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Gudgeon bolts rusted out: how to extract?

I noticed that the rudder on my Sunfish felt loose and when I looked at the gudgeon, I found that the stainless steel bolts on the upper aspect of the fitting had corroded away and broken internally such that although I could see the screw heads on the outside they were no longer connected with the shaft of the bolts.

There are four bolts altogether, and the two bolts on the lower part of the gudgeon are intact.

What apparently happened is that the "stainless" bolts corroded away and broke off so that the remaining portion of the bolts within the hull is now flush with the transom.

Does anyone have any tips or ideas as to how to remove the broken portion of the bolts within the hull? Any suggestions would be welcome since the rudder is obviously a key part of the boat and I don't want to screw it up.
 

L&VW

Well-Known Member
Chances are good that the lower fasteners don't have long to go, either. Back out the lower fasteners to see what exactly was installed.

Chances are also good that the wood backing is strong enough to support new fasteners. I'd leave the old rusted fasteners in place, and seal all four fastener holes. Raise the gudgeon a ¼-inch, drill new holes and replace with 2-inch S/S sheet metal screws. Go sailing! :cool:

But when my Clonefish rudder fell off, I cut an offset 6-inch inspection port, replaced all the fasteners with S/S bolts.

P6080026-001.JPG

From information that member mixmkr posted on this forum, I'd today cut access holes in the bottom of the hull, fix the gudgeon's fasteners, and epoxy the holes closed. The rear upper deck remains strong, and the hull-bottom is stronger-yet.
 

Webfoot1

Active Member
1. Fast Solution - Drill holes below broken bolts and install pop rivets.
2. Good Solution - Install inspection port and replace backing plate or try to remove studs with vice-grips.
3. I don't want no stinking holes in my boat Solution - Pop the rear deck.
 

beldar boathead

Well-Known Member
Pop rivets seem unwise for holding the rudder on. If it was a good idea, the Sunfish builder would have done it years ago as a cost-cutting measure. Drilling stainless is not fun, but you can drill new clearance holes in the stern bracket, then smaller holes in the backer that you will thread and use new stainless screws to attach the bracket to the backer. Or do as Webfoot says in option 1, and install a port as he says in option 2 to thru-bolt the bracket and plate. This is probably the easiest. If you do this, I would try to get the other 2 screws out before they give way and replace with fresh Stainless items.

Popping the rear deck is excessive work. Having an inspection port back there is handy for drying the boat, storing stuff, etc.
 

Webfoot1

Active Member
A 3/16 pop-rivet has a tensile strength of 320 lbs and shear strength of 260 lbs. If
that's not enough a 1/4 rivet gives 1240 lbs tensile and 1000 lbs shear.
 

L&VW

Well-Known Member
Correction: there is no room to raise the gudgeon. Leave the plate where it is, and drill four new holes instead.

A threaded rear plate would mean removing the bad bolts by using a left-hand-twist bit. Note the length, and go a ¼-inch longer. Use new bits to drill stainless—"Cobalt" is best, but any new bit is essential. Trying to drill stainless with a dull bit could "drill-start" a fire!

Then locate (or make) a "self-tapping" replacement bolt. ("catching" the old threads would be difficult—start new threads).

.
 

beldar boathead

Well-Known Member
A 3/16 pop-rivet has a tensile strength of 320 lbs and shear strength of 260 lbs. If
that's not enough a 1/4 rivet gives 1240 lbs tensile and 1000 lbs shear.
I'd be more worried about the rivet deforming in the hull as opposed to the thing shearing off or pulling in two. And I would prefer to not have quarter inch holes in my hull. Plus rivets are hollow and in the water a lot. If you try rivets, let us know how it works - it could be a good solution.
 
Foulweather Jack what year is your sunfish?
Thank you for all the suggestions. My Sunfish is relatively new: a 2013 model. I took the remaining stainless steel bolts to West Marine today and found that the bolts are actually metric o.7 threads (3/4" long). I did buy some bolt extractors from Home Depot and I'm considering drilling out the old bolts with a bolt extractor. With luck I should be able then to simply install new stainless bolts.

I sprayed the old bolt remnants that are lodged within the transom with an anti-corrosive/bolt loosening product today. I'll let that work for a day or two before I try to drill out the old bolts.
 
For what it's worth I've posted above a photo of the transom after the gudgeon was removed. The photo is upside down, so the holes at the bottom are closest to the deck: these are the ones with the remnants of the stainless bolts that are embedded within the hull and flush with the transom.
 

Webfoot1

Active Member
Pop rivets are not hollow, the pull-shank remains in the rivet hence they to not
leak water. No they do not deform the material being used and this includes riveting
together sheet metal. We use the same concept to to make repairs to aircraft except
they are Aircraft grade and called Cherry-Lock rivets. Pull rivets are used in blind holes
when you can't get at the back of the rivet to buck it.
 

Wavedancer

Upside down?
Staff member
Interesting (?): there's a second boat ID (under the gudgeon) on newer boats such as the one shown above (built year 2012).
 
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L&VW

Well-Known Member
Unless these were in subjected to severe saltwater use, nothing here tells me the old bolts are stainless—which would not react to a magnet—or only very slightly.

In stainless, should a bolt extractor break off, removing that would be much trouble. :(

My new extractor set:

Fullscreen capture 412017 55004 PM.bmp.jpg

I wouldn't trust this quality of extractor (those on the left) to work effectively, and there are much poorer quality extractors out there.

Even a new left-hand drill bit will dull its cutting edges drilling out one S/S bolt. With any luck, the new LH bit will "catch" and extract the S/S bolt from the plate.

You'd be back to "making holes" in the deck (or bottom) if new holes are drilled in the gudgeon. It'd be best to clamp the gudgeon into a drill-press and use oil to cool the (new) drill bit.

Interesting (?): there's a second boat ID (under the gudgeon) on newer boats.
'Wonder when that started? I'd guess that'd be for authenticating a stolen/recovery Sunfish claim.
 
I think the old bolts are stainless steel, since the gudgeon itself is also stainless. I live on a saltwater river, and the Sunfish is kept on a floating dock by the river so there's fairly constant salt spray on the boat.

The screws are metric self threading machine screws. At the suggestion of my local hardware store guy, I bought some new titanium drill bits, as well as some new metric stainless steel machine screws, and I've been experimenting with one of the old broken screws to try to drill a pilot hole into it that would accommodate an extractor tool.

Unfortunately the stainless steel is so tough that I'm unable to drill into it even with a brand new titanium 1/16" drill bit.

On the Sunfish, I sprayed the old bolts with some PB Catalyst spray in the hopes of loosening them up for future removal.

Does anyone have a suggestion for a type of drill bit that could drill a pilot hole into the old bolts? I suspect that if I can get a pilot hole within the old bolts I can remove them with a spiral type extractor.
 

Roller

Member
It's really finicky to try to drill out small broken bolts or screws, even if the part holding the screw can be clamped on a drill press table. Stainless steel can be an especially tough material to drill.

I wouldn't bother trying to drill out/remove the old screws/bolts from the transom. I would plug the existing holes in the transom with your choice of catalyzed goop and sand flat, then drill new holes in the rudder gudgeon close to the old holes. Mark new matching holes on the transom and drill through the transom and ss backing plate. Just to be OCD I would add ss washers under the heads of the new machine screws/bolts to more-or-less cover the original holes in the gudgeon. If the inside of the transom is accessible through an inspection port I'd use ss #10 or #12 bolts and ss Nyloc nuts with ss washers under the bolt heads and lock nuts.

A cobalt drill bit (M35 or M42) at slow speed w/ lube is the machinist's preferred way to drill stainless steel. Note: there are quantities of cheap, fake, "cobalt" drill bits on the market. A drill bit with "cobalt nitrate" coating is not the same as an M35 or M42 cobalt bit. A good quality high speed steel (HSS) bit at slow speed w/ lube should work for this job.

sunfish_gudgeon.jpg
 
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Roller

Member
Jack:
After re-reading your posts more closely I think you were able to remove the bottom gudgeon screws successfully. This obviously makes the repair even easier. You only need two new holes in the top of the gudgeon and through the transom & backing plate. Fastening through the existing bottom gudgeon/transom holes locates the gudgeon for the two new holes through the top of the transom.

The corrosion stains (rust??) behind the gudgeon and the fact that the old fastenings corroded to failure are surprising. Were the old fastenings in fact stainless steel? (i.e. non-magnetic or barely magnetic)?

From the internet:
The most common type of stainless steel is the "300 series", and the most common grades of 300 series are 304 and 316. The big difference between 304 grade & 316 grade is that 316 contains molybdenum, and the addition of molybdenum "... drastically enhances corrosion resistance, especially for more saline or chloride-exposed environments." 316 grade is commonly marketed as "marine grade stainless steel."

It's difficult to impossible to know, but I expect most big box/hardware store stainless steel is 304 grade at best, and might even be "200 series" which is less expensive than 300 series (200 replaces nickel with manganese), but which is also less corrosion resistant than any of the 300s.

It seems safest to use 316 (316L is even better) whenever possible. More ss info at: Stainless steel - Wikipedia
 
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L&VW

Well-Known Member
This

S/S 316 is the recommended grade for radiator hose clamps near salt water.

Anyone know what is keeping the S/S interior backing plate from falling off? :confused:

.
 

Webfoot1

Active Member
I got a Sunfish that I'm going to mess with soon, I let you know what the
backing plate is made of but I can almost bet with perfect confidence the factory
did not invest in Stainless Steel. I do believe it will just be a piece of scrap
metal of roughly the needed size. Personally, the easy way is to just put
in a inspection port, knock the plate out and buy or make a new one. Use bolt and locknuts,
pop-rivets, a metal tap or whatever you preference is. It's all good.
 

Webfoot1

Active Member
The new or the old boats? There was a switch to stainless at one point, probably
when Lazer 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.
 

Roller

Member
My '82 Sunfish has a rear inspection port. I reached in with a rare earth magnet and ran the magnet all over the glassed-in pintle backing plate--no noticeable reactivity (& the plate is clearly metal). When I moved the magnet away from the plate (still inside the boat and tight against the transom) the magnet easily held a big steel washer laid against the outside of the transom (so the magnet should have reacted with the backing plate if the plate is plain steel). 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.
 
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Still haven't been able to fix my gudgeon, despite buying new drill bits (both right and left handed) that are supposed to be able to cut stainless steel but no luck; I simply cannot drill out these old bolts.

So, before I hire a professional, I had one more idea to run by the group. What if I were to take a router and cut out a rim of fiberglass around the corroded bolts that are flush with the transom, thus giving me room to gain purchase on the embedded bolts with a pair of pliers, then remove the bolts and use West System epoxy to fill in the defects after the gudgeon is bolted back properly?

I appreciate all suggestions so far. Since the rudder is obviously critical to the function of the boat, I don't want to screw it up!
 

Webfoot1

Active Member
Keep it simple, put a inspection port on the back deck. May
not seem simple now but you'll see how easy it is after you
finish. Knock the backing plate out and order a new one, they
are really cheap. You can do the entire job in couple hours
and go sailing. You also get the benefit of a storage place
for you wallet, keys, etc. I don't think Sunfish were manufactured
with the intention they would still be sailing 50 years later so
a few changes are needed to keep things going.
 
Thanks, webfoot, for the suggestions. Any idea where I can order a new backing plate? Also, does anyone have a preferred brand of inspection port to install?
Finally, I'm assuming the backing plate is held in place with epoxy and/or fiberglass. Any tips for knocking that off without damaging the transom?

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.
 

Webfoot1

Active Member
Flat backing plate:
Sunfish Direct is $33
EBay is $15

I get my ports at West Marine. Bigger 6" for
me, others use a 4" inspection plate. Place 4 inches
from the rear of the deck edge with the rear of the
inspection plate ring on the 4" line.

Plate is held on with a fiberglass strap. After
all these years it should be easy to pull the strap
off. Plate should fall off.

It will take 2 saber saw blades to cut one hole.

Total difficulty level: 2 out of 10.

Good luck, Sunfish are as much fun to fix as they
are to sail. Something about low initial investment.
 

Wavedancer

Upside down?
Staff member
For me, sailing a Sunfish is a LOT more fun than fixing it, although from this Forum one might not get that impression...
:)
 

L&VW

Well-Known Member
"There is nothing - absolutely nothing - half so much worth doing as simply messing about in boats."
—Kenneth Grahame
;)

I had advertised for sale my collection of inspection ports—the following are about half of what I still own:

P8100014.JPG

I agree with the 6" port. The optional internal water-resistant storage bag can be added later.

The gudgeon symptoms suggest that your bridle-attachments may also need attention—and it's a long reach! :confused:

Sketches of inspection port installation process:
How to install an inspection port.

Factory photo shows what's under the deck near the transom—far left:


But your boat could be different! :oops:

Use nuts and bolts, but consider replacing the metal backing plate with a hard plastic cutting-board section: 'easy to drill and cut, cheap, no corrosion problems—and plenty strong. :cool:
 

L&VW

Well-Known Member
A cobalt drill bit (M35 or M42) at slow speed w/ lube is the machinist's preferred way to drill stainless steel. Note: there are quantities of cheap, fake, "cobalt" drill bits on the market. A drill bit with "cobalt nitrate" coating is not the same as an M35 or M42 cobalt bit.
I think you meant, "Titanium Nitride". (Or, TiN).

As a "wear-proof" coating, it's a pretty color. ;)

It's really finicky to try to drill out small broken bolts or screws, even if the part holding the screw can be clamped on a drill press table. Stainless steel can be an especially tough material to drill.
You got that right!!! :eek:

"...Personally, the easy way is to just put
in a inspection port, knock the plate out and buy or make a new one. Use bolt and locknuts,
pop-rivets, a metal tap or whatever you preference is. It's all good.
The hard way, would be to take a Sawz-All to the transom, and repair it from the inside-out. :eek:

Bond ¼-20" bolts to the inside plate—return the failed drill bits, buy cobalt drill bits—enlarge the gudgeon holes to fit the ¼" bolts, seal with silicone sealer, and fit Nylock ¼-20" nuts to the outside.

Use West System epoxy and bond everything back together. Better'n new! :)

'Course, isn't "easy" starting to look good? :confused:

.
 

Roller

Member
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).
 
So the bits I bought to drill out the old corroded bolts were supposed to be cobalt bits; purchased from my local Home Depot. An online search re cobalt drill bits results mainly in confusion. Can anyone recommend a reputable brand of cobalt drill bits?

So I dropped by my local West Marine on the way home and bought a 4" inspection port, mainly because the color on that one seems closest to my white gel coat on the deck. I'm hoping that will be big enough to do the repair, but if some of you have experience with this and are convinced it's too small please let me know and I'll get a bigger one.
 

wjejr

Active Member
So the bits I bought to drill out the old corroded bolts were supposed to be cobalt bits; purchased from my local Home Depot. An online search re cobalt drill bits results mainly in confusion. Can anyone recommend a reputable brand of cobalt drill bits?

So I dropped by my local West Marine on the way home and bought a 4" inspection port, mainly because the color on that one seems closest to my white gel coat on the deck. I'm hoping that will be big enough to do the repair, but if some of you have experience with this and are convinced it's too small please let me know and I'll get a bigger one.
I used a 4" inspection port, and it worked fine for me. I personally don't like the large port in the stern area, but some people don't seem to mind/care.
 

Roller

Member
Cobalt drill bits:

Grainger is probably the most accessible source for a bit or two:
Cobalt Drill Bits - Grainger Industrial Supply

Precision Twist is a well known brand used by many machinists, but it's harder to source single bits.
Precision Twist

Is there a machine shop in your town/city? Stop by & chat them up with the story of what you're trying to do. They may *give* you a used, re-sharpened bit or two. Buy 'em coffees & a dozen doughnuts. The pretty much standard grind is 135° point angle (they'll know).
 

Roller

Member
When drilling hard, tough material the keys are slow rpm, high feed rate, and lubrication. For a 1/4" drill bit aim for something like 300-400 rpm (slower = cooler). Higher feed rate means loading the bit by pushing it into the material (the bit should be cutting, not just spinning in the hole). Lube is usually a high sulphur cutting oil, but you can use any petroleum-based oil you have on hand (but not WD-40 which is too light-weight and evaporative).

As noted earlier in this thread it can be a little tricky to freehand holes in hard stuff with a small hand-held drill.
 
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