Rudder shear pins

[NateD]

After installing my custom foiled rudder (using fiberglass over pink rigid foam) two years ago, my rudder has a tendency to creep upward. I remembered Skip said he installed a snowblower shear bolt to stop this (http://cpyoa.geekworkshosting.com/forum/index.php?topic=6040.0). I did a quick search of the forum and Craig (http://cpyoa.geekworkshosting.com/forum/index.php?topic=6746.0) suggested a golf tee while fansbro (http://cpyoa.geekworkshosting.com/forum/index.php?topic=1752.0) mentioned a shear pin sold by Rudder Craft (the people who make Ida Rudders) (http://www.ruddercraft.com/catalog/product_info.php?products_id=297).

I'm thinking most snowblower shear pins are going to be too strong and may not shear before damage is done to my fiberglass/foam rudder. According to this data sheet (http://nucor-fastener.com/Files/PDFs/TechDataSheets/TDS_013_Shear_Strength.pdf), the shear strength of a 1/4" grade 2 bolt is 2,179 pounds. Since our rudders create a double shear plane, the shear strength is doubled to 4,358 pounds. A shock load (sailing along and hitting something) creates about double the force of a static load, so that brings the shear point back down to 2,179 pounds. If the rudder is 3' long between the shear bolt and the very bottom of the rudder, then the bottom of the rudder would experience (2,179/3=) 726.33 pounds of force before the bolt would shear. That would do some damage to my rudder. I'm not an engeneer, so my math could be wrong on this. Has anyone (Skip?) using a shear bolt hit something hard enough to actually shear the bolt? What size bolt were you using?

A golf tee, or a piece of wood dowel, would be a cheap homemade solution, but I would have to drill holes through to attach cotter pins or find another way to make sure it doesn't fall out. Otherwise the derlin shear pins at Rudder Craft say they shear at around 150 pounds of force on the rudder, which seems reasonable, and at $8 delivered to for 2 pins, they aren't a complete ripoff.

[Salty19]

Use a plastic license plate bolt for the sheer pin. Wood will soak up water and expand making removal for trailering difficult.

[jthatcher]

I agree with Salty,   I use a plastic bolt.. works very well.  I had to replace it  5 times  on my trip this summer...  they worked just like they were supposed to work     jt

[NateD]

I agree with Salty,   I use a plastic bolt.. works very well.  I had to replace it  5 times  on my trip this summer...  they worked just like they were supposed to work     jt

Wow, what were you hitting?

[brackish]

License plate bolt?  can you get them long enough?  

I too am in need.  I have the newest ComPac supplied NACA foil rudder, but don't care for the design.  You can only lift it horizontal and two inches stay in the water, so I have two inches of scuzzy grass growing on a surface I would like to keep clean.  It requires bending the steel lift handle to get the right tension on the tang to hold it down, mine won't stay down, and has a tendency for the lift handle tang to slide sideways which allows the rudder to ride up a couple of inches.  

I want to see if I can convert it to lift all the way up and add a shear pin to hold it down.  Almost think it would be worth the eight bucks to get the one Nate referenced for a pattern then buy a few feet of Delrin rod and make a bunch of them.

[jthatcher]

   "Wow, what were you hitting?"
the bottom       i developed a keen sense for shallow places along the ICW in jersey!   got lots of experience at pushing the boat off of sand bars  and replacing the plastic bolts!    I had a good supply which i picked up at the local hardware store.    it really  is an effective way to keep the rudder in place but to also protect if from damage..    of course,  once the bolt is broken and the rudder is raised,  you also need to protect it from the prop!    i learned that from experience too ( twice)    ok.. so i am a slow learner 

[skip1930]

Well slam in a wood dowel if you care for a snow blower shear pin. You could always cut more 'shear' away. Or a piece of foam. Piece of rubber, Piece of aluminum beer can, rolled, Plastic rod from ACE. Anything,

small 's' skip.

[brackish]

   of course,  once the bolt is broken and the rudder is raised,  you also need to protect it from the prop!    i learned that from experience too ( twice)    ok.. so i am a slow learner  

I got that one down pat.  Rudder kicks up, tiller automatically is going hard to port, rudder to starboard.  Only took one session with Marine Tex for me to figure that one out. 

[Bob23]

When I built and installed my wood foiled rudder blade, I devised a downhaul line which leads through the transom into the cockpit. It's about 90% effective in that although it will keep the rudder down, it will not pull it forward enough to keep it plumb. But the downhaul in conjunction with a shear pin would be the ticket. When the pin shears, the downhaul would prevent the rudder from kicking up.
Bob23
(ps: Maybe the shear pins could be renamed the JT pin! Hahaha)

[kickingbug1]

   i use plastic wire ties

[BruceW]

I just got the new rudder, and had ordered the pins. What are you folks tying the pins to, to keep them if they fall out?

Should be interesting to sail with; next step is figuring out how to miss it with the motor. Last time I had one of these, I had a device that was on my motor to add thrust, and it kept the motor from cutting the rudder. I kept the pieces to put on, but took too long, and can't find the danged things till I (shudder) clean out the garage.

Anyway, looking forward to easier and better sailing!

[Elk River]

My 19/2 came with a couple of threaded plastic pins and the previous owner put a cable tie through the hole in one end.  I just run my 'up-haul' line from the rudder through the cable tie and then tie it off at the stern rail.  I have yet to get plastic nuts for them, but have yet to have one work it's way out while sailing (even when trying to catch Koinona)

Elk River

[BruceW]

I had to drill out a hole for the pins, and then put them in with the nut on one side, the wire tie on the other. I put a little line through, and although I forgot to do it this time, I plan to take the pin out when I leave the boat, since sometimes the water leaves the marina when the wind shifts, and the boat is on the keel. I will have to decide if I cut the wire tie, and leave the small line in and draw it out on the nut-side, but that's what I"m thinking, since I usually drop stuff into the water every chance I get.

[Tom L.]

I used bungee cord to hold the rudder all the way against the vertical stop.

Here is what I did I drilled about a 1/4" hole in the leading edge of the rudder with in 1" of the top of the lower pivoting blade. I tied a small bowl in in a 3/16" piece of line. Inserted that through the hole and tied a bowl in on the other side of the rudder as close as possible. Now I have a line with a loop on both sides of the rudder. The knots will not pass through the hole so the line with the two loops reside in the rudder. I took a bungee cord hooked it in one loop passed the bungee up to the lower pintel passed it through the space between the hull and pintel back down the other side and hooked it into the loop on the other side of the rudder. The bungee was about 18" long and maybe 3/8" dia. It wasn't quite strong enough to hold the rudder all the way to the full down stop so I added a second bungee. Results were perfect. The bungee has sufficient tension to hold the rudder as far vertical as it will go but yet it gives when the bottom is encountered. I can still use the up haul line to pull the rudder up to horizontal if beaching. When pulling the rudder up the bungees will go above the pivot bolt and will actually start assisting to hold the rudder up to the horizontal stop. When lowering the blade, I have to release the up haul line and give the rudder a little nudge and it will go down with a satisfying clunk as it hits the vertical stop. Easy to do and very cost effective.

Tom L.

[BruceW]

I've got the white plastic pins Ruddercraft sent me for keeping rudder down. What do you folks do for keeping it up? At this point, I just use the friction device it came with, and since I just do this in the slip, no real pressure on it, it works fine. However, it isn't that easy to pull it up or push it down. I think I'd like another hole in the trailing edge, with a line in it. Is there a better idea than this?