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Typical 6M keel configuration info


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Modifying a planked hull around the 6M rule. 1510mm LOA

I would appreciate and dimensions or sketch of a typical 6m fin and planform ballast. I know the variation depending on the measurement formula.

Have cut off existing lead filled fin and will make a fixed fin around a fixed 14mm carbon tube so need a rough idea for fin depth, chord and length as a starting point.

Also looking for a ballast casting.

What is a typical ballast weight ?

Lastly:   Rule 3.3.7 appears to allow trimtabs. I am keen to incorporate one into the fin . I have not seen any evidence of them being used in the class however. Sorry but only ever seen one 6M in the flesh ! But I did once own a beautiful Dolphin hull obtained in exchange for a One Metre. 

Richard

 

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Hi Richard  I will apply a tale  measure  to my sixes in the morning and get back to you, Typical sixes are from 10 kilos to12.5 to 13 kilosthe12 something is probably the common weight  but lots depends on the complicated formulae

Mike Ewart

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Hi Richard 

right been out and about with the tape measure ,my fine are from a renaissance and a Ravenna and both are fitted into fin boxes, total dimensional of fin 60mms long bottom of fin 290 mms long, from hull to top of lead 80 mm, length at base of hull 223 mm.

the leads are .com Sails egg and are both the original shape, I believe there is a drawing on their website. 

do remember the draught of the yacht is set by the measuring and Carrie a high penalty in the titular so you do not want to exceed this it is determined by the overall length and the weight, I th will we some flexibility in fin depth and weight to get the best t r whatever design you have, what is it by the way.

sorry it is not more straightfrward, but the penalty of this rule am a and the most of the older designs change compete with the newer designs

Mike Ewart

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Thanks Tiggy Cat

Thanks MIke for the measurements really useful and give me a sort of benchmark of area to suit resulting forces from approx 0.7 sqm SA. I assume that you have Grahams inverted triangular fin. I think I will go for vertical leading and trailing edges though: offset the wetted area for maximising the end plate effect of the ballast, especially for such a short fin. Using experience from large boats here and very happy to be proved wrong.

I have acquired a scaled down (X0.66) Moby Dick ( J Lewis) hull, nicely planked and substantial enough to withstand surgery. I would guess a similar block coefficient to a Dolphin. to give you some idea where I am. I will not be able to turn it into a legal 6M but will make a sort of "super 6" for fun sailing.  Any comments on trim tabs ? 

This project is an un planned diversion from current efforts at foiling  with a very different sailing experience ( 15% foiling, 35% getting into position for a foiling run and 50% rescuing capsized tri)  A spin off is my rescue boat which has proved very successful, is very compact and uses ultra simple bits.

Richard

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Hi Richard

Take look at the pictures of the 6m Drisky and the RA Sir Percy on Taylormadeyachts.com for pictures of trim tabs on these two yacht designs.

If you're planning on using a trim tab, remember to reduce the surface area of the fin to get the best performance.

Regards
Damian
Note: personal interest in the above as I'm the builder for Tailormadeyachts

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Hi Richad,  from tabs are allowed  but my personal feeling is that they really only seem effective on long legs to windward,  that's a personal thing,but you for one and you don't like it just don't use it

Mike Ewart

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Like Dolphin, I have to accept that I cannot get a useful 6M from this hull, hence just using the rule as a sort of guide and possibly learning a bit about 6Ms along the way.

Damian, I have already looked at your Drisky, which certainly looks the business. I had not seen those pictures which are very informative. For example the trim tab is much bigger than I expected, usual problem with scaling for me there.  As you say, the fin area is interesting.  I am re thinking the chord length as we speak, not sure what thickness to use 14mm has been suggested, but seems a tad excessive. Not asking for any trade secrets here, you understand,  just a steer in the right direction. Going to build a fixed fin around a carbon tube and skin it with carbon sheet; thanks Dave for advising me against a removable fin and a finbox.

Do you make those ballasts ? That is the one item I'm searching for.

 

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Richard, I would say that a removable fin  and a tin box would be.my preferred route it makes it much easier to  change things in the future, apart from my humble opinion GB  nearly always used a fin box, imitation/flattery

Mike Ewart

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Richard, to add to Mikes last posting, both my current 6’s, which both date back to the ‘80’s and all previous other 6’s of mine have had a fin box and removable fin/ballast. Both of my 6’s are currently competitive, if I can get to start a race without breaking anything that is. That’s a separate tale. The main area where performance gain can be made is in changes and alterations to the appendages. You can’t make those changes easily if the fin is fixed. Obviuously the choice is yours. I understand that yours may be an old boat but when we get back to sailing again there is no reason why you can’t compete. We introduced a classic class to the RA fleet and there is no reason  why a similar approach with 6’s. could not be taken. There are an awful lot of Dolphins out there gathering dust and they should be out there doing what hey were designed for which is competing. Model racing yachts are what they say on the tin. 

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Bill and MIke; very useful and relevant comments and I agree that I would have a preference for a finbox arrangement. Possibly I am being driven by economics here and want to try lots of ideas out on this hull. Fins and finboxes are expensive. The best, I know, are engineering works of art and certainly worth the loot.  My fin will be removable though and I will be trying different fin shapes (eventually) 

I intend using the trim tab for any CLR correction as a simple expedient.  Also the rudder.  Intend floating the modified hull tomorrow to determine the sort of ballast weight required to come down on the WL minus estimated rig and radio gear weights of course.

This is a fun project and the aim is to get a really nice sailing  boat and try out some ideas.  

Richard

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