Str. "Betsy Ann"

Table of Offsets
for
Layout of longeron Detail

The top of each longeron is flat. This line extended to the bow will be the line of reference for each offset value. You use the edge of the board as your datum line.

Mark off two inch intervals. Using a square, layout perpendicular lines from each interval, mark the appropriate offset, position a bending batten and trace your line.

Measure your deck offset, and trace the deck lines. Cut carefully with jig saw, sabre saw, or bandsaw. Fair the resulting cut with sandpaper block to achieve a smooth flowing line.

Offset values are given at two inch intervals. Two offset values are given for points forward of boiler room front wall. These are the deck line and bottom line. Tracing of the finished line is best done with a bending batten, some assistance or, you can use finishing nails lightly pounded into the longeron (not through the batten) to hold the batten to the proper curve. Adjust until you have smooth flowing arc. Check to assure sufficient clearance at crank arm locations before cutting.

Use the first one to reproduce the other, they are indenticle.

Note that the arc forward of the boiler wall is actually the underside of the deck, while the arc aft of the rear wall (transom) is actually the top surface of the deck. You can draw your arc for either the top or bottom of the deck and then trace a second line 1/4" in the proper direction. I find it most natural to my eye to first trace the upper deck line and then measure down 1/4" on the fore deck to accomodate the thickness of the deck forward of the boiler room wall. The rear portion of the longerons must be sufficiently deep to accomodate the Dubro steering arms which will be used for crank arms.

The bottom line is offset from the bottom of the deck by the thickness of the foam 2 1/2" (2 3/4" from deck top line).

Longeron table of Offsets



       Bottom of deck line            Bottom Line
Bow
0            1/4"                   1/4"
2           
4
6
8
10
12         1-1/16"                   3-1/4  (Boiler room wall)
14                 
16
18
20            NA                    3-1/4" (Allows for thickness of bottom) 
22            NA
24            NA
26            NA
28            NA	
30            ..
32            ..
34            ..
36
38      (see below for detail)
         Top of deck line 
40          7/8"                  (Stern wall location)
42
44
46
48
50          7/16"                      NA


Boiler deck sidewalls are simply traced from the formed and finished longerons. The top and bottom lines for the wall are taken from the bottom line of the longeron. The upper line made sufficiently high to clear the motorcycle battery above the inside surface of the bottom line. As the upper deck line and the bottom line are curvilinear parallel this can easily be calculated:


     Bottom thickness          (-1/4")        (-1 ft)
     Foam thickness of hull     2 1/2"         10 ft
     Boiler deck thickness        1/4"          1 ft
     Boiler room wall height    3 1/4       12-13 ft
                             ---------

     Battery height            5 3/4"         23 ft


Trace the bottom of the boiler room wall from the longeron bottom line, measure an offset of 5 3/4" and trace the second line, again using the longeron bottom line. This will give a smooth parallel bow to both the boiler deck and the Texas Deck and subsequently the hurricane deck.

Notice the main deck fastens to the underside of the longerons aft of the rear wall with four screws. Forward of the boiler room front wall two screws are used to pull it down on top of the longerons. Thus, when the boat is being assembled the radio box assembly will pass into the radio box opening in the deck, and then the deck will be brought up at the rear to be screwed to the bottoms of the longerons. The fore deck is screwed to the top surface of the longeron. The entire deck can be removed as a unit after running out just six screws. This will be handy for painting and refinishing.

Wheel and Radio box opening


These dimensions are best determined by the dimensions of your radio box and longeron spacing of your model, which is dependent on the dimensions of your wheel!!!

The deck fits flush outside the longerons to the wheel, then it is cut to fit under the aft ends of the longeron to be fastened to the under side of the longerons.


Thus:

     --------------------------|     
                      longeron-|---------------

        radio box area             wheel opening

                      longeron-|---------------
     --------------------------|



See the section on cutting the main deck!