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Old 16-11-2008, 14:17   #1
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Wisker pole track install complication

Need to drill & tap holes for 4ft. mast track on leading edge of my mast,problem is power cable runs up inside of mast at front.How can I run tap in far enough to make threads without hitting/damaging cable.I can set my drill depth of cut,but tap must go additional depth.13 holes to drill.
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Old 16-11-2008, 14:43   #2
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It's always somp'm!

Are you sure the wires are in the front. A lot of manufacturers put the wire tubes in the back. If so, in your case, you may have to pull the wires first. You can connect them to a wire pulling tape that electricians use while you drill the hole and then pull the wires back in again.

One problem I see is if the screws are too long they may cause a problem getting the wires back in or raise hell with the wires once in. I think I'd use blind rivets. They leave a smooth ball on the back side. Plus you don't have to tap and you can still drill using a drill-stop.
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Old 16-11-2008, 14:53   #3
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Wires should be in a conduit if installed properly, but I agree Blind Monel Rivets best way to go, easier and less corrosion
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Old 16-11-2008, 16:22   #4
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Tap should be no problem

If the internal cables are in the front of the mast you can see exactly where the conduit is attached by looking for the fasteners. If you drill your track holes more than 3 inches away from conduit attachment points the tap will gently push the conduit away for the 1/4 inch or so that a true bottoming trap would protrude whilst still making good threads. After drilling your first hole you can test this by pushing a rod against the conduit to prove the point.

1/4 X 20 fasteners seated using Tef-gel will not corrode and will be stronger than Riv-nuts. The Riv-nuts will not be absolutely flush on the outside preventing a crowned track from fitting properly against the front of the mast and the Riv-nut alloy will not be an exact match with the mast alloy.
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Old 16-11-2008, 16:46   #5
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Thanks Rick,that was the answer I was looking for.There are rivets every couple of feet on front edge,and I know conduit is behind that.After I drill hole I will try to push conduit back slightly before tapping.Have 1/4 by 20 x3/4 ss and Lanocote gel,will coat generously.Fasteners should protrude about 1/8 in. inside mast.There is no way I would attempt to take conduit wire out,I imagine there are cable clamps at those rivet locations?
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Old 16-11-2008, 17:43   #6
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Hello Highseas and everyone else. How about that: a thread full of west-coast sailors! If it were me, the primary factor would be the wall thickness of the mast. If it is sufficient, then rivets are the ticket, but the purchase needs to be significant for a piece of hardware that might take some shock from time-to-time. You might also consider one-quarter by 28 TPI depending on the wall-thickness of the mast. You can hollow grind the tap drill so that it expells a slug instead of pushing through as a 59 degree point does. Then you can grind a bottoming tap to suit. You will have no difficulty with the conduit. Good luck.
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Old 16-11-2008, 23:37   #7
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I probably shouldn't say anything BUT misinformation is abundant on the net. All this talk about threaded holes in thin aluminum sheet metal is disturbing.

e.g.
Take a section of a mast/boom, drill & tap for a #10-32, twist in a screw, then take a claw hammer and pry it out. You will find that the threads will strip right out of it very easily.

Now, drill a 3/16" hole, put a SS or monel blind rivet with a tab under it to pry against and then seat it. Now try to pry it out. It will not come out until it creates an ass hole big enough for the flared end of the rivet to come out.

Which do you think took more power to pull out??? The rivet of course. And which do you want holding your rigging together. Even tightening a screw too tight might just pull the threads out. Another advantage with rivets is when they expand they fill the hole eliminating any movement leading to a shear factor.

Every GOOD Machinist knows that the depth of a hole should be tapped 1-1/2 times the diameter of the screw for maximum strength. 3 to 4 threads just don't cut it. Look at an airplane wing, all rivets. And even aluminum and steel electronic cabinetry uses threaded inserts.

Here, calculate it for yourself!

FUTEK Bolt Torque Calculator | Bolt Torque Calculators

Rivet - Wikipedia, the free encyclopedia
Quote:
Before welding techniques and bolted joints were developed, metal framed buildings and structures such as the Eiffel Tower, Shukhov Tower and the Sydney Harbour Bridge were generally held together by riveting. Also automobile chassis were riveted. Riveting is still widely used in applications where light weight and high strength are critical, such as in an aircraft. Many sheet-metal alloys are preferably not welded as deformation and modification of material properties can occur.
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Old 17-11-2008, 00:19   #8
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I agree totally, blind monel rivets the only way to go
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Old 18-11-2008, 17:03   #9
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Hi Highseas, you have got to be confused by now!

1. If there is enough room, then blind rivets are the ticket; your description led me to believe there was not enough room. This limits your rivet options to only one product that I'm aware of (but I've been away for a while, so there may be others) and that is Blind Hole rivets--quite a different product and not nearly as strong.

2. Any GOOD machinist knows that the one-and-one half diameter rule is a general guideline meant for mild steel and does not generalize well to non-ferous metals.

3. Likewise, any GOOD machinist knows that most sailboat masts are extruded, not made of sheet metal.

4. And finally, Delmarrey, YOUR TONE is offensive, it borders on being vile--keep it to yourself.

Good luck Highseas, you are on the right track.
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Old 18-11-2008, 18:57   #10
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johneri1, hate to spoil your west coast monopoly but I have a question thats very similar.

My mast has internal halyards as well and I am considering adding a radar. How are these attached so as to not interfere/snag the internals? Rivets here also?
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Old 18-11-2008, 19:02   #11
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Quote:
Originally Posted by johneri1 View Post
Hi Highseas, you have got to be confused by now!


2. Any GOOD machinist knows that the one-and-one half diameter rule is a general guideline meant for mild steel and does not generalize well to non-ferous metals.
Go to the chart it's even more for aluminum. See pict below....
As you can see 18+ IN. LBs thats not very much.

Quote:
3. Likewise, any GOOD machinist knows that most sailboat masts are extruded, not made of sheet metal.
Thin metal is thin metal whether is be extruded or rolled. Tongue-in-cheek so to say!

Quote:
4. And finally, Delmarrey, YOUR TONE is offensive, it borders on being vile--keep it to yourself.
Says you! I'm trying to be informative, not criticize.

Just because one disagrees (has an opinion) doesn't mean they are being "vile".
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Old 18-11-2008, 20:17   #12
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I think I will go with the ground end of tap method,13 machine screws over 4 ft. must have sufficient holding.Have'nt drilled a hole yet,but will soon.Will check into Monel rivets,possibly will go that route,after more research.
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