A Frame Masts

Discussion in 'Multihulls' started by Gus7119, Jan 20, 2016.

  1. pool
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    pool Junior Member

  2. Gus7119
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    Gus7119 Senior Member

    Thankyou for posting these wimd tunnel results. Am I miss reading these rsults r do they infact defunk what most of the theoretical issues raised are? And are they disputable? Cuase if they are saying the A frame is a good thing then I can see the comments like but there wrong they didnt do this or that. But I could be wrong and miss read it.
    Again very interested in what the experts here have to say. Thanks again I hadnt seen this nor do I think had many others.

    Cheers
    Gus

     
  3. Gus7119
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    Gus7119 Senior Member

    Cheers mate. How good does the rig look. It really suits a cat plus if you read the wind tunnel tests they seem positive. Didnt like the look of the helm till they bought out the food. Then I thought yeah thats not nad cabin stern helm and cockpit forward to see everything. Dont know if you could do it on a 35 to 38 lole Im building but still.
    I hope we hear back from the experts after theyve read wind tunnel stuff love to hear their thoughts. Join us at the csc 30 forum weve got a great group there working towards a build. Its an old post thats come back to life.

    All the best
    Gus:p

     
  4. CT249
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    CT249 Senior Member

    Gus

    You asked for "anyone with any experience OR KNOWLEDGE of A frame rigs" in your original post, so why do you get narked when people reply? If you only want people with first-hand experience to reply then please say so clearly, instead of slagging off at "one track minds".

    All I was trying to do is pass on what I was told first-hand by people like Lock Crowther and his staff, who had done the calculations on such rigs and who were willing to run through the issues and figures for me, and had raised some issues (like sheeting angles and sail collapse). If you just want people to say "these are fantastic, they have no drawbacks whatsoever" then just say so.
     
  5. waikikin
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    waikikin Senior Member

    Hi Gus,

    I think you should definitely have an A frame mast, once built you can sail side by side with the other CSC 30s & test the results and enjoy the advantages. I think very good for travelling under bridges with self bracing on lowering with the spread between tabernacles. Some of the negatives are offset as inefficiencies that become irrelevant when most sailing cats are motor sailed(as any sailboat with a schedule), that you can sneak under the bridges to the cheaper and more protected moorings... past Ryde road and rail... up the Hawkesbury.... under Tom Uglies & Como rail on the Georges, maybe even up past Woronora road bridge let alone our East coast rivers. I say go for it..

    Regards from Jeff
     
  6. upchurchmr
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    upchurchmr Senior Member

    I do too.
    Especially if there will be other boats to directly compare the actual performance on the same heading.
    Its a great experiment and its your money not mine.

    But I would really like to know the answer in practical terms, not in arm chair sailor terms - that doesn't mean everyone with a comment.

    Please, will you actually report what you get?
    Either positive or negative, an actual comparison report would be worth more than all the opinions (even mine :D)

    I might point out that there never has been a negative report in the years I've been on this forum. The whole subject just gets dropped.
     
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  7. Gus7119
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    Gus7119 Senior Member

    upchurchmr have you read the wind tunnel report. Thats the best comparison. As stated its a cruising boat and from real life users has some real advatages. But no experts that really dont like change will do a side by side once a post is made from a user or designer thats work or owns one of these rigs.
    Itd be great to get their ideas about wind tunnel test. Im leaving it for a few days to try get some thoughts. But if the other forums are anything to go by they seem to stop posting after info as mentioned above. Its a shame because Im very happy with sloop rigs. They are a pain sometimes but I dont know that there can be much more development to the design as its fairly tweaked.
    Anyway hope we get some good discussion a reasonable comparison.

    Cheers
    Gus
     
  8. Gus7119
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    Gus7119 Senior Member

    CT249 thanks for the post. I can only find one post by you with three questions Ill answer one right now its not a racing rig. And you didnt mention or give any refrence to where or who the data was coming from. Also that in your very first line you answered your own question. I dont see any info in three questions. There's no slagging off at all. Offense is only taken when someone points out something you dont like. Ive stated Ill take any comments but real life and comparitive data beats every discussion thats been had. Ive been fairly clear if you read through this forum.
    I said I wasnt intrested in the same old arguments about load and stays as every rig has these and every rig is compensated for. In fact some have made some good points. But your under the misconception that we are coming at this blind. Theres been forums and no one has mentioned the wind tunnel except once before I think. And each time a user asks for assistance in a comparison their told the dont respect the experts. I have full respect as you cant know everything. But whats th point when being asked for comparisons and saying your an expert and then having data prove otherwise thats scientifically collected. Plus as in the 80s there is still this stupid mono cat hatred thing.
    So sorry for anyone who offended, but dont say your an expert then make a statement like a 30-35 foot cat isnt able to be ocean going or is even to small as a coastal boat as an example of one guy who says hes a cat expert and then get offended and stops post because there are 1000s of cats crossing the globe of that size.
    If their offened sorry get a thicker skin. Dont post but nearly everyone thats intrested in trying for something different is asking the same thing and we are made to feel like our opinion is ridiculous by people who have no experiance wiyh rig have not bothered to read the data and then say respect me Im an expert. Well sorry buddy but I and many others are realky intrested in tracking down comparisons and real life data not just because a sloop rigs proven there not on race boats and the load is diffrent. It a cruising boat!
    Good day sir.
    Gus
     
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  9. waikikin
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    waikikin Senior Member

    I'm getting the impression from the wind tunnel "as tested" models/pics that the "traditional" style rig appears to have sails not going to full hoist of the mast, there was some other tables for "equal" height and sail area models but assuming these weren't test, is that what other see?
    Jeff.
     
  10. upchurchmr
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    upchurchmr Senior Member

    Gus,

    If you think a wind tunnel test is the best comparison, you are sadly mistaken.

    I work in Aerospace where wind tunnel tests are just one of many pieces of information used for design.
    When the aircraft gets into production and flight test there are inevitable changes required because wind tunnel tests are full of scale errors, simplification, and missed assumptions.

    The "experts" you so singlemindedly criticize would love to find a new fact they can confirm. They will then take that and turn it into new successful designs they can use to improve their reputation and fortune.

    You also ought to quit trying to force others out of "your" thread, because this is an open forum.
    Everyone has the right to state their opinion, no matter how right or wrong they are, and no matter what you think of them.

    OBTW, that wind tunnel report has been referenced at least 3 times (3 other threads) that I can remember. You need to quit assuming everyone but you is completely stupid.
     
  11. champ0815
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    champ0815 Senior Member

    If I read (and looked) correctly, the tested configuration is different of the SMG cats since in the test the mono model was equipped with an aft standing A Frame Rig leaning forward. A slight difference, but it allows for the overlapping double jib configuration most successful in the test.
     
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  12. saltdragon
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    saltdragon Junior Member

    Perhaps a couple of Guys could get together and experiment with two beach cats of the same class, rig one with a comparable A frame mast and sail against one another. Perhaps not totally applicable to cruisers, but it should give some real life results.
     
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  13. waikikin
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    waikikin Senior Member

    Great point Champ, the attraction is the A/ sheerlegs simplicity, I'm sure this can be successful but as noted by knowledgable people must come at an inefficiency of weight and windage... perfectly logical- more largish elements of structure must come at a cost, not neccesarily in dollars as the A "might" be put together at a low cost with the right backup. I feel the attraction is in the strength and self bracing for lowering, these can be achieved on a single mast with pivot geometry in line with lower shrouds and tabernacle but pretty cool on the A. The aft mast"wishbone" seems to me a complication with the "jumper" arrangement when lent forward a big multiplier on compression loads.
    It would be pretty cool to find a cheap platform or two same & go head to head out on the water with them.... just for fun:)

    Jeff.
     
  14. hump101
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    hump101 Senior Member

    I've been looking at A-frame masts, but from a slightly different perspective in that the forward shroud is also a compression member making a tripod, but the tripod only goes to shroud height, and a mast is then supported at this point, extending from deck to 50% further up. The reason I'm looking at this is that I want a rig in which the main can be dumped and feather at any heading, and with a tripod where the base of the mast is moved out to the leeward "shroud" base, this can be achieved. It also permits lowering of the mast and tripod from onboard, and reduces component lengths to fit in a container like the rest of my boat (2 piece mast section).

    Anyway, what is interesting is that, with rotating wing section tripod legs, the weight and air drag is not much different to a conventional rig. The mast section doesn't carry any compression other than downhaul, so can be relatively light, and the short tripod legs need little additional bracing.

    I appreciate that this is a different arrangement from that proposed, and is also a theoretical exercise at this stage, but this arrangement is certainly competitive compared to a free-standing biplane rig, which would be my alternative.
     

  15. Gus7119
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    Gus7119 Senior Member

    Sorry havent tried to force anyone out. Its only now we are getting data and comparisons no pay out of experts as they are experts. Again and really sick of having to say it COMPARISIONS and real life data most helpful. Your post helpful and I know yourright. I am in no way trying to make the A frame the saviour. I guess seeing as though some people are only readding replies to the post that have been made on other forums and what many see as unhelpful jabs I will make a list of stuff Im intrested to find out in the hope that it stops people taking offence where none is intended;

    1; with users of the rig reporting that ON CATAMARANS they find it easier and able to adjust for wind direction and speep are these in anyway backed up

    2; do the disadvantages on a CATAMARAN out way benifits

    3;"are the wind tunnel results s b owing there is some benifit to a rig like this b; and if so in whag circumstanses

    4; is it poosable that designing for the load diffrence that a rig like this could be useful on a CRUISING CATAMARAN maybe not the vest rig as a sloop rig might be but still provide so assistance for those novice sailers.

    5; while we have been given reasons is there any way to have a comprehensive comparison made up or is it to difficult.

    6; do the experts belive that there is no way to make a rig like this work to a spec that would be accept. Or do the load distrubutions negate anything fessable to make it work.

    7; without using a mast or boom furler is there any design that anyone iscawarw of that makes use of a furler for the main.

    8; with a wishbone attached as a replacement boom do you get a better shape on luff.

    Now last time. Ive sailed 40yrs since 5yr old starting in Manly juniors. Love the sport love the experts and follow their advice when its backed up. Love the new tech thats come to sailing and sailors to make it morw competitive while reducing the cost allowing many more people to get on the water.
    Yep no arguments here Sloop rigs are the best and for sailor easy to use. But once you get old or are new there can be issues with use.
    Again I mean no offense and all experts are welcome. But if your going to call yourself an expert, and I dont mean those with credentials, please be careful not to make statements that almost every sailor knows are not true.
    This like all other forums on the matter has turned into another slanging match thats not helpful, especially now that the real info is coming in, and no it may not all be correct but to collect it and compare it is helpful.
    Cherrs to all those scouring for info and real life reports and thankyou to all the experts whove wayed in. I am very happy to be corrected and admit when Ive been wrong but there need to be able to be a back and forth and im my own experience if you ask a question becuase your intrested in a post your told 1 your either just wanting yes men or 2 why are you bothering asking me if everything I tell you you question.
    I have questions because I seriously dont know and love to learn. I feel I been fairly clear on wanting to get to some answers without degeneration into the void like other forums about alternative rigs. I should also add any other rigs that may be interesting would be cool to look at.

    I think Ive covered most of it again (except I hadnt included a list before. That may be added to by anyone).
    Cheers enjoy
     
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