Planing in 12s.

[Jon_P]

How about a wake or water ski lake and the cable?
Jon

[Jimbo41]

Jon,

if you mean wake in the sense of the towing boat, I think the gantry idea's not bad. A gravel pit would be quite a good location too, since local boat traffic wouldn't get in the way and we'd have the whole day to mess about.

Are you in on this? If we have serious interest, it might be worth doing. It would be nice to have a few N12 designers around as well.....

Jim N3130 and N3470 (Don't let this thing drag on too long!!!)

[JimC (Guest)]

One way of doing it is to tow two boats, one each side of your launch, with scaffold pole or something across the bow with the boats and spring balances hanging from. That way you can arange it so they are in flat water out of the motor boat wake. Enables you to do two boats at once to speed up the process.

[Jon_P]

No i meant the wake boarding lakes that have a wire that towes you round rather than  a boat.  It would be difficult to pursuade them to help but would cut out the wake issue.  You have to be careful to make sure the way the boat  towing does not affect how it would plane.

i.e. if it was towed from its bow it might have a tendancy to lift or sink it depending onw here the tow was in comparison.

I would be interested but not sure how easy any of it would be to do and whether it would be of any use to anyone!

If it goes ahaead i might be able to help with measurement equipment if you decide what you want/neeed.  

Jon

[Mikey C]

Wakeboard tows are generally quite high so would end up with a lift component from the tow which is best avoided.

Aside from the gantry all thats really needed is a good set of digital scales and a dory... And flat water.

[Jimbo42]

[johnk]

I think testing should be at constant all up weight (displacement). Then we would get a better idea of how good older designs are rather that how much less drag a lighter weight boat has.

[Jimbo41]

[Mikey C]

Hi Jimbo, if you are agreeing with me you are agreeing with johnk! The only way you will get usefull info is if the same crew is tested in each boat. you also get rid of the trim variable as that crew will be able to trim each boat in a similar fashion.

[Jimbo41]

MikeyC,

What johnk wants - I think - is to take the hull weight factor out of the drag issue. In order to do that, the hull weight has to remain constant for every design. That means making modern hulls as heavy as the heaviest older hull design.

[johnk]

Jimbo has the correct interpretation of my views. I am aware that heavier older boats have a larger design displacement than modern boats. If we are looking at differing hull designs we should take out hull weight as a variable and test heavy hulls with lighter crew / ballast in them so they all have the same displacement. This displacement could well be that of a modern boat with crew rather than of an old boat with crew.

We could (but probably don't) have a situation where an older hull design built to the current weight rules has less drag than a modern design; but the extra weight in the older boat increases the drag so that it exceeds that of the modern boat.

[Jimbo41]

Good point johnk.

We could do both.....

Boat designers please note..  We also want your input.

Jim N3130 and N3470 (All you do is just put it in and drag it about a bit)

[philipcosson]

This experiment is getting a) overcomplicated and b) incredibly time consuming to perform.

It takes a crew od 10-15 highly skilled people with millions of pounds budget a whole week to get 2 or three runs of a land speed record car for example.

I think what you are proposing to do on a shoe string is impossible and would prove nothing beyond doubt, therfore would be worthless in the scientific sense (it might be a good day out mind:-)

I would propose doing this in software, or scale models. It would be interesting to get laser plots taken of several 'winning' boat designs. These would then be captured for posterity as the digital data can be archived in the maritime museum for longer than the hulls will actually exist, which will have some merit of its self. These 3D models can then be used to create exact scale models using rapid prototyping, or software models. These can be tested exaustively under a miriad of simulated conditions. (fresh water, salt water, differing crew weights, differing moments due to wind strength and heeling forces, etc... etc...)

I guess the results might interest a host of stakeholders such as magazines, software manufacturers, museums, universities etc. etc. some of these might be willing to fund the project.

I admit, it's not as fun as towing a few boats rond a lake - if you still want to do this, I suggest keeping it simple and using the average crew weightin a given fixed position with a given tow point at a given speed and on similat water. the observations should be as many as possible - because you will not be able to go back and repeat this easily - so measure EVERYTHING qualitative and quantitative (best to put a person in the boat and they can offer a 'seat of the pants' analysis as well!).

Philip
N3253

[Jimbo41]

Philip,

Thanks for your input. I'm not sure that software and scale models can substitute for a full-size, on the water trial, even if only one type of water were used. We have the full scale hulls, why not have a bash and use them.

Personally, if this trial comes to anything, I'd keep everything simple. The only altered parameters would be the hull type and the speed. The crew weight (and crew) would be the same throughout. I'd want to measure the drag at various towing speeds using a strain guage as well as the speed at which the boat starts to plane and at what speed drag starts to fall off prior to planing. This can be correlated with the subjective experiences of the crew. Hopefully, the boat starts to plane at the same time (speed) as drag falls off significantly.  We can then plot drag against speed and see how each hull type behaves. I think this would be an interesting exersize, which like this could be performed by dedicated amateur sailors and would also be a quite a fun day out, BBQ and beer included (mine's a Becks! )

It's also a great opportunity to get a bit of Y&Y and other magazine publicity....

What does everyone want? Do I have anyone interested? I'd be coming over 1500Km (not just) to do this trial.

It might be that we get some interesting preliminary data which are worth a detailed study. It's a risk, admittedly with a BBQ and beer and hopefully sunny day attached...

Well?  

[philipcosson]