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Roller Trough for a CS20.3 trailer . .

Pete McCrary

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My trailer for Chessie (a CS20.3 #4) had three keel rollers and a pair of side bunks balancing the boat.  Chessie's weight was about 1,400 lbs -- which included OBM & 9.5 liters fuel, sailing & cruising equipment (including about 7 gallons of fresh water in coolers and bladders), spars & sails, and a Two Paw 7 dinghy.  Almost all the weight was carried on the three hard-rubber rollers -- which, over time, suffered damage, becoming out-of-round, and not "rolling" as they should.


Inspired by Graham's "roller" design, I made a wooden "V-trough" -- which worked quite well for a launch or two.  However, the concept didn't work out, mainly because the friction built up after a few road trips.  Inspection showed buildup of considerable road debris in the trough.  So, I decided to make a roller trough copying Graham's concept -- substituting 5" rollers commercially available instead of rollers made from 3" PVC pipe.  Here are the details:


Shown here is a pattern board cut with the keel offsets provided by B&B specifically for the CS20.3 keel, indexed to the forward edge of the CB slot.  Chessie was lifted off [of her trailer] and the pattern board was place next to the keel [and located with respect to the CB slot] and the "as-built" keel profile was scribed -- which is shown on the next photo.



Then 13 small holes were drilled at the scrib marks at each roller location on the pattern board.  The board was placed on one of "cheek" boards [of the trough] and located so that the lowest roller would just clear the trough's bottom frame while the 1st and 13th roller axles were equal distant from the top edge of the cheek pieces.  The axle locations were then marked with an awl -- no measurement transfers required.



The two cheek planks were clamped together and the drill press rigged to drill thirteen pairs of  5/8" axle holes simultaneously.



Design concept with cost data.



Rollers and SS hardware.



Assembled and installed.  The cheeks are held to the frame bottom with 1/4" x 2" hot dipped lag bolts on 8" centers.



In order to help "channel" the boat's stem for recovery, guide boards are placed between the bunks and the trough.  Also shown here is the aft end of the CB "catcher" raised over the port-side guide board.  Now, if the skipper forgets to raise the CB (for launch or recovery) the board will simply slide over the board.



This is the position of the boat for the final "sea-trial" launch (video below).  There were three previous launches -- after which adjustment were made.



This was the position of the trailer at recovery.


The first launches went fairly well, but the recoveries required [I thought] too much cranking effort.  So, I made adjustments to the bunks so that they carried much less weight.  That helped reduce the cranking effort substantially.  Further adjustments may be required.  Originally, all rollers except #6 were in contact with the keel.  After reducing the load on the bunks -- all rollers (including #6) now contract the keel.  I think it's fair to say that the dynamic load on each roller has be reduced substantially -- from almost 500 lbs per roller to about 110 lbs, a factor of more than 4.


The next three photos shows my method of preventing the boat from rolling off the trailer unexpectedly.







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  • 2 years later...

Now, more than 2 years later, I recall a couple of things that I didn’t mention or would do differently.


First, I didn’t glue the side cheeks to the trough bottom.  That would have been a lot of trouble and I worried about how “pressure treated” lumber would react to epoxy as a binder.  So I just went with the lag bolts.  But after the first season I think they should be re-torqued.


Second, I worried that the side cheeks (not perfectly quarter-sawed) would “curl” inward and pinch the rollers.  I thought I would position the cheeks so that with time & moisture I could orient the growth rings such that the natural curl (of the plank) would be outward — but I didn’t know which way (it would curl).  So, I assembled the cheeks without regard to the grain.


However, I later thought of another way to take care of the concern.  When trimming the bottom board’s edges — set the table saw to cut a slight bevel, about 1 or 2 degrees outward.  Then when installing the roller-axel assemblies, clamp the side cheeks inward when inserting the axels — slightly stressing the side cheeks together.


By the way, I didn’t weigh the assembled trough with rollers, but it was heavy — difficult for me to lift.  Mt guess, about 50 lbs.

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