Design Observations

After viewing a few of the VOR designs (ABN Amro One I believe), as well as a few of the up and coming ORC Grand Prix class designs, I noticed that several of the boats have a hard chine for maybe the last 10-20% of the LOA. Any idea what the advantages of this might be? Just curious.

i’ve noticed that aswell. i think it has something to do with more form stability.
i’m gonna email a designer buddy now, and ask him.
he told me of this trend a couple of seasons ago, but i paid no mind to it.
must be a secret designers society thing.

i’ll post his reply when i get it.

I think it’s a way to get the water to leave the hull easily. a soft/round chine allows water to ‘stick’ to the hull longer, and that means drag. Also, the extra drag should make the steering less effective. the straight lines of the long boats help it go straight, which, IMO, is an advantage on the long sails like the VOR. You see this on powerboats, which usually travel at speeds morethan 3 kts.

The flip-side would be the AC boats, with the round chines, which are more suitable for maneuvering, and only the transom with the sharp edge, to let the water part easily. You’ll see this on p[leasure sailboats because it “looks nice.”

My 2 pence.

ya…form stability, and extra weight…remove what aint needed.

the “chine” as you call it is also to make the boat fit into the rule, and still make the boat think it is wider. the Volvo box is a funny shape, and so to hav ea boat that thinks it is 17 feet wide on the water line at “X” location you have to chop some stuff off to make the boat fit into the measurment box. i tryed it with a footy design at one point, and i am still playing with it… we’ll see what happens:rolleyes:

With respect gents - 420’s comment is the closest to correct. This was the most important reason for the chine towards the stern in the VOR boats. There are however elements of truth in the other responses too.

The biggest clue to such things is usually found in the rule to which the boat is designed. The ORC GP42 rule is a box rule too, thus also imposing beam restrictions.

I’m afraid the form stability argument doesn’t really fly in this particular example (although it is a valid comment in the context of some other hard chine hulls). The chine (on ABN Amro) is positioned well above the upright waterline and is only just starting to immerse at the normal heeled waterline. Remember that these canters sail relatively upright even to windward in a blow.

That said - the design for high form stability and the chine ARE related in the VOR boats, as the designers chose to go for as wide a boat in the aft sections as they felt they could within the box rule (yup - to give them high form stability and therefore sail carrying power, as well as the shape they were after for high-speed downwind boats). So by introducing the chine, well above the waterline, the could get the immersed shape they wanted without breaching the beam restriction of the box rule (as 420sailor noted). Just wouldn’t want y’all thinking that the chine itself was the contributor to form stability in this case.

With the chine in the water there is perhaps a bit of a benefit in directional stability and lateral resistance too, although I doubt (but do not know) that this was a factor, given that the boats had daggerboards for this reason (the keels losing their lateral resistance the more they are canted.)

The weight argument is a dead duck in this case, again because of the box rule - but perfectly valid in another context. I can think of some successful RC sailboats which are narrower on the deck than at their widest point for exactly this reason.

my words were from my buddy’s mouth. he is an employed naval architect.
his main response was the stability answer. he is my referance for anything to do with the teck parts of sailboat design, so i preety much go with what he says.

this is quote from his email reply to me:

“Yeah, the chine thing is all about form stability. It’s funny because for a long time everybody was worried about drag and extra wetted surface. But, with these new box rules the more horse power the better. Best way it was every discribe to me was by Dave Perry the design. The chine is the result of making a wide boat and cutting off everything that just adds weight, i.e. extra hull flare”.

Yes - his observation is consistent with my comments in my paragraph starting “That said…” He does not say that, in the case of the design sited, the chine itself adds form stability - he says it’s all about form stability.

He says “the chine is a result of making a wide boat…” He could have added to the second part of that sentence by saying something along the lines of having designed such a wide flat run aft, the turn at the bilge to fit within the box rule was so sharp it just made sense to introduce a chine.


there’s a new slant on this idea: square box- square hull.:smiley:

Just be on the lookout, my 1:10 boat will most likely have the same design feature.

mine as well.

Britt Ward of Farr yacht design offers this explanation of the chines on the latest IMOCA60 designs.

“The addition of Chines in the afterbody peels the water off at low angles of heel which helps reduce the drag at the typically high speed reaching conditions that predominate in many events,however,the wrapping of the flow around the leeward chine when sailing at higher heel angles can provide a drag penalty.Careful attention to the location and position has allowed us to find a good balance between chine effectivness at high speeds without excessive downsides when sailing at higher heel angles and lower speeds typical of upwind sailing.”


Interesting conversation.

I’m working on a 1300mm model with a design inspired by the ABN-AMRO 1. And it has the hard chine feature. My reason to put it there was that I think it looks sooo good on the amro1 slash 2.

My experience with racing dinghies with/without the hard chine shows that the ones with the hard chine are much more challenging to sail downwind in stiff breeze. Those hulls tend to steer very eagerly in the opposite direction of the heel - resulting in big problems if the heel is windward! (read: more heel, more steering, gybe, sailor under, boat over). Whereas the smooth chined boats are a bit less “quirky” in this sense.

I don’t know if this is applicable to RC-sized craft, but it’ll sure be interesting to see! I’m hoping that the canting keel (if it works!) is going to provide me some “buffer” over this effect.

Cheers, vrihu

The chine transition from radiused to squarish has been used for a very long time. 35 years ago I had a Proctor International 10 meter Canoe. Proctor made that little design feature so that the boat would be quicker to plane. Many IC sailors still use that design feature to good result.

I have some doubts about that application for our RC boats. We are cursed by having to drag a fin and bulb through the water. Our boats are not likely to plane. Sometimes they might surf a little bit but a full on plane is rare indeed. The drag penalty of the square chine part will likely work against us on a running leg, when the boat is upright. Square chines can become an asset when the boat is heeled to an appropriate angle. Exit flow is very nice under the right circumstance as mentioned in a previous reply.

Mllertime; I have been interested in Ray hunts 110 design as a model for some time. The hull construction could not be more simple. It is essentially a box, plumb sides and all. I labored at length over a plan set that resembled the 110. I could not get my mind at ease with the double ended feature. The reason for the reservations was the probability of having a rocking chair boat (serious pitching) caused by the pendulum affect of the deep bulb. The full sized boat did not have nearly as much (scale) fin depth as we are obliged to use. So it was not as seriously inclined to be bothered with excessive pitching plus it ad the benefit of movable crew ballast.

My 110 boat morphed into a scow with narrow ends. Hopefully that will dampen the expected oscillations. The scow is Marblehead size. 50" x 8.5" with 3" transoms at both ends. All up displacement 8.0 pounds. It has hard chines but they are softened forward with a half inch radius and taper to a very small radius aft. The boat will be ready to splash in a week or so. I do not expect that it will be a big time winner except in a narrowly defined set of conditions. That will be when the designed optimum heel angle and wind strength are in agreement and the water is not too lumpy. Under those conditions I believe it will be a ripper on beats and reaches. Some of my other experimental models have led me to this high hope.

Keep us posted about the hard chined 110