In addition to the ideas and comments already made, I'd like to add a few words of caution. Make sure you don't lose any necessary outhauling distance on the end of the boom. One lost inch of necessary outhaul will put about 3" of belly in the foot of your sail. (thanks to the power of pi)
All in all, Bill de Ment's suggestion for an external 2:1 outhaul is much simpler than running it inside the boom, and you don't need to worry about boom strength or cutting holes in your boom. You can install two smooth (no sharp edges) eyestaps longitudinally on the sides of the boom using SS rivets (and bedding compound for galvanic insulation please!). Run the outhaul from one eyestrap forward thru the clew of the mainsail, then aft through the eyestrap, the forward along the boom to a cleat with an integral fairlead. Tie the loose end to some 1/8" shock cord and attach the shock cord further forward. You won't lose any length that way. That'll keep the loose end from whipping around.
For one boom I built 2 years ago for a teaching dinghy, I installed a 2:1 outhaul externally like I just described, but also ran it down both sides of the cockpit so you don't have to shift your weight to adjust it (and gave it a 4:1 advantage for easy use by kids). On the other two dinghies (Force 5's), the outhaul runs inside the boom, forward to the mast and then down both sides of the cockpit.
I know I just said that external 2:1 outhauls are simpler but... When I built a new boom for Redwing, my P19, I installed an internal 4:1 outhaul. I used a much heavier extrusion than the original P19 boom, so there was little question of strength. It's 4:1 and exits from the boom about 2' aft of the companion way. The line exits the boom towards the aft of the boom, thru an aluminum v-cleat with a built-in sheave. A light 1/8" shock cord tied to the back of the boom pulls the dangling line aft, so it stays up against the boom. The outhaul line has a small Wichard SS carbiner that snaps into the clew of the mainsail.
It's really a sweet setup. You can outhaul it with 2 fingers even when pointing into a strong headwind, and then release it and it automatically goes into the v-cleat and snugs itself up against the boom. Loosening it is just as easy. You can adjust it on every point of sail except a dead run without even getting up from your seat or letting go of the tiller. Another advantage of running it inside the boom is that there are already too many lines dangling off my boom -- 4 reefing lines (two reefs, each with front and back lines).
What is the diameter and wall thickness of your boom? And where do the mainsheet and vang attach? I would want to know that data before cutting any holes in it for entrance and exit sheeves. I should think that if it's the same size as the P19 extrusion, it is probably strong enough to cut some holes in it. I think that you might be able to cut a hole in the bottom (downward facing part) of the boom, where the force on the bending boom is in strain, rather than in compression. Riveting an exit sheave will strength it at the hole. But you'd have to be careful about the location of the hole for the exit sheave, vis a vis the mainsheet and vang attachments.
Either way, internal or external, the outhaul works just fine. I chose to run the P19 outhaul inside the boom so there would be plenty of room for the reefing lines and lazy jacks. If you're interested in running it internally, and you want a diagram and parts list of how to rig a 2:1 or 4:1 cascade inside the boom, I can put one up on my website or email it to you.
Fair winds,
Judy B
1985 WWP-19 #266 Redwing
SF Bay, CA
Best regards,
Judy B
1985 WWP-19 #266 Redwing
SF Bay, CA
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From: Bruce Hood[SMTP:bhood@sunset.net]
Sent: Wednesday, December 15, 1999 2:24 PM
To: West Wight Potter List
Subject: Ideas for a P-15 outhaul
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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Hi fellow Potter Sailors..
I'm pondering the best way to set up an adjustable outhaul,
so I can flatten the mainsail, or set it fuller while on the water..
I notice that Dwyer aluminum makes a boom end-cap with an
eye for attaching the clew of the main, or a small block and
an eye for attaching the mainsheet blocks.. this would be
pretty simple.. just run a line from the clew around a small block
then take the line forward to a small fairlead clamcleat attached
to the top of the boom near the boom's inboard end.. then one
could just reach up and adjust it. While thinking about this it
also occured to me that you could just endcap the boom and
run a line internally forward within the boom, then exit the
boom on the underside.. However since the boom is fairly
slender I'm leary of making any holes in it that might cause
a weak spot... I need to end cap the boom to make it a little
longer than the location of the present end staple riveted to the
boom, in order to have enough length to stretch the foot a little
further aft... Has anyone else made an adjustable outhaul and
have any suggestions.. I thing Don Bergst made a beautiful hardwood
endcap with a hole in the center and a notch for the outhaul line that
the he routed the line forward along the boom with.. but I can't
remember if he routed the line inside the boom or not.. Any
further ideas, or descriptions of a working system are welcome..
best wishes,
Bruce
Bruce Hood, P-15 "Aillte" sail no. 1246
Chico,California