Let’s Rig This Boat!

[Chotu]

Originally Posted by meirriba

Splicing will be the best way to go, and there is no problem with mast strength (many production boats of good pedigree have spliced mast as standard).
If you add a long enough section at the bottom, you may also have a chance to add a boom vang which only few cats have.
As you want performance, a vang will be very helpful in broad reaching or running before.

Oooh! That’s a good one and a good opportunity for me to ask a question about multihull rigging.

Thanks for bringing up the possibility of a vang.

I have a follow on question.

My traveler track is about 18ft long. I also have a fractional rig with swept back shrouds. (3 stays on the boat. No back stay)

Wouldn’t that be good enough to exert downward force on the boom through the mainsheet since the traveler car can follow the mainsheet all the way out to near its maximum downwind setting before the mainsail rubs on the shrouds?

Maybe this is why catamarans don’t have a vang? Because the beam is wide enough to allow the mainsheet to be close to vertical on most all sail positions?

No idea. Just guessing. Never thought about this before.

Also, since the main is limited in functionality by the shrouds, is a lot more of the work running done by an asymmetrical spinnaker usually?

Is it best to have a screecher or code 0 on one furler and an asymmetrical spinnaker on the the more forward furler?

I believe they have these, right? Furlable asymmetrical spinnakers? If not, is there something to put up there that will work best?

What is a good overall headsail configuration for this type of boat?

[stormalong]

Originally Posted by Dave_S

Not a vote for the negative.... Just a caution.

I'd be very cautious joining a mast that I was going to push for 300nm days. I'd be very particular about who designed the joint and I'd insist they were involved during the work and signed off on it when complete.

I have a 64' mast with 3 spreaders and it flexes a great deal and I don't push it too hard.

You need to make it strong enough but at the same time it needs to flex progressively at the same rate a one-piece mast of that length would. It is important too that the repair doesn't introduce a torque around the mast when loaded.

Dave S: Odds are that your mast is spliced - you just don't know it. Most extrusions are limited to about 40 feet.

My 64 ft mast in spliced and you would not know it unless you stripped the paint. The only clue on my mast, short of stripping the paint was that I drilled a hole for a radar cable and went through the double thick section. Many joins are done like shown in the Youtube video above so that the mast can be shipped easier and assembled at the destination. My mast has a sleeve that is a perfect fit. A pattern of holes is drilled, the holes and the joined edges are welded. Once sanded and painted you would never know it was there. I didn't know how long the splice was until I had the mast stripped to bare metal and painted. I don't remember how long the insert is but IIRC it is about four feet long. The mast is a six by nine inch oval with an external riveted track.

[Dave_S]

Disclaimer, I'm not a qualified engineer, I have worked as a design engineer mostly in mechanical for more than 30years, however this is not in my area and I'm well out of my comfort zone with your mast.

So... I'm very happy to be corrected here.

IMHO I don't like the join in the video. It's not a job for countersunk rivets and it's not a job for resin, and it's not a job for two seperate pieces of joiner material. I think it is quite possible, maybe even probable that that mast will fail if it is subjected to the loads you might expect in doing ocean crossings in a performance catamaran.

The way he has made the join, it relies almost solely on the horizontal cross sectional strength of the two plates he has added and that's not much.

While I don't think the torque is the main concern here, it may be a contributing factor. There is torque in the mast from the sails. The torque in the mast may cause a failure by pushing the join material beyond its elastic deformation limits especially as it has very little support from collapsing inwards, this is true for flex as well. There is very little resistance to torque from the two plates.

I could well be wrong above, but if it were me, I would be looking for an expert so you can sleep at night.

[stormalong]

Originally Posted by Dave_S

Disclaimer, I'm not a qualified engineer, I have worked as a design engineer mostly in mechanical for more than 30years, however this is not in my area and I'm well out of my comfort zone with your mast.

So... I'm very happy to be corrected here.

IMHO I don't like the join in the video. It's not a job for countersunk rivets and it's not a job for resin, and it's not a job for two seperate pieces of joiner material. I think it is quite possible, maybe even probable that that mast will fail if it is subjected to the loads you might expect in doing ocean crossings in a performance catamaran.

The way he has made the join, it relies almost solely on the horizontal cross sectional strength of the two plates he has added and that's not much.

While I don't think the torque is the main concern here, it may be a contributing factor. There is torque in the mast from the sails. The torque in the mast may cause a failure by pushing the join material beyond its elastic deformation limits especially as it has very little support from collapsing inwards, this is true for flex as well. There is very little resistance to torque from the two plates.

I could well be wrong above, but if it were me, I would be looking for an expert so you can sleep at night.

Those are not rivets. They are 1/4-20 316 flat head machine screws. Look at the comments section where that question is asked and answered. I have seen many masts joined with machine screws. Nothing wrong with that as long as they use an anti corrosion sealant, like Tefgel or Duralac.

[Chotu]

Originally Posted by Dave_S

Disclaimer, I'm not a qualified engineer, I have worked as a design engineer mostly in mechanical for more than 30years, however this is not in my area and I'm well out of my comfort zone with your mast.

So... I'm very happy to be corrected here.

IMHO I don't like the join in the video. It's not a job for countersunk rivets and it's not a job for resin, and it's not a job for two seperate pieces of joiner material. I think it is quite possible, maybe even probable that that mast will fail if it is subjected to the loads you might expect in doing ocean crossings in a performance catamaran.

The way he has made the join, it relies almost solely on the horizontal cross sectional strength of the two plates he has added and that's not much.

While I don't think the torque is the main concern here, it may be a contributing factor. There is torque in the mast from the sails. The torque in the mast may cause a failure by pushing the join material beyond its elastic deformation limits especially as it has very little support from collapsing inwards, this is true for flex as well. There is very little resistance to torque from the two plates.

I could well be wrong above, but if it were me, I would be looking for an expert so you can sleep at night.

I agree, Dave.

I don’t like his sleeve.

I plan to use a real sleeve if possible, which is one piece. The 2 plates idea in this video is where it falls short in my opinion as well.

My understanding is to make a good sleeve, you cut the sail track area out of a third piece of the same mast section profile you are adding to your mast. Then, you are able to squeeze it small enough to fit inside the existing mast and add on piece.

In the splice, the main thing is you’re trying to keep it in column. So the original mast section rests firmly on the added section without slipping off, even during bending and torqued twisting.

That’s what the sleeve and fasteners do.

I think it’s also important to remember that every mast on every modern boat that is longer than 40 feet is sleeved like this. It’s not some new or crazy kind of thing. It’s on every single boat made since the 1980’s or something.

Order a new 40ft+ mast today from any of the top mast manufacturers and you have to put the sleeve in yourself.

But doing it right is important. I’m still a little fuzzy on what fasteners to use. I understand the pattern, I understand the sleeve, I understand the goal, but I have seen it using rivets or screws. Not sure which to use.

[Matt Johnson]

[QUOTE=Chotu;3543178

I think it’s also important to remember that every mast on every modern boat that is longer than 40 feet is sleeved like this. It’s not some new or crazy kind of thing. It’s on every single boat made since the 1980’s or something.

Order a new 40ft+ mast today from any of the top mast manufacturers and you have to put the sleeve in yourself.

[/QUOTE]


While most do, it's not correct to say that every mast has a sleeve. Depending on manufacturer, it's pretty easy to order a mast the length you need in one section.... It's just more difficult to get it to your site.

I have multiple quotes for both one piece and two piece aluminum mast in the USA from different suppliers. They just come as on deck cargo from the manufacturer if not extruded in the USA. I believe Sparcraft ships from South Africa instead of South Carolina if you want one piece

Personally, I'm not worried about a splice in a spreadered rig. And with you adding only 4' at the bottom, I'd be even less worried. Our mast is mounted on the cabin top, but almost none of the load is carried by the composite structure. It's all sent directly to the aluminum welded mast base/compression post that transfers the load to the bulkhead beam. The cabin top is just adding stabilization. Pretty easy to duplicate in your design.

Matt

[Thumbs Up]

Originally Posted by Dougtiff

I'd add enough to get the boom where you want it and call it good.

Glad you came to your senses, Chotu. I would by no means modify the upper portion of that rig in any way. To many unknowns. That video shows the standard method to splice a mast. An improvement would be to taper those plates so as not to create hard spots. Though being as it is, at the bottom, it wouldn't matter. The problem is, you don't have the matching extrusion. Think about ways to raise the mast step. A few photos of the area in front of the cabin, where the mast steps, would be helpful at this point. A custom raised mast step? Is there room to bolt a large flange?

[Thumbs Up]

Originally Posted by Chotu

Maybe this is why catamarans don’t have a vang? Because the beam is wide enough to allow the mainsheet to be close to vertical on most all sail positions?

No idea. Just guessing. Never thought about this before.

Also, since the main is limited in functionality by the shrouds, is a lot more of the work running done by an asymmetrical spinnaker usually?

Is it best to have a screecher or code 0 on one furler and an asymmetrical spinnaker on the the more forward furler?

Time to read up on Multihull sailing Chotu! Your cat (fractional rig) will have a smallish jib. A Code 0 flies off the masthead (unsupported). A code 0 is (more or less) a furling asymmetrical spinnaker that furls on it's own luff line. The entire thing can be left in place (need uv protection) or stowed (like a sausage) until ready to be hoisted. You can also have a spinnaker that flies off of the masthead (or further down, just above the forestay attachment, (more supported). Some have an extendable bowsprit. Catamarans normally make better SOG on a reach than DDW. Safety problems exist when the wind picks up because you can't depower the sail enough. You can't simply release the sheet either! (at times though, you can because it will produce sail twist which spills some air from the upper portion. You need a to have a thorough understanding of this problem. When caught downwind, needing to reduce sail, it becomes extremely dangerous (risk of capsize) to turn into the wind. Others can probably explain it better than me. You can only let the sail out so far before you contact the aft swept shrouds. A bad gybe has caused dismastings because of the boom slamming into the opposite shroud with great force! Consider having an emergency downhaul to allow you to reef on any point of sail. Catamarans normally have no vang. An easy to release preventer line is helpful in many situations to keep the boom from bouncing around (affecting sail shape) when off the wind.

[Chotu]

Originally Posted by Thumbs Up

Time to read up on Multihull sailing Chotu! Your cat (fractional rig) will have a smallish jib. A Code 0 flies off the masthead (unsupported). A code 0 is (more or less) a furling asymmetrical spinnaker that furls on it's own luff line. The entire thing can be left in place (need uv protection) or stowed (like a sausage) until ready to be hoisted. You can also have a spinnaker that flies off of the masthead (or further down, just above the forestay attachment, (more supported). Some have an extendable bowsprit. Catamarans normally make better SOG on a reach than DDW. Safety problems exist when the wind picks up because you can't depower the sail enough. You can't simply release the sheet either! (at times though, you can because it will produce sail twist which spills some air from the upper portion. You need a to have a thorough understanding of this problem. When caught downwind, needing to reduce sail, it becomes extremely dangerous (risk of capsize) to turn into the wind. Others can probably explain it better than me. You can only let the sail out so far before you contact the aft swept shrouds. A bad gybe has caused dismastings because of the boom slamming into the opposite shroud with great force! Consider having an emergency downhaul to allow you to reef on any point of sail. Catamarans normally have no vang. An easy to release preventer line is helpful in many situations to keep the boom from bouncing around (affecting sail shape) when off the wind.

I think it’s more that I mixed up the names of the sails. Right?

What I need is the following. I think. Correct me if I’m wrong anyone.

1) Mainsail
2) Blade jib (self tacking on my boat)
3) Code 0 (would like it left in place because I’m lazy)
4) Screecher (just a bigger jib, right?? Like a Genoa?) for reaches and a little bit upwind?? I don’t know.

Can all this be done on a fractional rig? Without having to go to the bow every time you want to change something?

And yes. You are right. I have owned a Catamaran before, but it had nothing to do with all of this type of sailing. Ha ha Ha. It may have had two hulls, but I did not have any performance or any of these types of sails. Just a standard mono hull rig and a spinnaker. One that you just fly without any support.

So is that above list what I am looking to do? Apparently, I have only one forestay at this point. I need to put a bowsprit and another forestay on I think. And then that still leaves the code 0? On its own support?

It sure makes a lot of sense that you could get into some trouble downwind. I can see that. You can get into a lot of trouble with my boat in general I think. I’m going to need all sorts of safety procedures to dump the wind out of the sails on occasion.

That’s why this thread is called “ let’s rig this boat!” Ha ha

Because I don’t know a damn thing.

[Manateeman]

Thumbs Up post is solid gold. Truly informative. Perfect.
Notice in one of the posts on mast splice the term WELDED.
So here is a manatee crew freebie. It’s Christmas.
After you cut the spar, take a flat aluminum plate larger than the spar and glue some fine sandpaper to it. Rub some marker on the surface of the cut and just a bit of wiggles will show you your high spots. The two cuts should be FLAT and 90 degrees to the spar and match.
The video of the DIY two piece system was interesting but not the way we would do it...the two pieces could have been sent to someone who knows how to TIG the flat pieces with additional material. One does NOT need a manufacturer supplied sleeve. Adding two flat bar pieces will give you all the strength you need.
One flat bar joins the forward end of the two pieces, the other sits just forward of the internal extrusion where the slugs slide.
Since the internal shape and dimensions of the extrusion remain almost perfect as the spar is extruded, it’s easy for a fabricator to bend and weld up a internal sleeve. A modern TIG welder will keep the heat zone to a minimum. The manatee crew wishes everyone a Merry Christmas.
Captain Mark

[Tetepare]

CAD can analyze stresses. And a marine designer would have real insights. I could offer opinions on splicing, but non-expert opinions aren’t worth a dime.

[Chotu]

Originally Posted by Tetepare

CAD can analyze stresses. And a marine designer would have real insights. I could offer opinions on splicing, but non-expert opinions aren’t worth a dime.

CAD doesn’t analyze stresses. Finite element analysis does.

But we don’t need any of that. It’s a splice at the base of a mast. Give it a rest.

You can take this disguised “can’t do” attitude post and read a different thread. Not interested in this type of posting here. Didn’t you read the first post?

If you have nothing constructive to add, don’t post. Simple as that.

None of this crap will be tolerated in this thread.

[Chotu]

Originally Posted by Thumbs Up

Glad you came to your senses, Chotu. I would by no means modify the upper portion of that rig in any way. To many unknowns. That video shows the standard method to splice a mast. An improvement would be to taper those plates so as not to create hard spots. Though being as it is, at the bottom, it wouldn't matter. The problem is, you don't have the matching extrusion. Think about ways to raise the mast step. A few photos of the area in front of the cabin, where the mast steps, would be helpful at this point. A custom raised mast step? Is there room to bolt a large flange?

I just don’t want the boat to look hideous. You know? It would look pretty bad to put in some big boxy monstrosity to hold the mast in place. Just want to use a regular mast step plate like all the rest of the boats have.

And yes. I didn’t mention it, but I was already going to put in the taper on the sleeve. Probably doesn’t matter much at the base, but, probably still a good idea to put them in.

Of course, yes. This is assuming I can find the matching extrusion. I will give it a shot. It’s a very simple shape. 11.5“ x 9.5“. 3/16” wall. Pretty much an oval. From a very popular old mast manufacturer in France called Francespar. This old manufacturer was swallowed up with a bunch of other ones. I think it all became Sparcraft.

[Chotu]

Originally Posted by Manateeman

Thumbs Up post is solid gold. Truly informative. Perfect.
Notice in one of the posts on mast splice the term WELDED.
So here is a manatee crew freebie. It’s Christmas.
After you cut the spar, take a flat aluminum plate larger than the spar and glue some fine sandpaper to it. Rub some marker on the surface of the cut and just a bit of wiggles will show you your high spots. The two cuts should be FLAT and 90 degrees to the spar and match.
The video of the DIY two piece system was interesting but not the way we would do it...the two pieces could have been sent to someone who knows how to TIG the flat pieces with additional material. One does NOT need a manufacturer supplied sleeve. Adding two flat bar pieces will give you all the strength you need.
One flat bar joins the forward end of the two pieces, the other sits just forward of the internal extrusion where the slugs slide.
Since the internal shape and dimensions of the extrusion remain almost perfect as the spar is extruded, it’s easy for a fabricator to bend and weld up a internal sleeve. A modern TIG welder will keep the heat zone to a minimum. The manatee crew wishes everyone a Merry Christmas.
Captain Mark

A good idea to bridge some formed plates with flat bar to make up the gap.

Should work great if I don’t find a section that fits inside snugly.

Also, definitely was planning to do the same for the flattening of the cuts. The flat meeting of the spar ends is crucial to keep stress risers out.

Thanks for a good post and participating in the thread!

[Chotu]

Originally Posted by Matt Johnson

While most do, it's not correct to say that every mast has a sleeve. Depending on manufacturer, it's pretty easy to order a mast the length you need in one section.... It's just more difficult to get it to your site.

I have multiple quotes for both one piece and two piece aluminum mast in the USA from different suppliers. They just come as on deck cargo from the manufacturer if not extruded in the USA. I believe Sparcraft ships from South Africa instead of South Carolina if you want one piece

Personally, I'm not worried about a splice in a spreadered rig. And with you adding only 4' at the bottom, I'd be even less worried. Our mast is mounted on the cabin top, but almost none of the load is carried by the composite structure. It's all sent directly to the aluminum welded mast base/compression post that transfers the load to the bulkhead beam. The cabin top is just adding stabilization. Pretty easy to duplicate in your design.

Matt

Well, it was basically just a figure of speech. Many figures of speech aren’t technically accurate.

If I can’t find the mast section, that’ll be my next step I suppose. Hoping I don’t have to resort to that since my cabin top does not cover the mast step area. But if if I can’t find a match... this will be the only option.

Would just have to find a way to make it not look awful.