TrailerTrash wrote: ↑Sun Jul 27, 2025 2:28 am
It can be made strong enough, but it probably has a weight penalty. It probably isn't enough to matter, but if I had a choice, I'd rather have one continuous extrusion of known material properties than something spliced together. Mast bend, if you're using an adjustable backstay, might be impacted.
I'm sure that I'm letting my OCD go to work, but just thinking about the potential issues.
Hi TrailerTrash!
Not really much of a weight penalty to be honest… figuratively or literally to be honest.
Firstly: Now I’m not telling anyone specifically how or what to do. I’m just describing in general terms what I would consider doing if it were my boat for my use based upon my experience. Your boat - Your rules.
Per standard engineering practice one typically has an internal or external space sleeve at least overlap 1-to-3x the tube diameter (D) to either side of the splice junction. For practical purposes one generally does longer than 1xD to space out any attachment hardware but longer than 3xD just doesn’t add much. (Mind you this would be a close/tight match sleeve fit, not a loosely-goosey slop fit). To mount the splice one would typically have 1-to-2 through bolts per splice side or a series of staggered heavy duty pull rivets.
So given our masts are made from aluminum and about 4” in diameter (rounding up) with a wall thickness of about 0.1 inch a splice would be between a minimum of 8 inches to a max of 24 inches in length. So what we’re looking at is a splice sleeve that would weigh between 1 to 3 lbs including attachment hardware.
So not an appreciable weight penalty to speak of.
As far as structural integrity goes a properly fitted splice will be easily be equal to or stronger than the original mast tube in bending, torsion or compression. So not really an issue on that count.
Now regarding the fabrication of the splice section.
My first aspect for simplicity sake would be to call BWY to see if you can get them to sell you one of their splice kits.
Failing that I’d fabricat what I’d need from 5058 or 6061 aluminum sheet stock that was slightly thicker than the mast wall thickness. Something like 0.15 inch thick or so.
I would fashion the splice in one piece wraparound (like a bun) ideally but more likely as two pieces (like a sandwich).
Aesthetically I’d be trying to place the splice internal to the mast but externally would also work and might be easier in some regards.
(If done externally I’d be skippy the sail track slot
)
I’d carefully bend form,
DO NOT HAMMER, the sheet stock to shape. (Hammering is a no-no as it would unacceptably and most likely work harden aluminum as well as permanently alter its internal material structure)
After forming the splice piece(s) I’d consider annealing it (them). From what I recall about 6061 I’d probably do this in the Admiral’s oven at between 350-to-no-more-than-400 F for about 1-to-3 hours then allow to cool to room temperature in the oven
without opening the oven. This should relieve any internal material stress or forming work hardening effects.
Depending upon where the splice was located my personal preference would be a removable bolted attachment if the splice location was such that I could have myself a two piece mast that I could easily store inside the cabin for the off season or during road transit.
Otherwise a properly designed pattern of heavy duty pull rivets would make a more permanent installation.
(Note: Pull rivets are not to be confused or conflated with hardware store type ‘pop’ rivets …. They are different animals.)
If making it a permanent repair I’d bed the sleeve(s) with 5200 before assembly (cleaned surfaces free of oxide).
This would be to keep any potential trapped moisture out from between the surfaces to minimize any corrosion potential.
So in general terms that is a potential repair process that I would consider for my boat if that was applicable.
Again, Your boat - Your rules!
Best Regards,
Over Easy
Thanks in advance, Laura and Steve