressive, and I never saw it happen to a solid metal mast. Bruce"

    But you should check Eric Sponbergs posts on the subject as he's the real expert. As is Ewen Thomson of www.marinelightning.com

    Just for comparison purposes, attached you'll see a rather poor photo of another windspeed V boatspeed shot. This time of a 32ft live aboard cruising catamaran (my Eclipse, 13 years ago). Complete with rigid dinghy in davits, solid fuel heater etc.

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     

    Attached Files:


  15. groper
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    groper Senior Member

    It doesnt have to be BS, a simple explanation for the first shot could be just a lull at the instant the pic was taken - the boat still has momentum but the wind speed indicated was lower than the average winds the boat had to maintain that speed... who knows, but at the end of the day the numbers are not "unbelievable".

    Now back to your sail area obsession... Schionning designs publishes the std rig designed sail area @ 95sqm (main and headsail). The new mast height above deck is around 12m. Dont know the exact cut of the sailplan, but it looks slightly square topped, so the area of 2/3*height*boom+mast seems reasonable. At this size, the sum of both sails including their wingmasts would be just under the designed area of 95sqm, down to around 90sqm. I still dont see the problem? Michael is happy with the way it sails and its performance is meeting his expectations. Seeing as he built it himself, doesnt that mean it does what he wanted it to and therefore its a great success story?

    Richard,
    i cant read that pic you posted, can you spell out the numbers for comparisons sake?
    Cheers...
     
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