Fastening to the Boom or mast

[John rolka]

One of my projects this weekend is to install a topping lift, 2 weeks ago I nearly dropped the boom on my wife and daughter while dropping the main sail and don't want to repeat that. I'm going to have a wire with thimbled loops then have 2 blocks, I'll tie off to a cleat on the boom. Installing the cleat on the boom, how does one typically fasten into the extruded aluminum material of the boom. I'd love to have a backing plate of some sort but don't know how I would get it in there. The material is 0.080 or thicker but certainly not 0.125. The load on the cleat and fasteners will be in shear. How is this typically done is just screw threads into a pilot hole? I'm an architect with engineering background and work with metal fabricating, curtain wall and windows so I'm familiar with how to do this work within that context but what is the standard job for this kind of work on boats.

Thanks,
John Rolka

 

[tommays]

SS Rivets work well as Alu is a bit weak and a .100 or less wall screws are marginal

 

[mark_swart]

Have a look at a few other boats at your marina if possible. Most topping lifts I have had normally just have a shackle that clips on the back of the boom fitting where the outhaul and reefing lines go through. I don't think there's a need for a cleat.

 

[Tim R.]

Why use wire rope? More chance of chafing on the leech of your mainsail. 5/16 line will do just fine for your boat.

SS rivets with plenty of tef-gel.

 

[tkanzler]

Both screws and SS rivets. The latter is the more professional approach, if the factory work on the boats I've owned are an indication, but for lightly loaded cleats, I've use screws into relatively thin Al members with good success.

If I'm understanding what you're doing, you're going to run a length of SS wire rope to the mast head, and at the boom use a 2-part (or more) system of blocks and line to adjust the topping lift. Sounds like a plan, as long as you can reach it when you need it.

You could always add a bail to the end of the boom, and use a lower block with its own cam cleat, like a basic boom vang, but that may be going overboard a bit.

Whatever you end up with, be sure the wire termination at the top won't chafe or otherwise wear as the boom swings through its range. I personally prefer line over wire for something like that, as line won't damage the sail if/when it gets chewed, and with line you can use a small block at the top and another cleat on the mast, which gives you the ability to adjust from either end (or just from the mast, for simplicity).

 

[mark_swart]

Upon further reflection... you could just buy a boomkicker and have a nice performance upgrade in addition to fixing your problem.

 

[Eric M]

There was recently (the past few months) a pretty detailed article in sail or maybe it was cruising world on how to get a backing plate inside your mast or boom for the purpose of installing a new cleat. I am a mechanical engineer and can say that I would have never come up with the process they outlined on my own, but it definatley looked like it would work. It was pretty similar to the process at:
http://www.quigs.org/Farrier/images/2006/2006-12-10-mast clutch/thumbs.html
Good Luck

 

[John rolka]

Thanks for the comments, I'll consider the rope for all, it will be easier all around to install, I looked at a boom kicker that was hundreds of dollars where this lift will be around 90$.

 

[Don12364]

I would do just as you proposed.
My boat came with a stainless wire topping lift which was actually the plastic covered lifeline wire. It has a thimble at the lower end using a Talurit aluminium (or copper) crimp sleeve.
It has low windage little or no chafe on the sail, no stretch, and is unquestionably still strong after 15 years.
The upper end I have spliced to a small diameter halyard running down inside the mast but, due to the weight of the boom, it needs a 4 part tackle at the mast heel to operate, one end of which I take back to a jamb cleat or stopper on the coachroof by the companionway.
I also tried your approach with the line led along the boom and that worked fine too but I led my line inside the boom using a spare sheave at each end and used the same tackle as above. This tackle being located vertically between goose neck and mast heel fitting.
It does not need much travel and I can set mine so that the topping lift is just slack with the sail hoisted and then only need to tighten it a little when lowering or reefing. The tackle line is marked with felt tip for both high and low positions so, after lowering the sail, I can raise the boom to get it out of the way (and to make the rain run towards the mast rather then cascading into the cockpit - this is England after all!)
You could use a plastic cleat and fasten with monel rivets which, being in shear as you say, should be plenty strong enough.
Unless you have a vertical tackle attached at the bottom to the deck plate, you will also need somewhere to attach the fixed block on the mast end of the boom.
Sorry no photo of my setup.
If the above is not clear I can make you a sketch. Just PM me via this site.

 

[Joe]

You can access the boom interior by removing the "boom end casting". Disconnect the mainsheet and outhaul if you want, then remove the two screws on either side. I have used rivets, self tapping screws and tapped screws. All have held well. The SS rivets, however, are difficult to remove and you do damage to the surrounding aluminum if not careful. I think backing plates on the topping lift hardware is overkill... there isn't that much stress on the fittings.

Although I no longer use the topping lift, because I converted to a rigid vang years ago, it can still be quickly re rigged.

My system was similar to your plan.... a 31 foot wire, thimbled eyes on both ends. The upper end was pinned to the masthead fitting's hole just INSIDE the backstay's. The lower end had a small block attached, which hung about 12 inches above the boom. The control line was 1/4 inch dacron... knotted to an eyestrap on one side of the boom then run up to the topping lift block, then back down to the other side of the boom to a small cheek block... the line was then run forward a foot or so to a small clam cleat with fairlead. The cheek block is placed as far aft as possible, on the opposite side from the reefing gear.

That said, I hated the damn thing, I was constantly having to adjust it to keep it from slapping my new, full roach mainsail. Plus the cleat was near the end of the boom, convenient when it was amidships, but unreachable if the boom was out past the life line..... I recommend you run the control line forward, either to the middle of the boom or all the way forward, then back to the cockpit.

However........ if you really want to make your wife happy, and make a terrific improvement to your boat... convert to a rigid vang... Garhaurer's is the most popular and the most economical.... and great people to work with.

I will tell you that the boom and mast brackets for my vang are attached wiith 1/4 inch fine thread hex bolts.

 

[Ray T]

A 1/4" line will work fine for your boat. The boom on a 27'boat doesn't exert much force on the topping lift. I believe the breaking strength on 1/4" sta set from new england rope is 1900 lb. Run the the line from the masthead to a block at the end of the boom and forward to an open foot cleat. Feed the line through the cleat and secure with a stopper knot. Before you do that allow enough slack in the line to clear the leech of the main. As far as what kind of fasteners to use on the cleat it doesant really matter. Any way you want to go will work fine. I used this setup on my 27' for years with good results. Some would have you think you don't need a topping lift with a boomkicker but I have one and I disagree. When you furl the main, a lot of times you wind up with the boom supporting your weight and a boomkicker at least the one I have wont do it.

 

[Paul Brinkley]

My boat did not have a topping lift so I made my own. I removed the aluminum rivets holding the end cap on the boom, installed a 1/4" eyebolt through the top of the boom (no backing plate) at the end, and reinstalled the end cap. I put an extra sheave in the chicken head, put SS caribiner on the end of a 1/4" line, and ran the line up to the sheave and down to a cleat on the mast. Works fine for reefing and for supporting the boom when the main is down, and cost very little. -Paul

 

[MaranaF]

Interesting question, I have seen many installations and installed a few dozen. Then I bought the boat I have now, a 50ft ketch and was surprised to find a wire topping lift... With no adjustment, it is fixed!

I decided to live with it for a while and see how it performed on the basis that it had been there for 20 years so there must be some merit.

Six years later I still have it and can see no reason to change it. It is simple, reliable, never on when I want it off and it works. It is taken from a u bolt at at the mast head plate to a spare eye on the boom end plate where I shackle it on so I can drop the boom when I need to.

As for the question about fixings. Rivets, lots of duralac or similar and a little thought about the direction of the load. Look for a cleat with four fixings if you are still concerned about loadings on the thin Walls of the boom. If you must screw it on then you must have a thread pitch that will allow three full threads to be in the material you are screwing in to. Using a M6 with a thread pitch of 1mm will only get two threads in the boom :-(