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Rudder Casting Delrin Screw

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(@martyr)
Posts: 631
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[#5554]

That is the official name for the little nylon or plastic screw that tensions the spring and plunger and cam on the Hobie 16 rudder system. Okay, as most of you know, I took my rudders all apart. I don't think the boat that I just got has had much rudder maintenance in a while, if any, being that it wasn't used much at all. The reason I started all of this to begin with was because the port side rudder was not locking down correctly and everything seemed to take more force than necessary to operate correctly. I took the port side rudder assembly apart first and found everything was dry as a bone, but it all came apart fairly easily. After inspecting all the parts, I used some blue marine grease to lube up the spring and plunger, even put some in the threads of the Delrin screw also. Then I moved on to the starboard side. The Delrin screw does not want to budge. I have soaked it in PB Blaster and I am going to try again to remove it. How would a nylon screw be so bonded in there in an aluminum casting that it won't budge? I want to remove all the parts and grease them like I did to the other side. So, my question, how the heck do I get this thing out so I can put a new one in there? Thanks for any advice on this subject.


 
Posted : July 10, 2016 5:24 pm
(@tamumpower)
Posts: 401
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Same problem, that screw is so soft I usually have to cut a deeper cut in it for the screw driver not to strip it out.

When mine was stuck I just took a propane torch and melted the old one out. Then took a bolt with some small notches cut in the threads, similar to a tap, to clean the threads in the housing.


 
Posted : July 10, 2016 6:05 pm
(@martyr)
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Yes, this thing is so stuck that when I try to unscrew it, it is chipping away. I still have enough slot left in it to get a good bite with a large flat head screwdriver. Was wondering if there is some special tool to fit into the hole and slot of the thing before I actually destroy it completely, something other than just a screwdriver. Anyway, I just don't see how a plastic screw could be in there so dang tight. Thanks for the input.


 
Posted : July 10, 2016 8:18 pm
Steve
(@dogboy)
Posts: 1305
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The screw is nylon. The problem is that nylon absorbs moisture over time and swells up, causing it to get stuck in the casting. The issue you're describing is very common with Hobie rudders. There are generally two options for removal and both involve destroying the screw, so make sure you have a replacement on hand.

Option one is to drill out the nylon screw using a drill bit which matches the minor diameter of the set screw (minor diameter would be the diameter of the inside of the threads, so you don't actually touch any of the threads with the drill bit). Then use a pick to pry out the remaining bit of plastic from the threads. Then go back and chase the threads to make sure they're clear before putting in a new screw.

Option two is to use a torch to either heat up the end of a large screw driver and jam it into the screw, let it cool, and then turn it out, or just entirely melt out the screw. You have to be extremely careful of the fumes and molten plastic generated when using this method, so option 1 is safer.

Either way, be sure to grease the replacement screws before installing.

sm


 
Posted : July 11, 2016 12:46 am
(@jalex)
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(@martyr)
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Thank you, I think I will opt to use the drilling method instead of fire. What about a flaming drill bit? Lol.


 
Posted : July 11, 2016 8:02 am
MN3
 MN3
(@mn3)
Posts: 7090
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Don't underestimate the pure bliss of putting a blow torch on a part that has caused you grief, and watch it melt away


 
Posted : July 11, 2016 9:03 am
(@martyr)
Posts: 631
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Haha, yeah, on second thought, torching that little booger sounds like a fun payback!


 
Posted : July 11, 2016 11:34 am
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