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Post by mart814 on Dec 12, 2009 17:27:21 GMT
I have found the recent newbuild thread very interesting; and New Boy's points on waterline length are also interesting.
I note that John Claridge wrote a very informative article in the Autumn Chrysalis - he says "Having drawn what we considered to have the maximum waterline length permissible we were very surprised to see the BMBA hull, at the dinghy exhibition with a distinct bump in the bow profile, which extended the waterline even further than that of the original Edes of March shape".
I think the differences are likely to be quite small between "legal" designs. The measurement stations at the bow are quite closely spaced and the tolerance is about +/- 12.5mm, so there isnt that much scope for bending the rules beyond what has already been achieved by others.
Who designed the BMBA hull? Has anyone compared Asbo to the BMBA hull - it would be interesting to know the differences.
Regards Mart814
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Post by graham7 on Dec 14, 2009 0:04:26 GMT
This issue was raised at the Agm and the committe have been working on this issue since and will publish findings and full explanation in the next Chrysalis out early Feb 09. Ian Howlet designed the Bmba boat as the current thinking on a fast shape ,the design was done openly and plans are currently available to BMBA members with the standard class plans,It has been measured by two senior RYA measurers and passed on the critical station10. Colin Hall and myself have lofted templates of what we consider constitute the limit of fair curve,the Bma,Claridge and my own boat 871 all conform to these templates and we can see no advantage exceeding these . My latest boat reverts back a more even curve having lines by another top designer. Asbos bow is of a different profile to the BMBA boat as its keel has less rocker and when this is projected forward produces a different bow profile , both gauges fitted ASBO a tad easier than the BMBA, It is my opinion that these two boats go as far as reasonable in bow profile and have minor advantage in some conditions but as with all things in design downsides in other conditions.ie slightly faster straight line speed in dead flat water but slower through any waves and manouvering. Regards Graham
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Post by Meat Pie ... on Dec 14, 2009 16:28:52 GMT
A little typo methinks Graham.... 870 was your last Boat.
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polyfiller
Mothist
14 x winner of the annoying git on the water award.
Posts: 126
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Post by polyfiller on Apr 25, 2011 22:38:41 GMT
Having joined up to the forums I thought I'd embark on some catching up and some difficult to resist necro posting ....... so ........
I read with some considerable concern the above. If there is / are discrepancies between an optimal design from JC and the BMBA boat, then something must be wrong somewhere. IIRC the fair curve template allowed zero room for interpretation - either the bow sat inside and measured or it didn't and therefore couldn't be a moth.
Reason for the concern is that everyone needs to remeber that the bow curve debate almost killed the class in the early 80's..... by virtue of make all boats built with less agressive bow curves obsolete overnight. Given that many boats built after 743 had some form of extended bow profile, the impact this time around if the ultra new boats having a more agressive bow will be less than when Ides of March first appeared. However Graham's comments about bow profile and therefore water line lenght being a minor advantage are a little cursory. I doubt there are many left around who actually sailed against the Ides. Goffo did, I did. It was like sailing against a laser. Yes there were many aspects to the boat speed (modern rig, sails etc.) However, having transplated a complete JC rig onto other hulls in the past I can vouch for the fact that nothing went upwind like a JC and nothing planed faster. Only one weakness I ever found was that getting up on the plane when there are any waves was easier with more rocker and less bow i.e. Skinneer shape.
I have no vested in the view I express above, just a conern and I really do hope that the new BMBA boat, and the new JC for that matter, does not require everyone to rush out and buy one in order to compete.
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Post by the black pig on Apr 26, 2011 13:42:09 GMT
roger has just won our open at leamington sailing an old skinner boat with a tin rig. no new bow curves or carbon to be seen on that boat.
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polyfiller
Mothist
14 x winner of the annoying git on the water award.
Posts: 126
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Post by polyfiller on Apr 26, 2011 15:02:58 GMT
There will always be anomilies to the impact of hull speed. However the bigger the water, fleet and given like for like kit and helm ability, the longer bow has a pronounced effect. With all due respect I doubt that anyone other than Goffo or myself are really in a position to comment on this.
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Post by the black pig on Apr 27, 2011 2:29:40 GMT
with all due respect, i was not commenting on hull designs only on your last sentance about having to get a new boat to be competitive. so i feel, with all due respect, that your last post showed no respect at all.
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polyfiller
Mothist
14 x winner of the annoying git on the water award.
Posts: 126
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Post by polyfiller on Apr 27, 2011 9:54:09 GMT
So apologies if you drew some form of offence from my post .... I understand you are pointing out that a Skinner won an open meeting .... however, bigger fleet, larger water, same helms etc..... if measured over time, the longer water line boats will statistically prove more succesful ... so my worry is over time that people will develop the opinion that they do need to buy to compete (takes a while for this to develop). What happenned first time around is that people weren't prepared to spend the money and those with Skinners spent much time complaining about the unfair advantage.
I think that the class is in a better position to avoid the issue this time around given the larger number of available builders and the fact that there is less performance difference between LWL boats and say, the Skinners & Clarke JEP's. Back in the early 80's, there was a much bigger gap between all available hulls and the Claridge boats.
Reason for my concern is best interest of the class ... so hopefully you can accept my comments as such. Thinking about it further ... the bigger issue may be the cunfusion / concern / perception that the class cannot control the measurement. In the flying 15 fleet folks that the measurements were fien - but year after year a newly tweaked hull shape was released forcing people to buy regularly to keep pace. This must be avoided at all costs IMHO.
It is really pleasing to see so much building activity and people investing time in development... just needs to be controlled ;-)
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Post by oldgreyfox on Apr 27, 2011 16:15:23 GMT
Talking about Flying Fifteens is a bit of a giveaway, especially if you currently sail one at the original home of Brian Skinner and his Moths.
If you are who I think you are you are very well qualified to comment on the performance of past designs, having had moderate success in several different boats!!!
The above mentioned gentleman is very saddened by the recent developments of the boat, carbon rig , dog leg boards etc.
His opinion is that the boat should have been kept to a strict one deign, with standard aluminium rig, standard shape rudder and centreboard which would retain the "one design" status.
The front page of the BM website states ONE DESIGN dinghy. Not quite sure about that?
OGF
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polyfiller
Mothist
14 x winner of the annoying git on the water award.
Posts: 126
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Post by polyfiller on Apr 28, 2011 8:56:46 GMT
Well yes I probably am who you think I am ... and therefore very well placed to comment. As stated above - the key concern is that the measurement can be controlled and in an enforcable way. I thought (memory isn't what it used to be) that there was a template for the fair curve which every boat had to fit inside at the bow curve.... not sure what happenned to this. Without there will always be What is fair and what is not debates .... although from my POV I think it is possible to implement a working description. Trouble is if this can't be done or done in an enforcable way, then each year there is a small chance someone will come along with hull shape number 2 .... then 3 then 4 ... each one with slightly more pronounced and less fair curve. Then there's the home build expert builder who might just push the limits and if they were a really robust person would fight any attempt to reject the boat for measurement. I've always wondered how that type of conversdation would play out ..... 1) Sorry, your boat doesn't measure so you'll have to change it 2) I'm not going to change it, your class rules have a loophole ... I built in good faith to the rules ... I'll see you in court. Would be pretty scary givent current woring re: fair curve methinks !
So to sum up my waffling - this has echoes of when the whole Ides thing was going on. Two takeaway lessons are still;
1) Don't lose control of the measurement and 2) Don't under estimate the speed LLW can give and the dissaffection it causes if boats look so much different or indeed new versions keep coming out to exploit.
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Post by graham7 on Apr 28, 2011 10:47:27 GMT
Polyfiller ,we understand and share your concern ,as a builder who has invested considerable time and money in a female mold to produce wooden boats I was pleased when Phil Morrison produced a set of lines with very even and fair bow curve and this boat looses a tad of ultimate WLL but compensates in handling and especialy upwind speed in waves.I have had considerable experince building one offs to investigate the advantages of ultimate WLL in a BM but the other natural features of the boat create negative aspects such as bow slam and the bow grabbbing when phase 2 planing with severe side effects, As BMBA sec I share your concerns but have learnt from my own experiments spending lots of time and money and getting very wet that ultimate WLL is not the only consideration and the modern Claridges and my own Xmoth look right and have other features which combine to give perfomance.Skinners and Goffos boats are still very much on the pace and winning the Champs ,it was only a broken boom that stopped a Goffo boat winning again in 2010 following very strong pressure from Roger,s Claridge.
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polyfiller
Mothist
14 x winner of the annoying git on the water award.
Posts: 126
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Post by polyfiller on Apr 28, 2011 11:09:55 GMT
Yes - good to see that the generally more modern make up of the fleet negates WLL to a greater extent ... althought the wave slam is not something I ecnountered..... biggest series of races we did in what can be considered choppy conditions was the championships at Parkstone ..... and Wein went upwind and through the waves so much faster than the Skinners I reckon it was a real advantage. Downside was alittle suction at start of planning - but given how much time we were up on full plane that week (most of it off wind) that it didn't really have any negative effect. I found the suction was easily counteracted by technique and boat setup.
Still doesn't really detract from question regarding control of the measurement - it needs to be controlled. Not really my problem .... but I was extensively involved in discussions and decisions during my time ... so I know some of the pain from a comittee POV.
I have to say that I've seen a couple of photo's on the main website of one or two boats which I would consider out of class .... but maybe a trick of photography I guess. I started reading up on fair curve definition (we never had t'interweb when rule was put together)..... geeees what a complex subject .... my maths is nowhere near good enough to understand it all. TYemplate (original approach) looks like best option. I wonder whatever did happen to that template ?
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Post by graham7 on Apr 28, 2011 12:39:17 GMT
Colin and I both trialled slightly different tempplates which were simply straight edges with pins set a certain distance apart and length,we both independently looked at the drawings and following ISAF Measurement guidelines drew what we considered the optimum interpretation of a fair curve and set them up on a straight edge working on the principle if the template touched it was out. With both templates the current boats passed,Xmoth built since is of obviously less acute curve,but it would be good to track down the old template. It has been robustly discussed at AGM and following our investigations we agreed we could police this and have tweaked the measurent wording slightly to tighten thing s up.The current web posted rules may not have been updated from the last AGM,
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Post by graham7 on Apr 28, 2011 13:01:31 GMT
Poly filler,your observations of the Skinners being relatively slower upwind is due to their trend towards a wide flat bow like the fashionable wide bow Fireballs of their time,which radically changed that class.The same effect was not so obvioius in the Moth but they still are very fast offwind and with good foils good upwind too. All this chat leaves outsiders bewildered but all one designs like Solos and Ents have certain builders whose boats excell at something and we are stilla very good value class where a well sorted secondhand boat for c £1000 with good sail and competent helm can challenge for open meeting or national sucess and have a lot of fun with us daft people that love this little boat. As a builder trying to sell new boats this can be very frustrating but we have to keep improving the breed or die.
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Post by robwilder on Apr 28, 2011 13:32:07 GMT
I still think the class is great value for money.. I bought Painted Lady and won the champs in 2006 in a Goffo Boat for a grand total of £1200. The boat cost me £1000 and I bought a second hand P&B sail.. In 2007 I sailed another Goffo boat this time with a Carbon Boom, alloy mast and a new Rowsell Sail think total cost was around £3000.. Managed to win that as well but was pushed hard by John Wayling in a Skinner who was borrowing my other sail (I still regret lending it to him that week ) and Tim in 834. The little tweaks that in the different hull shapes are to me what makes the class interesting along with different rig options and foils.. it doesn't need to cost a fortune... A new Solo costs around £7000 now and I think you can put a new moth on the water for around £4000.. Not quite sure what I'm trying to say in my post ..
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