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seo
05-30-2012, 09:07 AM
I'm getting to the point of putting cleats back down on deck of my Nevins 40, which raises a question that I'd appreciate hearing comments on. The way that Nevins did it was by bolting the Herreshoff cleats down through blocking. Each cleat straddles a deck beam, so there's blocking on both side of the beam, as deep (2.5") as the beam. I've seen other boat where there's blocking on one side, and the cleat is bolted through the blocking on one side, and through the deck beam on the other. On her foredeck anchoring cleats, there's solid blocking, and then an oak plank that runs on the underside of the deck beams and blocking, so that the whole structure is tied together. This makes sense for a foredeck cleat, which will see the biggest strains.
I'm curious if anyone has opinions on blocking.
The original blocking is white oak, and the grain runs perpendicular to the deck beams, and is not fastened to the 1/2" ply decking except by the bolting. There are no longitudinal bolts going through the blocks and frames. I guess they run the grain perpendicular so that if it shrinks it won't leave a gap, and if it swells it won't push the beams...
I'm also wondering about using pressure-treated yellow pine for the blocking. I don't have a lot of white oak around, and yellow pine sees strong enough. But the PT stuff is so wet coming out of a lumberyard...

wizbang 13
05-30-2012, 09:20 AM
Even on my wee 23'er, I ran a fore n aft piece of hardwood underneath, picking up 2 deck beams, and put the cleat between the two beams.
Not that I am planning on anchoring in a gale, I was thinking of being towed too fast .
Of course the problem is taking too much space, with bolts dropping down in the scalp zone, and those pesky rainwater leaks wiggling through all the blocking.
Isn't the blocking just a space holder? Can is be cedar rather than oak?

rbgarr
05-30-2012, 09:40 AM
Here's my read on blocking, realtive to larger cruising boats with laid decks (not plywood ones so much):

The purposes of the fittings are to take a load horizontally or at angles, sometimes both, depending on the type (cleat, turning block, track, etc.) The loads can sometimes be localized to bear most on one bolt out of many, again depending. Thus the longer the bolt, wider the washer/nut and denser/larger the block, the better. As long as the block isn't a wood that crushes and resists rot, via bedding, treatment and ventilation, it would do the job.

Something like a jib sheet block pad that ONLY bolted through a deck beam would tend to pull the deck beam upwards and perhaps off to leeward. I'd just want to be sure the deck beams were bolted to a sheer clamp in that case, not screw-attached only.

Thad
05-30-2012, 10:00 AM
No one better than Nevins for building practices, some different not better. Putting bolts through the beam will weaken the beam so have the block bear on the beam.

David G
05-30-2012, 11:39 AM
Seo,

My first thought was: why change? I can see some trade-offs with the existing configuration, but no big downsides. Are you experiencing or anticipating some problem that you're trying to address?

Or... is your real question: can this system be improved upon given that you have an opportunity now to do so? The answer to that question would be, 'likely'. But we'd need more precise and detailed information, drawings, fotos, etc. to specify improvements.

seo
05-30-2012, 12:44 PM
I think I'll take Thad's point that drilling bolt holes in the deckbeams weakens them, and I might even put a bridge under the blocking and deck beams, although that probably is gilding the lily. The plywood deck has a lot of panel strength. One thing that Nevins used on all the cleats was a flat plate under the cleat, with lots of screws all the way around the periphery. I think that had two purposes: 1) Prevent a heavy load, particularly a side load, from causing the feet of the cleat from crushing the deck, and 2) Make the cleat stronger in shear. The main bolts pass through tight holes in the plate, and before the cleat can shift sideways and the mounting bolts crush the wood of the deck, they first have to overcome the shear strength of 20-odd #12 screws countersunk into a bronze plate and driven into hard plywood.

Roger Cumming
05-30-2012, 02:51 PM
The purpose of the blocking on both sides of the deck beam is to engage two additional deck beams as well as the beam with the blocking on either side, for a total of three deck beams resisting the loads on the cleat. The deck, being fastened to the deck beams, transmits the loads to the beams and therefore bolting the blocking to the beams is unnecessary and would weaken the beams. If you restore the original Nevins details you cannot go wrong. Running the grain of the blocking athwartships better engages the deck, the strong axis of which is running fore and aft from deck beam to deck beam.

I would stick with white oak for the blocking or possibly locust if you can get pieces wide enough. The quality of the pine used for pressure treatment is usually very poor and I would avoid it.

Thad
05-30-2012, 03:05 PM
Thanks seo for recording and reporting these details.

Dan McCosh
05-30-2012, 03:22 PM
Not sure exactly what your original configuration looks like, but I did run into substantial problems with a Nevins-built boat due to the method used to block cleats and stanchions. Much of it involved a mahogany covering board or plank, with cedar blocking separating the upper board from a clamp running under the deck beams. Theoretical this made a bulky sandwich, with the cleat fastenings quite long to get through the whole thing. The first problem was the cedar--which eventually acted like a sponge, rotting out where most of the bolts went through the deck. The heavy blocking also interfered with ventilation. During a major deck rebuild, I installed hardwood covering boards and central planks where cleats, etc. were in the deck. The covering boards were through-bolted through the deck beams and the clamps below. The hardwood makes a substantial base for most cleats, stanchion bases and deck fittings. The heavy deck cleats are also backed with oak blocking below, mainly to distribute the potentially heavy loads. I think there is about 15 years or so now since this was done, and it still is quite solid. I think the use of large softwood blocking--which was particularly problematic at the stem and behind the transom, was an expediency, which was fine when new, but did have issues with longevity.

seo
05-30-2012, 03:41 PM
Dan McCosh- Does your boat have backing plates under the cleats? Also, is yours an NY 32 with tiller or wheel steering? If tiller, do you have any pictures of it? I'm thinking of switching to a tiller. Or maybe not...

seo
05-30-2012, 03:50 PM
I made the blocking out of white oak, and they are currently sitting end-grain down in a pan of glycol/borate. It is actually wicking up through WHITE oak. And yes, I do know what red oak looks and acts like. Maybe tomorrow I'll get the cleat installed, if the metal shop makes the backing plate for the cleat. The originals plates are monel, I think, and the new one will be 316 stainless.

Dan McCosh
05-30-2012, 07:11 PM
Dan McCosh- Does your boat have backing plates under the cleats? Also, is yours an NY 32 with tiller or wheel steering? If tiller, do you have any pictures of it? I'm thinking of switching to a tiller. Or maybe not... There are fender washers under the nuts, but no metal backing plate. We do have the original tiller--I think only one was converted to a wheel. I don't have any photos at the moment. It's great for sailing, but tends to clear out the cockpit during most maneuvers.

seo
06-01-2012, 09:26 AM
The backing plates on my cleats are elliptical-shaped plates of (I think) monel, 11 ga thick (1/8"), they fit between the Herreshoff cleats and the deck, and are drilled around the edge with countersunk holes for 8 wood screws, and have holes for the cleats' mounting bolts. I think they have three purposes: 1) Prevent a strong sideways load from "tipping" the cleat, causing the cleat to crush into the deck. 2) Share shearing loads on the cleat between the wood screws and the mounting bolts. Before the bolts can move sideways, crushing the wood deck, they also have to shear off the wood screws. 3) Give better water sealing. The area under the plate is bedded to the deck, while the cleat is bedded to the plate. Sort of two layers of protection. Water leaking down mounting bolts is a bad thing.