Fishplate design

/ Fishplate design #1  

bdog

Elite Member
Joined
Mar 26, 2004
Messages
2,632
Location
Texas
Tractor
John Deere 6130M
I am butting some 5" channel together to extend the rear of a trailer 5' or so. I am confident in doing this and have built several trailers from scratch but I am wondering what is the preferred method of fishplating? Seems some people say diamond shaped some say oval with no corners some say round. Just wondering what is best.
 
/ Fishplate design #2  
What you are trying to do is spread the stresses over a larger area which makes the joint stronger.
Most methods will work. I like 45* angles and also plug welds. (hole in plate welding between plate and channel)
With large trucks/Semi's the best way is to put a channel inside of the channel and they need to be bolted because those frames are hardened. ALWAYS fun to drill a 3/4" hole into!!
 
/ Fishplate design #3  
Most of the time I do a parallelogram. I hope I spelled that right. Sometimes the oval. I always round corners. I try not to have any points lining up in a straight line of load. I am not an engineer but I pay attention to how things are done to spec and how things fail.
 

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