What's the Deal With SPREADERS? | Sailing Wisdom
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- เผยแพร่เมื่อ 21 ต.ค. 2024
- Ever wonder why sailboats have spreaders? And why some have many while others only have one?
In this video, Herby and Maddie explain what spreaders are for and how they work. They also go into detail about keel stepped vs deck stepped masts, as well as typical single and double spreader setups.
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How many spreaders does your mast have?
Very clear explanation! My boat has a single spreader, keel-stepped Sloop rig - 1980 Sabre 34. In 1986 Sabre updated the model and made it a two-spreader rig.
I have met people who wanted to convert their single spreader rig to double spreader to “make the boat look newer”.
Spot on!
@@RiggingDoctor Add cost, complexity, and weight aloft to "make the boat look newer"??? That's nuts!
@@kimyoung230 Additional set(s) of spreaders enables a reduction in weight aloft, as the mast cross section (and thus weight per foot) can be reduced. However, the point about complexity is valid. More pieces = more opportunities for failure.
@04:57: wow, fantastic special effects; really enhanced the explanation of raked masts!
Thanks!
Exactly the video I was looking for! That was a really solid explanation, I sort of had a instinctive idea about how they worked, but this was very informative. Also good to be sure to have the right knowledge and not operate on false believes. Anyway love the way you explained it, with the buckling of the pasta noodle and the support of the stays. Didn't know about the minimal angle of 12,5deg. Great video!
Glad it solidified some knowledge for you!
Good explanation in terms basic enough for non-engineers to understand. In a sense, the mast, spreaders, shrouds/stays, and hull can be thought of an array of truss-like structures (and trusses are composed of triangles, as you mentioned).
A keel-stepped configuration can impose bending moment into the mast section due to load applied at the partners - this can be intentional or unintended. I feel that it is usually the best choice, in that compression loads do not have to be accommodated in the deck structure. For a cruising vessel less than ~50 ft LOA, I favor single spreaders and a robust mast section: reduced complexity and better tolerance for unintended stresses are well worth the modest weight-aloft penalty.
I admire your conservative approach to choices such as routing, sail plan and weather preparation. Racing with a large crew and limited concern for accelerated wear and increased risk of failure is much different than cruising. Your philosophy of provisioning conservatively, avoiding overpowering your vessel, and reaching your destination without catastrophe (even if it means getting there a couple days later than some would attempt) is so right.
Your channel continues to share practical knowledge and experience that should be of broad interest to the cruising community.
Thank you so much! We are trying to grow so that more people can see our videos.
Sharing our channel with your friends really helps out!
Very informative! Just bought a boat with one pair is spreaders and now I know what they are for 😆
Haha I’m glad!
this video will be a good one to show in a elementary school. Good job.
Excellent video. Your technical expertise is very good. Love your channel!!
Thanks!
Congratulations, after many years sailing thanks to you guys I finally understood what spreaders are for 😜
Yay!! Haha
Great info!! I always did wonder what the difference once with the amount of spreaders...🤗
I really love your vids. You are both very nice people and the content of your vids is always great, very interesting. I also like the way of your seamanship, to be safe is better than travling faster and less stressful for yourself and the boat.( I am refering to the guy who tried to urge you not to reef so soon). For me , it all make sense what you do. I also like the knot vids. In my opinion your sailing vlog is one of the best in the net. Thank you very much for all the good vids. Please excuse my bad English, but I am not a native speaker. Greetings from Germany. Fair winds.
That was an excellent explanation, informative and entertaining - Thank you :)
👍
Pcr = pi^2 * EI ÷ L^2.
column buckling. Halve the length, and Pcr goes up by a factor of 4. Cut L into 3 segments (double spreader rig) and Pcr goes up by a factor of 9.
Of course an unsupported spar becomes a cantilever beam as opposed to a compression strut...
Now THAT was pretty interesting, I had never even
Thought of any of that...!!
👍
Hi there! Nice video :)
Can you share your opinion about option of converting "conventional" 2 spreader, keel step mast, with narrow chain plates (high aspect ration), discontinuous, inline, to wide spread arrangement, no spreaders. Similar to imoca 60 on-deck spreaders. going far out of your beam. I'm aware of limitation in head sails size in this configuration, difficulty with docking or rafting. I'm only asking about the mast, do you think same mast can be converted to this setup (more lines holding the mast?). In imoca 60 they have them swept back and mast is rotating. I'm thinking about mass reduction and simplification of all setup.
Great explanations. Don't remember if you have a composting head, but if you do a segment about it, how it works, smells, materials, etc.., would be really cool. I am trying to decide what I want for my boat. Thanks in advance.
We do and we are in the process of editing that video, it should be up in the next few weeks
Thank you keep this knowledge you have going i am learning a lot.
A free body diagram on your blog would be nice showing the forces applied from sails and rigging through the spreaders would be interesting addition to this video.
John Roth, great suggestion; let's hope Herbie finds time to do that.
The load on the spreaders is rather simple. The forces are always in towards the mast, the force is then supported by the lowers right under the spreader.
They only work in compression.
That was awesome. Thank you
Awesome! Thank you so much!
You are very welcome
Great explanation and hi cost props😉
Great info Thanks
What made you choose your specific Model of boat? Design, space, full keel,cost? Love the video.
I wanted a fiberglass boat to make maintenance easier.
I was looking for a full keel, heavy displacement cutter that was over 30 feet long and in my meager budget. I found Wisdom for $20k and began rebuilding her. In the 60s, they didn’t really know fiberglass yet so they built them like tanks, giving her a rediculously strong hull which makes me less worried about holing and sinking.
I wanted to cross the Atlantic and with that goal in mind I began looking for this style of boat. I wanted as big as I could afford because I can always work to make her nicer. I can’t work to make her bigger.
@@RiggingDoctor thanks so much for responding. A good video that I saw on another channel was video that looked online for a boat..but he did with a focus on catamaran. But my budget can only afford a monohull. To me this would be a great vid. Thanks for great content. Hope your channel blows up to La Vagabonde level.
Thanks! Growing into a big channel is the goal!
Excellent explanation. What prevents the spreaders from being bent downwards from the stay tension? Cheers from Canada.
They are set at a bisecting angle to the stays, this keeps force neutral on the spreader and prevents it from buckling up or down.
And the end of the spreader is also seized to the shroud
@@RiggingDoctor The spreader and its point of attachment at the mast may be designed to tolerate the downward force imposed on the spreader tip by the shroud, which generates a bending moment at the point of attachment at the mast. I had a boat on which we experienced a failure of the socket at the mast while underway in about 20 kts apparent wind...rather alarming to look aloft and see the spreader wobbling around. The bisected angle (rather than straight/horizontal) configuration is so logical, it's hard to imagine why it isn't universal.
I see a lot of boats where the spreaders are horizontal to the horizon, and severely bent downward! They should have a slight upward sweep.
@@RiggingDoctor Where the spreader is seized to the shroud; is this a mechanical means done after tensioning the shroud? Thanks in advance. P.S. it's -11C here, mid Feb.
It is done after everything is tensioned.
Any consideration of the resonant frequency of the mast and rigging?
Loved it!
Thanks!
Great again.
Thanks for info..question , a spreader was bended downwards by a stepping on it the wrong way cleaning rigging...crazy ...what should be done to Check spreader to make sure it won't bend while on passage...I have certain ideas but more details if you know would be welcome an appreciated ..Muchas gracias...
Buenas, vas a necesitar hacer dos cosas.
Primero va ser chequear donde el spreader se conecta al mástil para verificar que no haya algo roto allí. Si todo se ve bien, vas a seguir a la segunda cosa.
Segundo, vas a mover el spreader tip hacia arriba por dándole golpes con to mano por abajo para moverlo hacia arriba. Quieres que el ángulo entre el spreader y el stay quedan iguales arriba y abajo, así sabes que el spreader está en el lugar óptimo para las fuerzas. Va a ser un poquito hacia arriba de horizontal.
Cuando todo está donde pertenece, vas a colocar un hose clamp o algo que puede agarrar al cable bien justo arriba y abajo al spreader tip para que no se vaya mover de nuevo.
Espero que eso te ayudará!
Herby
Brilliant thanks.
You’re welcome
Re how to ideas, some of the stories from the first 2 GGR2018 Finishers is interesting. Especially their choice of antifoul and the problems some guys had. 250 days at sea require the right decisions !
Cheers Warren
I’ll look into it! We are going to be painting our bottom again before we launch, so Now is a great time to try a new bottom paint.
My mast is 3/16" thick and 48 ft tall with a single spreader.
could you explain why certain boats have the spreaders point forward or backward instead of just straight to the side? what are the benefits there?
Swept spreaders offer stability fore or aft while lateral (straight out to the sides) spreaders only offer support to the side, no fore or aft support from them.
Modern boats, particularly on Hunters, have the spreaders swept so far aft that the cap shrouds do the job of both the cap shrouds and the backstay! This means that those boats now don’t need to have a backstay. Being able to remove stays from the design frees up the constraints of the boat design, allowing boats to be built in completely different ways!
Keel stepped masts transfer rigging and sail load forces to the keel of the boat better. Only it's a pain when the mast is in the center of the companionway. How do you feel about wood, aluminum or composite masts? I think a wood mast wrapped with fiberglass is a good way to go an keep it sealed from weather.
I prefer wood over aluminum and aluminum over composite. This is a personal preference because I feel more able to do repairs on a wood mast over an aluminum spar, and much more than on a composite spar.
We have wood core glassed over deck stepped mast with one spreader. But, there are deck stepped and deck stepped mast eg. production and custom made. Ours has supported “cradle” so the deck alone isn’t taking the load but it’s spread out to multiple points over larger surface. Makes unstepping the mast a breeze too
What about when a mast becomes inverted is that too much bend in the mast forward or backward
Are you referring to when the mast reverses it’s bend and instead of swaying back with the belly forward, the belly is aft?
That is usually caused by insufficient tension on the lowers. The forward lower bends the mast forward while the aft lower helps resist it.
With two or more spreader masts, there are no lowers opposing the bend or inducing the bend and they can pop in the wrong direction. In these situations, check and baby stays can play a huge role in keeping the mast with the correct bend.
Rigging Doctor yes that’s exactly what I’m referring too thanks for the reply cheers
Good one!
👍
Good explanation. The 12.5 deg number is interesting. Some multihulls , especially those with rotating masts and wide spreader bases have no spreaders! I hear 2 schools of though on deck vs keel stepped. Some very well respected offshore folks will not have keel stepped masts as in a knockdown or pitchpole they don't want a big hole in their decks . Hopefully you will never be in that situations.! Cheers Warren
I have heard the opposite thought on loosing a mast with a keel step: now you have a hole to mount your jury rig into.
I think that in those situations, you make do the best you can with what you have and hope you never have to!
Puts a different light on keel stepped setups though.
That is an interesting ring you have on Herbie
I was raised about a decade ago
Rigging Doctor: I believe you are a wee bit older than that!
lol nice... we have something in common other then sailboats. sailingwithmizzfitz.ca
Nice looking ketch!
@@RiggingDoctor Thank you brother. I have two years to go before I am on the high seas. I truly hope to meet you both when I am out there. Best wishes and fair winds! I will be following.
my spreaders seem to be lifting, should i just loosen the rig and get them flat again?
You can do it while it’s tight. Just go up there and go out to the tip and “smack” the spreader with your open hand (spreads out the impact so you don’t hurt it) into place.
at 4:34 it seems to me you gain nothing by the keel stepped mast. You still need to have the a a certain length above the deck so the deck doesn't really help support anything in the critical space above the deck i.e. the mast just has to be longer to reach the keel. What am I missing?
It adds an extra point of attachment which makes the mast stiffer.
A deck stepped double spreader rig is the same stiffness as a keel stepped single spreader rig.
Fewer spreaders is less rigging and less complexity (if you ignore the hole in your deck that needs to be sealed)
@@RiggingDoctor Thanks, but what I don't get then is why you would need a shorter mast from the deck up when you have a keel stepped mast. I have a 45 ft mast that is deck stepped...If it was keel stepped I would still need 45' that needs supporting above the deck in the same way, since the deck stepped one is essentially 'supported' at the deck where it is attached...no? From the deck up it is the same length and would need the same support.
With a junk or lug rig system where the mast stands alone, I can see the deck being a support point, but it still needs to be designed to take the stress of x length above the deck just like a stayed rig.
In my case there is a post under the mast into the keel that supports the weight of the mast and shroud tensions, but no hole in the boat and the mast comes off at deck level when needed.
Cheers and thanks for your patience.
If your boat were keel stepped, the mast would be 45 feet long plus the part inside your boat, so you would end up with roughly a 53 foot stick.
The benefit being that this long stick is stiffer and therefore relies less on the rigging to keep it up. This means in absolute 💩situations, the mast is stronger and might survive the nightmare.
@@RiggingDoctor OK, thanks. So it is not so much that the mast is supported better, but that it forces you to buy a stronger mast that is then heavier aloft as well....life is always a trade-off eh?
I would like to learn more about your lights. Spot lights, running lights, interior lights, how you converted to led (if you did) where you got them. I ve got an old boat that is used only 2 months a year and would like to upgrade. My 2 million power spot lights are dieing on me so they are scheduled to be upgraded. thanks.
Great suggestion!
FWIW, I bought my LEDs at marinebeam.com. I went there because of the good reviews I had heard about them, and I had a good experience buying from them as well.
Maddie show us a video with painting classes
Next video aluminum, versus carbon fiber, versus wood!!!
Allyn Onderdonk, that's easy; in your list: $$$; $$$$$; $
Once the mast is installed, maintenance is less a factor, though wood would require as much inspection and more maintenance.
Correct! Wood needs constant inspections for rot, carbon gets delamination and UV damage (to the resin binder) and aluminum corrodes.
Ok now let me try this in 1/700th scale. Wish me luck.
Good luck!
What about cat rig boats like Nonsuch and freedom? Using carbon fiber makes the rig light and stronger, if a little bendy. Why wouldn't more crusing sail boats use them? Cuts weight, supper stronger and little rigging.
They are great setups but all the strength is then coming from the deck and hull. Those boats are well built and can handle the loads, but imagine a Bendiboat trying to sport that rig! Rigging transfers the force to somewhere else, allowing builders to get away with making it flimsy.
Next time you see a cat rig, look at the height of the spar and thickness of the mast. It’s pretty short and very stout.
A single spreader spar is taller and a little thinner.
A double spreader is even thinner.
More than three spreaders and they look like uncooked pasta noodles!
Engineers love triangles ;-)
Did you cook the winning pasta? 🥴🥴🥴
Tasted like victory
I’ve heard discussions on spreader rake. Care to comment?
That is a whole different animal. Swept a little helps bend the mast back, swept further and backstays can be deleted!
One spreader.
So, then ... explain carbon fiber free standing masts
Also, with these flimsy masts we're seeing a lot more breaking in heavy weather.
It’s a trade off with racing.
We’re right next to a race boat on the hard. They had to do some major work to keep the tiny fin keel from snapping off! Compare that to an old full keel next to it.