improving performance

[Paddy_OReally]

i posted a while ago an idea i had about replacing the bilge keels on my corribee. it is feasable but looks to be a bit too involved. what i'm really looking for is to improve the performance a little. it strikes me that to get the hull moving faster you need to get it out of the water. having a trundle round the lake last weekend i noticed that most power boat hulls have flatter square hulls at the rear. also the dinghies i have sailed in the past also had sqaurer sections at the rear.
the rear section of my corribee is rounded. what i need to do is sqaure off the rear sections a little to give me a bit of hydrodynamic lift. i was thinking of shaping some sort of foam material and fibre glassing it to the underside of the boat to achieve this. do you think this will give me the lift to get the boat moving faster?

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[kateoreally]

Paddy, Improving performance indeed, its you who wid be doing that! Get right home here this minute before ye get us into trouble again.

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[ashanta]

You cannot compare your boat with a power boat or a dinghy!
Your vessel is a displacement vessel not a light weight planing hull. The laws that determine the speed of your boat is not the same as for those you compare.
It seems to me that you ought to think about what you relly want from a boat and go and buy the boat that matches your expectations. It's obvious that the great little boat that the corribee is does not meet your expectations at all.

Regards.

Peter.

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[graham]

Paddy what you need is something very light ,narrow ,waterballasted and with a massive outboard engine.(Must not mention by name).

Whatever you do dont read the instructions then take it out in all weathers under full sail and throttle at the same time.

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[Paddy_OReally]

i can see to a point what you are saying. my background has been dinghies for the last 19 years. looking at my little corribee its not much bigger than some of the dinghies that i used to sail. being only marginally bigger than say a wayfarer or an enterprise. these used to be spritely boats. even the sod's were as fast as the corribee and they are and old design using traditional wooden boat building skills. i know my boat will not be as fast as some of the dingies. improving what the designer gave must be a fairly easy task if one applies a little thought and is not beyond the scope of a keen amature. your thoughts on the subject are most welcome.

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[DanTribe]

It may be easier to replace the hull with something lighter, say a Sydney Harbour 18ft skiff. Having done that make an offer on the now redundant 18ft skiff's rig.
If you want to keep the Coribee authentic, you could always add bilge keels.

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[Twister_Ken]

Patent Applied For

Paddy,

I don't know if on Lough Ballykissangel you have a high speed ferry service, but if you do, you'll have maybe noticed that as the driver snicks it into third gear and puts his (or her) foot down the noble craft climbs out of the water and speeds gaily along suported by hydrofoils.

Now, with a bilge keeler, all you need to do is to build a wing between the lower extremities of the keels, heave in on the sheet, and watch her go. By the way, don't forget to slow down at the end of the lough, or you could end up parking on the yacht club baclony. The pix below should give you some idea of what's possible.

The see-through sails are optional, but they do add a certain je ne sais quoi.


<hr width=100% size=1><A target="_blank" HREF=http://www.writeforweb.com/twister1>Let's Twist Again</A>

 

[Paddy_OReally]

do you know you might have hit on a good idea. if i divide the bilges into watertight compartments and devise a way of pumping water into the windward areas then it would lighten the boat by quite a lot when empty and sailing downwind. it would also mean i could take out the blocks of concrete that are in there at the moment. all these modifications should make the boat sit quite a bit higher in the water. this would be excellent as i always seem to get the lee rail under when reaching.

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[BrendanS]

I've had the tarmac surface you laid on my drive inspected. It's 4mm thick at most. I'd suggest a refund or you come and correctly lay it again?

Look forward to hearing from you!

<hr width=100% size=1>There is no such thing as "fun for the whole family."

 

[ianwright]

Take the advice of our HeadMistress Peggie Hall... "Nothing gets to wind'ard better than 750 horse power"

IanW

<hr width=100% size=1>Vertue 203, Patience

 

[kindredspirit]

Reminds me of the time many years ago in a hospital when the swing doors swung open with a patient on a trolley.

1st nurse: "This man has 13 breaks in his leg!"

2nd nurse: "Oh. Really?"

3rd nurse: "No, O'Reilly."

.

<hr width=100% size=1><A target="_blank" HREF=http://www.begleys.com/kevin/weather.htm>Weather & other useful links for Irish waters.</A>

 

[StugeronSteve]

Re: Patent Applied For

Exactly what I was considering. By using inflatable bulbs he could probably set up some type of venturi effect between the keels, this would give the added benefit of a ram jet effect. Was tried once with disasterous consequences, but Paddy doesn't sound like the kind of man to shy away from a challenge. Mind you a pair of powered torpedos fixed to the keel would give Paddy the speed he craves without the need for too much boat modification. We Solent tars can soon locate a couple of those for him.

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[ships_parrot]

Power boats and dinghies have a much greater power to weight ration than yor corribee. The corribee won't be have the power to lift itself out of the water enough to gain any great effect, and putting flatter squarer aft sections will just increase drag, and so make you slower. It will also really damage the resale value of the boat.
Displacement boats go faster by reducing drag as much as possible within a compromise with stability. If you want to do anything, you could look at ways to make the waterline longer, as with displacement boats, waterline length is very important. You could also try looking to see if your transom is immersed, if so it may be worth continuing the lines of the hull until you can have a transom that isn't immersed (e.g. a sugar scoop), thus stopping you gragging all that nasty turbulence with you. It may sound small, but you can't make a boat do something it really wasn't designed for.. Also bear in mingd that you'll make the boat seriously out of class if you do want to race properly.
On the subject of water ballast, in windy conditions you could try plonking a big water container in the windward berth and stay that bit more upright with that bit more sail.
If that's not enough of a challenge I think selway-fisher have plans for a mini transat with water ballast and all those toys..


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[jimi]

Paddy, I'm trying to establish Kate's realtionship with you. Is she your wife,sister, mother or cousin?

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[StugeronSteve]

Or is she his wife's sister's mother's cousin, or something like that? To be sure.

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[jhr]

What relation?

Depending upon how small the village is that he hails from, possibly all four?

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<hr width=100% size=1>Je suis Marxiste - tendance Groucho

 

[chriscallender]

OK, I will risk making a serious reply in case this is a serious thread .... the most feasible way of getting some improvements in performance would probably be to make improvements to the rig and sails, rather than playing around with ballast or the hull shape.

How old are the sails, and the running rigging? If they are at all baggy or the haliards stretch then sorting that would be a good starting point in improving the performnace, and just knowing how to adjust everything to get the sails into a nice shape is an art in itself. Also, getting the standing rigging set up well can make an enormous difference. Ideally replace the old sails but if that is to $$$$expensive then there is quite a bit that can be done to get the most out of the old ones.

Also you can fit all sorts of gadgets to increase the amount of adjustments you can make - not familiar with Coribee but I'm thinking of stuff like mainsheet travellers, genoa cars etc since I guess the Corribee might have a fairly simple rig, with relatively little control over sail shape.

If you are interested in fiddling with this kind of stuff you could go on for years making improvements and still not exhaust the possibilities - perhaps it will be the first Coribee to sport spectra haliards and kevlar sails?

Getting everything right about the sail shape can make a pretty huge difference (assuming that its not right already). However you also need to think, its a small boat designed for reliable safe cruising in fairly exposed waters so its never going to be a planing hull. If thats what you're looking for then sell and buy something that can - after all, its better to spend the time saling than doing improvements in my opinion. But if you are interested then look for a good book on tuning the rigging and sails and take that as a starting point.



Chris

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[jimi]

Another serious answer. Keep the hull as smooth as possible. Ensure rudder really smooth with edges sharpish. Wash down hull with fairy liquid before launching and racing. Minimise weight and ensure rigging properly tuned. Decrease windage by reving sprayhood and dodgers. Remove flower baskets and patio slabs from cockpit. ... and always rember to pee of the back to increase forward momentum.

<hr width=100% size=1>.. whit way roon should it be again ..

 

[chriscallender]

Talking of harnessing the power of the wind

Howsabout vindaloo 15 pints of lager the night before, beans on toast for breakfast, brussel sprout & butterbean stew for lunch (would cauliflowers also be a suitable flatulant?), stand at the stern facing forwards bend down and get a brave crew member to strike a match. That should get the old Corribee on the plane if anything will. Although for safety's sake he should probably make structural modifications by welding in some steel to strengthen the backend, remembering that the entire structure needs to be fireproof and the above should never be attempted if piles are involved.

Agreed that patio slabs and flower baskets are only suitable for cruisers.

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[jimi]

Re: Talking of harnessing the power of the wind

Would certainly put the wind up the opposition, but the danger here would be a bit of a follow through, which could ensure any boats on the hind quarter resembling "The Black Pearl" after such an encounter.

<hr width=100% size=1>.. whit way roon should it be again ..