Better location for the mast hinge?

[mastreb]

As I struggled yet again to rig my solo from the trailer it occurred to me how much easier the process would be if the hinge wasn't at the foot of the mast, but 30" up, above the gooseneck and below the bolt rope slot opening. This would mean:

-- boom could be left on permanently while trailering
-- mast would be 30" shorter when horizontal
-- mast could be center supported when horizontal
-- spreaders would stay above lifelines
-- mast foot movement from the bow pulpit to the mast base would be easier and faster

The right hinge mechanism would be a little tricky, but no more so than the existing mast foot hinge.

Just a thought looking for criticism.

Matt

[Dido]

I like your idea, it would make things easier !

I would be paranoid about the hinge failing though as i'm sure there is something about the current set up spreading the base load of the mast across a larger area.

I was wondering rather than just and hing if you could also have a slideing collar or two sliding interlocking bolts that joined the two sections around the hinge to add more support to the mast join ?

[mastreb]

I like your idea, it would make things easier !

I would be paranoid about the hinge failing though as i'm sure there is something about the current set up spreading the base load of the mast across a larger area.

I was wondering rather than just and hing if you could also have a slideing collar or two sliding interlocking bolts that joined the two sections around the hinge to add more support to the mast join ?

It's true that the mast base is highly reinforced, and the way that the mast hinge goes down into the deck provides substantial spreading of sideways loads, but ultimately it's the stays and spreaders that hold the mast up. And as with the current mast, it's the forestay that holds the mast forward against the aft-mounted hinge. The entire current system is all about the hinge strength, as would this system be. All that said, I really like the idea of a slide-on collar that could be held in place easily with a clevis pin. I'll go through the various hardware catalogs to see what already exists.

I'm about to make my slightly bent mast a "spare", so I might be taking a cutoff wheel to it to experiment.

Matt

[Judy B]

Hello,

This has been successfully done here in the USA and in Europe. Have you ever seen the Compac Sailboat system? It's pretty slick, but not inexpensive.

http://www.com-pacyachts.com/mastendr-mastraising.html

Fair winds,
Judy B

[mastreb]

Hello,
This has been successfully done here in the USA and in Europe. Have you ever seen the Compac Sailboat system? It's pretty slick, but not inexpensive.
http://www.com-pacyachts.com/mastendr-mastraising.html

Yep, that's exactly it! I'm glad to see it's an existing successful system. Now I just need to figure out how to make a hinge

Matt

[frede]

Just call Com-Pac parts, tell them your Mastendr broke and you'd like to order a new one.

[Judy B]

Hello,
This has been successfully done here in the USA and in Europe. Have you ever seen the Compac Sailboat system? It's pretty slick, but not inexpensive.
http://www.com-pacyachts.com/mastendr-mastraising.html

Yep, that's exactly it! I'm glad to see it's an existing successful system. Now I just need to figure out how to make a hinge

Matt

Hi Matt,

If you hinge the mast, won't it hang extend way over the transom when it's down?

The mast on the compac catboat is a lot shorter than the Mac26 mast. The mast on the compac catboat is further forward than the mast on a Mac26



Fair winds,
Judy B

[restless]

With a rotating mast..... I love challenges, especially technical ones. However this one would seriously worry me. The stakes are very high. Get it wrong and you could end up in a perilous or even seriously dangerous situation should the set up fail in harsh conditions. (you sail the Bristol channel??)
For the advantages gained I would concentrate elsewhere for improvements. It would be difficult to foresee exactly where all the stresses go. I've repaired a 40ft mast before, and just can't get my head round doing this.

[mastreb]

All actual engineering involves calculation of loading forces. Fortunately I've got a mast I can destruction test this with and will determine what the actual load and torque limits are. Rotation isn't going to be an issue here since I would not be changing the existing mast foot.

I've found a shop that can MIG weld marine grade stainless, so I'm off to the finite state analysis CAD software to engineer the hinge.

Matt

[K9Kampers]

Hello,
This has been successfully done here in the USA and in Europe. Have you ever seen the Compac Sailboat system? It's pretty slick, but not inexpensive.
http://www.com-pacyachts.com/mastendr-mastraising.html

Yep, that's exactly it! I'm glad to see it's an existing successful system. Now I just need to figure out how to make a hinge

Matt

Hi Matt,

If you hinge the mast, won't it hang extend way over the transom when it's down?

The mast on the compac catboat is a lot shorter than the Mac26 mast. The mast on the compac catboat is further forward than the mast on a Mac26

Judy B - True, but Mastreb's hinge idea has the hinge seperating to move the mast forward when horizontal.

[mastreb]

Judy B - True, but Mastreb's hinge idea has the hinge seperating to move the mast forward when horizontal.

Correct--I'd use the same size mast bolt through the hinge and it would go forward to the bow pulpit the same way. It would hang off the aft far less.

Lateral forces are the major concern. All the tolerances in the holes and pins will correspond to lateral slop and the transmission of all lateral force directly to the hinge pin which would be subject to sheering. In the Compac system, that appears to be mitigated by the 1/4" lip on the bottom mast that inserts into the top hinge: Friction between the lower mast lip and the upper hinge transmits lateral force from the upper section to the lower rather than to the hinge pin. I'm surprised that 1/4" is enough to do the job, but certainly some amount of overlap is. What's not clear to me is why little enough lip to close the hinge is sufficient to compensate for lateral force.

I'll figure it out.

Matt

[K9Kampers]

As I struggled yet again to rig my solo from the trailer it occurred to me how much easier the process would be if (the process gets easier the more you do it) the hinge wasn't at the foot of the mast, but 30" up, above the gooseneck and below the bolt rope slot opening. This would mean:

-- boom could be left on permanently while trailering (why not leave it on with existing configuration?...raise the aft mast crutch for more clearance between mast & companionway hatch)-- mast would be 30" shorter when horizontal (30" is just 2.5' )-- mast could be center supported when horizontal (make a mast support for existing configuration)-- spreaders would stay above lifelines (simple mod - quick release lifelines)-- mast foot movement from the bow pulpit to the mast base would be easier and faster (same with above tried & true mods, without the tricky engineering)

The right hinge mechanism would be a little tricky, but no more so than the existing mast foot hinge.

Just a thought looking for criticism. (not trying to talk you out of it...just consider simplier mods for same benefits)

[mastreb]

not trying to talk you out of it...just consider simplier mods for same benefits

I've done the quick-release lifelines mod, and while it does make it possible to rig single-handed, they get caught up a lot.

But you are right--this is a lot of work for not a whole lot of benefit. The real benefit would come from some magical system that eliminates the need to move the mast forward away from the mast step at all.

Matt

[K9Kampers]

The real benefit would come from some magical system that eliminates the need to move the mast forward away from the mast step at all

Like a telescoping mast!?!!

[K9Kampers]

Lateral forces are the major concern. All the tolerances in the holes and pins will correspond to lateral slop and the transmission of all lateral force directly to the hinge pin which would be subject to sheering. In the Compac system, that appears to be mitigated by the 1/4" lip on the bottom mast that inserts into the top hinge: Friction between the lower mast lip and the upper hinge transmits lateral force from the upper section to the lower rather than to the hinge pin. I'm surprised that 1/4" is enough to do the job, but certainly some amount of overlap is. What's not clear to me is why little enough lip to close the hinge is sufficient to compensate for lateral force.
I'll figure it out.

To over-engineer this part this part of the mast union, I'm visualizing an internal 'splint'. An extrusion of whatever length that fits the inside shape of the mast and retracts up into the upper mast section via pull cable / line, allowing the mast to lower, yet when mast up, is dropped into place to add lateral strength to the joint.

...but 30" up, above the gooseneck and below the bolt rope slot opening.

I understand the 30" dimension you reference, but isn't that about twice height of space between the dack / mast when the mast is horizontal attached to the bow pulpit? The lower mast section would be too tall to support the mast @ horizontal, unless the attach point at the bow were raised considerably.

This mod idea reminds me of a tabernacle project that Puggsy recently posted. LINK