Mast Dent Repair

[okieundersail]

forestay broke, and turnbuckle mast dropped itsself backwards. the hard dodger broke its fall, which put a dent about five inches tall and two inches deep in the 30 foot aluminum mast, about two feet above the deck. the mast has survived without any noted gain in curve or bend or rake, but the dent is, at most, unsettling.
the going idea is to put a sleeve of aluminum around the dent, but the question is, how to attach it. we have considered fiberglass, stainless rivets with tefgel, or good old fashioned lashing. any considerations or recommendations would be appreicated.

[mike d.]

Mast are generally repaired/lengthened by putting a sleeve in side of mast. doesn't mean you can't do it from out side but have never seen, but then i haven't everything. you could also have a welder do the repair. i would at the least have a pro. look at it. it may be alright if the dimple isn't in a stress area like around boom-vang fitting if you have one.

[sww914]

I've fixed a lot of things and I consider myself very competent but I'd have a pro rigger look at that. Maybe 2.

[beetle]

Originally Posted by okieundersail

forestay broke, and turnbuckle mast dropped itsself backwards. the hard dodger broke its fall, which put a dent about five inches tall and two inches deep in the 30 foot aluminum mast, about two feet above the deck. the mast has survived without any noted gain in curve or bend or rake, but the dent is, at most, unsettling.
the going idea is to put a sleeve of aluminum around the dent, but the question is, how to attach it. we have considered fiberglass, stainless rivets with tefgel, or good old fashioned lashing. any considerations or recommendations would be appreicated.

Assuming the spar section itself is ok (which is a huge assumption, given the size of the dent...).

It's better to sleeve from inside the spar, if possible. Given the dent pokes in, you might cut out the dent and insert a slightly smaller section of aluminum inside the spar from the base. You may then also want to place an exterior plate on the spar as well.

If you don't want to do an interior plate, you can have a slightly larger section of aluminum attached from the outside. What's very nice is to do a repair using an interior and an exterior plate of metal. Use 6061-T6 aluminum, if possible.

To attach the patch to the mast, you can use aluminum rivets if the mast wall section is thin. If the section is thick (3/16" or greater thickness) then you will be better off with machine screws. Walk around the marina and look at how various spars are assembled together from two pieces (often around or above the first spreader) , you'll get a sense of the fastener spacing and joint size & shape.

Shape the patch to be tapered on the sides of the spar - you would prefer to not have a hard-spot where the patch ends.

As regards welders - welding an aluminum will soften the metal, something that is preferred to avoid if possible.

- rob/beetle

[captain465]

Fill the dent with an epoxy based filler and then wrap it with a carbonfiber patch. that section of the mast will be stronger than the rest of the spar.

[CDunc]

Fill the dent with an epoxy based filler and then wrap it with a carbonfiber patch. -

Dont do that, the carbon fiber will completely corrode the mast in about two weeks, if not less.

[GordMay]

Greetings and welcome aboard the CF, okieundersail.

As CDunc notes, Carbon Fibre should NOT be used on Aluminum.

[barnakiel]

The carbon sleeve will not work without complete and effective electrical insulation of the materials (carbon and alloy). From OP's description I guess it will be rather the chop and rivet method. With a length of pipe inside and alloy rivets will do - but do remember to punch out the remnant rivet's (hwww.. word?) steel pins.

b.