Drilling and mounting hardware on a boom

[RobH912]

Have never needed to drill and mount anything on to a metal boom and now looking to install an external outhaul system.

Is this simply a drill, tap, and machine screw project or am I missing something? Size of machine screw? Use thread lock glue?

My current really old boom has had too many previous iterations of internal outhauls with too many exit blocks installed into old exit blocks, etc. that I am just looking to do something like the 4:1 external system shown in this Harken outhaul system link https://www.harken.com/en/support/selection-tools/system-diagrams/outhaul-systems/ and need to attach eye straps, cleat, cheek block, etc.

Thanks!

[GreenLake]

(click to enlarge)

Rob,

I sidestepped the need for much drilling by lashing a double block to the end of the boom.

In the photo, it shows a single block lashed to the clew, but I later found that using the clew like a low-friction ring works just as well.

The setup gives me 3:1, which is plenty. The friction added by dropping the single-block and leading the outhaul directly through the grommet hasn't been an issue in practice, but I gain a crucial 1/2" in movement. Unlike any cheek block, the pull is straight back which may be one of the reasons this works rather well.

For the cleat, I believe I used sheet metal screws (don't remember tapping anything) but they are coated in Tef-Gel. (Expensive stuff, but a tiny syringe worth of it will last you....).

A V-cleat works great - if you have the right type of rope. The one I have now, would work better with a cam cleat. Also, my cleat position may be too far aft. The tail is tensioned by a weak bungee to keep it parallel to the mast. The idea is that you can operate the outhaul from anywhere in-board of the cleat, so both skipper and crew can adjust.

If you do need to add an eyestrap, you may be able to use pop-rivets for that one (use tef-gel on the eystrap where it contacts aluminum). Loaded on shear, they are stronger than you might believe. For the cam cleat you would need to tap as those usually come with machine screws. Use Tef-Gel instead of thread locker.

[jalmeida51]

Hi Rob,

I installed the Harken 4 to 1 outhaul system screws on my boat about 2 years ago. I read somewhere you should use machine screws to attach the hardware. I used stainless steel self tapping and I believe they were no. 10's. I used red loctite on the threads. The self tapping has never backed off. I installed a v cleat instead of the recommended cam cleat. It has worked well. Due to the small diameter of the boom I didn't have a cam cleat that would fit flush on the boom. I would have had to makeup a wedge for a flush fit.

Here is the problem I had the foot of the sail was too long or the length of the boom was too short. This only happened on windy days when I needed to flatten the sail. All I needed was 1/2 inch of a shorter sail or a longer boom. When I had new sails made by Schurr Sails I had them shortened the foot by 1 inch. The system works good now. The loose footed main also really helps when using the outhaul.

You should check the length of your boom and the foot of your sail to avoid the problem I had. because with the 4 to 1 you can really get the foot tight. If you don't have enough length use G.L.'s outhaul system.
John

[tomodda]

Drill tap and machine screw has done the trick for me just fine, including for my outhaul. One tip, the boom being round and drill bits liking to drift - use a punch tool. I FINALLY got myself a cheap center punch when setting up my reefing system and it's been well worth the $6ish bucks it cost.

[GreenLake]

The difference between 4:1 and 3:1 is not really that much. 33% more or 25% less, whichever you pick as your baseline for comparison. Getting an absolutely straight pull near the end, rather than one that is angled down will make up much of that difference. (If you are pulling tight and the outhaul ends up at 45 degrees as in the Harken diagram,the component of the force that points aft is only 70%. And there's that 30% again. So a 3:1 that pulls straight is just as effective in the end and avoids the need for floating blocks).

Sailmakers like to maximize the foot, if you use slugs/sliders in the mast track your sail will come further back and you'll likely end up without enough room to stretch the foot. Having the clew re-cut may be your best option.

[RobH912]

GL & Tom - Thanks for the quick responses and your set up picture GL. Love pictures.

I tried last summer with a similar lashing of a block on the end of the boom, but it didn't work well as some previous owner who was rebuilding the boom, riveted the end plate in upside down so that the metal loop that I might use for a topping lift or a block for the outhaul ends up hanging down. Lashing a block to this lower metal loop, with a long soft shackle just didn't work well... which is why I was interested in the Harkin solution.

GL if go with a hybrid of your solution I think I still need to drill and install some sort of eye strap that would run perpendicular to the sail track that would allow me to attach outer double block.

GL - So a couple of quick questions.

- I can see the rear double block lashed to the boom, I see the single block lashed to the sail, the cleat on the boom, but can't figure out where the other end of the outhaul line is attached to? Does the single block have a hole that is used as a becket and line starts there with a bowline hitch or something? Is there an eye strap on the other side of the boom?

- Had been thinking for this external system that I wanted to run the line along the boom farther than you did, so that crew might adjust outhaul. I know you single hand a lot, maybe that is where you wanted your cleat?

- If I run the line farther forward I'm thinking I might need a small fairlead on the boom also. Any thoughts on that?

I still see the need to drill into the boom and from your comment Tom, I think I just need a punch tool to start before drilling, get right size machine screws for hardware I am attaching

Thanks!

[GreenLake]

Rob, each boat is different. Case in point, your end cap.

First suggestion: drill out the rivets, rotate the cap, put new rivets in. Not hard to do and assuming that it's the normal "cap", the rivets don't need to be better than ordinary aluminum pop rivets for the loads. Alternative, if there's a reason the cap won't rotate: rivet a longer strap across the top side of the back of the boom, something like this one (upper right, almost out of the picture):

It has 4 holes, so it doesn't rotate. For this application you mount it at the end of the boom, but angle it back so the rivets clear the end cap, but the "bow" end is at or a bit past the top end of the boom. Then lash to that. (But only if you absolutely can't rotate that cap).

Third alternative, you can use two cheek blocks (one on either side) to replace the double block.

Next: my outhaul is tied to the clew. My current setup (which does not use the single block): lead outhaul into Port sheave of double block, run back through clew grommet, into Starboard sheave of double block, then forward. Up to the cleat, the outhaul will be under tension, even if slack, you'll be able to "snug" it without changing the sail trim. No fairleads required. I have one eyestrap at the very front to which I tie a very weak bungee. That holds the tail coming out of the cleat along the boom. You can grab the outhaul tail anywhere and adjust. When done, just let go and the bungee will keep it secured. (Photo above shows the setup before I added the bungee and even with using the boom vang bail, it sags - red line).

I use a rolling hitch (tautline hitch) on the bungee, so I can adjust tension if needed.

I keep my sail on the boom (even when I take the boom off) so all of this can stay in place.

[Hesedguy]

GL, thanks for the great pictures of both your outhaul and the vang. I've been quite unhappy with my 1:1 outhaul and 4:1 vang, so I just received my order for a double-block, (RF20202) for my outhaul, and a single block to cascade my vang to 8:1, with the option to go up to 12:1. I'll post some pictures when it's done. Next will be main downhaul or cunningham, whichever works better for my setup.

[GreenLake]

I have a boom downhaul, which I use almost always to the max, as it's easier to get the basic tension in the sail: as you can see in the photo (or guess from it) I still have horn cleats on the mast; they are fine, but don't work so great in getting the last little bit of tension; they always seem to give up the last 1/4" in the act of belaying. Boom downhaul fixes that. Cunningham I use less, usually only if I see real need to improve the sail shape. Many days, the conditions don't require the added tension.



Here's another closeup.

[RobH912]

GL - thanks for additional information. Upon further inspection I see that the end cap on the aft end of the boom was not installed upside down, but that the metal loop on top had broken off. The internal shape of the boom does not allow me to take rivets out and turn the cap 180.

Thinking I’ll go the bail route for the boom as the solution at the end of the boom.

Lots to think about, need to look at the design options and figure out parts availability. Simple is my goal.

I’ll post pictures when I’m done.

Thanks
Rob

[GreenLake]

You may find a bail that's not a simple U, but has a shape that supports attaching something at the apex. (I know such exist, because I've seen them, but don't have a picture or better description).