Pearson 40 Owners Association 

The Pearson 40 Centerboard Tube Assembly

The centerboard tube in the main cabin has turned out to be a very reliable installation on the Pearson 40. After more than 20 years of use and salt water emersion, the tube remains reliable.

The tube houses the centerboard control pennant. The tube is attached at the deck to an aluminum weldment via a 1/4" hex head bolt per the photo below

The lower end of the tube is retained within a split aluminum collar/flange and is sitting on a teak box which is attached to the plywood floorboards. The pictures below show the lower end of the tube  disassembled and the top of the box.

Beneath the teak box and floorboard there is a fiberglass "hump" which is part of the centerboard trunk. On top of the hump is a sheave box for the centerboard pennant per the photo below. Notice the nipple on the top of the sheave box.

Inside the aluminum tube is a red brass (bronze) pipe through-which the centerboard pennant passes. The red brass pipe is connected to a bronze union at the bottom. The bronze union is attached to the top of the sheave box nipple. The red brass pipe is surrounded by air conditioning pipe insulation to keep it centered within the aluminum tube.

One problem which has arisen on a number of Pearson 40's is the top of the teak box and sometimes the floorboards will start to compress or "droop". This is caused by two factors. One is that there is too much space between the top of the sheave box and the teak box. In addition, over time the loads on the centerboard pennant pulling down on the deck will tend to cause the deck to "sag" slightly, exacerbating the tendency for the teak box/floorboards to droop. To give you some idea of the loads on the centerboard pennant. look at the bolt below which was removed from the upper end of a centerboard tube.

There are two options for resolving the sag. The first and easiest is to "shim" or somehow fill the space between the top "hump" and the bottom of the teak box/aluminum flange. This should work to remove the sag.

Another option is to take a far more aggressive (and expensive and time consuming) approach. That involves replacing the aluminum tube and building new upper and lower tube ends. The pictures below show a setup, fabricated out of stainless steel, which replaces the original tube and tube ends.

While this modification is a lot of work, the result is a bulletproof centerboard tube installation which also supports the deck and strengthens the overall structure.

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