Fastening into epoxy plugs, having difficulty.

[Bowdrie]

The term "Lag screw" keeps being mentioned.
Do you mean "Woodscrew"?
Standard track uses a 5/16ths flathead fastener, in screw sizes that's a #20, IIRC.
What are the fasteners that you have and wish to use?
I believe that one or more of the "block" companies, like Schaefer, Ronstan, Lewmar, etc. have charts that show the load percentages, and it's not near what one might imagine because of the fairly shallow angle of the sheets.

[Uncle Bob]

Hi, I have in the past drilled and tapped the glass matrix, using a 1/4 inch hand tap with a not too fine thread. Still holding just fine. The coarse thread will have deeper threads and is great for glass, in my experience. Use a sealant on the threads to keep any water infiltration out, should be good for another 40 years. Lag screws are not what you want, just good old 316 metal threads.

[rkarakai21]

Yes I meant wood screws, they are indeed a 5/16 shank.

Had a look at harkens load calculator, with my 381 square foot number 1 Genoa in let’s say gusting to 17 knots it would be about 475 lbs of load, and that would be significantly over powered. Now I’ll see if I can find fastener pullout data for epoxy.

Tapping makes sense to me in this application, I just might have to approach the bank for a mortgage to buy the fasteners.

[Uncle Bob]

Originally Posted by rkarakai21

Yes I meant wood screws, they are indeed a 5/16 shank.

Had a look at harkens load calculator, with my 381 square foot number 1 Genoa in let’s say gusting to 17 knots it would be about 475 lbs of load, and that would be significantly over powered. Now I’ll see if I can find fastener pullout data for epoxy.

Tapping makes sense to me in this application, I just might have to approach the bank for a mortgage to buy the fasteners.

Find an industrial fastener supply business that does stainless, usually way cheaper than a marine store, especially if buying more than a couple.

[Bowdrie]

Originally Posted by rkarakai21

Yes I meant wood screws, they are indeed a 5/16 shank.
I just might have to approach the bank for a mortgage to buy the fasteners.

Ok, in a 5/16ths shank wood screw the thread pitch is greater than any tap you could get.
If you want tapped threads that means going to a machine screw.
Hold off going to the bank.
There is a trick that you might try first on a couple of holes.
Do you have, or can you get access to a Dremel or a die grinder?
If so, you can take one of your woodscrews and using the tool with a little cut-off wheel you can cut 3>4 grooves lengthwise on the screw.
What that will do is convert that screw into a tap that you can use on all the holes just like a machine screw tap.
Now, if the thread pitch matches, (and diameter,) a "lag screw", (having a hex head on it,) could also make a tap and would be much easier to use rather than a flathead slotted screw.
The epoxy plugs are not going to pull out.
You mentioned the huge force needed on a screw.
The pilot hole was too small, the precious poster who spoke of going-up in sizes by 64ths to achieve proper fit is correct.

[Uncle Bob]

Originally Posted by Bowdrie

Ok, in a 5/16ths shank wood screw the thread pitch is greater than any tap you could get.
If you want tapped threads that means going to a machine screw.
Hold off going to the bank.
There is a trick that you might try first on a couple of holes.
Do you have, or can you get access to a Dremel or a die grinder?
If so, you can take one of your woodscrews and using the tool with a little cut-off wheel you can cut 3>4 grooves lengthwise on the screw.
What that will do is convert that screw into a tap that you can use on all the holes just like a machine screw tap.
Now, if the thread pitch matches, (and diameter,) a "lag screw", (having a hex head on it,) could also make a tap and would be much easier to use rather than a flathead slotted screw.
The epoxy plugs are not going to pull out.
You mentioned the huge force needed on a screw.
The pilot hole was too small, the precious poster who spoke of going-up in sizes by 64ths to achieve proper fit is correct.

Oh OK, why would one not just use the correct fasteners and tools to do the job relatively quickly and efficiently, rather than trying to create a tool to do a job that can be done better and quicker properly.

[Bowdrie]

Originally Posted by Uncle Bob

Oh OK, why would one not just use the correct fasteners and tools to do the job relatively quickly and efficiently, rather than trying to create a tool to do a job that can be done better and quicker properly.

The OP already stated that he did not wish to take out a mortgage for new fasteners, i.e., machine screws.

Addendum for the OP.
Many years ago, Wooden Boat magazine had an article that gave the withdrawal resistance of various sizes of wood screws.
IIRC, a #14 that was sunk 2" into edge grain oak held over 500lbs.
Withdrawal resistance is not as big of an issue as you might think for your application.
PS. what the $(&# were they thinking using 12" bolts at the ends?

[rkarakai21]

Yeah no idea what they were thinking with many things on this boat, including alot of the deck hardware fastenings, I've pulled up different hardware bits and no sealant to be found under them, thankfully the deck was re-glassed a few years ago and so far I havn't found any serious water damage in the coring. What they did do well was build a pretty damn robust hull, which is why I bought the boat, love how she sails too. I'll find solutions to all the smaller issues, one at a time.

For now, getting these sheet tracks fixed up is my mission.

Thanks for all the varied info/opinions. Always appreciate the community here.

[sailorladd]

Your initial pilot hole should be the same size as the shank of the screw inside of the threads.
you can easily do this by holding a drill bit just behind of the screw and in front of your eye, offer them up to the light to see clearly, the shank of the screw will be blocked out by the drill bit, but the threads of the screw will be visible... sticking out on the sides of the drill bit... I personally would use a hard wood plug, and dip the screw in epoxy before screwing it home....

[Bowdrie]

Originally Posted by sailorladd

Your initial pilot hole should be the same size as the shank of the screw inside of the threads.
dip the screw in epoxy before screwing it home....

Same size as shank is usually for soft woods, hardwoods generally want 1/64th larger.
Sometimes #drill bits can "dial in" the best fit.
Whether face/edge/end grain can affect pilot hole size.
Too small of pilot holes are a common occurrence with amateurs, especially as screw lengths go up.
Dipping screw threads in epoxy does not ensure a weatherproof seal, but it sure can make future removal somewhere between difficult and extremely difficult, that is if you don't first strip the head with the screwdriver.

[Wind River]

I feel your pain. My tracks have 1/4" x 9" long machine screws with nuts on the inside. 30 per side and every one of them needed replacement.
Check Boltdepot.com, they probably have what you need.