mast splicing

[mikestevens]

I have been doing my research and I think I have found a source for the extrusion that matches my offshore spar, which is bent where it comes through the deck of my S2 9.1.
I think I know how we might make a sleeve to insert into the mast by quartering a piece of extrusion and re welding it back togeter.
Questions:
1. What about the part inside the mast extrusion on the back side of the channel for the boltrope of the main? Would I just leave a gap there when making the internal sleeve, or would I fashion a concave section that would span the gap?
2. What is the rule of thumb for sleeve length? the spar is 6 x 4"
3. What do you mean by taper the ends of the sleeve (from previous post)? By how much?
4. What type of fasteners would one use to connect the sleeve to the mast extrusion and what pattern/spacing might one employ? Tapped bolts or rivets?
5. Is it necessary to weld the joint?
6. Would it help to add adhesive when assembling?

[Brian Duff]

What do you mean 'bent' where it comes through the deck?
Are you going to have to discard a section of the spar, or are you buying a new section to splice on to the existing un-bent portion?


All I can tell you is what I normally do, which is based on my observations from assembling many spar builders two piece masts, and based on repairs we have seen hold up, or fail, and repairs we have done in the past.
It is not necessary to obtain a piece of mast section like yours and then cut it down to fit inside. This often results in a poor fitting mast splice piece anyway(the curves are all wrong). Our preferred method is to bend up some plates on the brake that can cover as much of the inside of the mast as possible. You will not be able to do anything about the area where the bolt rope track is. There may also be a conduit track in there that you will have to work around. That’s ok. Just get the plates to cover as much area as possible. The length of the mast plates should be twice the fore and aft section of the mast, so for you, 12" plates, plus whatever length you want for a taper. Very seldom are tapers seen on mast splices provided by the major builders. I can’t think of ever seeing a taper in those plates, actually. If you do chose to taper, and we do, then make the plates 18" long and taper the last 3" each side, removing the material from the sides of the splice plate and leaving the plates long on the front and back is my preference. The splice taper might best be described as a swallow tail taper.
On your mast, which is probably a bit over 5/32" wall thickness, I would use splice plates that are 5/32” or 3/16" thick. Use plates that are the wall thickness of the mast thick, or greater. We have even seen solid machined blocks of aluminum that seem to be working well, but this is not my preference.

I would fasten this mast splice with #10-24tpi Flat Head Machine Screws, 3/8" long. The fastener spacing you could use is 8x fastener diameter apart, as long as the fasteners are about as large in diameter as one of the mast walls is thick, this rule works well. The first row of fasteners from the joint should be placed 4x the fastener diameter from the edge of the joint. Stagger the fastener rows to create a more evenly spread joint.

It is not necessary to weld the joint. Many of the engineers I have consulted with concerning mast splicing argue it is harmful to weld the joint. We do not weld our mast splice joints.

Yes, it would help to use adhesive on the splice plates when making this joint. We use an epoxy from loctite, specifically designed for aluminum bonding, and recommend you do to.

This mast splice would be considered major overkill by many spar builders. We like overkill.

This is only my opinion on how to splice you mast, and you MUST consult the builder of your spar to discuss the technique they would like you to use. Spar builders are always happy to talk on the phone about their spars, so call them first !

[mikestevens]

Thanks Brian, for all your imput. The best benefit I am getting is the building of confidence that I can accoplish this.
I have a few questions for clrification.
1. How many rows of fasteners would you use on each side of the splice?
2. I think I understand the taper, but was wondering about the arch that I would cut out. Would it be steep or more rounded. Would I be removing more material that I would be leaving, for example?
3. Is the purpose of the taper to gradate the stiffness as to allow the bending loads to dissapate?

As for the bend itself. I think there was a crash gype somewhere in the history of the boat. It must have been dramatic as their is a repair to the bulkhead and the chainplate is in a slightly different location. There is a small kink in the mast at the partners (I think that is the right term for the area where the mast passes through the deck (correct me if I am wrong). In any case, I was going to cut the mast off above the damage and replace the bottom 6 feet or so with the new extrusion.

The butt of the mast is bent 2" forward from the partners to the mast step and slightly to the left. When it is in the boat I can center it and get it in column, but always have too much backstay as I am using it to pull the head back. The boat seems to perform OK, but I have no baseline. It does seem to be fast and high upwind, and not so fast downwind, but it might be a characteristic of the boat.

Lastly,
I sail in the bay, so I might see you around. Where do you operate out of?

[mikestevens]

Ah,
I see you are out of Annapolis.

[Douglas]

Hi Mike, T Y , for asking your questions on this forum. I am interested because I too am sleeving my 4.5" X 7.25" aluminum mast section in two places.

It was great to read Brian's reply, and that raised some questions for me too.

First question is what really is the need to taper both ends of a mast sleeve ?

Second question is what is the reason for using adhesive on the sleeves ?

Third, would there be any advantage to using oval head instead of flat head fasteners ?

Currently, I am copying a sleeved mast splice that I saw being assembled at a local boatyard, I have a photo of it, if you need it ?

I also need to order 4 new tapered spreaders , from where , I don't know . I placed a fax order one month ago, with Rig Rite, but have heard nothing from them, and after reading the Cape Dory forum, expect that my order has been sent to the round file, drats !

Douglas

[mikestevens]

Your welcome. Let's see. I hadn't considered oval head vs flat head. I guess I pictured oval heads because the flat heads would have to be countersunk and there is not too much thickness to the walls. In any case I would welcome any response on that issue. And yes, I would love a picture of it. my email is mike@exactimage.net.
As to the tapered spreaders, I have found JSI in FL to be a great resource. Perhaps they can help you too. (Dave Johnson [djohnson@newjsi.com])
Mike

[Douglas]

Hi Mike, I really like that we have such great sources of info available to us, on this forum, and I thank Brion Toss, for that,,,,, and on this occasion, Brian Duff too !

I discovered that there are heat-shrinkage and internal stress-tension problems associated with linear welding the sleeves in anticipation that the re-joined sleeve parts will fit "nicely" into the mast section.

Maybe that is why Brian Duff shys away from doing that, or maybe even for other reasons.

Since we don't have any riggers or rigging shops for sailing yachts, here in Singapore, I had to forage ahead with what knowledge I could find locally,,,, which wasn't much, drats !

I will try to contact JSI , or any other reccomendations from the forum, for the replacement spreaders, that I need , T Y .

Douglas

[mikestevens]

yes, this is a great resource.
I guess the idea of just bending the extrusion sounds easier than all that welding anyways. I can bring a piece of extrusion to a machine shop and have them bend it accordingly. this will be easier than having a friend bring down all his welding stuff.
I look forward to the picture of the splice.

Mike

[mikestevens]

Brian,
When you use flat head screw, that must mean you countersink them. Please confirm. Also,
1. How many rows of fasteners would you use on each side of the splice?
2. I think I understand the taper, but was wondering about the arch that I would cut out. Would it be steep or more rounded. Would I be removing more material that I would be leaving, for example?
3. Is the purpose of the taper to gradate the stiffness as to allow the bending loads to dissapate?

[Douglas]

Hi Mike and Brian , I was thinking of using oval head screws, for one reason only.

I have found that upon removal of flat head fasteners, the phillips head "cams out" all too easily,,,,,, where as the oval head has more "meat" at the driver bit insertion area at the phillips slots.

Sometimes for removal purposes, of a v stuck fastener, I use a center punch on the screw head skirt, after I have already "camed out" the driver slots, trying to remove it,,, and the oval head would give me more "meaty skirt" to pound on !

While on this subject , what is best chemical to use , to put on a "stuck" , ss fastener, to disolve the white powder, inorder to make removing the screw, easier ? Since caustic soda is used on aluminum, before anodizing to clean the metal, could it be used to remove the white powder around a corroded fastener,,,,, caustic soda, being a lye solution ???

Any knowledgable suggestions out there in rigging land ?

Douglas