Sailing in Company

jim.r · Post by **jim.r** » Tue Mar 25, 2008 6:59 pm

every one knows maximum displacement speed is related to waterline length,would a linked in company sail be faster with the boats linked serially with rigid objects such as spinnaker poles?

Rowana · Post by **Rowana** » Tue Mar 25, 2008 7:29 pm

I think you'll find that you can't just add up serially. Probably comes down to the lowest common denominator and you just achieve the speed of the slowest boat.

But I for one am not going to try it out. I much prefer to be in control of my own destiny.

jim.r · Post by **jim.r** » Tue Mar 25, 2008 7:59 pm

I can't see why it would'nt work, however probably best to put the ightest boats at the front and the heaviest at the back?

Rowana · Post by **Rowana** » Tue Mar 25, 2008 8:42 pm

Well, in my extremely limited understanding, once you get a boat up to hull speed, then it doesn't matter how much extra power you add, the speed does not increase. Unless you get up on to the plane, that is.

So in your theoretical "Train", once you get the boat with the lowest hull speed up to that speed, it won't matter how much you push/pull it with the others, you won't increase the speed.

Probably be less if anything, as apart from the first boat, all the others are travelling through disturbed water. Just look at a F1 car when it is following another.

Anyway, enough of this therorising, my brain hurts

ash · Post by **ash** » Tue Mar 25, 2008 8:57 pm

jim.r wrote:every one knows maximum displacement speed is related to waterline length

Why don't the RNLI know? Any time that you saw a tow on 'Seaside Rescue' the lifeboat crew seemed frustrated at the (relatively) slow speed that could be safely achieved.

Ash

moodysailor · Post by **moodysailor** » Tue Mar 25, 2008 9:50 pm

I'm not sure why I'm reply to this barmy idea. Must be cabin fever...

The speed/length equation is, I understand, related to wave length as created by the bow. Once the wave curve falls off the stern the boat sits down and then you are effectively sailing up hill. Joining boats together would only work if you could keep a smooth wave flow, which you couldn't.

It's not 1st April already is it

ljs · Post by **ljs** » Tue Mar 25, 2008 11:04 pm

This puts me in mind of Isaac Newton, when pondering the tricky subject of gravity and an apple fell on his head.
I think he said, 'What the .... was that?'

Olivepage · Post by **Olivepage** » Wed Mar 26, 2008 1:15 am

I would suggest its a question of wavelength.

If you can arrange rigid tows so that each boat can push as well as pull, then by arranging the distance between boats so that when one boat is pushing up its bow wave the boats in front of and behind that boat are sailing down the previous and following waves you should be able to reduce the losses of sailing up a wave by half.

Clearly this theory needs putting to the test.

It could bring a whole new meaning to flotilla sailing.

Post by **DaveS** » Wed Mar 26, 2008 11:17 am

However, taking the idea a wee bit further...

If, at each bow / stern connection, you introduce an inflatable hull shaped bag (with a suitable depression to accommodate the bow of the second boat) would it not be possible to achieve the necessary enlarged waterline length? Presumably if the overall effect is sufficiently streamlined then it will act as a single hull...

Magna Carter · Post by **Magna Carter** » Wed Mar 26, 2008 12:12 pm

Feck me..... the thought of a Claymore doing 28kts....... strewth.....

ParaHandy · Post by **ParaHandy** » Wed Mar 26, 2008 12:33 pm

DaveS wrote:However, taking the idea a wee bit further... an inflatable hull shaped bag...

I know where such an article resides. Its coloured grey, or maybe green, and is available this year. Would you like me to inform its owner that a use has been found for it?

sahona · Post by **sahona** » Wed Mar 26, 2008 2:23 pm

I worry about the depth/height of the resultant max-speed wave over several boatlengths: I think we need to pad out the middle bit of the flotilla with more boats (Preferably with asymetric hulls) so that the whole raft looks boat-shaped from above..... Then possibly fill the gaps with expanding foam.
As for being towed at speed ~ I've done horrendous knots in a corribee behind Troon lifeboat. They had to come back and put one of their men on to control the tow. Once hull speed has been forgotten in a small keelboat the experience goes through exhillerating to something else, as my breeks can attest.

jim.r · Post by **jim.r** » Wed Mar 26, 2008 2:48 pm

Under the CR would our maritime caravan be treated as a single vessel or tug and tow. What lights should we show at night?

Post by **DaveS** » Wed Mar 26, 2008 4:21 pm

I reckon that if the connections are reasonably rigid and the assembly is acting as a single combined hull then it should logically be treated as a single vessel and show lights accordingly, including a second masthead if long enough and motoring.

Might need "difficulty in manoevering" lights / shapes if very long and only the back boat steers. OTOH with cooperative steering by all boats aft of centre, and some reverse steering by those right at the front (I had to think about that bit!) the turning circle might no be too bad...

Magna Carter · Post by **Magna Carter** » Wed Mar 26, 2008 5:23 pm

DaveS wrote:Might need "difficulty in manoevering" lights / shapes if very long and only the back boat steers. OTOH with cooperative steering by all boats aft of centre, and some reverse steering by those right at the front (I had to think about that bit!) the turning circle might no be too bad...

hah..... i'd vote for you showing NUC.....

BLUEMOMENT

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