mast tube

[Randy Ricchi]

You folks are probably gonna think I'm crazy with all the nit-picking little questions I keep coming up with about my recently acquired '73 sunfish. It's just that when I get into something new I want to know everything about it. I'm going over every inch of it to make sure I have a water-tight vessel when I finally take it out.

My latest question is about the bottom of the mast tube. Looking down the hole with a light, I see a circular indentation at the bottom that is about a half inch deep. I'm wondering, if the bottom of that indentation is actually the hull of the boat, is the bottom of the tube sealed so that water going down the mast tube can't get inside the boat?
I would think so, but I want to make sure. I assume the indentation is there so that the mast doesn't end up sitting in a pool of water at the bottom of the tube?

Thanks for all the help you've been giving. I really appreciate it.

 

[sunfishkid]

Hi, I am in the same boat. I have circular base and I also had a hole so I know the bottom is the hull.

 

[Alan Glos]

The 1970 vintage Sunfish had a indentation at the base of the mast tube. As a result, the bottom of the mast rotated on a ridge of sorts and this ridge was prone to wearing thru and leaking. An easy test to see if the mast tube is leaking is to simply fill it to the deck level with water and see if the water drains out.. No leak and you are good to go. It it does leak, dry the inside if the mast tube completely, make sure the deck is level and fill the inside of the tube with thickened epoxy resin to just over the top of the ridge. Repeat the leak test to see if the leak is fixed.

Keep in mind that there will always be some water in the mast tube as waves break over the deck and water gets in the tube. Some water actually lubricates the base of the mast and reduces chafe.

Alan Glos
Cazenovia, NY

 

[Wayne]

I see a circular indentation at the bottom that is about a half inch deep. I'm wondering, if the bottom of that indentation is actually the hull of the boat

In essence, yes. You've got the hull lay-up and solidly placed on that is the flange for the mast tube to be fibreglassed to. The stack-up probably makes it a little thicker without accounting for the step you are also seeing.
http://www.sunfishforum.com/content.php?pg=construction

is the bottom of the tube sealed so that water going down the mast tube can't get inside the boat?

Yes, if not, you've got a leak to repair. The whole principle of a pontoon hull is an air tight chamber making it "un-sinkable" so long as it ain't broke.

I assume the indentation is there so that the mast doesn't end up sitting in a pool of water at the bottom of the tube?

More likely a trap for debris so the slightly feathering mast doesn't become a pestle grinding sand and small stones through the hull. The circular stand-off also levels the tube bottom on the hull’s curve.

 

[Randy Ricchi]

More likely a trap for debris so the slightly feathering mast doesn't become a pestle grinding sand and small stones through the hull. The circular stand-off also levels the tube bottom on the hull’s curve.

Interesting you should mention that. I have my boat upside down on some padded sawhorses, and I just looked up into the hole tonight. There was a lot of dirt in that recess. I knocked the bulk of it out with a long stick and a paper towel wrapped around it. I then took a garden hose and sent a jet spray up there to flush the rest out.

Good point by the previous poster too, about checking for leaks by filling up with water. The only thing is, if it does leak, then I have water in my boat that I have to get out. I guess if it leaks it will get in there sometime or other, better now while I'm working on it.

 

[Wayne]

I knocked the bulk of it out with a long stick and a paper towel wrapped around it. I then took a garden hose and sent a jet spray up there to flush the rest out.

That works, so does a vacuum cleaner.

Good point by the previous poster too, about checking for leaks by filling up with water.

I like the air test approach better because it will detect leaks immediately that could take days by the water method.

 

[baldessariclan]

The mast tube on our boat would fill up at times and then leak water into the hull (albeit very slowly). So I cleaned it out and "painted" all the inside surfaces and bottom with a penetrating epoxy. We also sealed off the hull and sucked a lot of air out at the same time, hoping the thin epoxy would be pulled further into any cracks and porous areas. Seems to have worked well so far -- hull stays dry inside.