Heat or not to removed seized screws?

[jaschrumpf]

I wanted to remove the mainsail from the track on the boom of my 1975 Newport 28, but the screws (stainless) were seized up in the boom (aluminum). What I wanted to do was remove the four screws holding the cap onto the end of the boom so that I could slide out the outhaul car and then the sail. What I ended up doing was removing the boom from the boat and sliding out the sail from that end. I couldn't move those screws either, but the slot was open on that end.

So I really don't need to remove those screws, but I'd like to have everything working as it should, and it's a lot more convenient to be able to remove the sail without taking the boom off the gooseneck (though that's not a big deal either).

Now I've got the boom on sawhorses in my garage, the sail is off and the outside of the screw heads have been soaked with PB Blaster. I can't get to the inside to apply any Blaster there, so I'm looking at using an impact screwdriver and hoping some of the Blaster can get in from the outside.

My question is should I use heat from a torch or not before using the impact screwdriver?

Thanks!

[nickmerc]

You can use heat to break the corrosion. However, since you have already applied PB blaster to the area I would see what the can says about putting a flame to it. Follow all of the normal precautions when using an open flame. You may not even need an impact driver after applying heat.

If propane does not work I have found MAP gas to be a good next step. Just make sure your torch can handle the extra heat.

The threads may be gone in the cap due to the corrosion so be sure to check this.

If the heat does not work and you do not mind using a larger screw after removing the cap you can always drill the screw out. You will need to get a carbide bit for the stainless. You will also need to make sure there is enough material to use larger screws.

After you get everyting apart use Tef-gel when reassembling. This will prevent the corrosion in the future.
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[n0w0rries]

If you end up trashing the head of the screw you might try an EZ-Out.

[tommays]

When painting my J24 mast and helping a friend with a C&C 35 mast and boom very few screws came out and left good threads at the lower levels

We had to go from a #10 to a #12 screw for example as we got higher in the air were they did not get as much salt spray things came apart pretty easy

[sailingdog]

Do not heat an aluminum spar if you can avoid it. Heating an aluminum spar will remove the tempering that gives it most of its strength. Most aluminum spars are heat treated alloys.

[RXBOT]

If a loctite product was used on the screws heat may be needed. A hot air gun should be safe, don't use an open flame. Sometimes if you try to tighten first the screw may move and might then back out. If retapping larger make sure the material is thick enough to have at least 3 full threads. 24 threads per inch fastner would need at least 1/8 inch thick material. If not use rivets.

[jaschrumpf]

I don't think I need to worry much about holding power, this isn't any kind of structural or support fixture.

I took a pic on my cellphone but didn't upload it so I can't show you what it looks like, but it's just the cap on the end of the boom. From the look of things the cap has a lip that slides inside the boom, and these screws/bolts secure it in place. There are no forces applied to the screws at all. There can't be nuts on them as the cap blocks all access to the bolt ends. I imagine that the holes in the lip are threaded and that's it. Gotta get it off first to be sure though, unless someone has a Newport 28 they've done this to.

Thanks for all the advice!

[Sanduskysailor]

RXBot is right, no open flame- heat gun but not too hot. Over a couple of days use alternately heat, blaster, and an impact driver. The aluminum casting for the end cap is tapped and accepts the stainless screw to hold it on. If all else fails use a center punch, then drill out the heads of the offending screws. Not much fun but the only way. Obviously use lanocote or equivalent when putting the new screws in.

Good luck!

[nickmerc]

If you do decide to use rivets use aluminum ones. Since there is no load applied to the cap there is no need for high shear strength. An added benefit is no more galvanic corrosion.

I don't think a heat gun will get the screw or casting hot enough to break the corrosion. Dog brings up a good point about the spar being heat treated. You might get it hot enough in spots to anneal the metal. Try to heat the cap since it is cast and not heat treated.

If you have let PB blaster sit on it for a few days while reapplying without any results you are going to have to use heat or drill out the screws.

[eherlihy]

'Ya all are gonna hate me for this, but I suspect that the siezed screw can be best backed out with an impact driver. (This is a tool that you use like a screwdriver, except that you hit it with a hammer to make the screw turn... awww, look at the pic. Cost ~$25)



I used to have trouble removing the stainless steel screws from the aluminum engine case on my RD400. As the engine would heat and cool, the screws would bind in the case. The only way that I could back them out without trashing them, or the clutch cover, was to use an impact driver.