OZIOMZ and measurement etiquette

Rcsailing.net General Discussion
41

Don - you are correct, in that there could be flair or not. If you look at next illustration, you will see a top view showing multiple waterlines. Some designers will include a split top view. In big boats they generally do half as a deck view and half as an interior view showing bunks, lockers, etc. In that case, you are correct in not knowing exactly what the designer had planned. This is where additional photos, or pond-side viewing would kick in and allow more accurate (to the eye) shapes to be built. In my “supposition” I thik I stated I assumed a flat side to waterline, and a circular section underwater for basis of keeping it brief. Again, I apologize if I lead you to believe you could “clone” a boat with only two views and no buttocks or water lines available. My apologies. I was trying to explain that you could get close to a design - but that is why we pay the designers money for thier plans, rather than posting a lot of detail dimensions which is why the guy is good (or maybe not) since he probably has gone through several iterations before getting it right (fast).

I just think that the original intent of the post was great - depending what the designer agreed to allow to be published. After all - I suppose we could wait for someone to post the calculations for a CAM program to feed into a mill to create the plug. Where does it end? At the point where the owner of the design agrees on how much he wants published, would be my guess.

Back to computer aided machining, I suppose you could take a known hull, turn it upside down and zero out all dimensions. Then using X-Y-Z axis, move a dial indicator all over until it just touches the hull, and record thos numbers. Will give you all the necessary points as well - but why go through the trouble to save a few bucks. If the boat design intrigues you (not you personally here - all of us collectively) then pay to buy it, or design your own determining your own template dimensions.

42

Thanks for sticking with me til I got it sorted out. I thought I was missing something that could be usful to me in understanding what makes these things tick. I have always thought that pulling a mold off a designers boat was theft but I am of the opinion that once he sells his first boat or allows pictures to be taken he has sort of released a few of his ideas to public domain. This pretty much has to be the case or nothing would ever develop beyond the first idea. Thanks again.
Don

Don Case
 Vancouver Island
43

With IOMs there is of course another element which helps in Dick’s process - that is a known displacement. The all-up weight of the boat will be designed at about 4kg (8.8lb). An adjustment is necessary for the water displaced by the keel (which - as lead is heavier than water, displaces less than it weighs) and the rudder. If using a computer tool to help calculate displacement you may aim at, say, 3.7kg or about 8.2 lbs. Thus, if you’ve got the deck and the rocker, and a rough idea (from photos or physical inspection) of the waterline shape (upright), playing around with your computer model until your displacement is right will help you in simulating the waterline design. Of course its a help only, by removing another variable - Dick’s, Don’s and Brett’s comment’s above all hold true. (You don’t need a computer programme for this - but it sure speeds up the process!)

Muzza

44

The way this discussion is evolving brings to mind another element. Dick has shown that it’s possible to get close to an existing design using key information as a starting point. Couger has admitted quite freely that he’d like to have a crack at replicating a couple of well known IOM designs. Is there anything wrong with this, and how does it compare to the earlier part of the discussion when we were talking about publishing significant detail about designs?

In my view there is a difference - as follows.

No designer - be it of boats, cars, of soda pops, expects to be able to keep the competition from coming up with something to compete with his product. We can expect that, as a starting point - the competitor will study closely the current leading products, designs etc. We can take out patents, protect copyrights and so on - but if our product is good, we still expect somebody to make a detailed study of it, learn from it, and attempt to come up with something better. The best we hope for, not just in boat design, but in other aspects of competitive life (business) is to maintain our competitive advantage long enough to come up with something even better, by the time the competition has managed to catch up with us.

So if I ever come up with a ground-breaking IOM design, I think I’ll keep some of the details close to my chest for a while - and I’d be a bit miffed if somebody reverse-engineered my boat and published all the details without my permission.

But…

if somebody took photos, studied the boat at the lakeside, and then went off to try to come up with their version of the lines, and either replicate them or improve on them - well I think I’d be kind of flattered.

Do you see the subtle distiction? The first is - at its extreme - theft. But the second is more like a game of catch-up, and trying to better what’s out there at the moment. The second happens all the time in business.

Of course it’s not clear-cut. The line is a continuum - and it’s not always easier to see where we cross from healthy competition into something that’s unethical and unacceptable.

As Brett noted - if you can replicate another design without buying the plans, then you can probably design your own boat. The process of coming up with that design - via the Dick Method - is neither quick nor easy. So if somebody, say Cougar (who I know has designed some of his own boats) wants to simulate a well known design for his own purposes - I see nothing wrong with that at all. That type of exercise furthers the development of a class or product. There are so many examples elsewhere.

Muzza

45

muzza
thank you. you have seen what we are saying. sure i would love to have a ts2. but what if i could take the ts2 and try a different fin? of a different bulb. all this matters. i , right now, have 3 IOMs in the workshop. 2 are cougar models. 1 is climate boat works “epoch”. i have learnd alot from epoch. and i am in the process of designing my new IOM. combining epoch, cutlass,bee gee, and the seawind, trying to find a balance in what i have on the water, and what is in my head( for all my friends out there. i do have a brain). getting the numbers for a ts2 would help. and in no way would i try to steal one. the ts2 belongs to craig. but i think getting a better copy would not be soo bad
cougar
long live the cup and cris dickson

46

All this creative talk - and it is - but no one has told me how wide their boat is, let alone the distance from the mast to the bow. I would love to collate some non contoversial stats. Is it at least possible?

N

Nick Lindsley
Australia 0418 727-727
Intl +61+418-727.727

47

For those interested, here is a quick analysis of mast position a number of IOMs I’ve looked at, including those that have their designs freely available on the web - and some others that don’t. The only designs I’ll name here are those that are in the public domain.

Distances are in mm and are measured from the bow (not from the base of the bow bumper - which is anywhere between 10 and 15mm aft of the bow). Not neccesarily Aussie designs I’m afraid Nick.

Furtherest forward I’ve noted happens to be a “free” design - the Tagati http://www20.brinkster.com/shermanyachts/index.html - which has the mast centre only 460mm back from the bow. You’ll note that the Tagati has it’s maximum rocker depth well forward and that CoB may also be well forward. This explains the choice of position of the lead - hence CoG and therefore CLR - which in turn drives the mast position. If the mast were any further forward, the jib boom counterweight would have difficulty staying within the forward limit of the boat - as is required by class rules. Thus this may be considered close to the practical limit.

The furtherest aft I’ve noted is the Triple Crown, with the mast centre at 507mm. The TC has maximum rocker, and (I presume) CoB well aft, and the interelationships between this as mast position are as explained above.

Perhaps also of interest is the relationhip between the mast position and the CLR - which as a proxy we might assume is the same as the centre of area of the keel alone (of course this IS as convenient assumption and not true in practice - but it’s close). Within a single design, this will differ depending on the planform shape of the foils, BUT, it seems to range between the mid 50s (the Arrow is 56mm) and the mid 80s (the Tagati again). The average is about 67mm.

Note that, above, I’ve made an assumption that the designer prefers to position the CoG of the lead under the CoB (if not known to me otherwise). This is NOT necessarily the case, and so is a spanner in the works. I’ve also assumed that CoB and rocker depth are related - they are - but each is NOT determined by the other. I need to know more about the boats to accurately estimate their CoB - and this is only possible with the freely published designs.

So what can we conclude from this?

Well - if, like me, you are building an own design, and you are unsure where to put the mast on the prototype, you might start by positioning your lead under - or near - the boat’s unballasted CoB, then positioning your keel fin such that it can support the lead bulb more of less centrally - i.e. near the bulb’s CoG. Too far fore or aft and you’ll introduce twisting pressures on your keel (unless of course this is what you want). Then you might position the mast centre 67mm forward of the keel fin centre of area, and allow multiple mast step positions 10mm either side of this. (By the way - 10mm either side covers all but the most extreme boats in my sample). Once sailing, you can experiment with mast position and rake, for various conditions and rig, until you find the formula that works best for your design.

Different hulls have different hull-shape influences on balance, and so there is no “magic” position of mast v CLR for an IOM. But the above range is a good starting point for the budding designer.

I feel this urge to caveat everything I’ve said (must be my job habits sneaking in) - it’s a simplified explanation only, and doesn’t cover all factors.

Muzza

48

well for what it is worth alot of ppl in this thread have just about exhuast this topic.
I read and understood Brads point of veiw and fair and I agree with also
I understand what Nick is trying to do which I think is agreat idea because I am looking at upgrading my IOM very shortly. The guy who suggest IOM are heading the same way as RM’s I would say Isnt it alreay there. Brad I arent saying your boats are too expenise. - joke- as I know the man hours and the quality reflect your pricing.
Now admittally I havent gone back to the start of this thread so forigve if I get my wires crossed.
It seems to me Nick is trying to have comparsion page of IOM’s So if that is the case I ask you When u r looking at buying yr next IOM are u looking at the techie techie stuff like upper for deck measuremnt and the mid quarter beam verses the mid beam whatever … and even if u are what does it mean to you. Oh I will buy this one because there it 2 mm difference into mid quarter beam section I think not!!! sure have what some guy mentioned about does it fits into a car overall lenght max height the basic stuff I think he said…
Now I am still deciding on which IOM I am going to get. How I am deciding is looking at the results
who the skipper was the wind conditons they won at things like that. I think it is horses for courses personal and is more skipper ablity more than hull design. My opinion is formed on the OZ Nat
Paul jones sailing a Cockatoo came 1st a cockatoo all so came 54th a disco came 3rd sailed by Brad a disco came 59th as well TS2 2nd Craig and 54th. so what am I saying …
I think the Craigs the Brads the Jeff of the IOM world here in australia as on the ball when it comes to a producing a competive IOM, so does all that super high tech spec’s actually help you mak eyr decession any easier.
Off the subject a little If the IOM is a entry level Class and low cost why isnt it a “ONE DESIGN” Class like the laser. I am new to IOM but inthe short time I hear that this design is the best or that one is I never hear Bob is the best sailor or Tom is. Question How would Craig smith go sailing a Disco how would Brad Gibson go sailing a TS2 I know it will never happen but both very good sailors. I could be wrong butin my researching didnt Paul Jones do very well with a disco, and here is doing very well with a cockatoo

Ok so I amthinking at loud trying to decide what design I should get …Pstttttt hurry up nick get the page ready

Cheers

Making the world a better place One yacht at a Time
www.rcyachting.com

49

There is way of calculating the COE of the sail area, this COE is then placed over the CLR. That is the most accurate method and works a charm, from this there is then minimal work required to set the yacht up then.
I have used this method before and it works.

Smile in the face of adversity and keep the world in suspense.

50

Muzza, and everyone else

I just wanted to clear something up, in July of 2003, I did an IOM design for Fernando Coelho called Merlin. After I sent Fernando the plans, they were passed around the net, and some how the name got changed to Tagati.

The design that is currently available on my website is called Vanquish. I created Vanquish in January 2004. She is slightly different from Merlin, and in my opinion is the all around better boat.

The plans for Vanquish are free, and can be found here.
http://www20.brinkster.com/shermanyachts/tech/page3/index.html