Stability at Rest Improvement for 28 Bertram

[Keelboater]

Small chine runners on the hull sides beneath the water line that will be out of the water at speed on the step?

I have given that some thought as well. On this hull they should not generate any lift because it will nose dive and become ill handling. They would have to be completely out of the water at cruise speed, yet large enough to add some stability at rest. The larger the hull, the more room you have to work with. So as usual, it's a compromise here.

 

[Mr Efficiency]

Is the boat lighter than normal, smaller engines or whatever ? That would not help.

 

[Keelboater]

No. It has standard power and no modifications. Fuel capacity in the new tank is the same as original, and it occupies the original location. I did add internal baffles to the tank to combat the free surface effects of sloshing fuel.
The 28 was designed by Dave Napier, as was the 35. There are similarities between the two. I'm not sure if Dave is around anymore. I would like to get his brief opinion on adding the keel.

 

[powerabout]

Here is a stock Bertram 35 with keel, similar to what I am proposing for the 28. It's relatively small, yet helps dampen the roll at rest. The 25, 28, and 33 Berts did not have keels. The hull shape of the 28 is similar to that of the 35 with the deep forefoot. I have heard that the 35 handles much better than the 33, so something must be right about this concept. Any comments?

I'll think you will find the fbsf did not have keels but thr fbmy's did

 

[Mr Efficiency]

If the boat has a motion on the drift you don't like, the best plan is probably to try and change the way it drifts so it is less beam-on to waves, by using a drogue, e.g. and see what difference that makes.

 

[Keelboater]

All of the 35' Bertram Flybridge Sport Fish hulls have keels exactly as shown in my previous photo.

Yes, I just had a discussion with a fellow boater regarding the sea anchor. I keep a small one on board and have used it several times, but for fishing a rip line for bass with heavy tidal currents, it does not fit the technique very well. The constant repositioning of the boat after making each drift turns the sea anchor into nothing but a PITA for this method.

 

[FishStretcher]

I have a 25 degree deep vee as well- a somewhat uncommon 25 foot sea craft cuddy- called a Seafari. I looked into this for similar reasons. Flopper stoppers might be an option. I fish, so they wouldn't work for me, I don't think. But they are reasonably easy to try. The other option which everyone said wouldn't work, is a anti-roll flume tank. The criticisms were that the boat is too small. But some others have had success with it, so it might be worth trying. The gist being that some water sloshing out of phase with roll tends to damp the roll. In my case, I have a full width step down cockpit that could serve as a location for a flume tank. More work, but as a M.E., you could handle the math for the pressure head and fluid drag calculations. It seems like one could construct a removable unit, which wouldn't devalue the boat.

http://en.wikipedia.org/wiki/Antiroll_tanks

Caveat: I haven't built mine yet. I am installing fuel tanks now, not anti-roll. But I did do the math and the math seems promising.

My original post on this:
http://www.boatdesign.net/forums/stability/fitting-anti-roll-tank-deep-vee-planing-hull-49240.html

 

[Mr Efficiency]

The constant repositioning of the boat after making each drift turns the sea anchor into nothing but a PITA for this method.

Do you mean the inconvenience of tripping the thing so you can motor back to start another drift ? You can run it off the stern if that makes it easier.

 

[Keelboater]

Interesting concept Fish. I am thinking about the rate of water transfer in relation to speed of roll. If you fish in open water large rollers it's completely different than if you fish in a short bay chop. Plus if you are boating a nice keeper and have two guys on one side of the boat, what prevents the water from joining you on that side? I get the concept, but think it may have to be analyzed a bit more. I see this working much better on a larger vessel with a much slower rate of roll, but I might be lacking the full picture.

M.E. - the average drift we make through a rip line while fishing on L.I. Sound is only about 5 - 10 minutes, depending on the tide. To constantly deploy a sea anchor for such a short time frame actually eats up valuable fishing time.