Baby Dot new saling dinghy design

[Tim Marchetti]

The reference is in F. S. Blanchards's "One Design Classes of North America. "Richard Sarby set to building a duplicate hull of his fastest class E sailing canoe class. After doing so he sawed off the last four feet and nailed on a transom." Design was for the '52 Olympic games.
Tim, really nice looking boat - My suggestions are just response after a first look - you've obviously spent a lot more time gazing at the lines! Nice to see your talent with Rhino. We use it extensively at USNA to cut models. Great program.
Comment - far too many modern "classic" designs don't have enough sail area. The outboard, to get us home has reduced the need for good light air sailing ability. Look at the huge sail plans of older boats - they are huge! Reefing was, I'm sure, common and done early - probably on the mooring. Glad to see the larger sail on your boat. Combined with light spars should make for a fun boat.

Thanks for the kind words. Any thoughts on the rudder design?

[johnw]

I think a lot of the comments on this thread have to do with people not recognizing that a gaff rig is not efficient by the square foot, it's efficient in terms of power versus stability. In any case, it's a lot easier to cut the rig down than to increase it, so if you start with what turns out to be too much sail, you can easily fix that.

[tprice]

Tim,
On the rudder, 2 things. The gap between the skeg and the rudder is probably a bad thing. The other is that the geometry of a rudder on a raked transom gets really weird when it's turned. It's now trying to turn into a dive plane! Really draggy. The raked transom is a signature part of your design and looks great but make sure your rudder is as un- barn door like as possible! I'd suggest extending it down on the leading edge to the skeg bottom then angling it aft. Take a piece of card stock and play with it and you'll see that with more rake, the rudder when turned isn't really deflecting water to turn - it tries more to depress the stern. You may end up turning because of asymmetrical drag from one side of the boat - which will be slow especially in tacking. Picture the worst case - a weird rudder hung down on a horizontal stern post (impossible but bear with me). Turning the now vertical tiller would angle the rudder but do nothing to steer the boat. Now add heeling and the slanted transom rudder geometry gets even stranger! Flow lines start to go diagonally across the foil.
Swept wing aircraft have to deal with weird rolling and yaw because of their ailerons on the trailing edge of swept wings but they have other axis foils to balance it.
Actually
One suggestion is to keep the transom rake - it looks great!- put on a tapered stern post (from little at the top to more at the bottom to minimize rudder post rake while retaining the nice raked transom? Angle the rudder blade aft below the skeg and keep it narrow.

[Tim Marchetti]

Tim,
On the rudder, 2 things. The gap between the skeg and the rudder is probably a bad thing. The other is that the geometry of a rudder on a raked transom gets really weird when it's turned. It's now trying to turn into a dive plane! Really draggy. The raked transom is a signature part of your design and looks great but make sure your rudder is as un- barn door like as possible! I'd suggest extending it down on the leading edge to the skeg bottom then angling it aft. Take a piece of card stock and play with it and you'll see that with more rake, the rudder when turned isn't really deflecting water to turn - it tries more to depress the stern. You may end up turning because of asymmetrical drag from one side of the boat - which will be slow especially in tacking. Picture the worst case - a weird rudder hung down on a horizontal stern post (impossible but bear with me). Turning the now vertical tiller would angle the rudder but do nothing to steer the boat. Now add heeling and the slanted transom rudder geometry gets even stranger! Flow lines start to go diagonally across the foil.
Swept wing aircraft have to deal with weird rolling and yaw because of their ailerons on the trailing edge of swept wings but they have other axis foils to balance it.
Actually
One suggestion is to keep the transom rake - it looks great!- put on a tapered stern post (from little at the top to more at the bottom to minimize rudder post rake while retaining the nice raked transom? Angle the rudder blade aft below the skeg and keep it narrow.

Thanks I'll draw something up

[Michael Wick]

Tim,

I have a John Brady designed Melonseed 15 1/2 by 5 1/2 (He calls it a melonseed cat), and it has taken me 300 miles in the lower Chesapeake this summer. It is very similar and is a fine boat. For a picture, see www.traditionalsmallcraft.com under PEPITA. Mike Wick

[Tim Marchetti]

Tim,
On the rudder, 2 things. The gap between the skeg and the rudder is probably a bad thing. The other is that the geometry of a rudder on a raked transom gets really weird when it's turned. It's now trying to turn into a dive plane! Really draggy. The raked transom is a signature part of your design and looks great but make sure your rudder is as un- barn door like as possible! I'd suggest extending it down on the leading edge to the skeg bottom then angling it aft. Take a piece of card stock and play with it and you'll see that with more rake, the rudder when turned isn't really deflecting water to turn - it tries more to depress the stern. You may end up turning because of asymmetrical drag from one side of the boat - which will be slow especially in tacking. Picture the worst case - a weird rudder hung down on a horizontal stern post (impossible but bear with me). Turning the now vertical tiller would angle the rudder but do nothing to steer the boat. Now add heeling and the slanted transom rudder geometry gets even stranger! Flow lines start to go diagonally across the foil.
Swept wing aircraft have to deal with weird rolling and yaw because of their ailerons on the trailing edge of swept wings but they have other axis foils to balance it.
Actually
One suggestion is to keep the transom rake - it looks great!- put on a tapered stern post (from little at the top to more at the bottom to minimize rudder post rake while retaining the nice raked transom? Angle the rudder blade aft below the skeg and keep it narrow.

either of these in the ball park?

[Tim Marchetti]

Tim,

I have a John Brady designed Melonseed 15 1/2 by 5 1/2 (He calls it a melonseed cat), and it has taken me 300 miles in the lower Chesapeake this summer. It is very similar and is a fine boat. For a picture, see www.traditionalsmallcraft.com under PEPITA. Mike Wick

Nice Melonseed Mike. It's a design I thoght about, but it is smaller than what I wanted. Here's the 16 foot Melonseed next to Baby Dot.

[rbgarr]

This boat the Presto 30, while twice the size of yours, has a similar shape and its kick-up rudder that has been proven very effective. Ryder is not far from you either, so a drive up there could be worthwhile. http://www.ryderboats.com/video_gallery.html

Thor Emory has a Presto in Rockland and lives in Lincolnville so ask him how well his version of the rudder does. http://www.thorfinnexpeditions.com/

[Tim Marchetti]

This boat the Presto 30, while twice the size of yours, has a similar shape and its kick-up rudder that has been proven very effective. Ryder is not far from you either, so a drive up there could be worthwhile. http://www.ryderboats.com/video_gallery.html

Thor Emory has a Presto in Rockland and lives in Lincolnville so ask him how well his version of the rudder does. http://www.thorfinnexpeditions.com/

thanks, I'll check it out

[Michael Wick]

Looks like you've got more freeboard; that could be a good thing at times. She does get wet, but very seaworthy.

[woodsail]

Take a look at these which are a smaller version, somewhat similar. They can be sailed in up to 25kt in reasonably sheltered waters. 250 pounds, 11'3" long 64 sq ft sail - all spars fit within the boat length.

http://www.youtube.com/watch?v=2n-d6O5SKNk

good luck

[rbgarr]

I wouldn't think that scow is suitable for Penobscot Bay.

[Michael Wick]

Tim,

My buddy and I are trailering the Marshcat he built to Key West and then sailing toward the Dry Tortugas. See our entry in People and Places. I will look to find out, but I think BABY DOT would be a perfect boat for that kind of trip.

[Tim Marchetti]

Thanks Mike I'll check it out. That would be a loooooong haul for me and a bit out of my comfort zone. I hope you have a fun/safe trip.

[Michael Wick]

Tim, I hope so, too.
How about the Small Reach Regatta ? That is closer and I'm bringing my Cortez Melonseed build.

[Tim Marchetti]

I have to see if I can get her built first

[rbgarr]

Nice mention of your CNC services in the Rockport Marine blog!

[Tim Marchetti]

Nice mention of your CNC services in the Rockport Marine blog!

Thank you for pointing that out. I had no idea.
I'll be making a bunch of those blocks soon.

[Tim Marchetti]

Well, I've started a build thread. Economics has got me considering the balanced lug rig, but I need some education first. Any advise on finding design information.

[Eric Hvalsoe]

I think the lines are sweet. I would not call the bilge slack, it is a round bottom after all.

[Tim Marchetti]

Thanks Erik. Now that I have the mold set up, I am liking the lines even more.

[Binnacle Bat]

Nice shape! Would it be 'shifting' water ballast?

Some comparisons, for what it's worth:

Your hull design is somewhat reminiscent of the Finn, 14+' long, which has quite a bit less sail area (115 sq. feet) yet is something of a demanding beast to sail, at least singlehanded. http://en.wikipedia.org/wiki/Finn_(dinghy) The Finn has a flatter underbody so it will be more likely to plane than yours.

The Cotuit Skiff, also 14+', has a gaff rig with 144 sg. feet of sail but the boom is 17' long, resulting in a lower CE to the sail area.

The 17' Thistle has about 155 sq feet of sail area in the mainsail alone. I've sailed them single handed with the main alone and they are a handful in anything above six knots of wind. http://en.wikipedia.org/wiki/Thistle_(dinghy)

The 17' Coquina has a shape more like your hull but 131 square feet of sail split between two masts: http://www.woodenboat.com/boatplansa...oquina-34.html

Thus, I suspect your relatively tall gaff rig will be a bit much for a single person to handle without being prepared to reef early, so it's really a two-handed boat for the most part.

Good luck!

That's all true, but this design has 400 lbs of water ballast to keep her upright in a breeze. I'd be tempted to rig the gaff less sharply peaked, so the center of effort moves less as you reef down.

The Thistle tends to be a bear under main alone as she is so out of balance, even with the center board well up and aft. I have two sets of reef points in mine, usually sailing alone, reefing early and often. I prefer a big rig, easily reefed, to an undersized one. There is a steep learning curve however.

Allan

[frank pedersen]

Tim,

I agree with Tom's suggestion re the rudder. The pivot point for the blade could be lower than in your post #56, which might give more strength where the head of the rudder attaches to the tapered stern post. Generally a somewhat high aspect ratio blade is desirable, and a deeper blade insures against loss of control with more severe heeling.

One problem with a double bottom for a self-bailing cockpit is that buoyancy in the bottom of a boat tends to encourage the hull to turn turtle when it is on its side after a capsize. While buoyancy under the seats will slightly off-set that effect, there was a version of the Wayfarer with a double bottom that tended to turn turtle in a capsize situation.

Question to Woodsail: What is that design in your youtube video?

Frank

[Tim Marchetti]

Tim,

I agree with Tom's suggestion re the rudder. The pivot point for the blade could be lower than in your post #56, which might give more strength where the head of the rudder attaches to the tapered stern post. Generally a somewhat high aspect ratio blade is desirable, and a deeper blade insures against loss of control with more severe heeling.
One problem with a double bottom for a self-bailing cockpit is that buoyancy in the bottom of a boat tends to encourage the hull to turn turtle when it is on its side after a capsize. While buoyancy under the seats will slightly off-set that effect, there was a version of the Wayfarer with a double bottom that tended to turn turtle in a capsize situation.

Question to Woodsail: What is that design in your youtube video?

Frank

Thanks Frank, I've already scratched the self-bailing idea. The flotation will be in the side benches and I am keeping the water balast option open.

[Nicholas Scheuer]

She looks absolutely lovely to me.

[Tim Marchetti]

Thanks Nicholas, I have started a build thread if you want to check it out

[Tim Marchetti]

My mind has been opened and I'm starting to like the idea of a balanced lug. My reluctance was due to ignorance of the rig. After doing some research I have discovered what several people that have commented here already know. So, here she is with a 140 sq. ft. balanced lug. My wife likes the dark red hull, what do you folks think.

[Lewisboater]

Careful with dark colors...they absorb solar heat and the epoxy underneath might soften in steady bright sunlight. A good bang against it when hot and tender might breach the coating and ruin the paint too. If it has cloth on it you might cause it to wrinkle if the temp and the impact is strong enough...even in Maine. Good choice on the BL...I really like it. I am also partial to the Sliding Gunter...kinda like a switchblade Marconi.

[wtarzia]

Careful with dark colors...they absorb solar heat and the epoxy underneath might soften in steady bright sunlight. A good bang against it when hot and tender might breach the coating and ruin the paint too. If it has cloth on it you might cause it to wrinkle if the temp and the impact is strong enough...even in Maine. Good choice on the BL...I really like it. I am also partial to the Sliding Gunter...kinda like a switchblade Marconi.

--- I've wondered about that since I coat the bottom of my boat with epoxy graphite, no paint, and though to do not store outside or upside down, I've thought about UV degration of the bottom through refraction in the water. I left outside (two years now) a piece of pine coated as I do my hull, in the open sun. It was a little scuffed to begin with (so more likely to absorb rather than reflect, and already had a chip in it down the raw wood, so moisture could get in. I have not examined very closely yet, and maybe the damage would not be eye-evident until too late, but so far, I have not seen serious degradation of his very black epoxy-graphite left out in an abusive situation (all but salt water, true). FWIW -- Wade

[Lewisboater]

Have you ever smacked it against anything after sitting in the sun for a couple of hours in the middle of the afternoon on a clear sunny day at the end of July? I have seen epoxy take a fingerprint (permanently) after sitting in the sun for an hour or so.