Installing Spinlock Rope Clutches

[smo10018]

Just bought a triple clutch unit of the Spinlock XAS rope clutches. Was at first surprised to see 6 bolt holes in the thing. After thinking about it I assume they are simply due to being 3 single clutches bolted together??? Am I fine in only using 4 holes to bolt the thing down or do I in fact have to use all 6 bolt holes?

They will be going on the coach roof underneath our dodger. Will make a backing plate for the install, 6 bolts seems like a bit of overkill.

We've never had rope clutches so this is all new to me.

Thanks!

 

[kappykaplan]

With the appropriate backing plate, I would think 4 bolt holes would be fine. What's the pattern for 6 holes?

 

[FastOlson]

Please do use all the mounting holes. These parts are engineered for XX pounds of stress, and their engineers did not spec out unneeded mounting holes in the base plate and frame of the assembly.
(I have replaced all of our OEM clutches, and filled in the old holes, and then over drilled- epoxied- redrilled holes for the new ones. )

 

[Ward H]

I just replaced an original triple rope clutch (Garhauer) on my C30. It was mounted with 6 bolts and I mounted the new one the same way.
@FastOlson has a good point. And if the factory had a choice of putting in 4 or 6 bolts, I'm sure they would have taken the easier and quicker way and only used 4 bolts.

 

[smo10018]

Yep good points will use all six holes. Thanks for the advice.

Sean

 

[smo10018]

Was wondering what do you think a safe thickness would be for a backing plate for the clutches? Would be using stainless, would 3/16" be fine or should I look for some 1/4"?

Thanks very much.

 

[Jackdaw]

Most builders use only the 4 corners.

 

[Ward H]

Considering a backing plate spreads the load over a larger area than commonly used washers, 3/16" or even 1/8" will be fine. 1/4" is overkill.

Edit: @Jackdaw sees a lot more boats than I do so I would probably follow his lead.

 

[smo10018]

Well thanks for the quick replies!

Will look for thinner backing plate material then.

Thanks for all the input everyone.

Sean

 

[Jackdaw]

Considering a backing plate spreads the load over a larger area than commonly used washers, 3/16" or even 1/8" will be fine. 1/4" is overkill.

Edit: @Jackdaw sees a lot more boats than I do so I would probably follow his lead.

Remember that the loads on a clutch are in SHEAR, and not TENSION. Washers are fine. They will never pull out on a load that basically runs down the length of the deck.

 

[thinwater]

Without describing the deck layup (thickness of skins, method of core replacment) any inquiry about backing plates and washers is a trick question. People can only suggest what would work on the deck they have in their mind. An ultra-light deck could need a good sized plate, and solid glass could require nothing more than a bolting washer.

 

[Tally Ho]

I replaced a quad clutch on my O’Day 322 and it used 8 bolts...

Greg

 

[smo10018]

Having never drilled a hole in the boat anywhere I can't say with any level of confidence how thick the coach roof is. The deck is balsa cored but don't know if this area is or not.

At any rate I am leaning towards making backing plates with drilled and tapped holes for the screws. The area I want to put the rope clutches is not as easily accessible from the inside of the boat as I expected so individual screws with washers would be a serious pain to hold in place while installing. I have a small machine shop so I think the backing plate idea is easiest all round for me.

Sean

 

[Jackdaw]

Without describing the deck layup (thickness of skins, method of core replacment) any inquiry about backing plates and washers is a trick question. People can only suggest what would work on the deck they have in their mind. An ultra-light deck could need a good sized plate, and solid glass could require nothing more than a bolting washer.

A load in tension, I'd agree. But shear? Unless you can't WALK on it safely it should be OK with washers. But to everyone, YBYC.