chamfer??????

trigx5 03-21-2003, 5:31 PM

I'm planning to install a tower on my boat so I've been reading everyones install tips. What's the deal with drilling the holes. It seems like chamfer is the same as counter sinking, what is the purpose of this exactly? The foot plate on my tower seems to have the holes countersunk so the screw head will be flush what's the difference...thanks for the help

chris_hargis 03-21-2003, 6:20 PM

You need to ask James McCallum about this. He is prety smart about this type stuff. He is on the board, so look him up.

(sdboardr99) · (sdboardr99) **Join Date: Aug 2001** 03-21-2003, 6:26 PM

The idea is to avoid having the bolt put pressure on the gelcoat. So you chamfer, or countersink, the the hole. The purpose is to prevent slight movements of the tower from cracking the gelcoat.

(norcalrider) · (norcalrider) **Join Date: Jun 2002** 03-21-2003, 8:20 PM

Countersinking and chamfering get confused. Countersinking is what you do when putting screws in a wood deck. This allows the screws to be flush with the surface of the deck. Chamfering isn't as deep as countersinking Chamfering bevels the edge of the hole. Same basic idea...

(s4inor) · (s4inor) **Join Date: Mar 2002** 03-21-2003, 9:34 PM

Sandpaper works far better for almost every application when dealing with fiberglass.

(atvr) · (atvr) **Join Date: Jan 2003** 03-22-2003, 2:40 AM

Actually I beleive that it you bevel a hole it is a countersink, if you bevel a straight edge it is a chamfer. Anywho, cracks are created from stress risers and initiate from sharp corners. The countersinking of the hole would help but the sandpaper idea is probably better because you can create a round transition from the hole to the gel coat (fillet), ie. no sharp edges.

(lsvlance) · (lsvlance) **Join Date: Mar 2002** 03-22-2003, 2:22 PM

I just finished installing a tower on my boat. The method of drilling that worked best for me was to centerpunch the holes, drill a 5/64" hole, then use a countersink bit to about 7/16" to 1/2" wide (not deep). Then come back with the 5/16" bit, go REAL slow and drill your hole. If the bit starts to dig in....back it up a bit and go back in slowly. Make sure you tape the area off with masking tape first and make sure you've marked the holes in the right spot before centerpunching.

The final size of the hole might be different for you depending on your tower's hardware.

(lsvlance) · (lsvlance) **Join Date: Mar 2002** 03-22-2003, 2:27 PM

This is what CAN happen if you don't countersink (or chamfer) wide enough and your bit grabs.

Also....don't scrimp....buy some brand new, sharp drill bits.

blackhawk 03-22-2003, 7:45 PM

If this will stop the gellcoat problems, what are the heim joints supposed to do? I want to build a tower per "Wakeboardin"'s plans (Modified to fit my boat of course), but I don't know how to mount it. Can anyone tell me how to do this?

(monstertower) · (monstertower) **Join Date: Mar 2003** 03-22-2003, 7:57 PM

OUCH, Just seeing that hurts!
IF you run the drill in reverse until you are though the gelcoat it makes a really clean hole through the gelcoat, once you get into the fiberglass run it the rest of the way in forward.

Also do the chamfer in reverse.

A Chamfer is a drafting term for a angle as shown above. I had never hear about sanding a radius in but that's a great idea.

Bill
www.MonsterTower.com