CS17 mk3 hull #3 "Carlita"

[Designer]

Phil,

 

Mat's chine runners was to be one of my tests. I was going to attempt to hot glue one on one side of the boat and go out and compare the course made good on the GPS verses the heading on each tack and compare.

 

Mat's boats have flat bottoms with vertical sides, he runs the chine runners out horizontally. Because we have a V bottom and the sides have flare, I was going to try different angles below horizontal. I never expected them to be that good but I saw one of his boats tacking in light air and it was better than I expected.

 

I carried the mizzen staysail on the bowsprit. To cancel out the lee helm I fitted a small bow board. it did appear to eliminate the lee helm but it needs more testing.

[PAR]

Graham, I've done some testing with chine runners and I've found (as you suspected I'll bet) that certain hull forms do well, while others don't. The hulls that seems to do well, had a lot of chine bury and/or bottom rocker, while flatter run plane hulls didn't respond, nearly as well. On a few plane hulls, the boat did decrease leeward skid some, but suffered a lot of additional drag once the wind was abeam or aft. 

[alexscott]

Stopper Knots

 

Graham- I consulted my guru on ropes, wire & rigging, Brion Toss (Rigger's Apprentice). Your idea of leaving a 6 diameter tail behind your sheet & halyard stopper knots is excellent, but instead of a figure eight knot, consider a Stevedore's Knot or an Oysterman's Stopper. Both have more turns, and should be more secure in modern slippery cordage "I felt the stopper knot unroll in my hand",

See http://www.handymariner.com/tag/stopper-knot/

[Designer]

Carlita gets a visitor.

 

Fortuitously we got a visit this weekend from Vlad "Crazy Russian" who with his partner LRock beat out Alan in the Ultimate Florida Challenge. Behind his car was a Matt Layden 14' Enigma with chine runners.

 

We sailed both boats at different times. I am still amazed that the chine runners work as well as they do but my best guess was that she tacked through about 120 degrees. My GPS batteries battery was flat,  I was inside and forward because there is no cockpit, trying to get some readings on my cell phone. It was windy and during a bad jibe she capsized and came close to a complete inversion. It would have been easy to swim out through the submerged hatch but I was trying to save the phone, there was a pocket of air so that I could breathe and keep the phone dry. Vlad worked the boat more on its side by the time Nat arrived in our dinghy. I was able to pass the phone out to through the now above water hatch to Nat in the dinghy. Nat rowed us back to the dock as we got the sail down and I cut down a plastic water bottle for a bailer and started bailing. The phone is still working so far. Alan took some pictures of the capsize, he might pot a couple.

 

We had a short sail in Carlita late yesterday in 10 knots of wind. After studying the GPS track I was pleased to see that she made good about 100 degrees between tacks. It is raining all day but tomorrow afternoon looks good to do some testing. For those builders who have already finished their build, I would live with it for a while see if the tacking is acceptable. I am still going to extend my board and trunk.

[Steve W]

Graham, that sounds more like the tale of a 15 year old! Adventures like that keep you young!

[Action Tiger]

Does that Enigma boat have a boom furler? That looks neat.

It sorta looks like a 60s trimaran without the amas. The boat, not the furler...

I still think Carlita looks really cool with that paint job.

[Designer]

Yes she has boom roller furling. It is quite clever but does have some issues. 

[Action Tiger]

I would think a junk style lug would be cool for a boat like that. They reef simply and quickly, and if built right can be quite light.

[Tom Lathrop]

Graham,

 

Are you planning on bringing Carlita to the boat show this weekend?  I will wash the Winter off Lapwing and bring it. d

 

Tom

[Oyster]

 

Tom, I may need to clean some fish blood off of my backyarder and run it over for the day, if the weather works in our favor.[dang quote feature does not work correctly for me. ]

[Designer]

Tom,

 

I did not realize that it is next week. I have no alternative but to go, Carla and Beth have decreed it. Carlita will have to go in her undergarments.

[Steve W]

Graham, one question I have about Carlita is how well your system works for filling and emptying the water ballast. I am a fan of simplicity and I am hoping not to have a complicated electrical system. The tank on the 20.3 holds about 45 gallons of water. I can see letting gravity do it's thing and then taking a few buckets and topping it off, letting any water that splashes run out the self bailing cockpit. Or if necessary adding a whale gusher style pump to top it off. I look forward to your observations now that you've had experience.

[Alan Stewart]

All,

 

Graham and I took Carlita out for a sail yesterday to further evaluate the tacking angle of Graham's CS17Mk3. 

There is no current in the Bay river and the wind was a gusty as always in the river but more steady to the eastern side with greater fetch. The boat was a joy to sail and it was my first time at the helm. She is very stiff with the water ballast and we were full sail the whole time. She would lay over but only to a point and then just drive on upwind. Graham and I and the two dogs stayed nice and dry the whole time in the cockpit which was wonderful. Like a magic carpet ride. 

 

As you can see, the tacking angle is not really that bad. To a seasoned racer it may be frustrating at times but for anyone going out for a pleasure cruise which after all this boat excels at, the boat is no slouch and didn't have any trouble going to weather just to keep the discussion in perspective with some real world testing. 

 

The red angles we determined to be "outliers" and didn't include in the average. 

 

In the second picture, you can see Graham tacking into the third checkpoint in the EC and deciding to take the southern route. We think that he had some favorable current in this stretch because we can see that his speeds over ground were about the same as in our afternoon sail but the tacks are compressed consistent with favorable current. It may also be the case that in the heavy air conditions and being reefed down, Graham had the boat more dialed in for upwind work that we had yesterday. 

 

The third picture is from this past saturday when Graham went out sailing with Vlad (AKA Crazy Russian) who was helming the boat in light air conditions. Tacks show decent performance here too. 

 

 

 

[lakeland]

Thats some interesting details, thanks for posting. How much would those angles be improved with the modified board?

[Alan Stewart]

Hard to say with any certainty. There are so many variables including wind and water conditions. I'd like to do more testing on different days and Graham would like to try some temporary chine runners. I think this would be a cool solution because it would mean even better shallow water performance. One consideration is that chine runners may add some drag downwind if they are always submerged. They will also add some drag upwind but its possible that the reduction in leeway may reduce lift induced drag so much that overall drag upwind is reduced which would mean pointing higher and sailing faster. Or just sailing faster or just pointing higher. The thing we will look out for is an increase in velocity made good upwind. The trick will be lots of data because it's nearly impossible to test with the exact same settings and conditions. Performing the testing with and without chine runners on the same day I think will help to reduce condition related variables. Even attempting to sail the same course and compare.

[Chick Ludwig]

You need a REALLY BIG wind tunnel...

[Blkskmr]

Sometimes better is the enemy of good. 

 

Please keep us posted. But I am OK with this data. 

[Designer]

There has been a lot of discussion on rub rails for the mk3's. 

 

Here is what I am going to put on Carlita. I am going to use mahogany and 3/4" stainless hollow back.

 

It is an essential part of the boat. It has been stressful using the boat without it as it will not take much of a bump on the dock to damage the boat.

 

Hollow back is lighter and a lot cheaper than solid. For some strange reason 1/2" is more expensive than 3/4". I also do not think that 1/2" is not tough enough for a hard hit.

 

I do not want the rub rail to be visually heavy. I like what Jay put on his boat but I think that this will look better.

[PAR]

One other consideration with designing up rub rails is the bottom profile, which should be sloped inward, as Graham's drawing shows. I like steeper slopes and the point is it fends of the dock or another boat. As the boat rises and falls with wave action, a perpendicular cut profile will catch a dock or another boat if rafting up. This will damage the boat quickly, but the sloped underside will allow the boat to bounce off and away. Seems such a simple thing, but not so much if the rail is poorly shaped and hangs on a dock, possibly leaving the boat suspended in the air, dangling off a small portion of it's rub rail.

[Pete McCrary]

Would clear & straight yellow pin be an appropriate material? I already have two 22' x 1.5" x 3/4" pieces that I used as battens to make "fair" the side panel / sheer strake joint.