Al Stall
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Last update, February 4, 2010

EC12 Equipment Chassis



Here is another chassis design that is one piece, simple to fabricate, and works.  It eliminates the multiple pieces presently required in the Building site chassis and performs the same exact function.  There is no complicated sheet routing or multiple blocks.

Only one block is used in the bow of the boat attached to the turning block shaft and the shaft is attached to the chassis with one screw. One solid ring or two, if you want a differential, are used as the attach point for the sheets. The jib trim is attached to the jib sheet with another solid ring.  See below for link to the rings or do an eBay search for “Popper/Jig rings”.  The one shown is SS, OD 8mm, ID 5mm, and 1mm thick.

The receiver is attached to the side wall of the hull with Velcro and placed as high as you can get it.  There is very little chance of it getting wet.  To keep the wiring neat, bundle and use a tie wrap to secure.

A piece of door jamb wedge is used to angle the winch to the bow.

All parts are secured with SS or brass 4/40 screws and SS lock nuts. No need for Loctite.

The shaft is hobby aluminum made by K&S, 3/8” OD X .014 wall available at any hobby shop. It is fitted with dowels on each end about 2" long to prevent collapse of the tube where the holes are drilled for the block and the attachment at the chassis. I use a piece of foam rubber to cushion the bow end where it butts to the hull.

The plan calls for .062 material but I actually fabricated a prototype of .032 aluminum and that is what is shown in the subsequent pictures.  I decided to use it and it is presently installed in my EC12.  I have not experienced any bending or other problems with it.  I originally used the chassis as shown in the EC12 build web site so the mounting slots fit my original holes toward the bow and I drilled new holes in the ballast to accommodate this smaller, more compact design.  Servo mounting holes and openings are sized for standard servos such as HS645MG and Futaba 3010.  Rubber cement the plan to the aluminum and fabricate. 



Make a cardboard template before fabricating the chassis.  This is an invaluable aid to insure everything works before you make your chassis.  Shirt cardboard is perfect.  If this chassis is for a new EC12, simply drill all holes in ballast prior to installing the deck.



Note that the turning block shaft rests under the ply wedge at the bow.  A SS screw, nut, and locknut are used to hold the block loosely in place.




Ignore the extra hole.  The dowel is inserted with about 1/4" protruding.  A piece of foam is added to provide a cushion where it contacts the hull. You don't have to glue the dowel.  The screw holds it in place.


Wedge for the RMG winch is fabricated from door jamb wedge material.


 Side View


I always use lock nuts on my servos-no need to use Loctite.  Note the shaft is mounted with a SS screw and locknut.  The dowel is inserted (it may have to be shaved a bit to fit) and flush with the shaft.

Top view


 Photo 9-Shows the shaft mounted to the chassis with a SS screw, flat washer & lock nut. Leave it just loose. Jib trim has an extended arm of .062 aluminum drilled and threaded for 2/56 screws to attach to the servo arm.  Two other 3/32 holes drilled and chamfered smooth for trim line.



Going from bow to stern, jib rack is most forward, mast step, switch along side mast step, chainplates, mainsheet fairlead, tension elastic fairlead and backstay.



Since the tensioning elastic runs down the center of the boat, I added a block and simple hook to keep the elastic from rubbing on the compression post and the mainsheet fairlead.



Sheeting system-the Dacron line to the left comes from the winch and is threaded through the top of block attached to the turning shaft at the bow.  The line is attached to the solid SS ring which in turn is attached to the 1/16" tensioning elastic cord.  The elastic runs lengthwise just under the deck and terminates through a fairlead about 10" aft of the mainsheet fairlead.  A simple knot will secure it on top of the deck at the fairlead.  The mainsheet and jib sheet are attached to the SS ring as show or knotted tightly to the ring.  The jib sheet is threaded through another SS ring which is attached to the jib trim servo.


To prevent the sheet lines from tangling with the gear works, use a vinyl sheet available as part of a presentation folder from an office supply store.  Punch a hole and slit to fit around the compression post.  It will not move.


Link for the rings:


Link to a photo album of a recently completed EC12: