Last update, February 14, 2004


Building shown in this section is for reference in the Classic Build. Some links may no longer have a source and suppliers may not exist...Rick West, December 2009


Construction and Assembly of the RMG Drum Equipment Board



Building the Board          Assembly of the Board


This section proceeds with the construction of the equipment board that includes the RMG SmartWinch. The board provides for jib trim, winch, twitcher and rudder servos and the removable mast compression strut. If you are using less than four servo positions, this board will still apply.


This procedure is to the build the unit as a module and ready to "plug and Play," if you will. Once the mounts are installed on the ballast, the complete module is removed, or installed, with just two machine screws.


Building The Equipment Board Structure


3/16” 4-ply Birch plywood sheet to fit, hobby store or Lone Star Models.

3/8” square basswood stock, hobby store or Lone Star Models.

4-40 Brass wood inserts, your stock, Du Bro.

4-40 SS Phillips machine screws, ½”, your stock.

#4 SS washers, your stock.

Keel ballast




Sand paper

Drill and bits

MinWax and brush


Design Position

The board structure design will be the same for three-servo operations as with four. Likewise, the equipment positioning will be the same with a wood structure as that when mounting directly to the lead. The center position of the mast is 25-1/2 inches. The positioning of all equipment is designed around this point. That is why the hull is marked beside the ballast on an adjacent line from a plum line to the center hole of the mast step, or at least where it will be. This position will be where the removable compression strut is installed and hence, dictates all the above. Why? “Balance, Vern?”


This is not to be autocratic or cute. It is to let you know the positioning of all gear in the boat is based on this and with THIS setup. If you want to move something to a different location it will change the nominal balance point to this mast position. It is okay to do so, just be aware of what is happening.

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How do we know this? Testing. We did not know the math and lived on a different planet with no EC12s around to snoop on. We read a lot and then built an incredible water tank. Then in this tank, we ran tests on trim angles to find zero at the least weight and +1 degree at full weight. The boat was not assembled yet. It was almost a soup sandwich. Then after six months of observations on the water it was found that nominal was a Ό” aft of what we had determined. Why, is going to be the subject of an article here so as not to bore you more than has occurred. The point here is that if you want a nominal balance point for the mast, and you are using our numbers, put the equipment where we show. “Know what I mean, Vern?”


Note: If you are building directly onto the ballast, the drawing template can be used to mark the locations of the equipment on the lead. The difference between ballast mounted and board mounted is 5/8 of an inch in height.


The Board

A 12” long piece of 3/16” ply is prepared, 2” wide at the front and 1-3/4” at the rear on center. All holes are drilled with a #31 bit using the template from the drawing. The compression strut hole is drilled with a 1/2” bit. The compression strut is only 3/8th but this size hole allows side movement to enter the hole and then slide the top into the slot. If the strut position has been dimpled with a 3/8" bit, the placement of the strut is secure.

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The two board mounts are cut from 3/8” square stock basswood, fitted and drilled to match the board. The front mount is placed 2-1/2” aft of the front edge of the board and clamped. This leaves ample room for the trim servo. The rear mount is flush at the rear of the board and clamped for drilling. Once pilot drilled with a #31 bit through the hole drilled from above, remove the clamps. A final hole is drilled in the mount, only, with a #17 bit for the 4-40 brass wood insert. These inserts have a very course thread and can be difficult to insert them cleanly. A 10-32 tap is used to score the hole and then use the brass insert as a tap for the insertion. If you do not have a tap then use the insert and carefully start the threading with a bit and back off procedure. Be careful to align it straight. They have a tendency to tilt in the soft wood. Later, when the mounts are tack glued to the lead, the inserts should be removed for the final gluing and varnish. Attach the board to the mounts with ½” SS Phillips head machine screws.


When tightening the board to the mount, a nice snug torque is all that is needed. Brass is soft…


Note: If you, in some way, notice in the course of your browsing that some photos show the forward mount glued to the ballast further forward than others, its because of the length of the ballast pour. So, do not let this confuse you. The board and hence, their mounts, are controlled by the position of the mast step and the compression strut.


Installing The Mounts To The Ballast

If you are going to ballast for multiple waterlines, please complete the keel ballast section before installing the mounts. It is better to cut the ballast before installing the mounts.


Place the primary ballast in the hull and snuggled into its comfortable spot. It has a fitted place. Measure back from the bow 25-1/2” and plum straight down to the lead. Mark the ballast with a line across the beam of the lead. Now mark the hull along this line so you can line them up again later.

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Lay the board, with the mounts attached, onto the ballast and align the center of the compression strut hole over the line on the ballast. Check your fit and that nothing is touching the hull. Good? Remove the ballast and block it up so that it is level on your bench. A 2x4 is used here with two long drywall screws. Another 2x is used to level it. Close is good enough. Mix a very small amount of epoxy, remove the board and dab a bit on the bottom of the mounts. Now place the board back on the lead and aligned like the above. Snug it down so it is level. Let it cure over night.


The next session is to remove the board from the mounts on the lead. Remove the brass inserts. Now, seriously epoxy the bond of the mounts to the ballast around the edges. Let this cure.


Water Proofing

Paint the mounts and the board with MinWax Polyglades. It is a vanish-like material. If you want to finish the board nicely, add two more coats with some rubbing of steel wool in between. When finished and dry, put them away till needed.

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Assembly of the Equipment Board



4-40 SS Phillips machine screw, 3/8" pan head Stock Item

4-40 SS Nylock nuts Stock Item

#4 SS washers Stock Item

6" Futaba servo extension wire, Tower Hobbies or local hobby store




Soldering iron

Rosin core solder

Wire cutters

Electrical tape or shrink tube

The photos shown here will be replaced as new building reflects the text below. The process of the text is what is recommended now.


Install the Servos

All of the servos for the equipment board should have been assembled with their brackets and the board finished and varnished with MinWax. The radio gear is in stock and you have batteries charged. If you have not done so, please return to the Electronics section and complete the servo assemblies.

Install each of the servos that will be used with the 4-40 screw sets listed above. The holes from the template should be very close. Some effort may be need because of the varnish in the holes. Leave the screw off the rear bracket of the rudder base as this is the board mounting screw to the ballast mount.



Above are two wiring diagrams for the RMG winch, one for a single battery and one for two. A second battery is not needed but it is an option. Adjust your weight accordingly. These diagrams are according to the requirements in Section 8, Alternate Connections, in the RMG manual. In both cases it is important to disconnect the red wire in the RMG servo ribbon wire to the receiver. The system will not work correctly otherwise.


We have standardized all the boat power switches here to be on when the switch toggle is pointed forward toward the bow…Go! Align the switch on the rudder bracket so that it will point forward and aft. The center terminal is common and the base of the toggle will point to the other terminal that is providing continuity. In this case the rear terminal. This can be checked if you have a cheap VOM. You should have one for testing batteries.


Note the difference in the two diagrams. The center terminals of the "Single Battery" system or connected as the common source of positive to both the winch and the receiver. The "Dual Battery" system separates the batteries so that one is to the receiver and the other to the winch. Adjust your wiring below accordingly for your option.


Route and size the red wire from the battery to the central terminal on the switch. Tin the wire end and the terminals on the switch. Solder the wire to the center terminal. Tin the red wire on the servo extension and solder it to the aft terminal. Thinking about the routings, then size the winch black wire to the extension black wire. Strip both and tin. Slip on a piece of shrink tubing and splice solder the wires and shrink the tubing. Use electrical tape as an alternate. Move the switch toggle to the aft.



Receivers generally are mounted under the hatch liner on the port side rather than on the rudder rear bracket as seen in some photos. This receiver positioning can be seen in a recent J class construction. The servo wires can be organized to route under the switch bracket to that area and bundled with small nylon ties. A servo extension wire may be needed for the jib trim servo. The RX will be installed later in the Sheet Line System before decking begins.


Meanwhile, bring the radio out and connect each of the servos to the proper channels in the receiver. Check your manual for this information. Connect a battery(s) to the switch wires and turn on the transmitter. Move the toggle switch for the board forward. You should get one beep out of the winch. Each of the other servos will twitch. Good. The wiring is correct.


Radio Check

Move your jib trim control to full out. Install the prepared control arm with the deck block so that the arm is pointing forward and up at about 45 degrees. This position should be close to pointing directly at the jib sheet exit guide. When the control is moved to full in, it will be almost horizontal with the equipment board. Install the retainer screw for the arm.


Install a 1" control arm 90 degrees to the rudder servo pointing to starboard. If you are using the twitcher, press on the control wheel with the arm attached. Check the throw and that the arm does not strike anything. Sometimes a slight bend upward to the arms will help. Remove it and put it away.


Play with the winch. There is no need to program it now. The unit will be programmed during the sheet line installation. The final number of turns will be set during the Pre-Tune section.


Put things away till needed.


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