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Self tapping screws

beldar boathead

Well-Known Member
Actually you just need flat or oval headed wood screws no more than a half inch long. Technically I don’t think they are self-tapping, but they will tap fiberglass (and of course wood.)
 

mixmkr

Well-Known Member
You need to pre-drill fiberglass for "self tapping" screws. I also recommend slightly "enlarging or countersinking" the drilled hole, prior to screwing the screws, to prevent gelcoat spider cracks from the drilled holes, in the future. "Grinding" with a Phillips head screw driver works fine for this vs a countersink bit.
Rivets have the ability to crack the plastic when installing. Nuts and bolts have the advantage of doing away with the pesky, pointed screw tips, reaching into the port.
 

signal charlie

Well-Known Member
Staff member
We like marine grade stainless machine screws with washers and nylock nuts underneath, to prevent pointy, rusty screw tips from biting future Skippers. Buy a few extra in case you drop something inside, they disappear fast. We get the screws just a little longer so we can reach them easier, the inner lip of the inspection port gets in the way of fingers, and use a deep socket to hold nylock nuts in place while we tighten them.

IMG_3237.jpg



 

Flieger

Member
We like marine grade stainless machine screws with washers and nylock nuts underneath, to prevent pointy, rusty screw tips from biting future Skippers. Buy a few extra in case you drop something inside, they disappear fast. We get the screws just a little longer so we can reach them easier, the inner lip of the inspection port gets in the way of fingers, and use a deep socket to hold nylock nuts in place while we tighten them.

View attachment 33692



So after the holes are drilled, you add some more of the sealant into the hole before you put the bolt in?
 

mixmkr

Well-Known Member
You want the caulk to squeeze up against the screw. Putting caulk on the holes only makes a mess on the threads that you'll not appreciate when putting on the nuts.
 

Flieger

Member
You want the caulk to squeeze up against the screw. Putting caulk on the holes only makes a mess on the threads that you'll not appreciate when putting on the nuts.
Sorry, but I don't quite understand. How can I get the caulk to squeeze up against the screw? Should I caulk around the hole to where the head of the screw squeezes down on the caulk?
 
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signal charlie

Well-Known Member
Staff member
There is a lot of caulk on there, when I turn the port it spreads it all around. Best for us to let it dry then drill through for the machine screws. Other times I'm in a hurry and I predrill holes, caulk and then deal with the messy screws. I am positive that all of our ports are not 100% leak proof, but we prevent a flood anyway.

You could also put a bead anywhere you want, or around the holes and skip the other areas. Plenty of ways crack that nut. Take pictures and let us know how it works!
 

mixmkr

Well-Known Member
Sorry, but I don't quite understand. How can I get the caulk to squeeze up against the screw? Should I caulk around the hole to where the head of the screw squeezes down on the caulk?
Put a bead around the entire permimeter of the inspection port where it will meet up with the hull. I also like to make small-ish "circles" around the pre-drilled screw holes. Feed the screws into the port flange and then install the port, lining up the screws, best you can as you go. You'll probably have a screw tip nab some errant caulk, but that's the way it goes. Now, when the flange is pressed down and especially when screwed, the caulk will squeeze out and if enough caulk was applied, should slightly come out around the edges and potentially out the holes, with the screws half sticking out. Kinda like squeezing an ice cream sandwich...the ice cream comes oozing out between the top and bottom cookie layers.
If you don't want your install to leak, too much caulk typically isn't the issue. WAY too much caulk just becomes a mess to clean up, never mind your hands and running your hand thru your hair, pulling up yer britches...!!! etc.

Lastly, some like to install everything with the sealant applied. Then let the caulk dry before final tightening of the screws. The caulk supposedly acts like a "gasket" as well this way and the potential to squeeze it all out when {over}tightening the screws occurs. That said, I never do this procedure.... I like to finish the job, once started. Also I see the potential of "disturbing" the caulk around the screws, when they are twisted again, "possibly" opening new pathways for water to come in. I've seen amazing amounts of water travel thru screw threads, when you'd think they are water tight. Picture a garden hose without the rubber gasket.
 
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Flieger

Member
Put a bead around the entire permimeter of the inspection port where it will meet up with the hull. I also like to make small-ish "circles" around the pre-drilled screw holes. Feed the screws into the port flange and then install the port, lining up the screws, best you can as you go. You'll probably have a screw tip nab some errant caulk, but that's the way it goes. Now, when the flange is pressed down and especially when screwed, the caulk will squeeze out and if enough caulk was applied, should slightly come out around the edges and potentially out the holes, with the screws half sticking out. Kinda like squeezing an ice cream sandwich...the ice cream comes oozing out between the top and bottom cookie layers.
If you don't want your install to leak, too much caulk typically isn't the issue. WAY too much caulk just becomes a mess to clean up, never mind your hands and running your hand thru your hair, pulling up yer britches...!!! etc.

Lastly, some like to install everything with the sealant applied. Then let the caulk dry before final tightening of the screws. The caulk supposedly acts like a "gasket" as well this way and the potential to squeeze it all out when {over}tightening the screws occurs. That said, I never do this procedure.... I like to finish the job, once started. Also I see the potential of "disturbing" the caulk around the screws, when they are twisted again, "possibly" opening new pathways for water to come in. I've seen amazing amounts of water travel thru screw threads, when you'd think they are water tight. Picture a garden hose without the rubber gasket.
 

L&VW

Well-Known Member
Just so we're clear, "self-tapping screws" are those with a drill bit formed into its working end. (Lately, better referred-to as "self-drilling" screws).

SelfDrillingScrewsx4[1].png

A "wood screw" has a taper for its entire length, so the holes should be drilled with a wood screw bit that approximates the taper. There is also a relief for the shaft—plus the chamfer—described earlier as "desirable" at the big end.

These would have to be carefully chosen for fit. :oops:

(Picture below now described as "vintage"—like my set—and me. :( )

VINTAGE-SEARS-CRAFTSMAN-WOOD-SCREW-PILOT-BITS-SET[1].jpg

A "regular" sheet-metal screw (stainless-phillips) is what I use, since I've collected probably thousands of them! :confused:

If you're using a relatively flexible inspection port and cover—say, from China—I'd suggest leveling the interface between port and deck using 3M 4200, or every fit between port and cover will progressively tighten early :oops: before sealing the port from water intrusion. :eek:

Ask me how I know...:rolleyes:

.
 

andyatos

Well-Known Member
I'd suggest leveling the interface between port and deck using 3M 4200, or every fit between port and cover will progressively tighten early :oops:before sealing the port from water intrusion. :eek:

Ask me how I know...:rolleyes:
Exactly. Ask me how I know! :(

- Andy
 

Flieger

Member
Just so we're clear, "self-tapping screws" are those with a drill bit formed into its working end. (Lately, better referred-to as "self-drilling" screws).

View attachment 33707

A "wood screw" has a taper for its entire length, so the holes should be drilled with a wood screw bit that approximates the taper. There is also a relief for the shaft—plus the chamfer—described earlier as "desirable" at the big end.

These would have to be carefully chosen for fit. :oops:

(Picture below now described as "vintage"—like my set—and me. :( )

View attachment 33708

A "regular" sheet-metal screw (stainless-phillips) is what I use, since I've collected probably thousands of them! :confused:

If you're using a relatively flexible inspection port and cover—say, from China—I'd suggest leveling the interface between port and deck using 3M 4200, or every fit between port and cover will progressively tighten early :oops:before sealing the port from water intrusion. :eek:

Ask me how I know...:rolleyes:

.
So leveling means spreading a bead of 4200 and let it dry, so it forms a level surface to receive the inspection port? Then add another bead to the bottom of the inspection port when installing it?
 

Sailflow

Active Member
Put a bead of caulk around the underside of inspection hull fitting, at the diameter of where the screen holes are. Flip over an insert and screw in. You do not need to level. I have installed many on sunfish and have never had a issue as there is not enough curve on the deck. If you were installing some crazy size port maybe. It is a easy project.
 

Flieger

Member
I did one inspection port with the self drilling screws, the other with nuts & bolts. Two of the self-drilling screws wouldn't completely tighten. Other than that, it worked ok.
The nuts & bolts method was more expensive, but also seems to be more solid.

I caulked with M3 4200, as shown below.

I noticed that due to the curvature of the deck, I had some gaps, so I decided to caulk once more around the outside of the the ports.
 

Attachments

Flieger

Member
phew...and it didn't explode! Well done! Time for a break...like some sailing time!
LOL. Almost there. Still need to install a drain plug, and make some repairs on the sail. Then take my son to college, and then, maybe, if there is wind, I'll get to take her out.
 

L&VW

Well-Known Member
So leveling means spreading a bead of 4200 and let it dry, so it forms a level surface to receive the inspection port? Then add another bead to the bottom of the inspection port when installing it?
What I meant was to apply to a flexible inspection port (made in China). The better brands (Beckson, Py-Hi) would still be served by building a small platform with 4200 and squish the port on top of it. (Trimming off the excess as it oozes out).

My three catamarans (four in life-ownership) had at least four inspection ports—each, and I had to make a tool to turn the covers; which fortunately, I didn't need to access far from shore. :confused:

They're fiddly, but bolts work especially well. Since you've done both :cool: what do you recommend?

Agree. I think this is a simple project that is being over engineered! Use lots of silicone and screw it all together!
Some cases require some foresight—like my "made in China" ports—which left a gap, and can't seal against water intrusion. :mad:

(Gap above "X") :

Fullscreen capture 8102019 12842 PM.bmp.jpg
 

Flieger

Member
Since you've done both :cool: what do you recommend?
Since two of the self-drilling ones didn't tighten completely (i think they stripped the fiberglass), I would probably stick with the bolts next time.

Some cases require some foresight—like my "made in China" ports—which left a gap, and can't seal against water intrusion. :mad:

(Gap above "X") :

View attachment 33770
For that reason, I put a bead of 4200 around the outside of the port. Not very pretty, but it works.
 
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