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Corrosion on lower spar, doubler?


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#1 Dex Sawash

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Posted 21 February 2014 - 08:21 PM

My new to me Force 5 has a big nasty corroded place where the vang bail was mounted just above the deck.

I have rescued this boat from its former salty beachfront home and corrosion should be less of a problem.

 

 

vang+mount.jpg

 

That is the worse side in the picture, the pitting is less severe on the other side.

Spar seems solid away from that spot. Those are 3/16" rivet holes.

To slow down the inevitable dismasting and new spar purchase wondering the best way to bandage it.

 

A. I have some 3mm or 4mm aluminum plate I can hammer to shape and rivet over that spot with drive rivets.

 

B. An 8" piece of 2.5" ID tubing to slide over the whole thing and rivet in place would probably cost less than $20 shipped.   

 

C. I have a spare laser gooseneck fitting that would bridge the damage and I could use that fitting to attach the vang. (maybe best not to repair galvanic damage by slapping a big chunk of SS back on and recharging the battery though?)

 

D. Something that I am too dense to have considered yet.

 

 

 

 

 

 



#2 Pinching

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Posted 23 February 2014 - 11:50 AM

E.  Piece of oak planed to shape and slipped inside the mast to above the gooseneck?  Yeah it's not optimal and the fittings/rivets would have to come off to get the oak in place.  But it's cheap and rot resistant and would not further damage the mast.  Both the gooseneck area and mast step are pretty highly loaded, as you know.



#3 Wet Spreaders

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Posted 23 February 2014 - 04:04 PM

If it was just two round holes and some corrosion, I'd ignore, or stick some rivets in the holes and ignore.

 

But it looks like there are two cracks propagating from the holes - one is obvious and big coming from the upper hole, the other seems to be less distinct between the holes - perhaps a photo artifact, but if not, it's a problem. I'd go with the sleeve idea .



#4 SloopJonB

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Posted 24 February 2014 - 02:10 AM

I'd drill holes at the end of the cracks to stop further propogation then form the doubler as you described. Once it is tightly fitting, sand the spar area to be covered and the inside of the doubler and epoxy it in place. Once cured, add an appropriate number of rivets around the perimeter of the doubler. It will then outlast the rest of the spar.



#5 Dex Sawash

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Posted 27 February 2014 - 10:51 PM

I formed a doubler from 5mm plate today.

Wondering if a pipe or larger plate would be better.

The old holes span almost 180 degrees of the spar between the ends, my plate does cover that by a few mm.

I only get one chance to fix this....

 

That was the largest piece of appropriate scrap I had laying around.

I have a couple of bumper face bars I saved, might cut one of those up tomorrow and see if it is malleable enough to form.

 

There is a side of me that just says fuckit lets sail.

 

 

plate2.jpg

 

 

plate.jpg



#6 Mike Dryver

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Posted 28 February 2014 - 12:50 AM

Hi Bucc  Looking at the last pic it sure looks like there is a crack/fracture leading from one hole to the other, ie from one side to the other side of the stick under your formed piece. If it was me I would cut the mast there and insert a sleeve inside. I would think that the piece you formed is to heavy and will make a hard spot. IE the flexing will be above and below the patch. A sleeve should extend about 8-10 inches above a break, on either side of a fracture.  If you look at large masts you will see they are sectioned because of transportation issues.  They are sleeved at least 3 times the front to back diameter of the extrusion. the reason is the relieve  the stress over a larger. I would not use oak inside the mast especially if in salt water.  #1 unless you seal it first it will expand and contract with moisture level.  Oak is one of the most expanding woods you can get. also the acidic nature of it's sap will increase the possiblity of internal corrosion!  Been there done that.  You are better off with spruce or fir.  



#7 movable ballast

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Posted 28 February 2014 - 06:30 PM

Why not take it to a welder and have the holes and cracks filled in?



#8 SloopJonB

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Posted 01 March 2014 - 02:14 AM

Welding aluminium spars destroys the heat treating.

 

I'd like it better if that doubler was the same or similar thickness to the mast wall but I really don't know if it matters. It should extend well past the corroded areas though.



#9 Ishmael

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Posted 01 March 2014 - 02:51 AM

How about a couple of wraps of carbon cloth with epoxy?



#10 duncan (the other one)

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Posted 01 March 2014 - 12:17 PM

a longer sleeve (your tube idea, split lengthways to make it spring-fit in) would be better... that part you made up will create hard points too close together, IMHO.

Create a couple of tapered triangles in the top part of your tube, whack it inside and rivet generously. Have the tube extend up past the gooseneck.

#11 Dex Sawash

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Posted 08 April 2014 - 04:15 PM

tube.jpg

Scrounged up a tube that will fit snug INSIDE my mast, .065 wall 6061 AL.

 

To avoid the hard spot at the end of the tube, thinking about a slash cut sort of as drawn in the pic.

Will make the angle a little steeper than drawn, probably 8 or 10" whatever max angle can cut easily.

 

Tube is long enough to reach from foot plug to above gooseneck.

Thinking the "short" end of the slash should end just above the gooseneck and the "long" side should be up the front of the mast.

So in that pic, the left will be the gooseneck side.

 

The mast is like .125 wall so the .065 tube I have shouldn't make an extreme hard spot.

 

Good, bad?

 

 

 

 

 






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