Mirror Kit

The cheque is in the post for my new Duffin Mirror kit <img src=icon_smile_big.gif border=0 align=middle>
I am told that as I am not building on a jig I will have to modify some of the panels by up to 20mm ?
Anyone built a Duffin recently ? Any advice on the build ? Any traps to beware of ?

I'm sure Duffin probably has!! He's usually pretty good about giving advice and stuff, have you tried asking him

I asked him. It was he who said it would need modifying as his are all cut to build on his jig.
What I dont get is surely whether built on a jig or not the panels should be the same ?
Has anyone built one recently not on a jig ?



Edited by - toddy on 12 September 2006 16:34:16

The kit comes as per the original design, not as per a finished duffin boat. I am just finishing one myself. All the dimensions will be right down the middle including the case position etc and will produce a traditional shaped mirror.

I am building mine on a jig so can't advise too much suffice to say making it fit is an intersting exercise, not for the faint hearted. If you have the time and can borrow a duffin or goodwin boat either take lots of measurements or templates or make yourself a temporary jig and then fit the kit to that.

Good luck and have fun

N2O

Trello, did you make your own jig ?
Looking at the class rules I could probably make moulds for the sections 1-4 using the sizes given less 5mm for the ply & use the transom as zero. Mount them on a strongback giving the curve from the base line as given in the rules.
To build a fast mirror are we working to the lower size tolerance ?

It strikes me as very odd that you have to trim the panels. The whole idea of the precut panels should be that you just stitch them together and out pops a Mirror. What happens if you do all this trimming and then discover it doesn't measure.

I know Duffin use a jig, but you shouldn't have to have a jig to build the boat, it was designed that way. Maybe Duffin ought to sell two kits, one for construction with a jig and one without.

Andy J

Gosh I’m naïve.

So in a strict one design class all the boats aren’t the same? Doesn’t this invalidate all the fuss about only getting kits and bits from Trident?

Daft or what?

Anyone from the Association wish to comment?

There are tolerances of up to 10mm in a lot of panels, but if you ever see the measurement booklet of a mirror you'll see there are a lot of things that have to be within a 2-3mm band. There's definitely not enough leeway for it to be called a "Development class" at any rate!!

I'm very concerned about what Toddy has been told by Duffin and have just written to Duffin (and copied to ISAF) for an explanation.

A walk around the dinghy park will show a vaste array of slightly different boat shapes, I suspect all comply to the building tollerences. Building on a jig just makes it easier to achieve the dimensions in a stable and uniform manner, it also makes it much easier to ensure the boat is built square, something I obsess about! The existing and mirror class building instructions and associated drawings give jigs of sorts, so nothing has changed there. Your suggestion of using the measurement stations and I might add a means of ensuring rocker is within rules is spot on as this will ensure the class rules are met. Panels only need to be trued to give a fair shape otherwise it's easy to make it look a bit boney. I have only had to fettle the panels to ensure the fit as well as possible. If you want to call me feel free on 07957197868

N2O

On looking into this futher and talking to Alaister Duffin you dont have to modify the panels and it is more fairing than modifying and may well be only a few mm eg shaping the bottom panels where they meet as in Guy Wilkins book. The kit as supplied can be built straight from the box so to speak.

After taking a slow walk around the fleet at Poole this year, and having been involved in the measurement of the event (as a helper) I can confirm without a doubt that nearly all the hulls are different from the original templates.
There are very obvious differences to a trained eye. These would include; huge differences in rocker shape, curvature of bottom panels from forward bulkhead through to transom, bottom panel shape at transom, placement of centreboard case fore & aft, height of thwart/centreboard case and these are just differences visible by eye. Run a tape measure over any of these (as i did) and you will find that most boats are now built quite close to the large tolerances allowed in the class rules.
It is a complete & naive misconception that any modern Mirror is built from the standard kit without modification.
Away from the hull - take a look at the Duffin spinnaker chute and how it forms into the bow fashion pieces. From the original kit pieces this would not be achievable but it makes very good building sense to do it this way - surely the problem is a class that is desperately trying to hang on to it`s simple beginnings and yet make a modern well constructed racing dinghy that remains competitive against it`s rivals. As i have said elsewhere on this forum - the measurements are all there - all you need to do is build within the tolerance (and pretty large they are too!) It is rule 1.3 that causes all the problems by stating that "no alterations or additions are permitted unless specifically stated" if this was re-worded to allow panels to be shaped within the measurement tolerances we may be able to build legally. As it is - just about every boat on the circuit does not conform to the original templates (ie in the middle of the measurement tolerances) as most of their panels must have been modified in some way to acheive the varying hull shapes that are out there - even if it was just a by few millimeters from the standard template.
It really is time this was addressed in a common sense way.
Alastair Duffin is not the first or will he be the last of builders both profesional and amateur who have 'tweaked' the panels to obtain a fairer, faster (possibly) hull shape with the measurements allowed.
This should be encouraged and applauded, it does not make the class a development class it is no more than artistic license within established measurements and if it acheives a better built, faster and more robust class then brilliant.
It would be nice to hear thoughts from people like Malcolm Goodwin, Alastair Duffin etc... both very well respected boatbuilders.
To Toddy - you really should consider building your own jig as without some form of accurate bracing and accurate reference points you are very unlikely to end up with a symetrical, fair and accurate hull - even without 'tweaking'the panels.
Good Luck

ASW Boatbuilding & repairs. 07966 513147

OK, I understand. So it is “Mirror Classâ€

Cush, don`t kid yourself that the so called One design moulded boats are any better. The one advantage the Mirror has over these is that it needs a certificate to race in events. The certificate is an endorsement that the boat meets the measurement criteria laid down in the class rules (granted within tolerances)
Take for example the good old Laser (+ all RS boats + all Topper boats and many others)These are produced from the same moulds so very little change in hull shape will occur therefore no need to measure the hull dimensions. How about weight? Mmmm! here we have a different story. From experience, I can tell you, there is a wide range of weight between so called identical boats. Granted this should not be the case and is, no doubt,down to poor quality control, but is nevertheless fact. I have witnessed 2 such identical boats (i will not divulge the class) that were 7 kg apart. The point is that a one design is built around a set of tolerances - such as Mirror, Fireball, Enterprise, Solo - the list goes on. A strict one design is supposed to give identical boats - but reality is they are actually less indentical than would meet the eye.
As for a cheque book class! there is nothing you can do or buy for a mirror that will make you top of the fleet - it is purely hard work, dedication and sometimes a little luck. Money will never buy success.

Take a look at some of the top names that have come through classes like Mirrors & Cadets - it has to be said that very few other classes have produced as many top names - it still remains a great boat for kids & adults alike.
All the best,
Andy

ASW Boatbuilding & repairs. 07966 513147

Once you have a good boat (Which needn't break the bank), it is all really down to good sailing. A well-tuned good boat will go faster than a poorly-tuned fantastic boat. If you look at Dave Gebhard's record, his boats were nothing spectacular, just standard-issue trident fibreglass. The same for Andrew Woodward, who dominated Irish racing for 2 years. His boat was good, but there were better boats out there. There is little difference between mirrors and moulded boats in that respect.