Hardware for the job, before I make it worse.

[dancing bear]

The original screws for the part in the picture below gave away, they were probably #12 screws. I drilled out the holes to 15/64" and used #14 screws.

The three screws shown in the picture seem to have taken to the job well. In the fourth hole, every time I put a screw in there, the threads get crushed and the screw does not take a bite.

Before I mess this up any further, I would appreciate any wisdom on getting this part on securely. What size holes should I drill for what size screw? The screw passes through the stainless steel unit shown in the picture, the extruded mast, and a bit of cast aluminum (mast cap). It would be a big pain to use a nut and bolt for this situation (because of the mast cap).

The piece in the picture is used as half a hinge, when stepping the mast, it faces pretty big loads.

 

[sailaway78]

Is it possible

Is it possible to put some epoxy in there, then re drill the holes. I would think also I would prefer to tap the hole, to maybe a 1/4 x 28. I think this would hold better than a sheet metal screw.

 

[dancing bear]

What kind of epoxy? I would not think epoxy would be strong enough to hold a bolt.

I do have a tap and die set.

 

[ITMaster]

After giving this a short period of thought, I might consider Devcon Aluminum Putty or something similar. Fill the hole back in and let it cure partially. Before it fully cures, try to accurately locate the center and place a small indent in the cure. After fully curing, drill it out and go back with the same sized and type screw that the remaining three are, or tap it and use a machine screw with threads and some locktite. This should have a compressive strength in excess of 8000 pounds that will hold the screw and form a lasting bond.

I also would wait for the jury to be in and see what other ideas come up....in case someone comes up with something else. Good luck and let us know how it comes out.

 

[Nereussailor]

JB weld

 

[Ray T]

There are flanged inserts with an internal thread. You insert the fitting up to the flange put the piece you are trying to fasten over the insert and tighten, the fitting mushrooms on the inside of the hole and you are good as new. the flange is thin enough that it shouldn't interfere. Cant remember the trade name for these but you might find them in a sheet metal shop. I would steer clear of epoxies and devcon for this application I think the threads would pull out.

 

[rardiH36]

At the risk of opining differently: In my many years of many times trying to use epoxy (of all sorts) for the type of situation you picture, I've never had much success. (Most attempts were not boat related, but around the home and for cars.) Epoxy might work if the depth to be filled was (say) at least 1/2", but not the ~1/4" thickness of the aluminum mast metal. And there has to be good strength for this high stress area.

My (brainstorming) thought would be to bore out the stainless steel hole a bit larger. But a must would be to put a collar on the drill bit as a depth stop so it wouldn't cut into and through the aluminum. Then use a tap to put new threads into the aluminum. Then a larger bolt than the other three. You would need to determine yourself the new bolt/thread size.

Alternative: Since the SS fitting and the aluminum are already up tight against each other, Might be OK to tap both the SS and alumimum to the next larger size than currently. Then add the next larger size bolt.

From what I've read before on this forum, use an anti-seize compound to prevent the SS bolt from corroding the aluminum.

Another item probably to look at -- is the aluminum behind the SS fittin still in OK condition? Galvanic corrosion from the SS could have weakened the entire area, in which case the repair might be more involved than just re-tapping.

 

[catsailor]

I used to have a Prindle! I believe those should be SS pop rivets.

The hole should be EXACTLY 3/16" for them to fit properly.

If the holes are over size, and you want to do it right...

* Drill out the rivets holding the mast base in (3/16") and ply the casting out. If they spin on you, grind of the heads an knock the remainder inside.
* Through-bolt as needed.
* Rivet the casting back in place.

The mast on a P-18 is designed to be watertight - that is what keeps it from going turtle - so seal EVERYTHING with silicone. I forgot after installing spinnaker fittings, dumped in a gust, and the mast slowly filled. It was a pain.

 

[Steve Dion]

Is there a possibility to use some strip of aluminum or a nut/washer and "glue" it to the inside of extrusion. If you can get a nut/washer in there you would be able to use a machine screw. If you use a scrap piece of alum you can drill and tap it. Something like JB Weld would hold it in place.

 

[Maine Sail]

I think...

I think you have two possible options here.

1) Re-drill the holes and tap them provided you have sufficient wall thickness in the spar & end casting. Then use Loc-Tite or Tef-Gel to prevent corrosion. You will likely find that those screws went into the end cap casting which runs up inside the spar a few inches so you'll be tapping both the end cap casting and the spar in one motion.

2) Re-drill and use Monel rivets. Even some heavy duty aluminum rivets would probably work for those loads. Professional riggers such as Brion Toss tend to prefer drill & tap unless you don't have sufficient wall thickness in the spar. To do this though you will need to know the nominal thickness of the end casting + the spar nominal wall to buy the correct length rivets. Because this end casting is likely located behind all of these screws any rivetused must be able to penetrate beyond both the spar and the casting to properly compres the two together and hold..

Forget epoxy it could prove to be very unsafe for this task IMHO ..

 

[Timo42]

1/4" structural rivets http://www.hansonrivet.com/w24.htm I don't know if they sell retail, but they will know who will, get the 1/4' rivet tool from harborfreight, it will work well enough for your purpose, don't use the rivets that come with the tool for this.
Just had a thought, are you screwing into the spar end fitting, or just into the tube? If the fitting, forget what I said and get a helicoil set for 1/4" bolts, will come with tap, drill, installer and coils to do the job.

 

[sailingdog]

I think you'd be better off using rivets there, although 15/64" is awfully large for rivets. It will be difficult to find a non-power rivet tool for stainless steel or monel rivets of that size.

 

[Rick Webb]

Old Flightline Trick

Not a permanent solution but as permanent as you want it to be. Stick a peice or even two of wire in the hole and put the original screw back in.

 

[Don12364]

Don't Drill Yet!

IMHO nothing by way of Rivnuts or epoxy putty will be secure enough for this vital part of the structure and increasing the fastener size might not be appropriate for the thickness of metal in the piece.
I suggest you resist drilling larger holes in the hope of getting a larger fastening to hold and I agree with you that you have stopped before making things worse.
From a study of your photo it looks as if, by removing the pin in the sheave at the root of the mast, you may uncover a slot into the mast base. That halyard has to go somewhere!
Then, using a thin blade such as a hacksaw with some playdough or chewing gum on it stick a suitable nut into this and bend or wiggle it into position inside and thread a screw in from the outside.
Of course the sticky stuff will not prevent the nut turning when the screw is tightened so get a suitable wrench and grind the sides away and bend the shank to pass into the mast to suit the job.
It might turn out so easy that you decide to make a proper job of the other three screws as well.
If you have trouble in bending a chrome vanadium wrench using heat then make one out of a bit of mild steel by filing an appropriate slot or drilling a hole and filing it hexagonal with a swiss file. It is surprising how little torque it takes just to hold a small nut from turning if the screw is being rotated from the other side and mild steel will be just fine.
Yes I know its trouble but the job warrants it.

Then; if that all goes wrong, you are left with either of the other solutions already offered or of removing the heel fitting altogether and having the hole built up with weld and re-tapped.

Persevere and it will be stronger than new.

 

[caguy]

My Sol Cat had the same piece of crap design with aluminum pop rivets. To take some of the stress I use to rap zip ties around the mast and then other zip ties wrapped around the bottom of the mast plate. Once the mast was stepped I cut away the zip ties. Personally I would re-engineer the hole thing and replace it with a hinged base plate and pin. My Hobie had a little better design but still same basic idea.
Make sure you get a mast float makes righting it a lot easier. There are some great ideas for levers that tuck under the tramp for righting it too.
Good luck,

 

[dancing bear]

For the three screws that are in, should I just leave well enough alone?

I think I will drill out the hole(s) to 1/4" and tap them (I have a tap and die set, I have no rivet stuff). If I do this, there is some concern that there is not enough material in the mast to hold a bolt on the upper holes. I assume I would still be able to rivet those holes as a back-up plan.

How strong is a bolt relative to a rivet?

This also would not preclude the taking the cap off and going the nut route.

Thanks to everyone for their thoughts!

 

[sailingdog]

DancingBear—

Be aware that the larger the fastener, the more depth of material it needs to hold securely. Drilling the holes out to 1/4" would require you to use a fastener larger than a 1/4-20 screw thread... you really need to see what size the hole is supposed to be for a given tap. I wouldn't use or trust any fastener that size on a threads that were made in just the skin of the spar, unless the spar was exceptionally thick wall—which I doubt is the case.

IMHO, you're really much better off getting a pop-rivet tool and pop rivets. They're very useful for quick repairs and hardware installations on a sailboat, and far more likely to hold securely in this type of situation.

 

[Ray T]

If the casting is behind the hole I don't think the method I suggested earlier or a pop rivit is the way to go. I think the only proper way to fix this is to take the end cap out of the mast and take it to a welding shop and have it filled in. Then you could re drill and tap for the right size. If the casting isn't behind the mast you could take the mast to a welding shop and have the hole filled. Bite the bullet and do it right.

 

[JungleJetJock]

Are there screw holes on the other side as well? If so, I am sure they line up with the ones on this side and if there are not a drill can solve that issue. I would through bolt it with a quality stainless bolt and a hex cap nut on the end to keep from anything snagging. Be sure to use some loc-tite to make sure nothing becomes unexpectedly loose.

 

[sailingdog]

Through-bolting through the spar is generally a bad idea unless you can get a compression post on the bolt inside the spar. It is far too easy to over-tighten the nut and damage the spar as a result.

Are there screw holes on the other side as well? If so, I am sure they line up with the ones on this side and if there are not a drill can solve that issue. I would through bolt it with a quality stainless bolt and a hex cap nut on the end to keep from anything snagging. Be sure to use some loc-tite to make sure nothing becomes unexpectedly loose.