Mast Splice below the partners???

[HappyMdRSailor]

Originally Posted by neilpride

Obviously is not the right place to splice a mast with a sleeve, right there at the bottom compresión loads are greater compared with the top, not imposible but you need to be sure that the sleeve fit even perfect at the inner section , a single row of 10 pan head screws at the main track área , 4 rows in the sides making a criss cross pattern with each other and doublé row in the FWD section if is wide enough,,, but again you need to be 100% sure the sleeve flow smoth and without gaps in each side , the FWD section with a finger ... use hig strenght lock tite in each screw and be sure the mast face and the sleeve face rest perfect , when you have the screws tight grab the mast at this área and shake it or try to bend it with your weight and retight the screws ..,,

BTW.. Sparcraft,, no idea whit what kind of BS seller or salesman you guys are dealing with, but so far so good we dont have any isue ordering parts , it take time due the location but we got always answers from the main dealer...... but is juts me off course...

Cheers....

Thanks Neil... I figured you were going to show up here with a reply for sure!

The factory splice sleeving is crazy thick and bullet proof... Not sure if I can get a giant length of it, but doubling from keel to above the gooseneck was my hopeful idea...

I love your fastener layout description... Sounds perfect...

What dealer are you obtaining your Sparcraft parts from??? Hell... I'd pay any amount for shipping if I could get what I needed!

[Cadence]

In my humble opinion. I believe you would do better with a compression strut and deck stepping. A splice at the highest point of stress seems risky?

[UNCIVILIZED]

Originally Posted by Cadence

In my humble opinion. I believe you would do better with a compression strut and deck stepping. A splice at the highest point of stress seems risky?

Cadence,
You can't directly turn a keel stepped mast into a deck stepped one, as the support afforded by the partners lets you run a tube from 25% - 40% as stiff as if it were deck stepped. It's called End Fixity.
The exact number (while an educated guess, even by experts) is based on a number of factors, but there's a BIG difference.

OP,
Glad to see that you were well received over on SA. And that they provided you with a wealth of info as well.
Hope you get your spar sorted out in a jiffy. Ah, & FYI, I didn't realize that your boat & rig were quite so big (SIC). So if you go with a taller spar, DEFINITELY have an NA do all of the appropriate math first.
- Though as a starting point, there's a lot of good reference info in the Dashew's Cruising Encyclopedia II as well as some of the key basics in Brion Toss's The Rigger's Apprentice

With some good math, & a bit of luck, you could actually wind up with a taller tube that's lighter, overall, than the one you started with (bigger or different [optimized] shaped section, & slightly thinner walls). Kind of a handy thing.
The other option for adding some SA is to go with a roachier main, & there's a lot of good info in the Dashew's book on that also.

[Mutt]

Works very well, looks OK and probably stronger than without the splice.
Make sure it is done professionally.

I attached a couple pics of spliced mast below deck.

Mutt

[Ostinato]

If you want some professional help I would recommend Sparman USA - Homepage
I used him a few times. He is personally knowledgeable about splices and will travel.

[HappyMdRSailor]

Originally Posted by Cadence

In my humble opinion. I believe you would do better with a compression strut and deck stepping. A splice at the highest point of stress seems risky?

Certainly is an option I am considering... What I'm gathering from the experts though... is exactly as Unciv states below... stick with the same moments stepped on the deck is too nooooooodle-eeee ....

Originally Posted by UNCIVILIZED

Cadence,
You can't directly turn a keel stepped mast into a deck stepped one, as the support afforded by the partners lets you run a tube from 25% - 40% as stiff as if it were deck stepped. It's called End Fixity.
The exact number (while an educated guess, even by experts) is based on a number of factors, but there's a BIG difference.

OP,
Glad to see that you were well received over on SA. And that they provided you with a wealth of info as well.
Hope you get your spar sorted out in a jiffy. Ah, & FYI, I didn't realize that your boat & rig were quite so big (SIC). So if you go with a taller spar, DEFINITELY have an NA do all of the appropriate math first.
- Though as a starting point, there's a lot of good reference info in the Dashew's Cruising Encyclopedia II as well as some of the key basics in Brion Toss's The Rigger's Apprentice

SA came up with some spectacular info to be sure... Lots of guys and sources I know, and lots that I was unaware of... The references are going to be pored over... This inquiry was a direct result of a "too good to be true" moment... a NEW old stock rig complete with all running rigging that fell in my lap and needed a snap judgement... will it work or no?? Jury is still out...

With some good math, & a bit of luck, you could actually wind up with a taller tube that's lighter, overall, than the one you started with (bigger or different [optimized] shaped section, & slightly thinner walls). Kind of a handy thing.
The other option for adding some SA is to go with a roachier main, & there's a lot of good info in the Dashew's book on that also.

Indeed.. I've certainly got ALL KINDS of options starting from scratch...

Thanks again man!

[HappyMdRSailor]

Originally Posted by Mutt

Works very well, looks OK and probably stronger than without the splice.
Make sure it is done professionally.

I attached a couple pics of spliced mast below deck.

Mutt

SPECTACULAR example!

Thanks for the "yes it can be done, here's proof" tally...

[HappyMdRSailor]

Originally Posted by Ostinato

If you want some professional help I would recommend Sparman USA - Homepage
I used him a few times. He is personally knowledgeable about splices and will travel.

These guys look like an outstanding resource... Thanks for the lead Ostinato!

[Cheechako]

"Cheech... So the splice was 5 ft above the step??? How much more to the partners??? There's been a couple "not such a great idea" replies from some of my surveyor, marine repair buds... But I can't see why I couldn't build it bullet proof like you??? I'm talking weight down low, and it is all concealed behind a panel in a cabinet..."

The doubler was about from deck level up maybe 5-6 ft max. It actually wasnt a splice just an inside doubler. It was done by Chesapeake rigging if I've got their name right.


I never have understood the keel stepped/ deck stepped difference... just things I don't know I guess. I know in compression loaded columns there is a thing called "slenderness ratio" or something like that.. basically the longer a compression loaded column the more at risk it is to failing... it's not that they fail due to compressive loads so much as to any slight bend that occurs from unequal loading.... then collapse (thus the need to keep rigging adjusted so a mast stays straight under load.)
It seems like deck stepped with support would make the mast less likely to fail... something I'm missing I guess.
Seems like most broken masts I've seen pics of are broken below the lower spreader..

[UNCIVILIZED]

[QUOTE=Cheechako;1748744I never have understood the keel stepped/ deck stepped difference... just things I don't know I guess.

... basically the longer a compression loaded column the more at risk it is to failing... it's not that they fail due to compressive loads so much as to any slight bend that occurs from unequal loading.... then collapse (thus the need to keep rigging adjusted so a mast stays straight under load.)
It seems like deck stepped with support would make the mast less likely to fail... something I'm missing I guess.
Seems like most broken masts I've seen pics of are broken below the lower spreader..[/QUOTE]

I concur, meaning that I'm in the dark on this, regarding the Exact "why", also. Though to date, Brion Toss's book's the best one I've read which both covers the subject, & lays out some (tidbits of) the match behind this topic, & some other key (rigging) ones.
- If anyone's got a fix on a better reference (book or website), I'd DEFINITELY appreciate it if you'd share it

The likelihood of a mast failure isn't related directly to the length of the unsupported span (mentioned above by another member), but instead, to the square of that length (in my understanding). And a mast's stiffness (all other things being equal) is calculated by a different geometric ratio from that (length) one, additionally.

On spars most commonly breaking below the lower spreader, you're spot on (as in, correct). This is true, even with all of the things which I mention earlier in the thread, done (almost, overly so) to maximally reinforce this area of a rig.
I'd be curious to hear the scientific explanations as to why this is a Very common failure area for spars (along with links, & ref's, math, etc., detailing such an explanation).

Some of the "why" is obvious, but other parts of this rigging, fact of life, surely seem counter-intuitive. Ergo, my curiosity.
Especially as, at a guess, there's more behind it than just the higher (vertical) compression levels which this section of a mast tube sees. Even when coupled with; mast partner loads, vang & boom loads/forces on the tube, mast loadings from the kite pole & reaching strut, etc.

I'm not trying to steal the thread, or to take it overly far OT. But rather, I'm seeking to gain a better understanding of some of the why's listed above, so that I can help other guys to understand same. In addition to helping cut down on the number of mast failures, especially in the area in question.
And as an FYI, I'm not at all opposed to doing studying on this, at the graduate level (or beyond, needs be). Especially with the seemingly unending support of members of this site.

Thanks!
Sincerely, as this kind of free info & guys being willing to share it, surely isn't necessarily a common thing.

[Jim Cate]

Not sure that I can express it accurately, but as I understand the situation, the difference is in the nature of the support at the deck level. A deck stepped mast is free to "pivot" at the step. The step does not offer any support to keep the lower sections from bending out of column. The keel stepped mast has lateral support at deck level, and the inherent stiffness of the tube means that any bending must start higher up the mast, and hence the tube can be a bit less stiff and still stay straight.

A practical difference is that the keel stepped mast will remain upright with little or no support from the stays and shrouds. This is handy when re-rigging in situ or when you need to remove the forestay in order to get into a travel lift... or when a wire breaks under load!

I hope that someone can say all this better than I have done (if it is in fact correct!!

Jim

[neilpride]

Keel stepped mast is where i put my money no matter what... just saying...

[HappyMdRSailor]

Originally Posted by Cheechako

"Cheech... So the splice was 5 ft above the step??? How much more to the partners??? There's been a couple "not such a great idea" replies from some of my surveyor, marine repair buds... But I can't see why I couldn't build it bullet proof like you??? I'm talking weight down low, and it is all concealed behind a panel in a cabinet..."

The doubler was about from deck level up maybe 5-6 ft max. It actually wasnt a splice just an inside doubler. It was done by Chesapeake rigging if I've got their name right.

Gotchya... ! You said splice, but looking back it's a "doubler spliced into" for your stress crack repair...

I never have understood the keel stepped/ deck stepped difference... just things I don't know I guess. I know in compression loaded columns there is a thing called "slenderness ratio" or something like that..

Yepper, you got it right... an Euler (dude) formula I used (or looked up a lot) in school as the Slender column ratio formula... Obviously cross section and length are the biggest factors, but end fixing/loading is a big modifier... It's fairly simple on a "PURE compression" column... But boy... start dynamically loading like rig, and the answer is more like voodoo...


basically the longer a compression loaded column the more at risk it is to failing... it's not that they fail due to compressive loads so much as to any slight bend that occurs from unequal loading.... then collapse (thus the need to keep rigging adjusted so a mast stays straight under load.)
It seems like deck stepped with support would make the mast less likely to fail... something I'm missing I guess.
Seems like most broken masts I've seen pics of are broken below the lower spreader..

Thanks Brudda!

[HappyMdRSailor]

Originally Posted by UNCIVILIZED

I concur, meaning that I'm in the dark on this, regarding the Exact "why", also. Though to date, Brion Toss's book's the best one I've read which both covers the subject, & lays out some (tidbits of) the match behind this topic, & some other key (rigging) ones.
- If anyone's got a fix on a better reference (book or website), I'd DEFINITELY appreciate it if you'd share it

The likelihood of a mast failure isn't related directly to the length of the unsupported span (mentioned above by another member), but instead, to the square of that length (in my understanding). And a mast's stiffness (all other things being equal) is calculated by a different geometric ratio from that (length) one, additionally.

On spars most commonly breaking below the lower spreader, you're spot on (as in, correct). This is true, even with all of the things which I mention earlier in the thread, done (almost, overly so) to maximally reinforce this area of a rig.
I'd be curious to hear the scientific explanations as to why this is a Very common failure area for spars (along with links, & ref's, math, etc., detailing such an explanation).

Some of the "why" is obvious, but other parts of this rigging, fact of life, surely seem counter-intuitive. Ergo, my curiosity.
Especially as, at a guess, there's more behind it than just the higher (vertical) compression levels which this section of a mast tube sees. Even when coupled with; mast partner loads, vang & boom loads/forces on the tube, mast loadings from the kite pole & reaching strut, etc.

I'm not trying to steal the thread, or to take it overly far OT. But rather, I'm seeking to gain a better understanding of some of the why's listed above, so that I can help other guys to understand same. In addition to helping cut down on the number of mast failures, especially in the area in question.
And as an FYI, I'm not at all opposed to doing studying on this, at the graduate level (or beyond, needs be). Especially with the seemingly unending support of members of this site.

Thanks!
Sincerely, as this kind of free info & guys being willing to share it, surely isn't necessarily a common thing.

All this most common failure at the lower spreader is fairly intuitive for me...... It's where the combination of high dynamic loading, relative motion of the cross section, AND obviously the stress induction because of the holes in the cross section... = Fatigue induced failure...

Sure the loads at say, the vang and goose are higher... But they aren't moving even close to what that section does moving dimensionally in X-Y, like the lowest spreader joint and your D1's... I'll bet if we had a way to watch the actual relative motion of a pencil mark on the section there... The elliptical path would give us the willies...

And... This ain't a hijack!

[HappyMdRSailor]

Originally Posted by Jim Cate

Not sure that I can express it accurately, but as I understand the situation, the difference is in the nature of the support at the deck level. A deck stepped mast is free to "pivot" at the step. The step does not offer any support to keep the lower sections from bending out of column. The keel stepped mast has lateral support at deck level, and the inherent stiffness of the tube means that any bending must start higher up the mast, and hence the tube can be a bit less stiff and still stay straight.

A practical difference is that the keel stepped mast will remain upright with little or no support from the stays and shrouds. This is handy when re-rigging in situ or when you need to remove the forestay in order to get into a travel lift... or when a wire breaks under load!

I hope that someone can say all this better than I have done (if it is in fact correct!!

Jim

Don't need to 'splain it better than ya did Jim! End fixing of the column and your intuitive understanding are in perfect harmony...