1997 Hunter 376 with the B&R Rig and a Z Spar mast. We discovered a depression in the mast extrusion behind the lower starboard spreader.

[Miles Hutchinson]

Check out the photos and share your thoughts. We are thinking about fabricating an aluminum plate to place between the spreader and the mast. This plate would be about a foot tall by 1/4" to 3/8" thick and would have cutouts for the mushroom spreader attachments points. It would also be bent to the original curve of the mast.

By The Way, I have heard from Selden Masts that we should definitely not to weld extruded aluminum in a high tensile application as it changes the molecular structure of the material and weakens it significantly.

We are wondering if the studs for the spreader mounting plate run completely through the mast from side to side. If this is the case, we are wondering whether Hunter inserted washers and nuts onto the all-thread on the inside of the mast using the view hole on the front of the mast, or whether anyone has ideas about how to do so now. With four all threads running through the mast like this, we believe this might permit us to somehow assist in pushing the mast out and back to its original shape.

Regardless, we are thinking about using threaded rivets in the mast to assist in pulling the mast bend out using the plate mentioned above. What are your thoughts and thanks so much for your input.

 

[Terry Cox]

Hi Miles, no mast expert here and not a metallurgist, either. My first thought though is to leave well enough alone, as long as there are no cracks or further distortion. I would defer to your mast maker, as you already have done, for their recommendations. Aluminum is not a very malleable metal. The amount of pressure/heat placed on the mast wall to somehow remove that indentation poses a number of potential risks, one being cracking, the other being weakening.

The plate might work as a shim to help spread the load and prevent the indentation from becoming worse. Seldon would be my go-to source for ways to solve the problem, not from some lay person like me, who has lots of opinions about this or that, none of which matters much.

 

[Whatfiero1]

I wouldn't add anymore holes if you can help it. Is the spreader noticable sweeping back more. Aluminum is strongest left alone and boat was over built anyhow.

 

[JamesG161]

This may help.

You can download your Owners manual too, from SBO, as I did.
I like to see how boats of that Hunter era are wired.
My Manual did not show the wire sizes as your 376 manual does.

That depression may have happened by over tensioning the standing rigging.

I would not worry about it, if your standing rigging is tuned correctly.

That is a ZSpar mast like mine. I would call them to get their thought on those bolts, if it worries you.
But...
Since the masts were custom design for each H376, those bolts were inserted at mast production time.
I would guess that the brackets were installed by ZSpar too.

The other standing rigging appears to be done when the mast was installed by the dealership.
Jim...

 

[Rick486]

Check out the photos and share your thoughts. We are thinking about fabricating an aluminum plate to place between the spreader and the mast. This plate would be about a foot tall by 1/4" to 3/8" thick and would have cutouts for the mushroom spreader attachments points. It would also be bent to the original curve of the mast.

By The Way, I have heard from Selden Masts that we should definitely not to weld extruded aluminum in a high tensile application as it changes the molecular structure of the material and weakens it significantly.

We are wondering if the studs for the spreader mounting plate run completely through the mast from side to side. If this is the case, we are wondering whether Hunter inserted washers and nuts onto the all-thread on the inside of the mast using the view hole on the front of the mast, or whether anyone has ideas about how to do so now. With four all threads running through the mast like this, we believe this might permit us to somehow assist in pushing the mast out and back to its original shape.

Regardless, we are thinking about using threaded rivets in the mast to assist in pulling the mast bend out using the plate mentioned above. What are your thoughts and thanks so much for your input.

Suggest you talk with Selden US 877.760.6278. They have always been helpful when I have called. Ooops. I just noticed in your post that you did talk with them. Did they suggest a way forward with this, or just "don't do this or that"?

 

[Miles Hutchinson]

Suggest you talk with Selden US 877.760.6278. They have always been helpful when I have called. Ooops. I just noticed in your post that you did talk with them. Did they suggest a way forward with this, or just "don't do this or that"?

US Spars suggested a new mast. Surprise!

Marlow Hunter suggested a 3" wide by 3' long piece of stainless along the rear edge of the mast to go under the rear of the spreader bracket. They suggested I drill and tap holes every 3" to secure it.

The retired general manager of Hunter suggested a sleeve with a new section of mast from the deck to above the bend. He also suggested contacting a naval architect for a more informed recommendation. I have not succeeded at finding his friend for said recommendation.

US Spars is sending me a 3' piece of z600 which is as close to my mast profile as possible (within 2mm). We plan to split that into two sides and custom fit it to the mast behind the spreader brackets for a symmetrical/custom fit. Ocean Rigging also suggested this fix. I understand many taller masts are in pieces with inner sleeves at the joints. Everyone suggested never to weld on extruded aluminum and to take the mast down and place it on saw horses to perform the repair/reinforcement.

Hopefully, this is an unnecessary support for what appears to be a longstanding depression that does not appear to be getting worse. It may not be necessary, but I will feel better knowing the mast wall is double thick at the point of damage and for at least 15 inches above and below the depression. I also suspect that, upon resale, it will probably add a degree of comfort for the next owner.

 

[Miles Hutchinson]

This may help.

You can download your Owners manual too, from SBO, as I did.
I like to see how boats of that Hunter era are wired.
My Manual did not show the wire sizes as your 376 manual does.

View attachment 191775

That depression may have happened by over tensioning the standing rigging.

I would not worry about it, if your standing rigging is tuned correctly.

That is a ZSpar mast like mine. I would call them to get their thought on those bolts, if it worries you.
But...
Since the masts were custom design for each H376, those bolts were inserted at mast production time.
I would guess that the brackets were installed by ZSpar too.

The other standing rigging appears to be done when the mast was installed by the dealership.
Jim...

Thanks for your input and the schematic. Note the absence of a through bar connecting the spreaders to each other. The through bar design is quite common on many sailboats of various sizes with aluminum masts before and after this B&R rig design first came out.

I am considering changing the spreader mounts to this design to incorporate a through bar which reduces the pressures on the mast significantly. This would require removal of the aluminum castings which may require new spreaders because it would shorten the overall length of the spreaders by about 4-5" on each side of the mast. Either way, this may also have a domino effect of requiring new standing rigging to retain adequate adjustment space in the turnbuckles. Alternatively this might be rectified by shortening the threaded ends of the shrouds connecting to the lower spreaders. I haven't calculated the geometry and the related impact on shroud length yet.
Any suggestions or observations would be greatly appreciated.

 

[Miles Hutchinson]

This may help.

You can download your Owners manual too, from SBO, as I did.
I like to see how boats of that Hunter era are wired.
My Manual did not show the wire sizes as your 376 manual does.

View attachment 191775

That depression may have happened by over tensioning the standing rigging.

I would not worry about it, if your standing rigging is tuned correctly.

That is a ZSpar mast like mine. I would call them to get their thought on those bolts, if it worries you.
But...
Since the masts were custom design for each H376, those bolts were inserted at mast production time.
I would guess that the brackets were installed by ZSpar too.

The other standing rigging appears to be done when the mast was installed by the dealership.
Jim...

Marlow Hunter suggested the bolts are inserted during production through the holes above and below the spreaders which are then used to position the mushroom mounts for the cross bracing shrouds above and below the lower spreaders. Thus, I don't think they are through bolts.

I'm still thinking about through bolts with washers and nuts snugged up to the inside of the mast on both sides which might help with load transfer away from the mast and to the spreaders. This would appear to rank between tedious and impossible. I don't know whether four 5/16" SS bolts will be of sufficient strength to help with load transfer. I also anticipate a potential problem with routing halyards through/around four all thread bolts.

Thoughts?

 

[JamesG161]

Thoughts?

Yes. Same as this one.

Aluminum is strongest left alone and boat was over built anyhow.

But what caused the depression in the mast, on that side?
If you can not determine that, then why won't it happened to the other side too?

The Bracket is an attachment point, that conformed to the mast shape, and spreads a point force load.
No fatigue is visible in your pictures, just a small gap.

One possible solution...
1) Have your rigger release the tension.
2) Fill the gap with 5200 or epoxy. Cure for a good period.
3) Properly set you standing ringing again.
4) Inspect that point after sailing for while. Look for fatigue cracks.

Your boat, your decision.
Jim...

 

[Rick486]

Check out the photos and share your thoughts. We are thinking about fabricating an aluminum plate to place between the spreader and the mast. This plate would be about a foot tall by 1/4" to 3/8" thick and would have cutouts for the mushroom spreader attachments points. It would also be bent to the original curve of the mast.

By The Way, I have heard from Selden Masts that we should definitely not to weld extruded aluminum in a high tensile application as it changes the molecular structure of the material and weakens it significantly.

We are wondering if the studs for the spreader mounting plate run completely through the mast from side to side. If this is the case, we are wondering whether Hunter inserted washers and nuts onto the all-thread on the inside of the mast using the view hole on the front of the mast, or whether anyone has ideas about how to do so now. With four all threads running through the mast like this, we believe this might permit us to somehow assist in pushing the mast out and back to its original shape.

Regardless, we are thinking about using threaded rivets in the mast to assist in pulling the mast bend out using the plate mentioned above. What are your thoughts and thanks so much for your input.

This is the first time I've looked at this thread and the deformation of the mast, so I ask forgiveness for being late to the party.

I'm a bit puzzled concerning the space that apparently appeared on the forward side of the spreader mount. It looks as though the forward bolts either deformed, or perhaps were not properly tightened during manufacturing. The deformation of the mast seems to be on the aft width of the mast. From a loading perspective, the aft moment on the spreader mount is caused by the aft angle of the spreader itself and the rigging loads on the end of the spreader, which are forces directed inward toward the center line of the boat. On boats with spreaders that are not angled aft, those loads are transmitted down the center of the spreaders, with no rotational load. The bolted joint design of the spreader base must depend on a snug fit to the mast so the moment of the spreader is spread over the mast surface, and not depend only on the bolts to carry the load. If the forward spreader base bolts in your mast were tightened properly I can't envision how the forward edge of the spreader mount can develop a clearance to the mast, while the aft edge deforms the mast but remains snug against the mast. If the bolts are the proper size in the original design, and were tightened properly, the loading on the spreader should be distributed over the area of contact with the mast, and not transmitted only along the aft edge of the spreader mount, which perhaps caused the deformation of the mast. I know you are more interested in repairs rather than causation but any fix would seem to include investigating those forward bolts. It would seem to be that any repair should include evaluation of those bolts.
Rick