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Gauge of Aluminum Sheet Metal for internal Boom Sleeve


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Replacing my outhaul hardware on my boom.  Going to tap / bolt new hardware on.  Was thinking to ensure they stay there for a decade or two, was going to buy a then sheet of aluminum that is bendable and cut the the shape of the bottom of the boom, then drill/tap and affix to the hardware area.  What Gauge aluminum sheet is best to use that will still be bendable enough to fit into the space?

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Aluminum that is easily formed, bendable, does performs poorly with threaded fasteners. Are you sleeving the boom to cover holes, repair a crack, as a backing plate, or only to hold fasteners?

 

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If it's curved, try getting since Al pipe or tube with a matching OD.  It will be easier than trying to bend it yourself evenly.

If the OD of the pipe is slightly too large, cut out into a bit more than a half circle and use a clamp to squish it until it's right.

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It's going to be hard to make that work. If you are tapping through both the original boom and the sleeve, getting them to the same shape so they are tight together will be extremely difficult, and with any air gap between the sleeve will carry no load. If drilling a clearance through the original boom wall and tapping only the backing plate, you need a pretty thick sleeve, thicker than is easy (or possible) to form from 6061. Maybe 5083. If you are through bolting, then the bolts will squeeze the two together and it might be successful. My advice in that case is to form it as well as you can, then drill and bolt one at a time in sequence - if you drill all at once, by the time you get some bolts in, the other holes will not longer be aligned. 

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I had a spin pole that got a significant ding in the side.  I cut about a foot of the same tubing and then slotted it lengthwise to make it a little smaller when closed.  I slid it in and then riveted it in a couple of places.  I don't know what your section looks like but if you could find a piece of the same section could you do the same thing?

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On 12/3/2020 at 2:17 PM, usa1136 said:

Replacing my outhaul hardware on my boom.  Going to tap / bolt new hardware on.  Was thinking to ensure they stay there for a decade or two, was going to buy a then sheet of aluminum that is bendable and cut the the shape of the bottom of the boom, then drill/tap and affix to the hardware area.  What Gauge aluminum sheet is best to use that will still be bendable enough to fit into the space?

Minimum Thread penetration for  5mm bolt is 5mm

The threaded backing plate thickness  must equal the fastener diameter you choose 

a typical backing plate is formed , then installed into thickened epoxy , with a single fastener used to fix the backer in place while the epoxy  cures 

After epoxy cure the remaining  fasteners are drilled , tapped and countersunk 

 

 

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What about simply drilling and tapping into a blob of epoxygoop to add thickness & spread load? Fittings on my cedar-strip kayak are mounted that way. (Though it's easier to simply coat the bolts with wax and set them in the uncured epoxy) 

 

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Any chance this is a Sparcraft boom? I am sure we would have an off-cut somewhere in Charlotte which would match the profile of the section if it is.

If you are making from scratch it is best to anodize the plate after cutting, shaping, drilling and tapping. For all the reasons. I know, easy for me to say with access to a 70ft tank.

As someone said above, start with 1X the bolt diameter and you will be covered in tension which is your worst case scenario. Guessing you are in sheer but no reason to skimp since you are adding material anyway.

Thanks.

Mark

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