Bonding Winches To Deck

[motorbike]

Actually setting the machine screws in epoxy sans nuts. The winch base is set in the top of a 12mm ply box coaming with another 12mm disc on top of that to make 25mm of ply to pot the bolts in. I could by strategically arranging the winches (lewmar 40's) get the screws to go into the 25mm mahogany outer coaming and hardwood doublers that run along the tops of the inside box coamings.

I want to do this because there is no room to cut a hole underneath and get a hand up to a nut. I could possibly cut a hole in the side of the coaming but since the winches are 1/2 mounted on fairing blocks that are glued to the outer coaming and will have to be potted or woodscrewed I thought why not epoxy the lot in place.

Clear as mud?

Really appreciate some experienced input. These are for the kite, boat has a grunty kite 45ft across the diagonal, dunno the area. The loads are in shear I presume the bolts are m6's ( I think)

[michael pierzga]

Dont know.

They say that its possible to equal the faster strength with good craftsmanship. I have never seen a bonded fastener fail.

Remember, after you professionally bond , a future user may need to remove the hardware and may not have the craftsmanship required to duplicate your work

I'm always worried about liability or misuse of the winch. Halyard winches are misused when a primary winch is used to hoist a sail or do work over the halyard winch.....ie two wraps on the halyard winch pulling high on the winch at a 90 degree leed angle angle . Winches are designed carry the load low, from only one axis .

I prefer when the halyard winch drum shaft breaks ,rather than the winch pulling free of the deck.

Best to use your own intuition on suitability. Bonded fasteners are very strong...I like the system

[motorbike]

Thanks Michael,

All that I have read tells me that it will work, however when I'm offshore and it pops of the deck, I will still be rather annoyed!

I dont have the engineering knowledge to calculate the loads, so overbuilding is how I would go about it, for example I did my genoa tracks the same way using 125mm m6 epoxy potted machine screws in to the gunwale. The reason was that I was going to get charged $30 per 200mm bolt (wide gunwale) and I needed 30 per side.

Then I read that 6 diameters would pull the heads off, not sure if thats true however.

[michael pierzga]

On the West system site they have the calculations for fastener bonding. The beauty is that you eliminate deck leaks and all the mess of backing plates.

No reason why it wont work.

I think the secret to bonding is good craftsmanship. Some bonded fasteners ...like vertical surfaces are difficult to get right.

Do remember to only load a fitting in the direction it was designed for.