Taken from the R/C Forum on why chines boats work thanks to Craig Richards SA 


There is a discussion on a boat design forum about chines. I have quoted an iteresting take below: 

I mentioned earlier that I thought the Britpop had a "light" bow .. this explanation would suggest that it allows it to point better upwind.

http://www.boatdesign.net/forums/hyd...m-41874-2.html.

“I read through the newsletter section about chined hullforms, and a few things are apparent to me from the discussion and the photographs. The picture of the IOM chined boat on page 14, compared to the pictures of other boats on later pages, shows the hull with comparatively full sections forward, a lot of rocker, and very slight sections aft. The other boats, such as the SKAs, have finer sections forward, less rocker, and fuller sections aft.

The new IOM chined hull seems to have better pointing ability because as the boat heels, the volume distribution and particularly the waterplane shape at heel promote lifting the bow. As the French designer in the article indicates, the chine is just a consequence of how he wanted to shape the heeled waterplane--he wanted slack sections aft, not full sections, so that as the boat heeled, the narrower waterplane aft allows the stern to sink a touch more and, correspondingly, the bow to rise, pointing a little more to weather, which is the direction you want to go anyway. And as the boat heels this way, it also increases the angle of attack on the keel and rudder, which increases lift, and with more lift, there is more power pulling the boat to windward. the boat balances better with less increase in weather helm.

This effect has been known for well over a hundred years, and as I have stated before elsewhere in this forum, most latter-twentieth-century designer types, collectively, seemed to have unlearned this lesson. This has more to do with heeled waterplane shape and controlling the center of that shape, the longitudinal center of flotation (LCF) than it does with the chine. Therefore, I agree with the French designer.

Capt. Nat Herreshoff, the winningest designer of the latter 19th and early 20th centuries, promoted this feature in his hull shapes--slack stern sections compared to fuller bow sections to control the LCF. As the boat heels, LCF should either stay in the same fore/aft position, or move forward slightly. As the boat heels, the bow lifts, the stern sinks, angle of attack is increased, the boat sails to weather better.

In modern times, over the last few decades particularly, we have seen hulls getting wider and wider and with fuller sections aft. Of course, you can get more stuff into such hulls, but at the same time, the builders and designers of such craft have been touting "powerful stern sections" as an indicator of superior performance. Nothing can be further from the truth, and in my opinion, "power stern sections" is a hoax. Such boats do not sail well, they balance poorly to more bow-down attitudes and pick up weather helm as a result. They're cranky. You'd see this in their heeled waterlines, they are fuller aft; the LCF moves aft as the boat heelsl. So, heeling over, they pick up more buoyancy aft, which raises the stern, depresses the bow casting it to leeward, and reducing the angle of attack on the keel and rudder--all just the opposite of what you are seeing on your new chined IOM models.

So, the better performance does not come strictly from the chine--rather, it is all about area distribution of the waterplane which is shaped by consequence from the chine to produce the desired bow-lifting effect. You can do the same thing without a chine, but the chine, in this case, seems to accentuate the effect.”


In the Photo page there are 4 photos of new chine boats

Hi,
This is my first posting on this site.

I was made aware of it by a colleague.

Interesting take/s on the effect of chines.

My first chined boat is the one in the photo in the Seattle news letter which Eric has referred to.I was asked to write a few lines re the effect of chines on an IOM R/C yacht. In brief I stated that what I saw was a reduced hull size, especially on the windward side.Reduced mass and what I regard as a useful function in providing "grip" on the leeward side.
This last function drew a contrary opinion from an unnamed source who stated that it served no such purpose.

I do not have letters after my name relating to boat design, but having sailed for longer than I like to remember and gathering information and designing what could be referred to as successful R/C boats, I think I have some idea of what happens to a hull when sailing.
After seeing chined R/C hulls and how they handled, especially in stronger winds, I decided to try my hand at designing one.

The result was a boat named Cheinz that performed very well "straight out of the box" at the 2011 IOM Worlds.
I still say that chines have an effect on minimizing leeward drift.Don't have to be a scientist. Take a piece of plywood and drag it sideways through the water at say 45 deg to the direction of drag. Now do it at 90 deg. Which produces the most resistance?.The chines angle the topsides to give a less angled "bite" to the water.
All the discussion about "lift" to windward from foils does not gel with me. I think they minimize slip to leeward.After all they are not like plane wings. They are uniform on both sides!. Some are better than others!.

If you can add "grip" from another source,(chines), it can only be beneficial as long as the chines do not have detrimental effects to cancel out the benefits.
Have yet to find out if there are detrimental effects so far and have tried the chines out on a 10 rater and a just launched Marblehead (Won 29 of 34 races in it's first event).This boat also has a reverse bow. On first tryout this also seemed to do the job. In one race (over rigged), it powered downwind with the bow depressed but not right under and still steered dead straight. Very encouraging!.

Still have things to try, but for me chines work. Don't fully understand why and don't have the training etc to try and explain. Sometimes ignorance is bliss. Ask a hummingbird!.

By the way, have discussed this subject with another R/C boat designer. First of the modern era to use chines and also another who designs big boats and both agree that chines provide resistance to leeward drift.