The title of this thread says it all. I'm looking to replace my deck cleats and was hoping to get some feedback from those who might have had a cleat fail and some insight over the material and bolting pattern. I'm planning on replacing my current eight inch cleats with a eight inch or larger cleat for room to double lines during storm conditions using 5/8" lines. Your thoughts are appreciated!
Deck Cleats - Four or Two Bolts? SS or Aluminum?
- Thread starter Blitz
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The rule of thumb for cleats is 16 times the line diameter.... this usually allows you to put TWO lines of that diameter, in this case 5/8", on the cleat... so you'll want 10" cleats.
I'd recommend going with FOUR bolt stainless steel cleats. The main reasons are the fasteners will be stainless steel, and if you use aluminum, they will form a galvanic cell... and aluminum is much more susceptible to fatigue.
Go with a backing plate that is at least FOUR times the size of the cleat base, preferably either circular or with well rounded corners so as not to create a stress line along the edge of the backing plate.
I'd recommend going with FOUR bolt stainless steel cleats. The main reasons are the fasteners will be stainless steel, and if you use aluminum, they will form a galvanic cell... and aluminum is much more susceptible to fatigue.
Go with a backing plate that is at least FOUR times the size of the cleat base, preferably either circular or with well rounded corners so as not to create a stress line along the edge of the backing plate.
I prefer stainless Herreshoff style cleats of known good quality. Many builders, including Pearson (see cleat below) used crappy hollow aluminum cleats. A solid aluminum four bolt cleat should be plenty strong but I still prefer stainless. The aluminum cleats on our CS are quite beefy, have not seen many aluminum cleats that heavily built, but they will still be deep sixed when I re-do the decks in favor of Herreshoff style stainless.
Photo courtesy Kismet:
Photo courtesy Kismet:
I have been leaning toward the Stainless steel four bolt, even though my current cleats are aluminum and lasted 26 seasons. Mainesail's picture is what I'm trying to avoid, even is Stainless is more expensive, the extra cost gives me a little piece of mind.
Is it normal, or do many people have Herreshoff style cleats on a sailboat? Seems more like a power boat selection.
Is it normal, or do many people have Herreshoff style cleats on a sailboat? Seems more like a power boat selection.
So are you meaning to say if the base is three inches wide I should try to get a backing plate 12" wide? (Don't think my combing is wide enough around the cockpit where the cleats are mounted - but may be 6" or 8")
My 2005 Catalina 310 came from the factory with stainless Herreshoff style cleats. I added them to my 1986 C-36 cause the factory set up SUCKED!!.
This is the 2005 C-310, ignore the cocktail and the connect four..
No you want it 3-4 times the foot print size. Ofcourse this is an "ideal" set up that can rarely be achieved anywhere near a toe rail. The foot of the cleat may only be 1" wide X 3" long. If on a toe rail you may never get longer but you can go wider... By using one large plate to connect the two feet this usually hits your 3-4 times model though this is rarely necessary unless setting up for a drogue. At a minimum the backers should be as big as the cleat feet.
Most all production builders use fender washers..
Something like this will certainly be a LOT stronger than fender washers..
Does Grainger have backing plates like that? Or can I use something else (besides plywood since the cyclic loading might squeeze it over the years). White starboard too weak?
No, four times the surface area, twice as wide and twice as long... preferably with well rounded corners to prevent a hard edge that can cause hinging and fatigue in the laminate.
So, if the base of the cleat measures 3" x 5", you'd want a backing plate, if possible, to be 6" wide and 10" long.
So, if the base of the cleat measures 3" x 5", you'd want a backing plate, if possible, to be 6" wide and 10" long.
1/4" aluminum or 3/8-1/2" fiberglass backing plates should do it. I prefer fiberglass, since it won't cause galvanic corrosion issues.
I know I could make my own fiberglass backing plates - put who might supply them (no, my yard does not have pieces lying around
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Blitz that is just 1/4" thick stainless bar stock with the edges softened/rounded. Any welding shop that works with stainless will sell you some scrap. It comes in all widths and thicknesses..
McMaster Carr sells G10 fiberglass plates... They also sell regular fiberglass, but the G10 is stronger (50,000 psi for 3/8" G10 vs. 30,000 psi for 1/2 fiberglass).
I don't like using stainless steel backing plates since they can be a PITA to drill. I recommend using a thickened epoxy to bed the G10 plates to the underside of the deck to take care of any irregularities in the surface.
I don't like using stainless steel backing plates since they can be a PITA to drill. I recommend using a thickened epoxy to bed the G10 plates to the underside of the deck to take care of any irregularities in the surface.
Big difference in shear strength between steel backing plates and fiberglass. Has anyone really looked at the failure modes and calculated the loads and material strengths. You will quickly reach a limit on size where it won't matter. My point is using fiberglass just makes the deck thicker, so you are trying to shear the thickness of the deck around the perimeter of the backing plate. The larger the plate the more area to shear so the more strength. But the other failure mode is trying to pull the nuts through the backing plate and the deck and the fender washer, that may be the weakest link once the force to do that is smaller than the force to shear out the backing plate through the deck. Seems like shearing the nuts through the fiberglass would be way easier than through stainless. Fiberglass is good in tension, not so sure about shear. apping a hole in fiberglass is a really bad practice for instance since it is so weak in that loading situation. The fiberglass backing plate for the through hulls is somewhat different as they are not severely loaded as a cleat would see in storm conditions. I don't doubt it will work here, just wondering if anyone has done the math?
As I think some more there is also the shear strength of the screws themselves to consider but those strengths are supplemented by the friction of the joint of the cleat to deck and with the clamping load on the cleat that friction force will be enormous. this is the force resisting sliding the cleat across the deck added to the shear strength of the four screws. Since the force to slide the cleat is mu times N (the normal force) with N a very large number since it is the force applied to the cleat by the screws.
Dave,
Have you looked at the specs for Garolite G-10? It is not your normal every day fiberglass. The stuff is bomb proof but also VERY expensive. West Systems engineering dept told me it would take over 1200 pounds of force to pull a single drilled & tapped 5/16" bolt from a piece of 3/4" G-10..
Generally I use stainless because it is cheaper and easier for me to get but I would have no problem using 3/8" G-10..
As I mentioned before most boasts use fender washers on a very thin skinned laminate and in many Nor Easters I don't recall seeing very many cleats torn out. If you go big on backing plates you'll want to "butter match" them to the underside of your deck to be sure they are actually distributing the loads not just hitting some high spots. This can be done with a thickened resin..
Have you looked at the specs for Garolite G-10? It is not your normal every day fiberglass. The stuff is bomb proof but also VERY expensive. West Systems engineering dept told me it would take over 1200 pounds of force to pull a single drilled & tapped 5/16" bolt from a piece of 3/4" G-10..
Generally I use stainless because it is cheaper and easier for me to get but I would have no problem using 3/8" G-10..
As I mentioned before most boasts use fender washers on a very thin skinned laminate and in many Nor Easters I don't recall seeing very many cleats torn out. If you go big on backing plates you'll want to "butter match" them to the underside of your deck to be sure they are actually distributing the loads not just hitting some high spots. This can be done with a thickened resin..
Has anyone ever seen strength ratings on cleats? I have not.I prefer stainless Herreshoff style cleats of known good quality. Many builders, including Pearson (see cleat below) used crappy hollow aluminum cleats. A solid aluminum four bolt cleat should be plenty strong but I still prefer stainless. The aluminum cleats on our CS are quite beefy, have not seen many aluminum cleats that heavily built, but they will still be deep sixed when I re-do the decks in favor of Herreshoff style stainless.
Photo courtesy Kismet:
The above picture of a failed cast part with no related deck damage or bent blots does not give much confidence, does it? I have always found myself wondering about 4-bolt cleats in the past, not knowing the strength of the metal surounding the bolts (typically 4 x 1/4" on an 8" cleat). 2-bolt cleats (my boat, any way) have 2 x 3/8" bolts, and I can calculate failure modes based upon known bolts strengths. Certainly we are talking about a failure load of over 5,000 pounds and probably closer to 8,000 pounds in a good deck.
Of course reality, as Maine Sail hinted, is that a line will chafe through first, and even some pretty poor installations hold up pretty well. Surprisingly well... but not dependably.
I had a winch installed by a PO with no backling plate, no fender washers, and not even small washer (just the nuts) on a cored deck, and they sailed it for that way for many years... and then I bought her and pulled the nuts into the deck. I can only guess they never pressed the boat too hard.
My current cleat removed
Although it doesn't look so good it held up for 26 seasons without a problem: four - 1/4" fasteners with no corrosion and non sealed plywood backing plates.
Although it doesn't look so good it held up for 26 seasons without a problem: four - 1/4" fasteners with no corrosion and non sealed plywood backing plates.
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Did you read the specs I posted earlier. 3/8" G10 has a tensile strength of 50,000 lbs per square inch... Not really going to worry about the backing plate failing IMHO, if they're Garolite G10.
SailingDog,
Yes I read your specifications. 50,000 PSI TENSILE STRENGTH is not my concern in this application. You are not pulling on the ends of the sheet to try to fail it in tension. You are trying to pull a nut and washer through a plate of fairly thin material in SHEAR. The SHEAR STRENGTH of the material was not included in your post and the relationship of shear strength to tensile strength in composites is drastically different. The strength of a composite comes from the tensile strength of the fibers and applications for composites align the fibers in the directions of the loads to take advantage of this property. Carbon fiber can be a lot stronger than many steels in tension, How do you think it will be in compression or shear?? Sort of like pushing on a rope?
Mainsail....1200 pounds to pull the bolt by shearing the threads in the G10 doesn't sound very strong to me. In a tapped hole in steel with 4 or more threads engaged I would expect the bolt to break before being ripped from the hole. In my applications in the aerospace industry fasteners in fiberglass are always thru holes or inserts are molded into the part to accept the screw and spread the loads over a much larger area than the threads of the screw.
I don't doubt in this application it (G10) will work OK but I do object to gut feel being considered adequate when a proper design method will involve calculating the strengths and applying a factor of safety so you will KNOW it won't fail. Even then a good design team will break the part as validation that their calculations are correct. You should see them break the wings on an airplane, pretty spectacular test.
No hard feelings guys, just insisting on rigor in the process.
Yes I read your specifications. 50,000 PSI TENSILE STRENGTH is not my concern in this application. You are not pulling on the ends of the sheet to try to fail it in tension. You are trying to pull a nut and washer through a plate of fairly thin material in SHEAR. The SHEAR STRENGTH of the material was not included in your post and the relationship of shear strength to tensile strength in composites is drastically different. The strength of a composite comes from the tensile strength of the fibers and applications for composites align the fibers in the directions of the loads to take advantage of this property. Carbon fiber can be a lot stronger than many steels in tension, How do you think it will be in compression or shear?? Sort of like pushing on a rope?
Mainsail....1200 pounds to pull the bolt by shearing the threads in the G10 doesn't sound very strong to me. In a tapped hole in steel with 4 or more threads engaged I would expect the bolt to break before being ripped from the hole. In my applications in the aerospace industry fasteners in fiberglass are always thru holes or inserts are molded into the part to accept the screw and spread the loads over a much larger area than the threads of the screw.
I don't doubt in this application it (G10) will work OK but I do object to gut feel being considered adequate when a proper design method will involve calculating the strengths and applying a factor of safety so you will KNOW it won't fail. Even then a good design team will break the part as validation that their calculations are correct. You should see them break the wings on an airplane, pretty spectacular test.
No hard feelings guys, just insisting on rigor in the process.
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