mast splicing
 

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?

one way to stick'm back together
 

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 !

stick em back together
 

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?

southbound
 

Ah,
I see you are out of Annapolis.

Mast Sleeves
 

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

mast sleeve
 

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

Welding the sleeves
 

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

mast splice
 

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

for brian Duff
 

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?

Oval Head vs Flat Head Screws
 

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

Screws ?
 

I'm considering a similar project, but was planning on using pan head screws so I could leave as much metal as possible under the screw. I may be confused on the terminology but wouldn't both a flat and oval head require countersinking? Is there a reason not to use pan head screws? Mike, I'm curious, where are you planning on splicing the mast. Are you putting the splice at the deck or further up the mast? Would there be an advantage to moving the splice to a less stressed area of the mast, maybe slightly above the gooseneck or would that mess with the mast bend?

Fh, Oval h, Rh, Pan h, Screws and Sleeves
 

In my opinion, pan head, or round head screws come to bear flat on the metal underneath the head,,,,, where as flat head and oval head need to come to bear in counter sunk holes.

There are round head machine screws in various places on my boom, and a few times I have had to use vice grips on the screw head to break it loose.

What ever the fastener, ( I think Brion, mentioned on this forum), corrosion will eventually effect it ! SS, Monel, Aluminum and Steel fasteners, included .

A nightmare of mine would be while on hardstand, the mast is lifted out with a crane, and the sleeved joint parts under shear loading on the fasteners, and someone on the ground gets hurt, or worse, you damage your boat with the falling lower mast section.

Mike, this is a dam good question of yours,,,,,,,
" 3. Is the purpose of the taper to gradate the stiffness as to allow the bending loads to dissapate? " ,,,,,, hope we get an equally good answer !

As you suspect, an untapered sleeve end , being a hard edge inside the mast, might just be where the mast could buckle and bend again .

On sectioned sleeved dinghy masts, I usually don't see a taper on the sleeve end, just a rounded edge .

Douglas

I haven't had occasion to splice many masts, but I've certainly had to deal with many many fasteners on masts, broken, mangles, frozen, or otherwise!
Based on nothing other than personal observation/experience, panheads are weaker than tapered (ie., needing to be countersunk) screw heads, on account of the more abrupt transition between the shank diameter and head diameter. Additionally, countersunk screws show more metal-to-metal surface area, equating to a better distribution of force and less chance of loosening. Panhead screws seat best on a flat surface, whereas a countersunk hole can be applied to most any profile.
Agreeing with Douglas, ovalhead screws have more "meat", which can certainly make them easier to remove when needed! Here in the islands, ovalheads are harder to source, but I can't see how the barely-protruding head has any other drawbacks, unless the splice is at some area where halyards.sails are likely to chafe.
While a self-tapping screw will "draw" pieces together, I can't help but wonder if greater strength and serviceability might be had from tapped-in machine-screws, provided the internal sleeve fits closely enough that "drawing in" is not required.

screws & things
 

Hello all,
Good thread eh!
For a corroded & stuck fastener, try vinegar, not caustic, it can dissolve the white powdery stuff. If the mast is not anodized then a bit o' heat can work wonders.
On the subject of screws, oval & flat head can be considered equals mechanically, however oval are much more pleasing asthecially. Oval head screws can tolerate slightly different countersink depths and still look good.
On the practical side, you can assemble the splice and drill, countersink & tap without further disassembly. Pan head screws would normally require two step drilling (unless you are very brave and willing to try without making the tap hole too big) and bunch o' pan heads just doesn't look as nice.
The splice material taper AND rounded "taper bottom" are to prevent stress risers. It's a stress riser that caused the damage in the first place (the deck opening).

Cheers, Russ

more important (IMO) than the fastener type, splice plate taper, or splice location, be sure that the mating ends of the two extrusions being spliced are a perfect fit. The ends must be square and true. The rig will not tune straight or bear compression properly if they joints are not perfect. take the time here to get it right. I spent 5 hours once until I was happy. Oh to have a large chop saw for masts !

Most mast splices are not glued, I am the only rigger I know that does this. My thought is that there are no disadvantages to the glue, but the possible advantage of a more even transition of stress is worth the effort of the gluing process. It is not necessary to use adhesives.

Flathead or Oval head screws are stronger because of the less dramatic angle at the bottom of the head to the shank of the screw, (they also offer less resistance to wind, and look better).

mast splicing
 

Brian,
Thanks for sticking with this thread. I give a lot of credibility to what you have been saying. In your first post you suggested flat head fasterners. I want to confirm that you are then countersinking. And that seems to leave you with enough meat to tap?

Also, Das Haus, I know your boat. Colombia Defender right. I think I saw your boat up in Block on my way down to VA and then I saw you again in Norfolk. Could that be? The current name on my boat is RIP Curl, but that is changing.

Yes, flat head machine screw fasteners. Only the mast wall gets a countersunk and clearance hole, the splice plate receives the tapped hole . IF the head of the #10 is too thick, use # 8's (or a diffenet angle or undercut screw head, or any of so many options...)
I do not know what mast you have, but guessed at its wall based on the dimensions you gave. It is important to obtain the 'drawing in' of the splice plates to the mast wall. This is another reason that the splice pieces shouldn't be one piece. When splicing something like a 'pipe' mast where it is easy to obtain an extrusion that fits well inside, we split it lengthwise so the fasteners can draw the plates tight to the mast wall. I usually use three complete rows of fasteners each side of the splice, then two more rows with half as many fasteners.
Russ L is right in that the idea is to avoid stress risers. We also (sometimes, depending on the budget of the client) thin the plates toward the ends, as as antoher way to taper the material away. Most spar builder splices I have worked with have not done either type of tapering. some of the builders of spars use just three rows of fasteners each side, with a rather closer fastener spacing. Some have way more fastneners...

call your spar builder and have a chat with them about your plans, thats what we do.

heat works to loosen corroded stuck fasteners on all masts- anodized, powdercoated, awlgrip, or bare, you just gotta be careful ! Impact tools also are very effective at removing stuck fasteners. PB Blaster can help too. If a splice with mechanical fasters was corroded enough to "fall" apart, that should be clearly visable to even an untrained eye. Use some 'goop' to help slow the corrosion of fasteners in aluminium.


Self tapping screws are only to be used on wood. Do NOT use self tappers on aluminum or fiberglass, as it is WRONG. Self tappers are weak becasue they have both a smaller root diameter and must have less thread grip as well (in such hard materials) becasue the threads cannot compress the material away like in wood. It seems to me that self tapper screws in fiberglass are alway leaking, and the surely delaminate the fiberglass where they go through. thats for another thread though, if someone wants to start one....

mast splicing/fasteners
 

Thanks for the reply brian.
If the splice is 12" long, plus the 3" tapers, than that gives me 6" on each side, not counting the tapers. If I make the first row 1" from the edge of the splice, then that leaves me with 5" until I get to the taper. if I follow your spec of 8X the thickness of the screw or about 2" apart It seems I would have room for only for 3 rows on each side of the splice.

Now for a new question. I have stripped the mast and was wondering how to do a dye penetration test to the standing rod rigging. Easy? Hard?
Mike.

Also, for managers of tghe site; is ther a way to post images?

to dye for
 

Hi Mike,
Your source for the dye penetrant kit is likely going to be an auto parts supply that has engine rebuilders as customers.
The kit will have a cleaner, penetrant & developer. Follow the directions on the cans... easy!
Brion recommends a small microscope to check for cracks.

To post images: you include a link in your messages to images that are stored elsewhere on the net. No provisions to send images to the Spartalk server.

Cheers, Russ

Mike,

You might also want to do a web search for a dye penetrant called "Zyglow". After it dries you shine a blacklight on it and the die in the crack shows up really well.

Rick