Gudgeon bolts rusted out: how to extract?

beldar boathead

Well-Known Member
#41
Discarding the pilot-drill part, use the smallest hole saw to make a deep cut around the unwanted machine screw. Then use a thick washer to shield the surrounding fiberglass from heat, and use a propane torch to melt/burn access to the defective machine screw. (Vise-grips are made in a needle nose configuration).
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At first I was thinking some sort of grinder, perhaps a dremel, would be easier to use than the burning idea. But then I realized that the simplest and fastest approach would be to get a small bit of plastic explosive, attach it around the screw, and blow it up. It'll quickly provide access to the backing plate.

BB
 

L&VW

Well-Known Member
#42
A backing plate has appeared at eBay. Those of us who've worked with stainless steel would guess this backing plate isn't made of stainless steel.

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mixmkr

Active Member
#43
I made a backing plate, in which you can really use two pieces of your choice of metal, not to mention some fender washers. A couple of pieces of "L" bar of aluminum worked great. I didn't have any plastic explosives though. Vise grips, sledge hammer and a chain saw are the only 3 tools you'll ever need working on a sailboat.
 

L&VW

Well-Known Member
#44
My point re: "cobalt" drill bits was:
• there are bits made of cobalt steel
(a molybdenum series high speed tool steel alloy with an additional 5-8% cobalt)
• there are many fake cobalt bits
(bits of unknown quality steel with a cobalt surface treatment sold as "cobalt" bits)

Cobalt bits may or may not be TiN coated (titanium nitride surface treating applied by physical vapor deposition).
If not TiN coated, the cobalt bit just looks like tool steel (which is why the fakes are easy to pass off).
Uncoated cobalt steel bits will drill extremely tough, hardened materials.
If the cobalt bit has been TiN nitrided it will look like the commonly available (big box) TiN steel bits (iridescent gold in color).
TiN coated cobalt bits are superior to uncoated cobalt bits (until the bit is sharpened and/or the TiN wears off).
Found while reading a Florida blog:

"I twisted off two exhaust studs on the engine head when replacing the muffler on a Kohler 20 hp engine this week. “Dismayed” is not strong enough to describe the feeling. They snapped off short leaving angle-jagged nubs that were not very accessible to grab with vise-grips or to flatten and center-punch for drilling, but I found a solution that may help others.

I threaded on a rod coupler, or more like hammered one on in one case.

"Rod Coupler"...:


Then I got a drill bit that just fit through the rod coupler and drilled a crater in the end of the broken stud that was well centered, thanks to the rod coupler’s guidance. Then I switched to a small drill bit to make the pilot hole. After about 4 hours of dulling drill bits and generating a lot of metal shavings and sweat, I had a very nearly perfectly centered hole through each stud that left only the threads to remove with a die tap.

The common recommendation for removing broken bolts or studs is to drill a hole in them and then screw in an “easy-out”. My experience with that method has been mixed between either a successful removal or an easy-out snapping off in the broken bolt. Even when using an easy-out, the first thing needed is a well centered drill hole, and the rod coupling trick works very well for that.

Another recommendation given on the internet is mig welding a nut onto the broken stud and then using a socket wrench on the welded nut. Not that I had a mig welder available, but if I was welding something to the broken nub, it would be a piece of bolt, and I would just use a few washers under the nut to take up the space where threads were destroyed. For me, it doesn’t have to be pretty or new, it just needs to work well."


In addition to the above "workaround", I think it makes sense to drill as large a hole as possible to relieve the stress or rust keeping the stud immobile. Meanwhile, shoot some WD-40 through to the invisible side of the broken stud.

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Thread starter #45
Sorry for the late follow up, guys. Having spent over $50 on cobalt drill bits (both right and left hand), as well as numerous screw extractors, I finally bit the bullet and installed an inspection port just forward of the transom. I used a hole saw to make the hole for the inspection port. After removing the lower screws from the gudgeon, I was able to take a punch and knock out the backing plate with a hammer and retrieve it through the inspection port. The backing plate was secured with a single layer of fiberglass cloth which was easy to cut with a utility knife.

Next I was able to place the backing plate in a vise and back out the broken bolts from the internal side of the plate with a vise grip. Once the broken bolts were out I was able to replace the same backing plate over the transom and secure the gudgeon with new stainless steel screws.

I figured out the reason why the two upper screws had failed in the first place: at the factory, the plate was fastened such that the lower aspect of the plate was flush with the transom whereas the upper aspect of the plate was not; thus salt water was able to repeatedly contact the inner aspect of the bolts thus causing them to corrode and ultimately fail.

When the gudgeon was replaced I made sure to fasten it symetrically so that the shafts of the bolts are no longer exposed to the elements.

I appreciate all of the advice on this forum for such a seemingly simple repair. Had it not been done properly it could have been devastating to the structural integrity of the boat.
 

L&VW

Well-Known Member
#46
Thanks for the update. Most of us haven't experienced this kind of gudgeon problem, but DO have experience with "easy" and "difficult". :confused:

Once the decision is made to install an inspection port, I would have replaced the factory's machine screws with s/s bolts and "Nyl0ck" locking nuts. Not sure where I read it, but some through-hull repairs have been done by filling-in holes (drilled larger than necessary) with epoxy, then threading them for the new bolts. (Assuring water-resistance).

My '82 Sunfish has a rear inspection port...There is always the chance the plate is aluminum (which might help explain the failure of Jack's ss screws due to dissimilar metal corrosion if the backer in his boat is aluminum), but the backer in my boat is not plain steel.
Though not stated, the above update strongly suggests that the backing plate is stainless steel.
 
Thread starter #47
LVW,

I did indeed use new stainless steel bolts with "nylock" locking nuts in my repair. As far as I could tell, the backing plate appeared to be stainless steel, although I didn't test it with a magnet. The plate itself had no corrosion. I sealed the holes with 3M silicone sealant when I placed the new bolts.
 

L&VW

Well-Known Member
#49
Thanks again.

Is that s/s plate as thick as it appears? (Maybe 3/16th-inch)

Or are the sides folded in—like this ?

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L&VW

Well-Known Member
#51
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#53
For those of you who are used to working on these boats I'm sure many of these questions seem basic but it occurs to me that there is a real possibility of creating significant damage if I don't think this repair through properly ahead of time.

Intensity has the 5" ports for $8 or $20 with a storage bag insert. I Just installed one of each on Monday. Measuring is easy, as the inner lip of the screw in cover is exactly the same size as the needed hole. You simply trace the inside ridge with a sharpie and cut the hole with a Dremel tool, using a new fiber-reinforced cutting wheel for each hole and fine tuning the cutout with a Dremel sanding drum. The port is mounted with a dozen SS #6 x 3/4 screws after drilling pilot holes. Coat the ring on the port with pure silicon before the screws go in.
 

Webfoot1

Active Member
#54
The plate will be Aluminum. There is no way the factory is going
to free hand drill stainless steel and not make a mess. Aluminum
allows quick and easy drilling without going through a ton of drill
bits. I did see a vid somewhere of factory production and someone
was using what looked like a pneumatic hand drill.
 

L&VW

Well-Known Member
#55
For those of you who are used to working on these boats I'm sure many of these questions seem basic but it occurs to me that there is a real possibility of creating significant damage if I don't think this repair through properly ahead of time.

Intensity has the 5" ports for $8 or $20 with a storage bag insert. I Just installed one of each on Monday. Measuring is easy, as the inner lip of the screw in cover is exactly the same size as the needed hole. You simply trace the inside ridge with a sharpie and cut the hole with a Dremel tool, using a new fiber-reinforced cutting wheel for each hole and fine tuning the cutout with a Dremel sanding drum. The port is mounted with a dozen SS #6 x 3/4 screws after drilling pilot holes. Coat the ring on the port with pure silicon before the screws go in.
I'd agree that your measuring the exact diameter is a good idea. In my collection of inspection ports (for sale elsewhere here) the openings are not "as advertised" by the manufacturer! :confused:

Your approach is to reduce the local "fraying" damage to the edges that a saber saw would cause? :(

I might go one step further, and attach a reinforcing ring to fit inside. Two "C" shapes in aluminum, or one of cured fiberglass--bent to fit inside--would be my choice.

BTW, save those cut-out pieces for possible repairs later.

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#56
My opinion on saber saws and Saws-all cuts would be that any side to side movement tends to bind and pull rather than cut cleanly. In Sunfish fiberglass, the blade would be very dull half way around a single hole. That makes the binding worse and will rip and smash rather than cut. This is not just theoretical, I'm a high school carpentry teacher and we often have students build a beach game they call "corn-hole" that has a 5" port in plywood.
Even though I have a high end jig-saw with the ability to choose orbital and straight cuts and 40 years of carpentry experience, my odds of doing that on a Sunfish without tearing chunks of gel-coat are less than 90%.
 

mixmkr

Active Member
#57
That's why you use a fine tooth blade and tape over where you are cutting. Although pricey, a quality hole saw of that diameter is the best method.
 

L&VW

Well-Known Member
#58
The new or the old boats? There was a switch to stainless at one point, probably
when Laser Performance took over.
Before that all the blocks were wood with exception
of the backing plate for the new rudder. The boat I have is mid 1970's something so I'm not
expecting much. It does have screws holding on the Gudgeon so it tapped into something, or
they just used a wood block with bolts and nuts. I'll try removing the screws tomorrow and
see what happens.
My latest Sunfish is a '78 — and has a rear inspection port. :)

Not sure if I can get a better image, but it appears to have a stainless-steel backing plate. :oops: (For "The Record") ;)
The (added) transom drain passes through a much thicker piece of Sunfish than my '76. :confused:
The interior stainless-steel plate appears to have been glassed over. (?)
The dual ?? in the photo indicates some kind of margin. Is the margin that "glass-over"?
(The "—C/L—" is the vertical centerline of the gudgeon).
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