Cleat conversion: countersunk to studs

A change by the N.A. on deck reinforcements and backing plate thickness has raised the need to modify pre-purchased cleats. The horn of these cleats overhangs the countersunk bolt entry points, with not enough head space for the required bolt lengths. Changing to different cleats is not an option.

With strength, durability and uniform finish as the criteria, what would be specified to convert these into studded cleats?

 

Studded?
Shouldn't they be through bolted...?
You can come up from the bottom with bolts... hopefully.

 

Probably safest to ask the NA for their recommendation. Through bolt preferably, with dome nuts and thread locker, over washers, maybe 1" - 1 1/2" (25 - 35mm) outside diam. X 7/32" (4 - 5mm) thick. Modifying the cleats themselves is not recommended, you may weaken them, and someones life may depend on their integrity.

 

If they are stainless or bronze, thread the mounting holes, screw in stud from below, weld the stud to the cleat base using the countersink, grind flush, polish and passivate. For studs you can use 316L allthread, an appropriate size bolt and cut its head off afterwards, or do it right and use bar stock, threaded only at the ends.

If they are Al its more difficult to keep the bases flat, you need to have a countersunk head welded on the stud in place. A good machine shop can do it, but it's a lot of fiddling and it will cost a pretty penny, probably more then the cleats are worth.

 

I would not do away with a countersunk bolt at the cleat as anything that comes above the cleat base could cause rope chaffing. Particularly the midship mounted spring line cleat with
multiple ropes and an angular load approach to the cleat.
Some more information needed? Each of these questions has a goal.
1) material of the cleat?
2) material of the gunwale?
3) distance from the bottom of the top bar of the cleat to the top of the cleat base?
4) thickness of the gunwale?
5) thickness of the backing plate?

In any case,
An easy solution and one that does not rely on welding and possible strength reduction would be using a top countersunk head down through the cleat as long as possible then come up from the bottom with
Poorest choice --- long rod nuts- barrel sleeves- with a corresponding hex head bolt from the bottom. (removing in the future might be more than difficult)
Best choice---- a concealed thread bolt with a hex head

Personally, I would acquire some stainless hex material and have a machine shop drill and tap a long internal
thread, and then machine the points of the hex off ( thereby reducing the size of the hole coming up through the hull material) leaving only a shorter head to tighten the bottom of the this bolt.
If you go this route, you would want the bottom internal thread bolt to come up as close as possible to the countersunk head to reduce bending stresses in the top and bottom portions of the bolt.

The primary external forces on the bolt will be shear and bending(tension and compression). (torque to a lesser degree) The longer the bolt, the more stress a fixed load will put onto the bolt itself due to the bending forces and hence my comment underlined above.
The image below shows the concept with the bolt (not the sleeve portion) being a countersunk head and the bottom, machined out of hex bar being a the barrel portion

A quick check on the internet show various sources of already drilled and tapped stainless connector bolt. Ie 1/2 ID and say 2 inches long, which then all you would need to do is have a machine shop cut off the peaks of the hex up to the head

PS I am not a fan of the sharp edges on the cleat base. A rounded or chamfered edge would be better

 

It needs to be only as strong as the substrate below it. Naval architect should be able to tell you some ballpark numbers on strength. Threading holes and running all thread is a solid idea as is a doubler plate to clear the cleat. All depends on how rugged the deck below is.

See guys accidentally over do it on cleats, natural thought is beefy and unbreakable... until it leaves with the line and segment of deck.

 

Thus is typical of horn cleats. I have rarely been able to install with bolts that would fit under the horn.
My usual installation technique is to slide the proper length bolts in at an angle before dry fitting. Then lift the base from the deck to apply beding compound.

Very rarely do I have to trim an ear off of the bolt head to allow it to cross the horn.

 

Shouldn’t the strength of the line to be used be the fusible link, parting before the cleat (or its fastenings) fails?
I favor building up the cleat area with tapering laminations to distribute the load as gently as possible.
As for the bolts, I’d weld in studs and grind flush on top, some great advice on that is already given above.

 

In instances I've seen it's not caused by the lines aboard as they are the logical link it's lines that get introduced. I.e. a much too large a line from a well meaning person in a stressful situation. Have seen more than one person introduce an ovkill line in a storm surge situation and instead of parting a line it parted the cleat or the section of bulwark it was bolted to.

Probably not a super common occurrence, but have seen it happen enough to put the idea forward. There is a curios panic that sets in when things go haywire. We had one storm surge where everybody ended up with some dyneema blend tie up lines. Zero stretch left some squishy or cracked decks and more than a few horns missing. I've been there as well, had a double braid tie up line part. In haste to get out of the rain and surge grabbed a swatch of spectra from the big boat to replace the line... only to just spread the shock to the next component.

I'll concede line is a better method overall.

Guess a better point would be if thread and tap or a welded on wider 4 screw base shaves of x% of strength, but is still within design parameters it's probably OK to be under instead of over.

 

What exactly is this change? If the NA wants thick plywood, he might be convinced that a thicker laminate, and/or a backing plate of G10 would suffice without significantly increasing the thickness.

 

What a dog's breakfast your NA has allegedly set you into.
Ask them how they propose to accommodate your pre-purchased dream cleats.

There is a huge lack of info here.
I see you've posted this in a steel boat category.
Weld the cleats to the deck.

OR

Get different cleats that accommodate your needs.

Also, answer the questions asked of you above.

Good luck, let us know how it turns out.

 

Thanks Barry...
The cleats are AISI 316
Gap between the bar and base = 1 3/4" (see below photos).
Inward flange hull/deck joint, polyester laminate 1/4" thick (no core), with an alum toerail through-bolted every 4" with 1/5"bolts that are fiberglassed in.
Bonded to the underside of deck is a vac panel (12 layers of biaxial)
N.A. prescribed G10 backing plates 3/8" thick
Cleat spec sheet has them rated at 35 Kn SWL. Assume manufacturer applied a safety factor of 2:1. Relevant ISO requirement is 38.5kN break load.
The cleats will also be subject to pull out loads.
Good pick-up on the cleat leading edges...they should be more rounded.

 

I would stay away from welding in any stud due to some of the following reasons stated in the following article and take note that they are probably assuming a complete penetration weld
involving fusing all the contact points. Without welding the bottom of any through stud and grinding back the weldment, this would be quite difficult to produce a complete and voidless weld.
How Welding Affects the Properties of Stainless Steel https://nsarc.com/blog/how-welding-affects-the-properties-of-stainless-steel/

 

Damage to the cleat from welding a solution was raised in our layman discussions.

How could a secondary base plate be made to provide the studs and reduce mechanical losses to the cleat?

 

First, by the time you fool with all the welding, etc, will you spend more than $93? Is there enough room for the wider base on the cleats that are tapped from below or have the 4 bolts outside the horns?

The web site that Barry linked mentions sentization without explaining it, which would be my major concern with welding. The rest of the article shows that the writer knows enough to be dangerous.

All steels contain some carbon. 316 is an austenitic grade, which should have very little carbon, but enough to cause some problems at high temperatures. Run of the mill 316 can have just enough carbon to form carbides near welds. It is often in a very narrow band in the heat affected zone, called knife line attack. These carbides are prone to corrosion. The fact that the cleat is a weldment probably tells you that it was made from the low carbon weldable grade, 316L, that does not suffer from sensitization. Sensitization is eliminated by heating welded type 316 to 1900F and quenching, which would cost more than just using 316L. I would assume that it was 316L If it was my cleat, I would still ask Vetus if it was 316L before welding on it. If it isn't 316L, was it annealed after welding to avoid sensitization?