Rivets or Machine Screws When Splicing a Mast?

[s/v Jedi]

Originally Posted by Chotu

These machine screws were blisteringly expensive. Wow. $700. For screws.

Which screws did you end up with and how many? $700 sounds excessive.

[Chotu]

Originally Posted by s/v Jedi

Which screws did you end up with and how many? $700 sounds excessive.

316 socket flat heads. 1/2” dia x 3/4” long. Coarse thread

It takes 130 of them to do the job. Well, I think it was 112 but a few extra in case.

Where are those “you get what you pay for” guys???

I want them to get on here and congratulate me on getting the finest screws money can buy. Ha ha

[stormalong]

Originally Posted by Chotu

316 socket flat heads. 1/2” dia x 3/4” long. Coarse thread

It takes 130 of them to do the job. Well, I think it was 112 but a few extra in case.

Where are those “you get what you pay for” guys???

I want them to get on here and congratulate me on getting the finest screws money can buy. Ha ha

Well, you are still way ahead vs having a new mast built. Take solace in that.

[s/v Jedi]

Originally Posted by Chotu

316 socket flat heads. 1/2” dia x 3/4” long. Coarse thread

It takes 130 of them to do the job. Well, I think it was 112 but a few extra in case.

Where are those “you get what you pay for” guys???

I want them to get on here and congratulate me on getting the finest screws money can buy. Ha ha

Can’t easily find 100 degree countersink. For 82 degree good deal though: https://www.amazon.com/Socket-Counte.../dp/B07CPL72T6

[Chotu]

Originally Posted by stormalong

Well, you are still way ahead vs having a new mast built. Take solace in that.

Waaaaay ahead. Definitely.

[Chotu]

Originally Posted by s/v Jedi

Can’t easily find 100 degree countersink. For 82 degree good deal though: https://www.amazon.com/Socket-Counte.../dp/B07CPL72T6

There are no 100 degree ones to be found. 82 is what I got.


Yes, I got ripped off by $250 apparently. However, the ones coming to me are from a known source and are the absolute best quality possible.

Boltdepot.

[Chotu]

The welder is thinking it’s good to weld the butt join together. I’m thinking no. I don’t see others welded.

[rslifkin]

Originally Posted by Chotu

The welder is thinking it’s good to weld the butt join together. I’m thinking no. I don’t see others welded.

With a 5 foot long sleeve in there, I can't see it making a big difference either way.

[thinwater]

Originally Posted by Chotu

The welder is thinking it’s good to weld the butt join together. I’m thinking no. I don’t see others welded.

It won't do any harm because the mast is cut there anyway (zero strength), the plug will not see much heat (the welder should aim for less than 100% penetration and aluminum conducts welding heat away lightning fast), and the weld is away from the bolts. But it also won't reliably do any good (it might add a little strength to the mast and it might damamge the weaken the plug a little).


So no real advantage. There will be a LOT of selant in the mast. As you say, it isn't done and they don't fail there.


Masts fail in buckling not tension, and the splice at the cut will be stiffer than the rest of the mast. It will buckle somewhere else.

[team karst]

Welding might stink up the sealant? But, welding might be good option if a dry assembly. Has some ability to keep out seawater too.

[s/v Jedi]

Originally Posted by Chotu

There are no 100 degree ones to be found. 82 is what I got.


Yes, I got ripped off by $250 apparently. However, the ones coming to me are from a known source and are the absolute best quality possible.

Boltdepot.

Take a little more care and time in these buying decisions Chotu, it saves significant amounts of money. The link I posted is for 500 bolts, certified top quality as well. Boltdepot is a box pusher just like Newport Fasteners.

I write this because I was in the same situation and decided to change that after learning how big the savings can be. If I buy something over $100 now, I put it in the shopping basket but don’t check out until at least a day has passed. During that time I try to find alternatives a couple times, think if it’s really the right product to get and sometimes I even change design to be able to use another, much more affordable product. In almost 50% of the cases I end up buying something else or from another place

[RaymondR]

Originally Posted by thinwater

It won't do any harm because the mast is cut there anyway (zero strength), the plug will not see much heat (the welder should aim for less than 100% penetration and aluminum conducts welding heat away lightning fast), and the weld is away from the bolts. But it also won't reliably do any good (it might add a little strength to the mast and it might damamge the weaken the plug a little).


So no real advantage. There will be a LOT of selant in the mast. As you say, it isn't done and they don't fail there.


Masts fail in buckling not tension, and the splice at the cut will be stiffer than the rest of the mast. It will buckle somewhere else.

There are a number of mechanisms involved in the buckling of a column depending on whats known as the "slenderness ratio". At small ratios where the column is short and diameter relatively large the failure is via yielding of the material. At larger ratios the mechanism is governed by what's known as "Euler buckling" which does not involve materiel yielding in it's initial stages but does as the buckle progresses.

The loads the mast are being subjected to depends upon the sails set and relative wind directions. A most apparent example of this is the use of running back stays where the mast is subjected to high compressive loading from the action of the masthead back stay concurrently with high bending loading from the action of the sails centre of pressure.

Spreaders also subject masts to fairly high concurrent bending/buckling forces wherein the loads generated on the upper stays are translated unto lateral bending loading where the stay passes over the spreader.

[Baby tug]

Originally Posted by RaymondR

There are a number of mechanisms involved in the buckling of a column depending on whats known as the "slenderness ratio". At small ratios where the column is short and diameter relatively large the failure is via yielding of the material. At larger ratios the mechanism is governed by what's known as "Euler buckling" which does not involve materiel yielding in it's initial stages but does as the buckle progresses.

The loads the mast are being subjected to depends upon the sails set and relative wind directions. A most apparent example of this is the use of running back stays where the mast is subjected to high compressive loading from the action of the masthead back stay concurrently with high bending loading from the action of the sails centre of pressure.

Spreaders also subject masts to fairly high concurrent bending/buckling forces wherein the loads generated on the upper stays are translated unto lateral bending loading where the stay passes over the spreader.

This might as well be a foreign language to me , I find it hard to believe there’s a lot of load on a sailboat mast considering it’s only attached to the boat by small tab on the bottom of the mast, And the wall thickness is probably 3/16 or so , The side forces are shared by the whole length of the mask , Very little on any one place , in my Neanderthal way of thinking , Grinding a valley and tig weld was my recommendation because if i couldn’t do it myself it wouldn’t get done , i just happen to have a tig welder and enough scrap laying around the cost to me , couple of pieces of filler rod and a tungsten tip , I did say what I would do , Fish plate Both sides,It’s not like you couldn’t keep an eye on it , You’re not supposed to weld a truck frame either but I’ve done it more times than I care to remember, I lengthened a frame on a semi truck and added an axle , then went to work hauling 60,000 pounds down the interstate just saying

[s/v Jedi]

Originally Posted by Baby tug

This might as well be a foreign language to me , I find it hard to believe there’s a lot of load on a sailboat mast considering it’s only attached to the boat by small tab on the bottom of the mast, And the wall thickness is probably 3/16 or so , The side forces are shared by the whole length of the mask , Very little on any one place , in my Neanderthal way of thinking , Grinding a valley and tig weld was my recommendation because if i couldn’t do it myself it wouldn’t get done , i just happen to have a tig welder and enough scrap laying around the cost to me , couple of pieces of filler rod and a tungsten tip , I did say what I would do , Fish plate Both sides,It’s not like you couldn’t keep an eye on it , You’re not supposed to weld a truck frame either but I’ve done it more times than I care to remember, I lengthened a frame on a semi truck and added an axle , then went to work hauling 60,000 pounds down the interstate just saying

There’s these wires attached to masts… we call them shrouds and stays, and they take the (side) load, not the bottom of the mast

[RaymondR]

The point I'm making is that sail boat masts in use are subjected to a number of forces which may work together to create stresses which a simple analysis does not identify. I used the example of running back stays to illustrate where this might apply on a sail boat.

The combined stresses created are known as bi-axial or tri-axial stresses and now that we have computers the primary technique used to identify them is known as "finite element analysis". This technique breaks the structure down into small volumes each of which is analysed to identify the stresses on an x,y, z axis basis which stresses are then translated into the adjoining volumes as starting points for their stress analysis.

I'm not an engineer so would not swear to any of that in a court of law but during my oilfield career bent and broke a lot of stuff and had quiet a few of the engineers who investigated the incidents explain to me how I had screwed up.

In laymen's terms, the analysis of masts is complicated **** bro.