Tunnels on a 28 Bertram

Sounds like a waste of time effort and money not to mention the boat.

Tunnels will not help the boat their only real purpose is to reduce draft. The perfomance gain by reducing your shaft angle would be offset in the extra drag and turbulance created by the tunnels. The older 28s were a fine design, if it were me I would just maintain the boat in pristine condition.

That is a radical thing. Do you know anyone else who has done it with the 28?

With the amount of deadrise that a 28' Bertram has I would be concearned about getting enough lift. I would try to get some professional advice about that if possible. I have only put tunnels in 2-3 hulls but, they were pretty flat aft. They didn't handle very well in reverse either. I have always had trouble docking Bertrams but I was never sure if it was the hull shape or the small rudders.

Rudders docking?

Of course. I use them every time except maybe sometimes with a stern thruster.

What advantage are you looking for?

Use rudders and a thruster (a stern one at that) docking a 28 footer with twins? You must dock side to with less than a foot over your length between boats. Unless walking, those rudders have virtually no effect at docking speed and I'd be embarrassed to use those thrusters in less than a gale.

What kind of speed increase are you expecting? Having never seen this done on a 28 Bertram I'd be concerned with the results adversely affecting the running angle and it's ability to back down on prey. Please let us know how it turns out. Personally, I'd like to do some tank testing before doing something this radical on my own boat. Has anybody out there tried this?

Fair enough, but then I'd be looking at going to a surface piercing drive. I don't see just reducing the shaft angle using tunnels providing any significant improvement.

Tunnels or prop pockets take a tremendous amount of time, effort and testing to get right, but if they're done right they'll greatly improve the running characteristics of the boat. Remember though that your running gear will be custom and getting the right rudders will be trial and error as getting the rudder design in a boat with tunnels (especially one that's a deep V and can run over 25 knots) is no easy task. The boat will plane differently and depending on how much you reduce the shaft angle, the boat will run much better.

Give you an example, take a look at the Cabrerra modified 31 berts with pockets, the 31 with pockets runs MUCH better than the identical boat without.

I looked up Cabrera, they do a nice looking job on they modifications, could not see anything about tunnels and in the process of modifying the boats they add quite a bit of weight and about 200 more horsepower.

The problem I see with putting tunnels on a 28 Bertram is that it has such a deep v, that putting tunnels will further reduce any flat surface you have aft and running at cruise it will have much more of a tendancy to run/lean on one side of the V or the other and not run flat. Tunnels will also lose some docking manueverability, and it will be a lot of effort/money/and work and you'll gain a little less draft. But the 28' Bertram doesn't draw enough to start with that you cannot go just about anywhere in the Bahamas or US that you want to anyways.

There is a reason a good surgeon has a tray of instruments and uses more than a scalpel.

Only quacks claim they don't need or use the tools available to do the job well.