Ram install on J/34c

[Roam]

I'm going to be installing a B&G T1 ram autopilot on my j boat. I was wondering if anyone had suggestions on how to mount the ram securely.

Currently I'm planning on building a 24x8" shelf which will be epoxied and glassed to the inside of the transom and the port side hull. I'm thinking 3 layers of glass top and bottom which will extend a foot above and below the shelf.

Thanks,
Hugh

 

[longy]

I installed a lot of (earlier) in J-120's & other J's of that time. I would build pads on the underside of the cockpit sole, cut away a bit of the 1/4-3/8" plywood verticals too allow for motion. Pads were about 5" thick, with a double layer of glass between each 1" of plywood. Ram was bolted to pad with 5/16" ss lag bolts with pre-drilled holes backfilled with (liquid) epoxy when lags were screwed in, so lags could not work out under the cycling loads. This kept the rams almost completely hidden under the cockpit & kept the aft laz storage completely open. Ram was aligned fore/aft. Be very carefull with all the installation angles - very important for full power, stroke & lifespan of the unit.
Ram was attached directly to the top of quadrant with a ss fitting made to hold the ram pin & spread the load out over the quadrant. On the 120's this point would be over the joint in the quadrant with thicker casting. No failures ever with any of these installs

 

[inneedofadvice]

How/what did you use for stops to prevent ram from self destructing?

 

[longy]

J boats quadrants all had stop plates bolted to quad on each side. They stick out about 3". These were covered with a bit of rubber. There was a vertical glassed in rib down the centerline of the transom, the stops would hit this rib to limit rotation. All the J's I worked on had rudder rotation limited to within spec for the rams/drives. But I have re-built a number of autopilot mounts that did not follow dimensions and broke. I was commissioning J's for the dealer, so did quite a few installs. Had acouple of jigs, & standard plans for the various models to get it all aligned quickly

 

[Roam]

How large were the pads you epoxied to the cockpit sole? Wondering how large of a surface I need to spread the load from the ram.

The pad I was planning to make would be two layers of 3/8 or 1/2" marine plywood with a layer of glass in between and another 3 layers top and bottom.

 

[longy]

IIRC (been a bout 30 yrs) the base of the ram was about 4" x 5". So top of block was maybe 5 x 6" (not much room for error, I used jigs a lot) sides tapered out at 45 degrees until needed vertical distance was achieved. This also gave a bigger bonding area for epoxy to grip. I glued these mounts into place, no glass. 24 grit surface texture, remove most gelcoat layer. I recall these (J 120) being about 6" thick. The glass in between the wood layers was to give move strength for the lag bolts to bite into, nothing to do with holding the layers together
How big the base needs to be will be determined by what other structure is close by. If you're mounting to a large flat panel you need more - if there are any bulkheads/ribs that provide 90 deg stiffening to the panel, just butt up against them
IIRC I usually had about 9 x 12" of base surface

With your thin block I'd have thicker layers on top & in joint to give the lags more support. If your layout/alignment is correct all loads are shear on the fasteners

 

[Roam]

Here's some photos of my installation. The base is two layers of 1/2 marine ply with three layers of fibreglass between them. There's 4 layers of fibreglass on the top side of the platform and three more on the bottom attaching it to the hull. I forget what the fibreglass is called but it's chop strand on one side and woven on the other. Definitely the heaviest stuff I ever worked with.

The tiller is made of 5/8" aluminum. It's bolted to the 'quadrant' and is a snug fit to the rudder post. I also filled in any gaps between the tiller and post with epoxy. It appears that the 'quadrant' used quite a bit of filler also to get a snug fit on the rudder post.