Chine runners???

Is chine runners like road runners? fine as long as the Wily Coyote ain't about!!

 

The problem with genius is, the margin between it and insanity is sooo narrow ...

Which side are we on by now?

 

Ok, I'd already made my decision about the road runners but I see that the thread is taking a turn of sorts. I'm leaving myself open to the possibility that they suck bat sh't, in which case I'll add a dagger board.

The margin between genius and insanity should take into consideration the employment variable. "The devil makes work for idle hands".

 

Chine runners can offer a substantial difference over some hull shapes with restricted lateral area, but it's a limited return at best. Aspect ratio is what appendages need, aside from a reasonable section and sufficient area in a respectable plan form.

In other words, a hull with limited lateral plane, especially fat or well burdened, flat bottom shapes, will seem to come alive with this type of improvement, but this is only because they truly sucked before. A properly sized set of appendages (rudder and dagger/center board) will make marked improvements over runners. On a hull where there is sufficient lateral area and having reasonably shaped appendages, their addition may actually detract from the performance a bit if the hull has good abilities or hardly be noticeable if the hull shows an average performance envelope.

 

Like everything else use of chine runners is a compromise to accommodate individual preferences and sailing conditions. A trailered boat intended for shallow tidal waters will not have a deep lead keel but a keel boat would be my choice for blue water. I myself use a Bruce foil to minimise heeling in a boat not intended for sailing which suffers from inadequate freeboard and stability.

It seems logical to use chine runners on a boat that desperately needs them, particularly a broad hull that would gain lateral rsistance as it heels. A center board might do the same thing but can be a nuisance inside a cruiser's cabin, and nobody loves leeboards except on a Thames barge.

We're getting a lot of opinions but maybe not from knowledgeable boat designers; are you guys out there and reading this thread? (Apologies to anyone on this thread who meets that criterion). Anyone got actual numbers on the effect of chine runners on leeeway and drag? Do they offer any advantage (not just in the performance) over bilge keels?

 

Best I can Figure...

If the sides of the hull and the rocker are the same section of a circle the runners form a straight blade the full length of the hull under the waterline. You just have to angle them properly from the tip of the blade to the side of the hull, otherwise they are curves which cause drag and all that bad stuff. Also it seems to me that the force of water on the heeling runner might make it difficult for it to come up above the water.

It's hard to get a good photo but you can kind of see it in the attachment.

 

and the odd [thousands of] Dutchman!

 

A chine runner is an end plate folks. It slows "cross over" flow.

The comment about rocker and hull sides is a Bolger comment, though I don't remember where (probably one of his books) and he was referring to eddy making resistance at the chine of flat bottom boats. By making the hull sides and bottom of similar curves, the pressure waves are similar, thus less turbulent at the chine.

The runner would act much like the beavertail seen on bulb keels, in regard to what it does to flow. A curved runner would have a small envelope of effectiveness, but if the hull was held at that particular angle, she'd perform some work, though, again not a substitute for proper appendages.

 

From what I've read, chine runners are only supposed to be 1/3 the length of the hull, and positioned in the middle of the hull. In other words, they do not extend anywhere near the ends of the hull.

They are basically lateral extensions of a flat bottom, but only in the middle 1/3 of the hull.

 

I have been influenced by Bolgers designs mostly because they are simple and provide allot of storage for a small boat. I haven't read anything by him that explains in detail, how chine runners work. If I accidentally quoted him w/out giving him credit I am truly sorry but I don't think he's the only person who has made the side and rocker of the same section of a circle. it's just logical.

As for the 1/3 length runners that Kengrome refers to, I have also seen them here and there and considered trying them.

Here is a link to Bolger's "afloat on seas of peas" which discusses in detail his ideas concerning the relationship between the side, the rocker and resistance and all that stuff. http://homepages.apci.net/~michalak/1sep04.htm

I will look into bilge keels, Thanks for all the comments folks,

Chris

 

I think Matt Layden is the pioneer in the use of chine runners in his shallow draft cruisers, isn't he? He's the one I got the 1/3 length measurement from -- not directly, but via his or someone else's website where a boat with chine runners was being built according to Matt's specs.

 

Back to the drawing board...

I think the chine runners are evolving into full LWL shallow twin keels. any thoughts folks?

 

Still think a 'chine runner' is the Chinese version of the Road Runner - Bleep Bleep!!

 

Twin Or 'bilge' Keels...

Hello...

See http://www.brayyachtdesign.bc.ca/article_twinkeels.html ...

Also http://images.google.ca/imgres?imgu...allast+twin+keels&as_st=y&hl=en&safe=off&sa=G ...

Ahah - these are the UK boats I spoke of earlier - see http://www.selectyachts.co.uk/redfoxhome.asp - these have assymetrical daggers...

All said though - I would go with PAR - proper appendages are not really all that hard to build - and a centerboard - even offset into a berth front allows you to change your CLR a bit - I used to sail my Holt Enterprise with just the main in a blow and trimmed the boat with the position of the board...

There are some photos in my gallery of twin keelers in Looes and in Calais - North Americans tend too poo poo the things - but they can be very useful...

I still want to play with assymetrical fixed keels canted outboard to 15 degrees - one hangs vertical pulling to windward while the flying one is trying to right the boat...

Anyway - there is a lot of info out there - mostly European...

SH.