fuel tank replacement

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  • February 08, 2013 10:26 PM
    Reply # 1203196 on 772857
    Hi Doug,

    Thanks for the info on your tabbing method... Would you do that even for the large bulkhead ( four 3/4 pices of plywood ) in the bilge on which the I beam sits taking the load from the compression post.? Ours was glassed tabbed to the hull - it was pretty cobbed together from the factory... The bulkhead contour was not equal distant / traced where it was in contact with the hull... Part of the bulkhead was in contact with the hull sitting on top of some micro ballon resin mix.  Other areas were cut at least an inch or more from the hull with no filler and tabbed to the hull leaving the 1 inch area void... I was thinking of placing 1/2 inch spacers along where the bulkhead would sit so that the weight of the bulkhead would not press the filler out. Then mix some filler and set the bulkhead in the filler so that a good contact is made. Then make a nice radius, and tab to lower hull..... I would resin the entire bulkhead fist so that when tabbing the plywood would not draw too much resin from the tabbing mat / cloth..

    I talked a little to an engine installer today about the Yanmar. I asked him about the 
    100 hp. He mentioned that the 100 hp engine may not be working / running at it's proper  optimum operating RPM due to the hull speed of the W42.. He mentioned that this may lead to glazing and turbo issues ... He thought that the 75 Yanmar might be better.. He said that he would work on what the best / largest prop size would be, the boat could swing, etc. Work backwards from the prop, figure proper transmission ratio and then see what size engine would work. 

    What size and type of prop are you using and what type and transmission ratio  with your engine...?

    Thank again...


  • February 09, 2013 7:47 AM
    Reply # 1203443 on 772857

    George, I am sitting here waiting to go out and shovel 3 feet of snow in New Hampshire!  Anyway, regarding the tabbing the bulkheads below the interior deck levels, I would still consider some type of interface between the bulkhead and the hull.

    Because of the proximity to the bilge, I would look to use a material other than a kerfed piece of plywood.  On other boat building projects, I had used a pliable foam material such as airex or the like.  This would allow the foam to be encapsulated in glass and to be relatively impervious to water intrusion.  These strips need to have beveling on the side, but the top surface should be the same width as the thickness of the bulkhead:  3/4" for a 3/4' bulkhead.  This encapsulated base protects the hull, as well as provides a very nice beveled surface across which to spread the load on the tabbing.  If done well, the encapsulated base eliminates the need for any additional filleting for a smooth tab.

    Our floor bulkheads were tabbed directly to the hull at the factory, and they have survived very well over the 35+ years the boat has been alive.  The solid glass hull is thick enough to accommodate the load.  The method used by the factory is certainly OK, but the method I mentioned above takes the process up to another level.  That upper level could be considered over-kill, but you will have to prepare some very smooth fillets to ensure the strength of the tabbing bonds. 

    It may boil down to what is an easier method for installing the bulkheads in your situation.  You know, how much access do you have to make the encapsulated bases or to prepare the fillets.  Do you have access to a foam product to make the base out of?  Etc.

    On the Yanmar, I had similar questions for the engine rep and the distributor regarding optimum loading and glazing, etc.  I was told that even though the WS42 is a heavy displacement vessel, I would be OK and that there was no risk.  I still have to figure out the prop question.  We have a large 3 blade prop now, but I am sure it was tuned to the Perkins 4-108 that was originally on the boat.  I have to address that once Spring rolls around.

    Now, one thing I was very pleased about with the 110 hp Yanmar, is that the distributor though I had a good chance to get our WS42, Harmony, up on plane with that size of engine.  Boy, I can't wait to do a little wake boarding once we're in the water.  Heck, I might be able to save on bottom paint if the boat lifts that much out of the water!

    Kidding of course!  But imagine the possibilities!!!


  • February 09, 2013 2:33 PM
    Reply # 1203643 on 772857
    Deleted user
    A foam stringer will give better results than ply straight onto the hull.  You can make a strip of foam, saturate with resin and then tab the whole mess to the hull.  It will be stronger and resist rot.

    For my boat I used Bluewater coosa 26lb 3/4" in the belly of the boat. I doubled it up and laid a fillet of epoxy then stitchmat over that for the tabbing.

    Aluminum is very good for fuel.  Black iron is great too but only in apps where maintenance can be routinely performed.

    I would consider using aluminum then coal tar epoxy paint and make sure its blocked up to keep it out of the water.  Tilt the tanks slightly to keep condensation from sitting on the tanks. Limber holes to the bilge.  Also be careful with wires especially sending unit wires to prevent electrolysis and or galvanic corrosion. 
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