I have been making a few modifications today on my NACRA 5.2 mast, changing the diamond tangs to a heavier version with 1/4" rivets and changing the mast rotation setup from a single rod that was below the boom to the wishbone arrangement above the boom. Eliminating the old rotation rod leaves two sizable holes in the base of the mast. To a point I am not too concerned about plugging them and could just leave them wide open. But if there was a reasonable way to plug and seal these holes I might consider it. The reason I am not too concerned is that in all the years and the times I have flipped this boat, it has never gone turtle. In fact I have always been a proponent of having a small hole at the base that could drain any water that did get in the mast. But these are fairly large holes. I am not a fan of having someone weld them up either. That could create bigger problems.
So what have you all done to plug unwanted holes, particularly large ones 5/8" or so?
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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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Plugging Mast Holes
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Posted: Jun 13, 2016 - 07:32 PM
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Posted: Jun 13, 2016 - 08:01 PM
grind off any rust, seal with epoxy and paint
or use thickened gelcoat
if the holes are big you may need to use a little cloth, or use a shim and make a gimmick to hold some epoxy
or use bondo, prime and paint to match your mast
any will work -
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Posted: Jun 14, 2016 - 07:51 AM
I the holes are only about an inch or so from the bottom, remove the mast base and cut just above the holes and replace mast base. -
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Posted: Jun 14, 2016 - 12:13 PM
I had several holes in the front cross bar of my SC15 where an improper mast base had been installed. I had a co worker who was handy with a mig welder plug them. I then ground and brushed them fair. I have had no further problems. A proper mig weld is the only structural fix.
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'82 Super Cat 15
Hull #315
Virginia
Previously owned: '70 H14, '79 H16, '68 Sailmaster 26, '85 H14T
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Posted: Jun 14, 2016 - 01:23 PM
?????
This does not make sense to me.
if you cut the mast by a few inches... your side shrouds will no longer be the correct size
your forestay will also be longer
IF you plan to do something like this .. you better check your adjuster plates and make sure you can take up any slack that is produced by hacking your mast down a little bit
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Posted: Jun 14, 2016 - 06:13 PM
The holes I am concerned with are about 16" up from the base.
I am not comfortable with having the holes mig welded up. A round hole is a bad enough stress riser, but a weld can be a really big stress riser when it can't be finished out with grinding. So I won't be going there. This hole is very near the boom connection. This area of the mast is under all kinds of very high loads. I think the epoxy patch route will work just fine for this situation. My only concern would be the thermal expansion cycles of the aluminum over time may exceed the strength of the epoxy bond. But by getting the patch both inside and outside of these holes even if this bond does break the "plug" would still be in place and could be further sealed with silicone if any cracking appeared.
As soon as I have applied the wash coat to the mast I can effect this repair and I will show what the results look like in my technical photo album on the rebuilding of This End Up.
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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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Posted: Jun 14, 2016 - 06:22 PM
I apologize for the double post, I'm getting server time out or other error messages that make the upload appear not to happen.
I should also mention that one of these holes is elliptical about 1" x 3/4", so fairly large and on the front (wet) side of the mast.
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dg
NACRA 5.2 #400
This End Up
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Posted: Jun 14, 2016 - 09:10 PM
Go to your local hardware store, or automotive supply. They make all kinds of rubber plugs, in all kinds of sizes.
Just Google "liquid tight Bushings", grommets, or rubber hole plugs.
http://www.heyco.com/Hole…In-Liquid-Tight-Bushings
Prep time is zero, they are dirt cheap, can easily be pulled to drain/dry mast, & they work.
I removed mast rotation on my 5.7 & was going to re-install the bolt, with flat rubber washers & a dab of silicone, then I found something like these.
Edited by Edchris177 on Jun 14, 2016 - 09:14 PM.
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Posted: Jun 14, 2016 - 10:52 PM
I like that idea and will be spending some quality time at the hardware store and NAPA soon. I can modify the elliptical hole to better accept a plug.
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dg
NACRA 5.2 #400
This End Up
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Posted: Jun 15, 2016 - 09:17 AM
I Personally would prefer the epoxy vs a rubber plug on a mast in this area due to the stresses on the mast -
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Posted: Jun 15, 2016 - 02:08 PM
The first time the mast flexes the epoxy will either pop out, crack, or crack the mast. I wouldn't do it.
My first thought was to put some stainless rivets in the holes, but if they are that large then a soft plug of some sort sounds in order. -
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Posted: Jun 15, 2016 - 02:24 PM
the holes I epoxied closed on my beam and mast a few years ago would disagree with your statement -
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Posted: Jun 15, 2016 - 09:14 PM
Hello,
Note I am unsure of what you mast is made of but If you want permanent go with 3M 5200 or Sikaflex. You can get complex with this but If it were just a rivet or screw hole I would put a metal screw in of the same type as the mast and then 5200 (just don't mix stainless steel and carbon and seal without an epoxy barrier between carbon and stainless). Note that prep is everything so sand and acetone prior to 5200 application.
James
H17
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Posted: Jun 15, 2016 - 11:38 PM
Those old style,(stiff) masts don't flex much in the lower portion. They are stayed much the same as a transmission tower, almost no movement in the bottom.
I wouldn't worry about a bit of epoxy strengthening the mast, that era is stronger than needed. I have seen masts with dents, holes, bent...thy still rarely break.
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Hobie 18 Magnum
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Posted: Jun 16, 2016 - 04:06 PM
This mast is very light and very bendy. I just uploaded an image of the large hole I have to deal with in my Technical Album. It is not round and I'm not too keen to make it round either, because it is already too big. I think the rubber plug approach could work on the small hole 5/8" hole, but even it would be challenged because it is through the groove for the sail, so nothing flat for a plug to really seal against. But I am going to look at those options.
Another not so pretty idea I had was to take a piece of thin aluminum and make it conform to the shape of the mast and then rivet that in place using silicone as a sealer.
I do think I could make the epoxy patch work well enough too, since the patch would be both inside and outside of the mast like a sandwich. Even if it debonded or cracked it would remain in place and again could be sealed with silicone.
I'm doing a lot of work here and a solution that is pretty and gets the job done will get the go ahead.
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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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Posted: Jun 16, 2016 - 04:23 PM
Holy whole bat man
I didn't expect that -
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Posted: Jun 16, 2016 - 06:46 PM
A properly executed mig weld will be as strong as the original material. The holes I had welded up were in the middle of my 4" dia tubular crossbar. I put a wire wheel on a length of all thread chucked it into a power drill and cleaned the inside of the tubing to the point that I could re insert the reinforcing tube at the mast base. If you've ever gone to an arena concert all that really heavy stuff over head for the show is suspended on welded aluminum trussing. Go find yourself a good welder. It's the only structural solution.
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'82 Super Cat 15
Hull #315
Virginia
Previously owned: '70 H14, '79 H16, '68 Sailmaster 26, '85 H14T
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Posted: Jun 16, 2016 - 10:02 PM
The hole through the back of the mast in the picture above is the small one and could be plugged with a wooden dowel and silicone and be fine for a very long time. The big hole through the front of the mast is really the bigger concern. That is the wet side and I don't want to be slowly taking water on through whatever I use to seal that side. That hole is getting to be large enough to be a structural concern, but there are larger holes at the spreader that have survived over all these years.
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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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