Composite Deck Hardware Options/ Methods

Ok, so the idea of minimizing crevice corrosion and deck perforations etc, has finally filtered down to the "street" level

I thought it would make a good thread to pass around infornation useful to amateur builders, who want to get in on the latest composite hardware methods. Any anecdotes etc, from those who have built and actually used composite fittings-- especially chainplates, padeyes, cleats, stanchions hinges and the like, ie, what problems have you had, and what solutions? How do you estimate strength- are there any general rules? What about chafe? UV? Vacuum methods/tricks? Can you build a padeye around a plywood piece, encapsulate it etc, and have the same strength as aluminum or ss? And it doesn't have to involve carbon for that matter.

I understand that much of this stuff is case specific, especially with really critical parts, like chainplates, which should be professionally engineered, but there is a lot of other stuff I want to learn to do on my build where I would substitute an epoxy /glass part for a stainless or aluminum one as much as possible. Any comments, links or pictures? Thanks.

 

Take a look here:

http://ptwatercraft.com/blog/?cat=28

Professional Boatbuilder magazine did a story on Russell Brown and one of his specialties is carbon fiber hardware

Way cool. A little wax, a little epoxy, a little carbon fiber, a little sanding:

Steve

 

Thanks Steve! Good site. I can see making up a bunch of those over a half round mandrel and cutting them to individual size with a chop saw or something. I want to have something like those EVERYWHERE on my cat..you just can't have too many places to tie off stuff on a boat IMO.

 

Show and Tell--Birdhouse

Heck, it's too wet to do much outside, so I decided to do some experimenting. I have never done this before, so any suggestions, reprimands or other comments are all appreciated.

I have to make up some "L" brackets. The plans call for 5/16 aluminum. or composite. These are for the bowtube mounts on the forward ends of each hull (catamaran). There is a watertight bulkhead below, that gets a bracket up against the deck, and thru bolted into another identical bracket up on deck, which accepts the bowtube clevis pin, one on each side of the bulkhead. four brackets in all. two below deck two above deck.

So here is my first stab at it.

 

Its just two pieces of shelving board, squared up and rounded ar the "ridge" with the router.

A hole drilled to accept the vac tube, and other holes drilled in the "gable ends" to allow air to circulate.

some 6mil poly covers it first, then some bubble wrap goes on the "eves" to allow vacuum to diffuse.

then a layer of peel ply is stretched over, and held to the deck with staples

The bag, which is another layer of poly, is slit for the hose to go through and sealed. I sealed that end permanently with liquid nail, but I can still peel the bag back and re-use it a few times (I hope)

The lay-up goes on top, with another piece of peely ply to finish off

Also I cut two pieces of formica to size and taped on bubble wrap to the backside (but the shiny side goes down, against the peel ply), so this goes on last. The idea with it is to keep the laminate smooth, so the bubble wrap pattern won't telegraph through.

I used rope caulk, around the rest of the perimeter to seal the vac. It sucked down pretty hard I thought.

So I used ten layers of 20z triax. with the 0 degree running up and down the "roof" and a layer of 10 oz. on the very top and the very bottom.

Will it be strong enough???

 

When it cures I will cut into it and see how thick it turned out to be, So then I will know that much at least. The thing is I have no idea what the comparison strength is with aluminum.

Also, I am wondering if it should be through fastened through the deck as alumnum brackets would be. The plans show the brackets through bolted to each other, back to back through bolted through the bulkhead, and also through bolted botttom to top, through the (balsa) deck. Seems part of the whole idea of composite is to do a way with fasteners, so maybe I should lace them up with some tow fabric isntead?

Also, I didn't put much taper in around the cove. most of the fabric pieces are full size. I did cut three strips of varying width and staggered them on first (after the initial 10 oz layer) I wanted to keep a true 90 degree angle as much as possible. Should I taper these out more than that?

Feedback appreciated!

 

I'll guess you'll be in the 3/8" range, probably closer to 7/16", assuming really good resin/fabric ratios. I'll also guess it's heavier and less stiff then T-6 aluminum angle stock of similar dimensions.

 

indeed charly, why use bolts to hold everything together? it doesnt make sense, glass it all in and forget the bolts i say... now if that makes sense, why make the L-brackets in the first place if your going to glass it all in! does that bow tube NEED to be removable with clevis pins? why not just lace the ally tube to the watertight bulkheads using lots of uni tape, similar to making a composite chainplate?

One of the best things about composites is you can do away with all the expensive SS fasteners...

Another idea is to make a composite clamp for the tube. Lace the bottom half of the clamp to the bulkhead/deck area with uni tape etc and tapped either side to accept vertical bolts from above. Then mold a top half, glass, clamping cradle over the tube and hold it down with 2 bolts either side that tighten the clamp as you tighten the bolts. This would work neatly if an oval tube was used and mount very low profile on the deck, tube center @ deck level. The tube or clamp can have endplates to stop lateral movement.

 

I thought it turned out beautimous! A little skinnier than PAR guessed, and that I had hoped for, but I know I can use it somewhere. The underside of the bridgedeck gets a couple of padeyes for mounting the swinging tube for the outboard motors. These should do nicely for that, cut into smaller pieces and glassed in place back to back.

Lessons learned:

formica still needs a coat of wax for easier removal.



cured epoxy can be wicked sharp (note bloodstains)

 

Good ideas Groper and thanks.

The foward area below decks in my particular build is going to be pretty tight to get at. I was hoping I could be able to reach in there and prep, and then bed the piece in some structural bog, maybe covering the whole thing in a final layer, or (staggered layers) of glass. Sounds like lacing it, vs thru bolts, is the way to go.

 

Hinge Construction

Hey guys, I have been thinking some more about building some composite hinges, for my flush deck hatches. I have six total on the boat, and have already cut out the holes, and added a flange (1/4) ply, with some built up channels. The channels will drain to a 3/4 inch pvc elbow in each corner, and will be directed out, through drain pipes to the topsides from there.

Anyway, I thought it would be cool to layup and bag some offset hinges. They would need to be pretty stout. I could mortise them into the hatch itself, and then fair over it. The deck would have to be mortised also, with the hinge pin assembly glassed in pemanent. I am squeamish about making something that permanent, but I can't figure any other practical way. Any suggestions? What should the pin itself be made of ? I am thinking of some sort of mandrel made up first, with a (wooden?) dowel, overlwrapped with fabric (uni?) , then maybe kevlar (?) Then slick it up and layup the hinges around it??

Anyone done anything similar? To write it all out sounds complicated, but I am thinking it should be fairly easy.

 

If anything eventually goes wrong, then you have to make more hinges, tear into the hatch and deck, then repair and fair it all up and paint it with some custom color that hopefully will match the aged color of the surrounding area.

I don't think it's practical at all, but if you do it, try and pick a composite that will stand up to the repeated action of housing a turning shaft. Picture some grit or sand in with the pin and how long the composite will last before the pin wears the hole out and it gets all sloppy.

 

Good point. I guess the best practice would be to wrap the pin in kevlar, and use a kevlar bushing inside the hinge? what about lubricants? Obviously you wouldnt want something that would bleed all over the place.

I keep trying to envision some way of bedding in the pin, which would run wild of the hinge for an inch or two, into a trench or something. But making the whole thing removable would sure make servicing easier...

 

whats those measurements

That one of thoes strange rulers will funny marks on it !! should turn it to the other edge so us people that understand metrics know what your on about !!
If ya want to release anything ya got to use wax fella even Whacker know that !! took a while mind you !!!!

 

I aint studyin no metric.

Too much else to learn here. There is probably enough material in this section alone for several textbooks...