dissimilar metal or worms?

I have a 37' wooden chesapeake baybuilt. At the stern of the boat on the topside the previous owner mounted the bronze rudder box he used stainless steel bolts. I started to notice that the wood around the rudder box flange was getting spongy looking and corrosion (like a corroded car battery). OI bought some silicon bronze replacement bolts to switch out the bolts. I started to scrape the wood real good and clean it off to get rid of the corrosion. As I was cleaning it I noticed I could get my fingers down into the wood and the wood was like mush( black mud). The main beam that the rudder box is mounted to is about 8" *8". Basically there use to be about a 1.5" diameter whole originally now there is about a 3" hole. What is the best way to remidy this situation? I wanted some advice on my options to fix this.

 

Yep, the bad stuff has to go, but it doesn't have to be a real pain in the butt, assuming the rot isn't very extensive.

Drill oversize holes for the hardware mounting, insuring you're back into good wood. Wet out with unthinckened epoxy, then with a fresh batch mix up a thickened mixture with cab-o-sil or other high strength filler and fill the holes. Drill for new through bolts, into the cured epoxy and bed properly. That's it and not too painful. You could install a Dutchman using the same technique, if you're uncomfortable with a 4" hole saw and a big butted drill. This is little more the plowing out the general area, until you're into good wood, fitting a new piece (of the same or similar species) and then drilling for the fasteners.

Did your neighbor ever sell his Block Island beast?

 

The Senior Chief is right. The best method is to get rid of the bad wood and replace it with good wood, then refasten. I don't think you have worms, sounds like just plain rot. Once rot gets started the only way to stop it is cut it out. Kinda like cancer. There are products that claim to kill the rot and solidify the wood, but the are just a temporary fix at best.

 

Thanks for the reply. I will try to take some picks and post them for some further advice. No this is not a yacht quality boat it is a workboat, a very nicly built workboat (white cedar/white oak). The builders of this boat have been building chesapeake bay workboats for generations and even though they are simple boats they take pride in thier work. The boat was built in 1980 but not launched until 1983. I am putting a lot of time and money trying to get this boat right. Once I post the picks we can talk further about my options. The boat is built very well it literlay does not leak a drop.

PAR,
My neighbor did not get rid of his Block island skiff. He actually was going to donate it to some block island historical society but somehow he was not confindent that they were going to restore it. He didnt want it to be just a yard ordament. The deal fell through so since then he is having the boat restored to its original style. Can I post pics to this site or do I have to email them? If you send me your email I can send you some pics of his boat (old pics and pics of the restoration). My email is kelkevmac@yahoo.com

 

I do not know how to post pics. Is there directions?

USCGRET/E8,
Yes this is the typical deadrise workboat style. The main beam down the center of the boat is about 8" *8". At the stern the main beam has about a 1..25" hole drilled down through the center of the beam(I think the rudder sharft is 1"). A typical rudder box has about a 3" square flange with four 3/8" holes in the corners. Four lag bolts fasten this down to the main beam. I would say I probably have a 2" to 3" diameter area that is rotted out (wont know completly until i get the boat out of the water. (I will still try to post some pics). Are you all saying I should:

1. remove the rudder/rudder box. At this point I have about a 2" hole through the boat.
2. Drill, scrape, whatever to get rid of all the rotten wood around the big hole plus inside the old lag bolt holes.
3. Wet out with un-thikened epoxy (the large hole and the cleaned out old lag bolt holes)
4. Fill entire area (big hole and lag bolt holes with thickened epoxy W reinforcing filler).
5. Once dry re-drill large hole for rudder, and drill four holes all the way through the beam.
6. re-install rudder box with silicon bronze through bolts.

If this is correct I have a couple questions:

1. should I attach a temporary piece of wood on the bottom side of the beam to hold the epoxy in place until it dries?
2. How do I re-drill the 1.25"-1.5" hole down through the center, should I just use a paddle bit (I dont own a 9" deep holesaw). What is the best method to get the holes drilled straight down (should i set up a jig to ensure holes are drilled plum?)
3. When I insert the through bolts should i use 4200 or 5200 around the bottom of the bolts?
4. What is the best caulk to use to bed the rudder box in?

Thanks for all your help.

 

You say use lag bolts again to fasten the rudder box back down. Is it Ok to lag through the eopxy? I thought it would crack the epoxy?

 

Her are a couple pics of my problem. I have a pic from the front and from the back. You can see the back is pretty bad.

 

Lags are famous for loosening up with time. You sound like you have a singe sided rudder port, which is as you've described it, a flanged port with four mounting holes to bolt it down to the keel or deadwood. This is the least costly port available (and most popular) and has been pointed out by the chief, the portion of the deadwood or keel, where the shaft comes through on the wet side is so close to the shaft, getting paint inside the hole is imposable. This means the wood there has little protection and moisture or beasties have had their way for some time.

This can be eliminated with a double sided port (basically two flanges, one inside and one recessed on the outside). Often the shaft hole is drilled over size and a PVC or 'glass tube bonded to the keel/deadwood so moisture ingress in this difficult area is staved.

Bolts are a better answer for both the single or double port arrangement. They can be dogged periodically, easily removed to renew bedding, repairs, etc. You seem to have a grasp of the repair, but a paddle bit will chip up the cured epoxy pretty good as it goes through. A hole saw is a better choice as is a step drill.

I grew up with those old Chesapeake deadrise boats (sharpies, dredgers and log canoes too) and it's a common difficulty in many of them.

The bad wood has to go. You can bond in a new piece of wood, then drill this or just use epoxy and drill that. I'd prefer to do a combination of both. Scab in a new section of keel, nicely bonded with thickened epoxy, then an over size hole for the fasteners and shaft, which get filled with epoxy and drilled for the shaft and fasteners. Machine bolts, particularly fine thread will hold a lot better, especially if bonded. The rudder port itself can also be bonded. Doing both of these things (bonding the fasteners and port) will make a much less troublesome area, which is stronger and less prone to difficulty down the road.

Proper bonding isn't difficult and greatly increases pullout strength and water proofness. You can read about it in the "how to" section at WWW.WestSystem.com. It boils down to drilling over size holes, usually about a third bigger then what the diameter of the previous hole was. Wetting out and filling with thickened goo. The bolts are best inserted when the goo is wet or green. A lag will not cut threads in the cured epoxy, just chip it up, this is why they're inserted when wet. You can coat the fasteners (and port) with wax or a release agent to permit easy removal, but I find it's not necessary, as they come out easy if you apply a little heat to the piece being removed.

Instead of 3M 4200 or 5200, use 3M 101 (a polysulfide) as your underwater bedding compound (or one of the more traditional compounds like Dolfinite). The polyurethanes (4200 & 5200) stick so well, that removal is difficult without damage and they don't like sticking to wet wood, unless under considerable pressure when bedded down.

 

Par & Chief,
Thanks for your reply's. Chief this picture was taken after I scraped and gouged the crap out of all the wood around the rudder box flange. the back view did not have that hole until after all my cleaning and scraping. The rest of the wood is pretty solid.
I like the idea of using a sleeve, I think I will try to use PVC if i can get the correct diameter.

I will read up on the west system site on how to repair the holes, I did read thier booklet a long time ago but I need to refresh. I am not an expert by far with fiberglass work but I have done my fare share.

I have the same problem with the four bolts holding my strut on the boat, its not as bad the bolts are 3/8", and they were just a little wobbly and a little wet around the bolts (probably .5" to .625" holes). A few years ago when I noticed the problem I pulled them out and just filled the holes with 4200. I plan to drill them out and fix them right with thickened epoxy.

Thanks again for all your help.