Trim Tabs

     I pulled the trim tabs off the boat in order to barrier coat behind them, and also to clean and check them over before re-installing. I did some rough calculations on the size of the tabs while they were off the boat, and started to get that uncomfortable feeling I get every time I look at the design compromises the factory has to make when building a production boat. A bit of searching on some Internet forums confirmed my fears - the tabs on the 340s of this vintage are undersized. The tabs on the diesel version of this boat are 6 inches wider - 12" x 24" instead of the 12" x 18". But if you look at the hull, 24" wide tabs really don't fit that well, since the flat section of the hull, between the lifting strake and the prop tunnel, isn't 24" wide. Don't get me wrong; 24" tabs can be installed, but they won't allow for a smooth flow of water at the edges, and that is NOT how I intend to maximize speed and economy. With the price of gas the way it is these days, every little bit counts.
     So, what to do? If you consider that the tabs main purpose is to provide lift, it is clear that a longer tab is more effective than a wider tab. A longer tab applies the lift farther from the center of rotation of the hull, and therefore has more leverage. It follows that, for a certain amount of lift, a longer tab can do the job with reduced drag. Take a look at Mercury Racing's K-planes - they are long, stiff, and not very wide. Since a longer tab is more efficient, and my hull won't support a wider tab, I decided to modify the existing tabs to maximize performance. (I just can't leave well enough alone, it seems).
     Here is how the tabs looked when I pulled them off the boat:

     That's the cleaner one. First, I ground the 4 rivets that secure the cylinder mount/reinforcement to the trim tab. Then, I separated all four components, and gave them a thorough cleaning with fine rotary wheels on my die grinder. The cleaned parts looked a bit better:

     I then had the local metal supply house shear out some 1/8" thick, 304L stainless steel plates, in an 18" x 22" size. Once I had these home, I layed out my corner radii, corner notches, and bend lines, as seen here:

     The corner notches were cut with my band saw, while the radii were carefully hand shaped with my disc sander (seen in the background). I also carefully de-burred and smoothed all the edges. Then, I returned the plates to the metal supply house, and had them put in the reinforcing bends:

     The four holes are located to allow the plate to be fastened to the old trim tab at the rivet locations, while the single hole is for the trim tab anode. The picture shows the bottom of the tab - the two parallel bends will actually be facing down when the tab is installed, and will act as directional stabilizers. A third bend, facing up, is in the trailing edge of the tab extension, to provide strength and prevent vibration underway. After I bolted the tab and extension together, I TIG welded them at intervals, with approximately 1 inch beads. Finally, I sealed the leading edge of the tab and extension with epoxy, to prevent water from flowing between the two pieces while underway:

     Lastly, I modified the mounting brackets, by slotting the existing mounting holes 1/8" of an inch, so that I could raise the forward edge by the same amount as the additional thickness, thereby maintaining a flush transition from the hull to the tab's running surface (again, to minimize drag). I also added additional mounting holes, between the exiting holes, to increase strength, since the tabs will potentially see additional loading. The finished install looks like this:

    Bottom line - increased directional stability, a flatter running angle, and reduced fuel consumption / higher cruise speed. The surface area of the tabs has been increased by 60% with this modification. I would not increase it any more without adding a second hydraulic cylinder.
     This coming weekend, I am lifting one of the engines in - it's time. The other will follow soon after.

Cutlass Bearing Installation

     Before beginning installation of the cutlass bearings into the strut, you should check the strut alignment. Ideally, the strut bore and shaft log should be parallel and coaxial. I my case, I used a 2 inch diameter shaft that was sanded down slightly in a lathe, and I carefully slid the shaft through the strut until it slid into the shaft log. Since the shaft passed into the shaft log "dead center", I was comfortable proceeding with the cutlass bearing installation.
     As an alternative, you could use a suitable straightedge, held tightly against the strut bore in several locations, to verify the strut alignment. If the strut is not well aligned, you would have to dismount the strut, and shim accordingly until the alignment was correct, then secure in position (with the proper sealant, of course). Since mine are both well aligned (Sea Ray uses a laser alignment system at the factory, so it should be correct unless the strut came in contact with something harder than water!), I am not going to enter into a lengthy discussion of the multiple ways a strut alignment can be corrected. There are many resources available for this information, and I would be happy to answer any specific questions in this regard, if necessary.
     So, on to the cutlass bearings. First, the strut needs to be prepared for the new bearing. I posted previously about removing the cutlass bearing, so I will pick up at that point. I first removed the 2 set screws, and re-tapped the threads. Then, I ran a cylinder hone, chucked in a 3/8" drill, through the bore, to remove accumulated deposits, and also to smooth the bore. The honed strut looked like this:

     Note that you are not trying to change the diameter of the bore with the hone - just clean it. The cutlass bearing is an interference fit with the bore, and this fit should not be altered.
     The next step is to fashion a tool for installing the bearing. I made it from a length of 5/8" fine threaded rod, with 2 large bearing washers and a nut at one end, and a machined fitting at the other end. The fitting is stepped, such that the smaller diameter is about 0.010" smaller than the cutlass bearing inside diameter, and the larger step is about 0.020" smaller than the strut bore, so the tool cannot get stuck inside the strut during installation. It looks like this:

     Out under the boat, I lightly greased the inside of the strut, and mounted the cutlass bearing / tool in position:

     It is important to start the bearing in straight, so proceed slowly, and make sure it is going in correctly as you tighten the nut. Continue tightening until the bearing is centered in the strut...

Ablative Paint - and it's done!

     Finally, I am done painting the bottom. Five coats of barrier (Interprotect 2000E from Interlux), followed by three coats of Micron Extra (also Interlux) copolymer ablative antifouling paint. There's nothing glamorous about the job - just painstaking work. But now that it's done, I can get back to the engine room and mechanical systems. I will be installing the cutlass bearings in the struts, running the new cooling lines to the shaft seals, running fuel lines, and generally preparing for the engine installations. In the meantime, here are a few shots of the finished bottom:

     You may have noticed that the trim tabs were removed from the boat. I am modifying the tabs for improved lift, since the factory tabs on the 340s of this vintage are generally recognized as undersized. I'll discuss those changes as soon as I have them completed. Now if only I didn't have to eat and sleep...

Barrier Coat

     The barrier coating is done. Five coats total to get the required film thickness. Thankfully this is a one time job! Here she is, all smooth and sealed:

     Before I applied the barrier coats, I had to reinstall the underwater exhaust discharge castings. These are made of bronze, so I sandblasted them first, then applied 3 coats of barrier to them, inside and out, as a corrosion preventer. This was folowed by 3 coats of ablative anti-fouling paint, on the inside only, to prevent growth. The same process was repeated on all the thru-hull fittings, before they were installed:

      They are shown here during the coating process. Once they were ready, I barrier coated the hull where the hull penetrations were located, then installed the thru-hull fittings with the new seacocks (detailed in a previous post), and installed the underwater exhaust. Then I barrier coated the hull and fittings together. I can't think of a better way to do it, or one that is more labor intensive. But the results speak for themselves. From this point forward, the maintenance should be a snap (relatively speaking), and galvanic corrosion will be minimized.
      The ablative antifouling paint has been applied to the hull (3 coats), and I'll post some pics in the next post, after I pull off the striping tape.

They're here....

     Well, I have 3 coats of barrier coat on the bottom now. I think I will have the bottom completely done by the end of the day Sunday. Another barrier tomorrow night, then one Saturday morning, followed by the first layer of copolymer ablative later Saturday. Sunday, I will do 2 more coats of the ablative paint, and she's done. Thank goodness - I hate doing bottoms.

     Now, on to the subject of tonight's post - power. They arrived last week, and here's what they look like:

     I don't have much else for tonight. I'll get some pics of the boat bottom this weekend. The engines need to be uncrated, and then I'll consider a couple modifications. I hate the inverted oil filters - they're too small, and upside down! And the water pump is in a terrible location for service, as is the fuel cool unit. They're may be some engineering design changes coming...

Bottom Preparation

     This job has to be one of the worst. I have spent about a week and a half under the boat, sanding imperfections, filling scratches, sanding some more, smoothing, shaping, etc. It is not easy work, and you have to wear a dust mask the entire time.
     When the boat first arrived last year, I hired Tri-State Soda Blasting  to soda blast the boat, and remove the old, hard bottom paint.They really do a nice job, but the bottom is still not ready for barrier coating when they finish. More details need to be attended to.
     I started by carefully grinding open any pinholes with a Dremel tool and a small grinding wheel. Then, my wife and I slowly scanned the entire bottom of the boat for scratches, and circled each one with a magic marker as we found them. Each scratch or ground pinhole was carefully filled with epoxy fairing compound. Once the compound had fully cured, I sanded each faired area smooth with a small, 1/4 sheet sander. Be careful if you are stripping and sanding a fiberglass boat bottom - the gelcoat is not very thick, and you really don't want to do anything more than clean off any old paint, and slightly roughen the surface to accept the subsequent coatings.
     Next, I sandblasted the struts and rudder ports with a small portable sandblaster, and then my wife and I cleaned the boat bottom in preparation for the barrier coating. The fully prepped bottom looked like this:

     The cutlass bearing bore of each strut has been cleaned, and lightly honed with a spring loaded cylinder hone mounted in a 3/8" drill. The same procedure was used for each rudder port.
     Then we masked off the appropriate areas with blue masking tape, and started to prepare for the barrier coat application, which I will discuss in the next post.