Do I dare use 5200??

[ArmySailor]

Hi all,

This post is about the dreaded "F-word" - fiftytwohundred. (and a question about boat design?)

The stern-hung rudder on my Shannon 28 has exactly two attachment points to the boat 1) 2 inches of rudder post sitting in a gudgeon(?) at the aft of the keel and 2) a small bearing assembly that is fixed to the stern of the boat through which the rudder post also passes. (see photos)

I pulled the rudder off when I hauled the boat, and I removed that bearing assembly. There was some kind of sealant on it, but I have no idea what. I bought a new bronze ring, because the other was worn down due to the swing of the rudder over many years and had become oblong.

The piece wasn't *too* hard to remove, and everything came off clean. (no chunks of fiberglass or anything). I cleaned up the small teak piece, bought new bolts and washers, etc.

Should I put something to help hold the teak and bronze together and on to the stern, or is the weight of the rudder borne by the bolts alone?

I'm just nervous because it is only two bolts going through fiberglass, with a wooden backing plate on the inside of the boat.

The forces that I imagine to be involved on a hundred pound rudder going through heavy seas lead me to believe this piece should be 5200'd on (and maybe somehow another fixture should be made in the future.

What kind of force would be required to strip bolts out the back of the boat and allow the rudder to fall into the sea? hmmm Is this a seaworthy design? It seems dicey to leave the fate of the entire rudder to two bolts/nuts.

The backing plate inside the boat that this piece depended on was kinda ate up - plywood that was spongy. I stripped it all off except for one FINAL ply that I could not get off. (it looked like fairly good wood, was about 1/4 inch thick) So just glassed over it with 8 pieces of fiberglass today and we'll see if it's thick enough once it cures. If not, I may augment with a small piece of starboard. Or more glass...

Thoughts? Gentlemens and Ladies?

Gracias!

[Orion Jim]

It looks as though the upper assembly is essentially a pillow block while the shoe must hold the weight of the rudder at the base. Hard to tell from the pictures.
Use a real backing plate not some starboard. Stainless, G10, or bronze. 5200 should be your last resort, 4200 or 4000UV would be fine. You have a great boat if it is maintained properly

[mike d.]

Replace the parts, soggy, wet what ever ! That is usually a sign of deferred maintenance/neglect ! If it ain't broke don't fix it ! Why are you trying to re-invent the ? It has held up for how many years, as built ? Re-bed what needs to be re-bedded, replace the wood sections that need it, or change to plastic/glass alternative !

[JPA Cate]

Just mho, I think the teak backing plate is fine, no need to replace. I'd repaint the one the paint is falling off, mainly to slow the soft grain of the wood from getting eaten out.

What holds the bits is the through-bolting, so just use sealant, you don't really need glue-sealant. 5200 is a strong glue, but all you want to do is keep water out, right. As long as all the alignments are correct, sealant, and you're good to go.

Ann

[Suijin]

5200 gets a bad rap. It's an amaaaaazing sealant because it's an amaaaazing glue. I just stripped my whole deck, 32 years old, everything bedded in 5200. Found one small leak and that looked like installation error. If you want something to not leak, use 5200.

That said, that part being above the waterline and not actually subject to a tremendous amount of force except perhaps laterally when in a very heavy seaway, I don't think it needs 5200. It's all about the mechanical fasteners.


I would consider replacing the wooden standoff block unless you're wedded to the aesthetics of it. You could shape similar out of G10 or some other composite and never have to worry about it again. As for a backing plate, I would go with aluminum plate or G10. Bed the plate with caulk, then bolt up the assembly.

I would only use 5200 if you replaced the wood with something more durable. That way you'd basically never have to worry about it again for the lifetime of the boat.

[flyingfin]

I saw a mechanic unbolt a 200 hp motor from the transom of a center console. Removed the bolts, only thing holding the motor onto the transom was the thin bead of 5200 around each of the four bolt holes and the transom plate. They put an engine hoist on the motor and lifted the 26' boat and motor off the trailer! Then they spent hours using razor blades to cut thru the thin layer of 5200 that was holding the motor onto the hull

[thinwater]

Originally Posted by flyingfin

I saw a mechanic unbolt a 200 hp motor from the transom of a center console. Removed the bolts, only thing holding the motor onto the transom was the thin bead of 5200 around each of the four bolt holes and the transom plate. They put an engine hoist on the motor and lifted the 26' boat and motor off the trailer! Then they spent hours using razor blades to cut thru the thin layer of 5200 that was holding the motor onto the hull

But they didn't use Debond. I was developed specifically for 3M 5200 an does a pretty fair job if you follow the instructions.

That said, 3M 5200 is for gluing things together, not sealing. It is too stiff for that.

[ArmySailor]

Thanks for the help everybody.

Orion Jim – the upper assembly is actually a bearing made for a horizontal shaft support, it’s a special bronze assembly from Edson called a “self aligning bearing” (part number 629A in their catalog) Now that I have about ¼ inch of home made fiberglass as backing, I may put a sheet of G10. I researched it and I think you nailed it. Thank you.



JPA Cate – The teak is fine. I did totally strip it and re-cetol and it looks amazing. As for sealant vs adhesive, sealant is not a huge concern. It’s above the waterline and the fiberglass at the stern is not cored, everything is solid. 5200 would, I think, seal plenty good enough for the occasional wave battering on her stern. So it’s not an issue of real good sealant vs 5200, but rather, should I use 5200 because of the “permanence” of it.

Sujin – I am not married to the wooden standoff block. But there’s nothing wrong with it. Perfectly sound, after I sanded it and looked closely, there was no rot, no weakness, etc. Just a solid block of teak.
*good point about the 5200 and usage of the teak. You’re saying the 5200 permanence may outlast the teak standoff. Good point.


Thinwater – Concur, as I understand it 5200 is not solely a sealant, but if it’s holding pieces together that firmly, it’s inherently watertight, right? Or….at least for a piece above the water line… I should say it’s “not going to let in gallons of water through two bolt holes” water tight enough for this application.

So it looks like I’m going to shop for a piece of G10 and use that as backing, and use 5200 for the teak block and bronze. Or maybe craft the G10 piece(s) as a standoff piece as well. –Though, I do like that teak quite a bit : )

[foufou]

5200 is easily softened with a heat gun. Jus don't over heat and damage the hull.

[Suijin]

Originally Posted by flyingfin

I saw a mechanic unbolt a 200 hp motor from the transom of a center console. Removed the bolts, only thing holding the motor onto the transom was the thin bead of 5200 around each of the four bolt holes and the transom plate. They put an engine hoist on the motor and lifted the 26' boat and motor off the trailer! Then they spent hours using razor blades to cut thru the thin layer of 5200 that was holding the motor onto the hull

That's one bad mechanic.

[sazarac]

Originally Posted by ArmySailor

Thanks for the help everybody.

Orion Jim – the upper assembly is actually a bearing made for a horizontal shaft support, it’s a special bronze assembly from Edson called a “self aligning bearing” (part number 629A in their catalog) Now that I have about ¼ inch of home made fiberglass as backing, I may put a sheet of G10. I researched it and I think you nailed it. Thank you.



JPA Cate – The teak is fine. I did totally strip it and re-cetol and it looks amazing. As for sealant vs adhesive, sealant is not a huge concern. It’s above the waterline and the fiberglass at the stern is not cored, everything is solid. 5200 would, I think, seal plenty good enough for the occasional wave battering on her stern. So it’s not an issue of real good sealant vs 5200, but rather, should I use 5200 because of the “permanence” of it.

Sujin – I am not married to the wooden standoff block. But there’s nothing wrong with it. Perfectly sound, after I sanded it and looked closely, there was no rot, no weakness, etc. Just a solid block of teak.
*good point about the 5200 and usage of the teak. You’re saying the 5200 permanence may outlast the teak standoff. Good point.


Thinwater – Concur, as I understand it 5200 is not solely a sealant, but if it’s holding pieces together that firmly, it’s inherently watertight, right? Or….at least for a piece above the water line… I should say it’s “not going to let in gallons of water through two bolt holes” water tight enough for this application.

So it looks like I’m going to shop for a piece of G10 and use that as backing, and use 5200 for the teak block and bronze. Or maybe craft the G10 piece(s) as a standoff piece as well. –Though, I do like that teak quite a bit : )

McMaster-Carr has lots of G10.

[TrentePieds]

ArmySailor:

You are right, the gizmo bolted to your transom would be called a "gudgeon", though this one is not quite the garden variety. Best that I can judge from you pic - which I enlarged - you should be able to split it so that the "cap" comes off the "base" that would then stay on your transom when you take the rudder off the boat. It doesn't show clearly, but is there not a couple of bearing shells made from some sort of plastic-ey material within the cast part of the gudgeon? It seems unlikely that the designer would have neglected such a simple prophylactic against the inevitable slop resulting from wear. To machine a coupla new shells would be child's play - literally. That's the sort of work you give the new apprentices to play with :-)

The bottom "socket" that is integrated with the "heel" of the keel looks plenty strong enuff to take the weight of the rudder, and is nicely designed so that the odd float-line from a crab trap won't be able to get in between the keel and rudder. All looks good in that department. There again, it would be natural to design the socket with a replaceable bearing liner.

As for the transom mounted gudgeon, IF it can be split, as I suspect, then by all means, when you re-mount it, use 5200, for you should never have to take the base off the transom again. On the other hand, since you say the bore in the gudgeon has worn oval over the boat's life, then, perhaps, in another twenty years, you or someone else WILL want to take it off again. If you think that is likely, then DON'T use 5200, for as Ann sez, it's the through bolts that will take the forces - not the goop. The goop is merely a sealant to keep water out.

That water would come from two sources only: 1: Seawater sloshing up against the transom when you've the seas behind you. As the water smacks against the transom it will be dispersed, and the force behind the slops will be so little that even butyl tape would do the sealing job. 2: Rainwater driving down the transom. Again the force behind the water is so little that butyl tape will do the job.

What IS important is that the bore for the through-bolts is PRECISELY that of the shank (the unthreaded portion) of the bolts, so that the bolts are what is called a "slip fit" in the holes. The length of shank should be that of the total depth of bore (through both transom and backing) MINUS three threads. You may have to buy bolts that have too long a shank and then "run up" the thread with a threading die until the remaining shank is the right length. I would, on having inserted the bolts, then slip on a "fender washer" (a washer of large external diameter) and a "lock washer" (a washer that prevents the nut from turning loose). I would use an "acorn" nut (a nut with a blind bore into a "dome" that gives a nice, clean, professional finish to the assembly). Once everything is "dry fitted" to you satisfaction, I would take it all apart again, and then, before slipping in the bolts to assemble it all again, cover their shanks with contact cement, elegantly known in these parts as "monkey snot". Do that, and no water will ever intrude!

On a nice little boat like yours, it is worth taking the extra care to do things to this standard :-).

TP

[Cadence]

Maybe I don't understand you. If I do, just use a sealant. On the inside if your down to a good layer of ply for the backing block add piece of any hard wood and don't worry about it.

[Mojadito]

Never use 5200 on something that may have to be removed in the future. Better backing / larger bolts may be the best answer.

[Flyingriki]

If losing the rudder is a serious concern (like maybe happened before in the model?) a safety strap might make you feel more secure. Used on a lot of crucial things in all sorts of transportation. Good luck. Read about sealants vs. glue to understand why using each where it belongs is best practice.