E40 Directional Stability and Rudder
Date: June 7, 1999
From: Van Stoffer abnjp@erienet.net
After correcting the rudder pull problem, it became apparent that 'Falcon' did not track at all well despite the full keel. Trying to keep it on course was like trying to balance a pencil vertically on its point. It would almost immediately drift off course and go off faster the farther it went - like positive feedback. The best the autohelm could do was + or - about 10 or 12 degrees which resulted in a snakey-looking wake! In George Town, Bahamas I met Jeff- the owner of the E40 'Tiffiny'. He asked me if I had a tracking problem with 'Falcon' which I readly admitted to. He told me that it was due to the aft end of the keel being hollow inside allowing it to 'dish' in. He said some boats had been re-inforced from the inside- a very expensive operation as this area is very difficult to get to from inside. His cure was to fill in the low spots with Bondo and strike them off with a straight-edge. At the next haul-out I checked the aft end of the keel and found at most about 3/16" of dishing-in a 2-1/2' x 2-1/2' area which hardly seemed enough to cause so much trouble. After considering that the average pressure is over 200lbs per sq. ft. on this area when in the water, it has to be assumed that dishing increases underway. I removed bottom paint and put Bondo on both sides striking it off with a 3ft metal straight-edge. Then starting at the top of the keel with a felt tip marker, I put a dot anywhere I could see light between the straight-edge and the keel. I dropped down 2" and repeated the operation until I had worked my way to the bottom. I put Bondo on the dot areas and struck them off. After the third repeat of this procedure no light could be seen anywhere. I then put a layer or two of fiberglass over the Bondo and 3" or 4" beyond to stiffen this area and help retain the Bondo. A little lite sanding to feather it in and all was done in a day and a half [I work rather slowly!]. After launch I could not beleive the improvement in tracking. "Falcon" would now run for several minutes at a time without correction and the autohelm had no trouble maintaining +or- 2 or 3 degrees. Thanks again Jeff!
Next fix: Lets get rid of that salt water from the prop and rudder shaft packing glands that runs over the top of the fuel tank to the bilge.
Date: June 27, 1999
From: Van Stoffer abnjp@erienet.net
Paul Uhl,
Thanks for the welcome to the Endeavour Forum. The first problem encountered with the Endeavour 40 was the severe pull to starboard on the rudder. The quick fix was a 4" x 14" exposed area stainless steel trim tab bolted to the aft edge of the rudder and bent 30 to 40 degrees off the plane of the rudder. After one tweek on the angle, the rudder was balanced and the wheel could be released and would stay centered. On the next haulout a study of the rudder (eyeball) showed that it was not molded equally on both sides causing more 'lift' on the starboard side. Starting at the top of the rudder with a disc grinder, I ground fore and aft on the large bulge of the starboard side - careful not to gouge in anywhere. The rudder is molded with foam and is easy to grind down. Grinding continued until both sides of the rudder looked equal. I also feathered down the aft edge of both sides of the rudder from about 1/2" thick to about 3/16" as this reduces drag and improves rudder efficiency. I then put a couple of layers of fiberglass on to protect the foam core on all ground areas. Total labor time was one day. When we left Solomons, Md. in the fall we could hardly keep 'Falcon' from going to port as I had not removed the trim tab. I was unsure of the results of my rudder modification. At the first anchorage I went overboard and removed the trim tab. I was very gratified when we left the following morning and found the rudder perfectly balanced. The autopilot liked it too!
