Chines and tracking

B

bmacpiper

New member
Hi all,
Posted a while back about following seas, and have been experimenting with them since then. I've learned a lot and have gotten much more familiar with the dory. One thing I notice is that the boat is very willing to slip sideways and/or roll when I'm quartering off the following seas, which makes for a lot of work on the wheel and throttle.

I searched this site for past discussions on adding chines or keel strips, and found a little info, but mainly it was relating to much older C-Dorys. I am still wondering whether anyone with a more recent hull has added chines, what the results were, etc. Are there pre-fab kits, or would I need to glass these on myself?

Any strong arguments for or against?

Other than this handling issue, I have been having high times with the new boat--finally got the new garage door installed so she fits at the house now.

tx,
bmc
 
bmacpiper, you rally have me confused. The C Dory by defination is a hard chine boat. What do you want to modify? Chine

:Nautical. The line of intersection between the side and bottom of a flatbottom or V-bottom boat.

One of the reasons that the semi dory hull forum is very seaworthy is that is will slide sideways and not trip on a keel or a deep V.

I think that you would negate some of the seaworthy properties of the hull form by adding a keel.
 
I can relate. Until I discovered a simple tool that made those necessary snap moves a snap, I endured following seas and all that came with them.
It seemed I was neither agile or fast enough to out steer them and the fun meter was way low.
When I discovered the "Steering Ball", suicide ball, whatever, my woes ended. I built mine, have used it all year and would not own a boat without one. Yep, it helped that much.
Might think about giving er a try.
Mike
 
Thataway: From Chapman's, "Some modern boats are designed with multiple chines (longitudinal steps) for a softer ride at high speeds in rough water; this is often referred to as deep-vee design. Larger round-bottom vessels may be built with bilge keels--secondary extenal keels at the turn of the bilge that reduce the vessel's tendency to roll in beam seas."

So here's what I'm after. In a following or quartering sea, the dory slips sideways and rolls a lot. It is very discomforting and takes constant attention to the wheel and throttle. What I'm thinking about is two chines that run from the transom forward, roughly halfway between the mini-keel and the turn of the bilge on each side. They would be triangular in cross-section, with a vertical side towards the keel, and a tapered side towards the gunwale. Thought being that it would resist sideways motion (slip/yaw and roll), but not affect forward motion/drag. I would expect it would take a vertical face of 1.5 to 2 inches at a minimum to affect much change, but that's the question: what have others done to address this, what results, etc.???

Alasgun: do you have a link for this? I'll google as well, but if you know of a good location for one...

Thanks to all,
bmc
 
bmacpiper said:
So here's what I'm after. In a following or quartering sea, the dory slips sideways and rolls a lot. It is very discomforting and takes constant attention to the wheel and throttle. What I'm thinking about is two chines that run from the transom forward, roughly halfway between the mini-keel and the turn of the bilge on each side. They would be triangular in cross-section, with a vertical side towards the keel, and a tapered side towards the gunwale. Thought being that it would resist sideways motion (slip/yaw and roll), but not affect forward motion/drag. I would expect it would take a vertical face of 1.5 to 2 inches at a minimum to affect much change, but that's the question: what have others done to address this, what results, etc.???




Buy a different boat? What I do in following seas is trim motor way up & gass it, if you are being overtaken by the wave behind you you are not in the throttle enough! It is amazing how much BIG WATER these little boats take!!!
Good luck! :mrgreen: :beer
Click to expand...
 
You have a semi dory--this is a type of hull. With it come some good features. This is also what I mean by people buying a C Dory and not understanding the boat.--I am not picking on you--but you want a different type of boat, or so you think. You cannot make a semidory into a deep V by adding strakes. If you drive a deep V in a following sea, you may very rapidly change your mind. The deep V is more in its "element" going into seas.

By attempting to put some strakes,--and that is what you are describing--not chines--(chines are a part of the hull, and you cannot change that), you will seriously modify the handling of the C Dory. 1.5 to 2" bilge keel will do nothing, but perhaps slow the boat down a little. I can tell you what you are suggesting will not work--and it may cause other handling problems.

As tsturm says, you have to drive the boat so it stays on the back of the wave--and work thru the seas--this is the nature of this little sea worthy boat! Some dealers have recently started carrying a different brand of a hull which is a down east type of hull; it has a keel, and there have been some folks who didn't understand that type of boat and were terrified by it in the same type of conditions you describe.
 
tsturm":2ysluh0x said:
What I do in following seas is trim motor way up & gass it, if you are being overtaken by the wave behind you you are not in the throttle enough!
Click to expand...

Please clarify for me what trimming the motor way up does for you under these conditions.

Thanks,
Warren
 
thataway--
OK, we can argue about what they're called--strakes or chines--but you get the idea. I don't want a different type of boat, I want to improve the one I have (if it is indeed possible).

So you mention slowing the boat down, it won't work, and possibly inducing other handling problems. Please elaborate, if you care to. Generic statements like that are not helpful unless you can help me understand the why of the matter. Are you saying that the sideslip and roll make the dory more seaworthy? If so, why?

tx,
bmc
 
Very seldom do I make throttle adjustments, generally finding a workable setting and concentrate on the steering. With a ball, split second changes are easily accomplished. I find myself making corrections just before they are needed and can actually maintain a good course thru a most uncomfortable sea. We have several locations in Prince William Sound where a confused chop / sea condition exist and when combined with any wind a real challenge exist. I have literally been thrown out of my seat on a couple occasions when trying to negotiate these areas BEFORE I got onto the steering ball.
Someone on this site got me thinking about these balls a while back and I believe their post related to docking. Believe me, it will help more than your docking. A side benefit is my 4 yr old grandson can steer quite well by getting on his knees and using the ball.
The better marine sites list an Edison brand which runs upwards of $50, ebay has some automotive types for under $20.
One more tidbit that will reap a long term benefit, be patient , there are some real sailors on the site who are quite willing to help out.
Mike
 
bmc -

With all due respect, you are asking some very difficult questions. Experienced marine architects debate these issues endlessly, leading to dozens and dozens of of hull designs, optimized for various conditions.

When I took a Power Squadron course, they spent several hours describing the pros and cons of various hull types, barely scratching the surface! Round bottom displacement hulls sit down in water; they don't plane, they go slow, but they carry a lot of cargo, and are very economical to move through the water. OTOH, they roll terribly without some sort of stabilizers. Deep-V hulls cut through the chop more smoothly and reduce pounding, but require higher speeds, and therefore much more power (and fuel) to get up on a plane than a flatter dory hull. The C-Dory planes very easily, but tends to pound at higher speeds. A C-D might have to slow down for a more comfortable ride, but it will still stay up on a plane at these intermediate speeds. If a deep-V slows down much, it drops off the plane and must go much slower -- there's no 'intermediate'.

All designs are compromises, and many are hybrids (semi-displacement hulls; fast trawlers), but each feature provides its own advantages and disadvantages under different conditions.

These comments do not directly address your handling questions, However, it is very unlikely you are going to 'improve' the handling of your current boat any more than you'd be able to re-design (and build) a new suspension for your car. (Sprung weight; un-sprung weight; tire size, width, pressure; spring coefficients; shock absorbers; wheelbase; turning radius; not for the faint of heart!) It is MUCH more likely you will make the hull worse -- maybe dangerously worse.

You mention 'slipping' and 'rolling'. The 'rolling' may not be comfortable, but if I understand what you are saying, the 'slipping' is actually preventing even more rolling. Your proposed design could cause the hull to 'catch' as it attempts to slip sideways -- if you think you're rolling now, you ain't seen nothin' yet!

I'm sure Bob will comment further, but the practical goal should be to learn how to handle your current hull under a variety of circumstances, and/or know when and how to avoid those circumstances if necessary. If those circumstances are common, and you want to be out there under those conditions, and the boat simply does not handle to your satisfaction, you may indeed be better off with a different hull design altogether.

Good luck!

iggy
 
Hi Folks,

When I took my 1983 C-Dory across Nantucket Sound in 25 to 35 Knot winds, I had the wind on my port bow, and had to "play" with the wheel as the waves came by. When a big one came, the boat just rose with the wave,and the wave went under the boat. (In breaking seas it might had been a different story.) The boat responded beautifully, but it was a lot of work.

Would I ever do it again? No. Am I glad I did it? Yes. I got to see how the C-dory handled rough seas and high wind. Just beautifully.

Fred
 
Hi Bmacpiper
IMHO you should not change your boat.

One thing to consider is your load. How much excess weight is forward?

The main tools are your helm and throttle. I like to stay on top of the swells in a following sea. I back off throttle when it feels like I am dropping into the swell. If the swell passes you can throttle up and stay on the back of the swell, this is a safe place. When a swell lifts you, if your not into surfing it, then back off throttles till you are on top, then throttle up and stay there.

I am not talking about doing this in breaking waves. Then you want to be on the back of the swell or better yet in port. Practice, practice and practice.

1tuberider
 
Lori Ann":10bfz97q said:
tsturm":10bfz97q said:
What I do in following seas is trim motor way up & gass it, if you are being overtaken by the wave behind you you are not in the throttle enough!
Click to expand...

Please clarify for me what trimming the motor way up does for you under these conditions.

Thanks,
Warren
Click to expand...

It keeps your bow from digging into the wave in front of you. Kind of allows you to ride the back of the wave in front of you! :mrgreen: :beer
 
Thanks again to all--I do appreciate the varied input. Of course my first choice is avoidance of the seas mentioned, but I also want to be ready if and when I get caught, which we all do. For now I'll keep practicing and getting comfortable--I had made a decision when I bought the boat not to make any significant changes until I have at least a year behind me, and this is no exception.

Looking forward to meeting some of you down the road!

bmc
 
tsturm":38b2hqs4 said:
It keeps your bow from digging into the wave in front of you. Kind of allows you to ride the back of the wave in front of you!
Click to expand...

Doesn't that increase the chance that the props will be out of the water more as you rock forward and aft with wave motion?

This is not something I have experienced yet, so I am not trying to be contentious, just trying to understand what I should do when confronted with those conditions!

Thanks again,
Warren
 
Greetings. Here's another possible solution to handling problems in larger seas: Run with a prop that's as low pitch as your general boating will allow. I don't know - you may already be doing this. The effect is to "downshift" your engine and therefore give you quicker throttle response, the ability to stay on/climb the backside of waves in a following sea, better load handling, etc. We almost always run heavily loaded and often in rough seas, so I tend to choose the lowest pitch prop of the range normally recommended. Good luck! Mike.
 
bmacpiper;
Keep in mind that you are in a very small boat. Those responding to your inquiry are runnirg 22 and 25 foot boats. There is a world of difference in what you can do in a 22-25 foot boat compared to a 16.
Am advice is to accept tour boat's limitations or move up. As for myself, I have traveled the other direction, 22 Whaler to 17 Arima to 16 C -Dory and an having the most fun ever!
 
Lori Ann":38ir612e said:
tsturm":38ir612e said:
It keeps your bow from digging into the wave in front of you. Kind of allows you to ride the back of the wave in front of you!
Click to expand...

Doesn't that increase the chance that the props will be out of the water more as you rock forward and aft with wave motion?

This is not something I have experienced yet, so I am not trying to be contentious, just trying to understand what I should do when confronted with those conditions!

Thanks again,
Warren
Click to expand...

I am POOR only 1 prop to worry about :lol: You just bump the Mtr. down if it Cavitates :mrgreen: :beer [/size][/color][/color]
 
bmacpiper
Capt Jim noted something which I was going to also note. The boats do not "scale" up and down exactly--ie the way the 16 handles does not necessarilly relate to the way the 22 and 25 handle. (and they are not exactly the same either).

The 16 is a small boat--especially for heavy seas. I had a 16 foot dory, which I used to row at least 6 miles a day--sometimes in the open ocean where it was rough. The Grand Banks fishermen trusted their lives to the dory configuration, as did the early attempts to row across the Atlantic Ocean. The reason is that the dory hull slips sideways when on a wave, it does not dig in, it does not trip. The semi dory has a wider stern, than the "tomb stone" transom of a dory. I suggest you by a book, by David Gerr; "The nature of boats". David Gerr is a very good Naval Archetect who explains hull types. A true multi chine boat, has semi rounded "sides" where the hull attatches to the bottom. The C Dory has almost a flat bottom (some rocker fore and aft)--with an abrupt angle at the sides. A multi chine boat, would have several pannels where there is a transition to the side of the boat, and is usually a semi displacement boat.

The strakes will modify the way that water flow under the craft, and it may make the boat "squirley" at higher speeds, They may "dig" in just when you want the boat to slide sideways.

The alternative to sliding, is for the boat to heel, or for the boat to dig in. This can cause the boat to broach or to capsize. The "cork" effect of the flat bottom, is what makes the C Dory so sea worthy. The ability to slide down the face of a wave, without broaching or digging also adds to this seaworthyness. The origional 22's were more of a true semi dory, with no "v" foreward--this caused slightly more pounding, but had some other virtues...so there are always trade offs.

When we were building boats, we had shared space with a number of other builders--and some folks came in and modified their boats. Many times the boats behaved poorly afterwards--same for amateur designed boats--"new and novel ideas"--the could not sell the boat afterward.

In order to modify your boat, you would have to grind down the boat to the glass. Then glue in place foam or wood for the "forum", and then cover this forum, with glass and epoxy. This would have to be faired in with the rest of the bottom of the boat. You should not screw anything to the bottom of a C Dory for the risk of water intrustion into the Balsa core. Probably the best way to do what you want to do, is to turn the boat upside down. Then you can use weights to hold the material in place while the epoxy goes off on the forum which forms the "new" strake.

Trimming up--just enough to bring the bow up, not to bring the prop out of the water. In fact you want to avoid bringing the props out of the water.

Heavy seas--we were caught in hurricane force winds crossing the Atlantic East bound. (not in a C Dory) We kept the boat on autopilot except when the dog had to go to the bathroom...Then I had steered, and took the boat straight down the seas (40 to 45 feet and breaking) and I attempted to keep any waves from breaking on the boat. The boat rolled to 90 degrees once--and over 75 degrees a number of times. A well designed boat, handled properly will handle a lot of heavy seas, and survive.
 
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