interesting failure- dyneema rig terminal

[Benz]

Now that you've been through this, ask yourself whether there have been any savings over just buying Colligo Cheeky tangs in the first place.

I have this same dilemma every time I want to save money by making my own kit--that every once in a while I spend more money learning how not to do something than buying an expensive bit of hardware that somebody else engineered already.

[Sailer_Med]

I like this design much better! I am relieved to see you’ve ditched the all thread rod and the coarse threads. . It does matter though; you’ll achieve your design torques with greater reliability with that AN fastener. It’ll also be capable of enduring the case of slippage of the assembly and shear loading without damaging the holes in the rest of the assembly. It’s a fine point I know, but since your are doing the work anyway…

I attached my input with respect to assembly of the shrouds and maintenance. Once again these are fine points, but easy enough to address in the design at this stage.

[markxengineerin]

No savings, but by the same logic I shouldn't own a boat or learn the skills to sail, because it's cheaper to charter and hire a captain.
With hobbies, the enjoyment factor comes in, and a good amount of my satisfaction comes from failing, learning, eventually succeeding (or even if I don't, it's still interesting). Cost savings attempts = thinly veiled excuses to get my kicks by this process. There are so many ways to get kicks out of cruising.

[markxengineerin]

Sailer-med, I'm not sure I want the shroud to come off without fitting removal. I could go either way on that one. Colligo makes sure their design captures the shroud with a (removable, in their case) fastener. It seems unlikely but possible that the shroud breaks, and an emergency repair does seem a little easier if it's not totally captured. Other than that, I don't mind taking the whole thing apart in 7 years or whenever replacement is needed. Seeing more for inspection purposes is a good thing in that case.

[Sailer_Med]

Ya, it’s one of those things. Just pick your trade-offs…

I also want to thank you for sharing this experience. I took an early retirement because I could. But I still enjoyed my work at the time and do miss the challenges of an engineering project. Apparently I don’t break enough things on my own

Thanks!

[markxengineerin]

Sure thing, and this forum is a good design review panel, lots of clever and experienced people here, so I'll keep posting. No shortage of broken stuff on my boat.

[Patrick of M]

Excellent thread, lots of different perspectives etc.
Basically what the internet is good at, and nobody called anyone names or even got all shirty.... yahoo

[markxengineerin]

Couple more carnage photos

[markxengineerin]

The compression tube is a lot smaller than it looked!

There is a huge washer welded to each side of the mast, but the actual tube is tiny.
I have not run the calculation, but a high bolt torque would easily crush this, so all the recommendations mentioning a semi-loose or certainly not very tight bolt seem wise.

This complicates things for me, because I'm assuming the uppers have the same situation, which means I'll need to reinforce them as well.

[markxengineerin]

Some progress on making about 3/4 of the repair parts

before and after hanger thickness

[neilpride]

Jesussss!! you are hired if you want a rigger job..

[Patrick of M]

My 2¢ suggests radius/soften edges of the hard plates more. Your repair looks plenty stout, which is great in one way, but masts flex alot, so hard points are problematic...a softer edge may help

[markxengineerin]

You're right about softening being beneficial- the whole spreader+repair section now moves as one because it's so rigid compared to the rest of the mast. I did look at a big radius shape for the repair plates, but it put a stress concentration at the tip of the radius (blue arrow).

It looks better to keep this flat and react the bending evenly across the biggest area that the geometry allows.
That being said, a taper in the thickness of the plate, or maybe just a thinner plate (i'm using 1/4") would be more ideal. I decided what I had was "good enough" and to proceed with making it at that point, as I'd already been through a number of revisions and had to stop somewhere.

if you want a rigger job..

In another lifetime, interested, but doesn't sound like it'd be easy to do that while on the move..

[markxengineerin]

Made some more progress today- the mast is now ready for gluing in the backing plates as the next step.
Template for cutting

Area for lowers finshed

Area for uppers finished

Tiny old compression post vs. my new ones

The old post is .060" wall 3/4" diameter, only capable of supporting 4500 pounds of bolt pre-load in before yielding in the best case scenario, reality probably less. Torquing this bolt too much would have been dangerous, so this must be something riggers just know.

[double u]

...why use in-millions-of-cases-tried-&-true-stainless-standing, when you can go to these length to have rigging your angry/drunk/idiot marina neighbour can cut with a knife...