E27 Length Modification

[Sinbad]

I have a 1972 E27 with a 2 foot transom extension. Can anyone give me a good reason that this would be done other than to add extra dollars onto the storage and docking fees? I have a few ideas, but none that are probably correct. A little help here. I haven't had the chance to tack her out yet as I only bought her last fall and she is still blocked on land.

I ruled out a class upgrade ,unless there is a break at break at 27ft-28ft.

 

[Sven]

I have a 1972 E27 with a 2 foot transom extension. Can anyone give me a good reason that this would be done other than to add extra dollars onto the storage and docking fees? I have a few ideas, but none that are probably correct. A little help here. I haven't had the chance to tack her out yet as I only bought her last fall and she is still blocked on land.

I ruled out a class upgrade ,unless there is a break at break at 27ft-28ft.

Depends; if the length extension makes the waterline longer you'll go faster at top speed. The theoretical top speed is something like 1.34x(square root of WL (in feet)). The number 1.34 (from Skene's elements of yacht design) assumes a typical displacement hull. For a cat with a hull width of a foot and WL of 20 feet (Toronado class) the number goes out the window.

It is a theoretical number because if you are tied to a cable attached to the Queen Mary you'll go as fast as she does, no matter how short your DWL happens to be.

Bulbs on tankers (and some 12-meter boats !) are there to extend the effective WL. I think the Queen Mary uses the bulb to also store zillions of gallons of Guinness (http://www.guinness.com/) at below optimum temperature.

A sailboat is one of the most beautiful compromises in the engineering world. When you add to the WL you increase the wetted surface which may slow you down unless you have a lot of wind. Lots of factors adding and subtracting from performance.

The most telling performance indicator is beauty ... pretty designs sail better ... almost without exception.



-Sven

 

[NateHanson]

I've got a Columbia 26 MK2 that also had about 18" added to the transom. The rather blocky stock transom (which was vertical) was capped with a nicely sloping transom, and I expect when sailing it might add a bit of waterline length.

I have no idea why this major upgrade was done to my boat though. I can't imagine it was for speed. More likely for aesthetics, and in that regard it was a success.