CD 28 powerboat

[Joe O'Neill]

I love the lines of the CD 28 but I'm concerned about the single engine configuration.

My fear is that it will be extremely slow on long hauls, say from Southern Connecticut to Martha's Vineyard, and that it will be trickly to maneuver into tight slips.

Are these fears well founded?

Would I be better off with the CD 30 given its twin engines?

All opinions appreciated.



joe_o'neill@mvbms.com

[Pete Asensio]

I just bought a beautiful CD 28 open with a 210 HP Cummins diesel.
Cruising speed is an easy 16 knots, with 20 possible (but loud).
I think you would be happy with a CD 28 with a good diesel, unless you want a planing hull.



pase@uconect.net

[Walt Bilofsky]

The 28 and 30 are substantially different boats. The 30 has a much larger salon and cabin. It's much heavier - 12,800 lbs. vs 8,000 for the 28. The 30 has hard chines on a semi-displacement hull; the 28 has rounded bilges.

As far as speed, there is not much to choose between the boats. I came back from the CCDO Rendezvous in Benicia last month on my 30, cruising with a gas-powered 28 FB. We were both doing about 13 knots at cruising speed - I could maybe push another knot out of my 30. The 28 was turning 3100 rpm, which is the canonical 70% of his WOT 4000 rpm. (I have no idea if these figures are typical.) When my 30 was new and didn't have all the equipment on it, it did more like 14-15 knots cruising and I actually saw 24.9 kts at WOT when it was brand new, clean and light. Now I might get it up to 19 at WOT if trimmed right with a clean bottom.

IMO the reason to spend the extra money for the 30 is if you want a substantially larger boat in 2' more LOA. Bear in mind that it's larger but doesn't sleep any more or have (if memory serves) very many features that aren't on the 28 - just more elbow room, a nicer (island queen berth) cabin, and more storage.



bilofsky@toolworks.com

[Paul Anastassiadis]

I have a 1986 28CD. I normally cruise at 11 to 13 Knots and Altough I dont know the distance that you mentioned I think that the speed is Good,assuming you are not thinking that you want to make the trip and back in one day. No matter what you will get there in style.
As far as docking is concerned,because of the Keel, I found out that it was easier to dock this boat than one with an outdrive or outboard. You will be pleasantly surprized.
Buy the 28 it is a Great Boat.
PA



Paul.anastassiadis@SMC.com

[Burt Polishook]

I just got my CD 28 (1989 hull #193) and I find it real easy to handle. I've backed into my slip
twice now and had no problem either time. The key seems to be a light touch on the throttle
and just getting it moving back or forward to position the boat. As for speed,
I am getting 16 knots at 3400 rpm, but that is with trim tabs that I just put on the boat.A great
boat. Don't worry about the single screw.
Burt

My fear is that it will be extremely slow on long hauls, say from Southern Connecticut to Martha's Vineyard, and that it will be trickly to maneuver into tight slips.

Are these fears well founded?

Would I be better off with the CD 30 given its twin engines?

All opinions appreciated.

polisho@ibm.net

[Jay Valentine]

Joe, you should not worry re trip to Nantucket. I have an fbc 28' single disele. Average curise is 13-15 knots depending on tides. we had a great trip in smooth and rough seas (10 footers). In and around docks was a piece of cake. That big keel and "barn door" rutter made it a dream in and around docks. We went straight through to Nantucket from Pilots Point Marina in Westbrook, CT. Against the tide all the way was a 10 hour trip-104 natical miles. coming home 8 hours slack tide and cataching the tide with us at the end. Takr the trip you will love it. Oh yes stop at several islands on the way. We have done them all. You and your family will have fond memories.



valentinejay@hotmail.com

[Walt Bilofsky]

As for speed,
I am getting 16 knots at 3400 rpm, but that is with trim tabs that I just put on the boat.

Interesting you should mention that. The trim tabs on my 30' flybridge boat add one to two knots in cruising speed for a given RPM. I'd have to think they pay for themselves in fuel savings.



bilofsky@toolworks.com

[Tony Raymond]

You guys have me all excited 1-2 knots!! That's about 10% increase.
What is the technical explaination for this? I thought they were intended to adjust heel angle while underway. Was a speed increase your initial motivation to put the trim tabs on?
Thanks
Tony



tony.raymond@digital.com

[Burt Polishook]

The trim tabs (30 x 12,Bennett) were put on to adjust the heel angle. However, I hoped for some speed increase on the basis that the boat would be pushing against less water. It seemed to work.
Burt




polisho@ibm.net

[Walt Bilofsky]

You guys have me all excited 1-2 knots!! That's about 10% increase.
What is the technical explaination for this? I thought they were intended to adjust heel angle while underway. Was a speed increase your initial motivation to put the trim tabs on?

My 30' boat came with trim tabs.

At speeds over hull speed (1.34 times the square root of the length at waterline, or LWL) which is roughly 7 knots for these boats, the boat needs to rise up out of the water in order to go faster. As speed increases, the stern first digs in ("in the hole"), pushing lots of water out of the way, making a big wake, and running inefficiently. Then at higher speeds the stern comes up, the boat climbs its bow wave, and more or less gets up on plane. Cape Dorys are semi-displacement hulls, so they don't plane as well as ski boats, but any boat that is going much faster than hull speed is planing.

The advantage of being on plane is that there is less surface in contact with the water, which reduces drag, and the hull is more level, so it is more riding over the water than pushing water out of the way. The trim tabs allow the hull to be leveled more, so it gets on plane at lower speeds and pushes less water. As it turns out, this advantage more than makes up for the extra drag of the tabs.

Different forces dominate at different speeds. At speeds around 14 knots, my boat does best with the bow trimmed down. At WOT, which can be from 19 to 24 knots depending on loaded weight, hull condition, sea state, etc., the best speed is achieved by trimming the bow up again somewhat, reducing the wetted surface. And of course the effect of tabs varies from boat to boat.



bilofsky@toolworks.com

[Tony Raymond]

Burt, I'm going to install trim tabs this spring and was hoping you could help with any tips or advice. I will go with Bennet 12X30 as well. Did you make a spacer to compensate for the curve of the transom? Where did you locate them on the boat?( A sketch, dimensions or a photo would be wonderful if you are up to it. ) How did you connect the hydralics as they came through the transom. Do you have a 6 foot arm? or a very small mechanic? Actually did you use the through transom connection or the external routing to a more convienent location?
Thanks for your help in advance.
Tony




tony.raymond@worldnet.att.com