Mast Rotation: Do You Pin It For Trailering?

[fishheadbarandgrill]

Luddite!

Thank God for Wikipedia, otherwise I would have thought the thread had moved on to some new type of marine adhesive...

Bob

[BOAT]

Excellent Wood Piece.

[BOAT]

Okay, how did I do?
>>

[fishheadbarandgrill]

Looks good to me.

Bob

[BOAT]

Cool, I'll have my daughter paint some fish heads onto it. Thanks.

[stuendan]

Hey "Boat" et al - I've only rigged the boat a couple of times and found that mast rotation and lining up the mast foot for the removal of the pin fron the pulpit, and then reattaching it at the mast step a little difficult. Certainly a pinned foot would assist here (E2's solution looks good) as you could manouver and support the mast under your arm to line up for the mast step locating bolts in both cases.

Please note that I'm doing all this single handed.

However, the main bugbear I've found is the movable/rotating spreader arm. You need to lift the spreader arms (angled down) over the stantions as you move the mast back when rigging. I found it would flop one way or another and make this job a real b, so pinning the spreader to the mast to prevent this would be a real bonus - at least till the mast is stepped. I think you also need to release the front attachment of the lifelines as well so that they droop down the cabin sides well out of the way, or else you need to manouver the spreader arms under the lifelines one at a time by swinging the step end of the mast from side to side while moving the mast forward/back, all while you have no control over the spreader position. I am not a complete newbie to all this as I had a 24 ft trailer sailer before the Mac and with a non rotating mast and straight spreader arms, rigging was straight forward. I did make up a mast raising system copying the Mac system which was very good. I also had a roller fitted rear support post for the mast while trailering and found that I had to make up a PTFE insert (bush) before the rubber roller would work well - another mod needed for the Mac. Cheers all.

[BOAT]

When I got the boat home from the factory and tried to roll it into the side yard driveway for the first time it did not fit.

The safety line stanchions on the very top of the deck hit the eaves on my garage. They were about 4 inches too high. I got a pipe cutter and cut the top two stanchions about 5 inches from the base, and pulled the boat into the yard. I figured I would deal with the issue later.

So, the first time I raised the mast (at home) there was no starboard safety line. I stood on the port side of the mast walking it back the first time and by just taking a step to the right, (starboard), the spreader came right out from under the port safety line.

Therefore, to me there was no issue with the spreaders. Mast went up, mast went down, and everything seemed fine.

Then, I fitted stainless steel sleeves inside the stanchions so I could put them back together. The long stainless pipe inside the stanchion made them even stronger than they were originally and also gave me the ability to remove them whenever I want. (My first 'MOD'!) So, I fixed my stanchions and all was happy.

Few days later I raised the mast again. What a PITA!!! I got on this site asking for help! It turned out people were undoing their safety lines to raise the mast. Another guy in a yacht club I belong to said he could rig in 13 minutes. I watched him. His spreaders did not touch the safety lines! When I asked he said he cut 4 inches off each spreader (!!!!!!). Not right in MY book so I came back here looking for more help. I got 2 options: undo safety lines or remove spreaders. I tried both and both added a lot of time and hassle to rigging.

So you already know how I solved the problem.

I just went back to removing the starboard stanchions and - mast goes up, mast goes down, and everything is fine.

[Hardcrab]

I was talking with Mike Inmon at The LA boat show at least two years ago, and he told me the newer M's were getting the 4" shorter spreaders.
The factory had ample negative feedback about the Mac Mast Dance to do the shortening of the spreaders.
As I recall, he went on to say that no stay mods were required with the shorter spreaders; the standard vernier toggles had enough adjustment to tune the mast as is.
New stays would be slightly shorter however.

I am curious if his conversation ever really ended with the shorter spreaders?
The "old" spreaders are 44" long, (at least my 05 M's are).
Does anyone have a 2011, 2012, 2013 M they could measure?

If 40" is in fact found, then a mod to eliminate the dance might be viable and somewhat "factory issued"?

[BOAT]

I have a 2013 boat.

[Hardcrab]

So, if you still have to do the dance, then Mikes 4" chop did not happen.
I know we talked in Feb, 2010 or 2011.
That's when I placed an order for a factory aluminum trailer.

He sounded very convinced it was happening back then.
I recall that they had tested and found no design reason not to chop.

I now wonder at the reasons for why not doing it?

(Roger could get a "free" spreader every 10th one, right down his alley you would think).

[BOAT]

The spreaders were not made shorter. I guess they could but I would rather not do that myself. I think the longer spreader is actually a good thing and aids in supporting the mast.

The guy with the shortened spreaders had and X and was also using his own home made gin pole and he did not use side supports on it and it went all the way to the top of the mast opposed to only 1/3rd up like the factory winched gin pole. His was a block and tackle to the top and he raised the mast by pulling a rope. If you tried that with a 2013 boat with the rotating mast the whole thing could crash sideways on you about ¼ of the way up the raising process, and forget about doing it on the water – it would never work with a leaning boat.

The factory gin pole is designed to use on the water even with a rocking boat.

The spreaders could be shortened I guess but I highly recommend you talked to those engineer guys like mastreb or catgale or all the other guys that know the math before you cut yours. I will not cut mine.

[Tomfoolery]

Shortening the spreaders changes the loads in the shrouds, the spreaders, and the compressive load in the mast at various locations. Make them short enough, and there will be zero load in the spreaders and inner sidestays, and the full compressive load will exist from the upper shroud attachment all the way to the base. But the total reaction at the chainplates and mast base remains essentially the same, even though it's distributed differently among the elements.

In the graphic, I shortened the spreaders in 4" increments (each), then jumped in the last one to where the spreaders have no load, as does the inner sidestay. "F" is some unspecified later load where the sidestays attach, and all the other forces are some multiple of that force. The force at the chainplates with a leteral F load at the top as shown would be the same as the mast base vertical load (but in the opposite direction, or 6.41F upward), and F in the same direction as the applied F load. This doesn't change as the spreaders are shortened, even to where they do nothing. But that outer sidestay takes increasingly more load, to where it's doing it all when the spreaders are too short to take any load.



It's a bit simplified, as the spreaders are swept back, and therefore there is fore/aft bending moment in the mast from the spreader force, and of course, the main sail spreads some of its load along the mast, but that takes a lot more work, and really isn't necessary to include just to see the trend as you shorten the spreaders.

Just thought it would be an interesting excercise.

[BOAT]

The drawing is very revealing and if the guy who cut his spreaders saw it I think he would be more worried. (For all I know the guy never leaves San Diego Bay). I sail in the OCEAN, I have no choice, there are no protected waters where I am at. Your picture is very revealing.

Adding extra load to the outer stays has got to be the dumbest idea anyone ever came up with. The outer stay is the most important part and if it goes the mast breaks in half.

In my opinion people adding that extra 5% of load on to their outer side stays are not people I want to get any advice from.

[Tomfoolery]

It's more like 10% increase on the outers. 100% increase with no spreaders. If the spreaders were drawn upswept, to subtend the 163 degree included angle between the vertical and the upper part, the shroud tension would be the same above and below the spreader, but I didn't want to work that hard. But it does show the trend as the spreaders get shorter, which is all I was trying to illustrate.

I've stayed away from making any judgements about the suitability of shortening the spreaders since I don't know what the actual worst-case loads are, what the accepted loading profiles are for marine stays (as a function of breaking strength), and so on. There's too much industry specific stuff in there that I'm not aware of. But I was curious as to what happens as you shorten them, which is readily apparent from that graphic.

What IS rather interesting, though, is that regardless of the spreader length, or even the presence of the spreaders at all, the fixing point reactions are the same, i.e. the chain plates and the mast base. The resultant force at the chainplates is the same magnitude (6.49F) and direction (81 deg) for ALL of the cases in the previous graphic, even with no spreader and just a single stay on each side, which is what you get effectively when you shorten the spreader to where it takes no load. 3.20F + 3.36F * sin(72.67) = 6.41F vertical and 3.36F * cos(72.67) = F horizontal. The square root of 6.41F^2 + F^2 is 6.49F, and the angle is arctan 6.49F/F is 81 degrees (rounding errors are in there, of course).

With no spreader, the inner stay also takes no load, at least in this simplified static point-load (at the top) scenario. The way it's all distributed gets lopsided of course, with more load on the outer stay and less on the inner (and the fittings and pins too, of course), plus larger compression load in a longer unstayed mast length (with no inner stays), but the net result is the same at the deck.

Just a little fun with line drawings and hand calculator.

[BOAT]

It's not the load at the deck or chainplate that concerns me the most but the change in the dynamic at the middle of the mast. In all the reports we have read here on Heath's and Comrad Klmores blog site we see that almost ALL MacGreggor dismastings occur at the hole where the hound is for the spreaders. And that's really normal for fractional rigs, I looked up the dismastings on the web for small fractional rigs like ours and most break in the area where the spreaders are becasue in a fractional rig there is top loading that is not supported at all by the rigging.

The top of the mast just flys willy nilly and it's going to put a lot of dynamic force on the part of the mast BELOW it because of LEVERAGE just like a see saw.

Altering the rigging so that there is more dynamic movement at the spreader connection is just plain stupid (to me) and asking for trouble.

I'm sure it's okay for tooling around the harbor but swinging a loaded mast back and forth in a 4 foot swell sailing downwind with lots of potential jibes is going to eventualy weaken the mast where the bolt holes are if that area is not propery secured. Loosing an outer stay is scary - I had it happen before on my old Aquarius. The Aquarius did not have spreaders so when the stay broke the mast was not forced into bow like I think it would be on 'boat'.