Go Back   TeamTalk > Maintenance Tips, How-tos and Refurbishing Topics > General / Other

Reply
 
Thread Tools Display Modes
  #1  
Old 10-15-2020, 01:35 PM
williamsatown's Avatar
williamsatown williamsatown is offline
TT Regular
 
Join Date: Sep 2020
Boat: No
Location: Southeast
Posts: 43
Best way to drill hull

Hey guys,

What do you typically use to drill out a hull for larger diameter holes?

Iím installing some of the Mastercraft pull-up cleats and they look like a 3/4Ē diameter. I drilled into the gelcoat of an old Supra once for a simple Bimini top attachment and it broke apart a splintered some even at low drill speed with a new bit. It wasnít a clean and smooth hole in the end.

I know it is a hole and will be covered, but I donít want to create a future problem with such a large diameter.

Thanks for any suggestions and sizing help if you happen to know the diameter of those mounting posts. I got them from Marine Depot Direct and another member on here.

Thanks
Ben


Sent from my iPhone using Tapatalk
Reply With Quote
  #2  
Old 10-15-2020, 01:37 PM
clrussell's Avatar
clrussell clrussell is online now
MC Addict
 
Join Date: Jul 2012
Boat: none
Location: midwest
Posts: 6,305
Good quality hole saw.

Painting tape over the area, run backwards, then forward once through gel
Reply With Quote
  #3  
Old 10-15-2020, 01:39 PM
Strreamline Strreamline is offline
TT Enthusiast
 
Join Date: Aug 2016
Boat: 1988 Mastercraft Platinum Prostar 190
Location: Canada
Posts: 249
Quote:
Originally Posted by clrussell View Post
Good quality hole saw.

Painting tape over the area, run backwards, then forward once through gel
This is exactly what I did when I installed my pop-up cleats and it worked perfectly.

Do better than I did tho, really inspect underneath where you're mounting them (BEFORE YOU DRILL), so the support braces doesn't interfere with the mounting hardware.
Reply With Quote
  #4  
Old 10-15-2020, 01:40 PM
carlsonwa's Avatar
carlsonwa carlsonwa is offline
MC Fanatic
 
Join Date: Aug 2009
Boat: 2006 Prostar 197 TT
Location: Minnesota
Posts: 759
Tape over the area and use a nice new sharp forstner bit.

https://www.homedepot.com/p/DIABLO-3...-005/100098840


To make sure you don't have any interference with something in the back. I used a couple of high power magnets to be certain i knew exactly where my hole would come thru.

My Prostar had black ABS pads "pre" fiber glassed into the hull. I aimed right for the middle of them.
Reply With Quote
  #5  
Old 10-15-2020, 01:43 PM
williamsatown's Avatar
williamsatown williamsatown is offline
TT Regular
 
Join Date: Sep 2020
Boat: No
Location: Southeast
Posts: 43
Thanks Guys!

Baby steps for me. I look at the mechanical posts on here and it makes my head spin!


Sent from my iPhone using Tapatalk
Reply With Quote
  #6  
Old 10-15-2020, 11:21 PM
FrankSchwab FrankSchwab is offline
MC Devotee
 
Join Date: Aug 2004
Boat: 1998 Maristar 200VRS
Location: Phoenix, AZ
Posts: 2,151
I've been quite successful with step drills (https://www.harborfreight.com/2-piec...lls-96275.html). They self-center in whatever existing hole you have, they drill slowly and controllably, and they leave nicely beveled hole through the gel coat. I run the drill backwards for a couple of seconds with pressure once I get to the right sized hole to melt/smooth the edge of the gelcoat to reduce the likelihood of spider cracks.
__________________
1998 Maristar 200VRS
Reply With Quote
  #7  
Old 10-15-2020, 11:55 PM
mikeg205 mikeg205 is offline
Super Moderator
 
Join Date: Aug 2011
Boat: 1995 Pro Star 205 5.7 Liter
Location: Plainfield - Joliet, IL
Posts: 18,291
Send a message via Skype™ to mikeg205
Starting a pilot hole tape and use a good drill in reverse, reverse prevents grabbing and chipping

Sent from my SM-G955U using Tapatalk
__________________
...A bad day water skiing still beats a good day at work...1995 Pro Star 205....
Reply With Quote
  #8  
Old 10-16-2020, 08:46 AM
CantRepeat's Avatar
CantRepeat CantRepeat is offline
 
Join Date: Jul 2008
Boat: Passively looking for a CSX 265
Location: Roll Tide!!
Posts: 16,178
The issue with pilot holes and hole saws is he is drilling out a small hole to a larger hole so there is nothing to hold the pilot or hole saw in place.

It would be a lot of extra work, but I would suggest glassing in a block of wood to the back side so you can center up on the hole. Use lots of painters tape on the outside, fun the hole saw in reverse until you are through the gel and then continue in forward.

my .02
__________________
-Tim

Making boomers great again!! Boomin'
Reply With Quote
  #9  
Old 10-16-2020, 09:20 AM
barneyferd's Avatar
barneyferd barneyferd is offline
TT Enthusiast
 
Join Date: Aug 2019
Boat: Mastercraft X22 2020 6.2L
Location: Midwest
Posts: 167
i like to take a fine rounded finishing file on a 45 degree angle to the gel at the edge of the hole to make sure there aren't any sharp edges. Follow that up with 1000 grit sandpaper to really smooth it out. Gets rid of any irregularities that can cause stress risers that turn into spider cracks.
__________________
Jerry

2020 X22
2018 XT22
2014 Aqua Patio
2003 Malibu Response LXi
2001 Malibu Sunsetter
1978 Ski Supreme
Reply With Quote
  #10  
Old 10-16-2020, 09:52 AM
Tsumi Tsumi is offline
MC Devotee
 
Join Date: Feb 2012
Boat: 2001 X-star 5.7L LTR, 2000 Prostar 190 5.7L LTR, both dark green
Location: Pacific
Posts: 1,310
I used regular drill bits, since that's what I had on hand. Started small and stepped it up slowly, I think I used in total 6 different bits before getting to the 3/4" bit. Ran in reverse until I was all the way through the gelcoat, then forward through the fiberglass. To finish up, I used a 15/16" bit to chamfer the gelcoat. Just a little bit in reverse to smooth out the gelcoat.

One trick that I found to work well for me is to use a 5/8 bit as your last bit before getting to the 3/4" bit. Put the cleat up against the hole, and if it is out of alignment, you can run the drill in reverse and widen the hole in the direction it needs to go. As long as you aren't too far off and widen it so that it's even on both sides, the 3/4" bit will go in perfectly.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -4. The time now is 11:53 PM.


2020