Deep Draft vs Shoal Draft Models

[Warren Kaplan]

Many boat manufacterers make both a shoal draft and a deep draft of the same model boat. Other than the draft difference, from my reading I see that shoal draft boats tend to be the heavier model, perhaps to use weight to make up for the loss of leverage stability below the waterline.

I'm interested if there are any other important differences in sailing characteristics between the two models of an otherwise identical design.

For instance, does the deep draft model point better than a shoal draft model. Does the deep draft track better than the shoal draft? When the weather and sea conditions get blustery is a deep draft boat more seaworthy than a shoal draft??

Any other comments about the characteristics and differences between deep and shoal drafts are welcome.

Thanks

[Clay Stalker]

Hi Warren-

Hope things are well with you. I believe the main purpose of shallow draft designs is to enable the boat to access shallower areas such as the Bahamas, Florida Keys, and some shallow coves and harbors. A deeper draft boat will definately point better, which is why most race boats have deep draft....they need to sail closer to the wind to be competitive on the race course. Stability and tracking are a different matter. Stability on a shallow draft boat is achieved either by widening the beam or placing more weight on the keel. Stablility on a deep draft boat is achieved by placing the weight lower and can result in a narrower beam, generally better for racing. Think J-Boats vs. Island Packets. Tracking is much better with a longer keel (think Cape Dory) but pointing ability is somewhat compromised. A deeper draft fin keel boat will point much better than a full keel and will tack quicker and with less effort. But fin keel boats are more difficult to manage on a run while a full keel boat will track much better. It's difficult to get it all in one package, so you have to decide on what aspects of boat performance are important to you....ex. speed, windward ability, stability, seakindliness, etc.

[Parfait's Provider]

I am feeling cantankerous today and would like to disagree with everything that Clay said; but I can't.

BTW, we watched Wind the other night and enjoyed the sailing shots a lot, the plot not so much, but it was fun.

[M. R. Bober]

Warren, with the shoal draft model there is a tendency to run hard aground closer to the shore than with the deeper draft version. Trust me on this. I have done some work in the lab, back in my Catalina days.

OBTW: RESPITE's winter cover came off on Saturday just before the rains came.

Mitchell Bober
Sunny Lancaster (not to be confused with Lancaster Court House), VA

[Warren Kaplan]

Warren, with the shoal draft model there is a tendency to run hard aground closer to the shore than with the deeper draft version. Trust me on this. I have done some work in the lab, back in my Catalina days.

OBTW: RESPITE's winter cover came off on Saturday just before the rains came.

Mitchell Bober
Sunny Lancaster (not to be confused with Lancaster Court House), VA

Mitch,

As with everything in this world, location is everything. I suspect on this one the nod goes to the shoal draft boat as running aground closer to shore is a definite plus over running aground far out in the anchorage!!

Lest you think I'm unappreciative, I thank you for doing all that yeoman's research in your Catalina to produce this report!!

[Dick Barthel]

Just to add a little more to what Clay has so well stated, I think that all things equal, the narrower beam (relative to length of course) also makes a boat more seaworthy for offshore work at the expense of initial stability. I think that's why Cape Dorys, like the 25D with only 8' of beam, have a reputation for being initially "tender" but they stiffen up after they begin to heel and end up with favorable capsize numbers. The broader beam boat has more initial stability but is more suspect offshore.

Assuming Clay is right that the shoal draft of the same model might be beamier, you would be deciding between the pros and cons of offshore vs. shallow water cruising which would involve compromise (as usual with most anything associated with sailing).

Warren, might you be shopping for a new boat?

Dick

[Warren Kaplan]

Warren, might you be shopping for a new boat?

Dick,

Decidedly not.......not unless my situation changes where I have infinitely more sailing time and would like a larger boat.

Actually, I was talking to a friend of mine at the yard the other day who owns a 30 footer. He actually said he'd love to scale down to a smaller boat because the big boat is too much trouble.

For what I do now, my CD27 is really perfect. As I said, if I had a couple of months off to do some serious cruising, a large vessel would be in order.

[Neil Gordon]

Assuming Clay is right that the shoal draft of the same model might be beamier, ...

I'd be surprised if a production boat with a choice of deep or shoal draft keels would pop the same size/model boat out of a different mold. I think it's just whatever keel they bolt on.

[Zeida]

Just this past week I had the opportunity to go for a sail in the Shannon 35 Shoal Sailer that is berthed right next to my CD-33. This is a brand new custom boat... extremely wide at the stern, with two wheels and two rudders and only 30 inches of keel and lots of very nice, plastic features. My CD looks and feels so much more solid next to her.

Although with lots of room inside and out, in the huge cockpit, perfect for a party boat, she did not point well at all, was mostly hobbyhorsing, very slow to get her moving. We ended up having to motor sail because the owner was embarrassed we were so slow in a very nice breeze. Under the same circumstances, my CD-33 would have been making 6.5 knots, while this shoal cruiser was barely doing 4. The owner told us Shannon was trying to lure the older sailors that are mostly leaving sailboats and going for trawlers, but this shoal sailer was neither, more like a hybrid, neither trawler nor sailboat. This was hull # 9 and not many more may be built. The model is not being too successful. A very powerful Yamaha was needed to really move her. The owners use it mostly for day sails and going to restaurants here and in the Bahamas...

[Cathy Monaghan]

Location and weight of the ballast (as well as all of a boat's cargo and tankage) also effect the center of gravity, center of buoyancy and righting moment of a vessel.

A shoal-draft vessel will usually have its CG (center of gravity) located higher in the boat than a deep-draft vessel, so the deep-draft vessel will have greater righting moment.

CLICK HERE if you want to read some technical stuff.

[Clay Stalker]

Dick and Neil-

I did not mean to suggest that the same boat could be modified with a different beam. Only that increasing beam is one way to increase stability. And this is only initial stability, not ultimate stability. Ultimate stability is a function of ballast displacement ratio and design.

Zeida-

Interesting comments on your experiences with the Shannon Shoalsailor. You are correct that probably no more will be built....it was an idea of Walter Shultz's that did not find a market....the idea is cool, the boat isn't. Shannon Yachts is located in Bristol, R.I. very near where I moor. They have for the third time emerged from bankruptsy and are now called Shultz Boat Company. They primarily restore old wooden boats and do factory overhauls of older Shannons.....very sad to see these old classic boat companies no longer able to compete in the marketplace.....

[Zeida]

Hi Clay... when the classic Shannons came into the market I still had my llittle CD25. After seeing the S-27 in a Miami boat show, I thought this is the boat I will want next... but the price then was too much for me, so I never was able to afford one, There is still one of them sailing in Biscayne Bay and you can spot her from a distance... I mean, the real classic Shannons, so beautiful inside and out, very much resembling our own CD's... Yes, it is a shame, that more and more the boats being built are the 60's and up... big racing machines, for a very limited kind of owners, I think. in the meantime, I am very thankful that the Cape Dorys existed and I ended up with a fantastic 33! Everyone -including me- would say what am I doing with so much boat? I should have kept my 25, since I mostly singlehand, and then I look at my 33 in her slip and my heart flips. I will do, and continue to do whatever it takes to continue sailing her for as long as I can, and I still can not believe that this big beauty is really mine.

[Warren S]

Alas I must weigh in on Cape Dory's shoal-draft design in so far as pointing and tacking are concerned. Even though it is a different design (Empacher), the keel, when overlaid with the Alberg design, is almost identical save for the depth. It's as if its the Alberg keel held to a belt sander. In cross section there is the same amount of garboard in the hull as the fixed-keelers, which was a primary reason I limited my initial search to "these types of boats": they'll tend to bust through waves rather than pound on top.

Now the cool thing about this design is the centerboard. While I'm not looking forward to having to do any maintenance on it in the coming years, it is fun to dial in (or out) the weather helm by partially raising or lowering the CB. Frankly, it's well balanced boat with the board full-down, and with a full 7 feet of draft in that case, she really tightens into the wind and will tack quickly.

Granted: sailing upwind in with no centerboard (entering a shoaled creek), 3 or 4' waves and a reefed down to the 2nd points, she tacks like a lime-juicer! You have to have to be making good way hard onto the wind and make every move count, or else it's time for Dr. Westerbeke.

If you look at any satellite image of the Pamlico Sound, and notice you can see the sandy, muddy bottom in many areas, you can guess the other reason we are happy with this one...