where to drill a comptip drain hole

I am trying to figure out where the best place to drill a drain hole in the comptip section of my mast would be. I drilled out one of the upper rivets in the mainsail hook assembly and just got through to some spongy material that I assume is mast plug or excess sealer. I didn't get any water out, but it did feel a little moist. I don't want to just drill out more rivets and drill more holes willy nilly until I finally find the right place to get the water out. I am sure someone here will know where I need to drill this hole. The mast is head down on the trailer for transport.
I have searched for and read several threads about water in comptip masts, and another about removing a comptip mast head assembly. I have also replaced mast bases and heads and replaced mast plugs on solid masts. But, I have not found anything that will tell me where to locate a drain hole.
I currently have water in my comptip, and I haven't had the chance to take the whole mast off and submerge it to find out where it's getting in, and with the season waning fast here in Pennsylvania, I may not get the chance before winter sets in. I am most concerned about getting the water that is in there out now, so it doesn't end up in there when it freezes. I can figure out where it's getting in later, I just want to get whats in there out now.

I'd consider removing the head. Pull out the old plug. Drain and reseal. Paint the leading edge (rough seam) with resin as well.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Matt, in the only post I saw on this forum about removing the mast head assembly, the guy said he removed the pulley sheave and put a piece of wood in the sheave pocket and beat it out of there. He also noted that he had no luck with a heatgun to loosen the adhesive and that there was a hidden rivet like 5 inches down that he didn't know about until he was done, which would have had to be behind the sail track???
Is there any way you could link me to a picture of this masthead piece out of the comptip so I know what I can see how long it is and where the rivets might be. Or did I totally miss some much better instructions in a thread somewhere else.
When I only got some dampness when I drilled out that first rivet I got to thinking that maybe there was a mast plug just below that head, and that taking it out was a waste of time if the water was getting in along the front seam as you mentioned....
It's no mystery to me where the water came from....I was playing in some small craft advisory weather on lake Erie and flipped and was driven turtle pretty quickly by the big waves and wind, and was upside down for awhile while I untied my righting line, so we could get back far enough to bring her back up on her side. There's a lot of pressure 30 feet down...that's why I'd hoped to just drain the comptip now and then submerge the mast to see where my leak is before I risked ruining my comptip in the removal process.
If you really think it needs to come out, either some pics of the bare masthead insert or a link to a better description of the process would be nice.

Take the mast head off, remove the plug. Dry the comptip. Purchase epoxy, color it black. Paint the front seam while another person holds a vacuum on the open end to "suck" the epoxy into the voids of the comptip seam. Turn off the vacuum and final fill the seam. Alow to dry, sand smooth and paint to protect it from UV. Install the plug and head. Test for leaks. Enjoy sailing.

_________________
1989 Hobie 18 Worlds Boat, Magnum Wings & Spinnaker
1987 Hobie Holder 20 #273

dale.vanlopik"at"att"dot"net

Thanks for the reply DVL. Just got done talking to a local who had his masthead off... He gave me some of the answers I was looking for, but couldn't remember some specifics...like how many of the halyard hook rivets need to come out to get the masthead off.. He had some cracking up high from the mast falling from it's winter storage perch in a big snowstorm and was reinforcing the upper tip. He quit digging when he got to the upper plug you also mentioned, because he didn't have any water in his comptip and didn't know how big the plug was or how far down it went, so he came to the... if it ain't broke don't fix it, conclusion. He did tell me that the masthead wasn't really epoxied in, which I thought it might be. My water pocket isn't just below the masthead it's below that upper plug, and above the comptip/ aluminum mast seam
I had my mast off the boat and submerged today and really didn't see any bubbles. NOTHING on the front mast seam..(.My boat is always stored inside and my comptip is in really good condition with no UV damage to speak of.) I asked a friend to look too, and he said that he did detect a few bubbles ( like one small one in half minute or so) coming out from behind the mast track, that could be just air that was really slowly migrating out from behind the track itself, or I guess there must be a mold seam under there too, as well as the one on the front, that I should be concerned about.
I ASSUMED that I got this water in during my Erie turtle event, but now I hear that these comptips breathe just enough that they can collect atmospheric condensation like my heavy equipment fuel tanks often do. I'd still like to know just exactly how far down from the top or up from the aluminum extrusion, and where on the comptip that I could drill a small drain hole that I could then plug with a scew and some rtv. I'd be good to go for winter then, and I could see if I ever got any more accumulation of water again, before I had to tear into it
A friend suggested, that if I can find the guru who can tell me where to drill this hole, that I should kind of flip your good advice about using the vac to pull the epoxy in, and instead pressurize the comptip, and use soapy water to pinpoint any possible leaks.

Well just in case anyone else is dealing with this same issue, I have some things to share now. Yes, all 6 of the halyard hook rivets also engage the aluminum masthead, and have to come out to free it up. The mast head base extends down into the mast to a point just below the lowest of the six rivets.
When I pressurized my comptip with my shopvac, I discovered that my leak was a 6 inch long crack in the bottom of the groove that accepts the sailtrack, about a foot down from the top. How it got cracked in there is anybody's guess.
After all the rivets were out, I was able to put a large crescent wrench on the pulley housing, and twist some to free the masthead, but if you do this just WIGGLE IT BACK AND FORTH AND ABSOLUTELY LESS THAN A QUARTER TURN, because the aluminum masthead is not round. It is quite a pronounced oval shape, and you will split open your perfectly good comptip, and then end up with a nasty repair, just from the pressure created by the rotation. Just get it loose and then rely on tapping it out, as straight as you can.
When I finallly got the masthead out, it became clearly evident that I was not the first one to do so. It was set in some non-factory sealant, and the rivet holes are all poorly drilled out. The mast plug that people say is supposed to be below it, no where to be found.
I will have time to fix it right with epoxy and cloth now, because I put my other old silver full length mast on the boat.
I was hoping to just drain, plug, and finish the season, with this one. Now it will get fixed right though, because I have NO reason to hurry.
In hindsight, I might have been able to drill a SMALL drain hole , get the water out, use the same hole to pressurize the comptip with a really low pressure setting on my air compresser, find my leaks(s) with soapy water, and then apply a vacuum to the same hole to pull my repair epoxy into my repair areas, like someone mentioned above. I could then have sealed my work hole with some more resin at the end of the project, and never removed the masthead at all.
The comptip is really quite flimsy at the upper tip, and taking this head out and replacing it really does put the whole unit at risk of damage. The problem with my plan B, is not knowing how far down that upper mast plug is and how long it is. I hope I never need to know again.