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wbarksda
04-26-2010, 09:23 AM
I am adding 2 vents to the side of my LSV and need to know what to use to cut through the viber glass and where to get it. Went to Lowes yesterday and they didn't have too many options.

mmandley
04-26-2010, 01:11 PM
What are you cutting and how big is the hole?

Some pictures of the vents you want to install or something to help us out. Lots of people here have cut holes in the boats and can help, just need an idea of exactly where and what your installing.

wbarksda
04-26-2010, 01:16 PM
A 1" vent next to the bilge and another indenticle one on the other side. They will have the same rubber piece as the bilge

Razzman
04-26-2010, 01:20 PM
Forstner bits make very clean and crack and split free holes. You can also use a hole saw but you do risk the chance of gel chipping with the larger teeth of the hole saw. Just remember to take it slow and that regardless of what you use start from the outside with the bit/saw in reverse until your through the gelcoat into the fiberglass. You can then reverse it and drill forward until through. I've heard some say they drill in reverse all the way through but there's no benefit to that. Make sure to clean/chamfer holes on the exterior when done.

mmandley
04-26-2010, 01:22 PM
Ahh ok cool. You will want to buy 1inch circular hole saw. You can buy these in many kits at many places.

Harbor Freight is the best place for things like this as they are cheap but still decent enough for these applications.

Or just go to any tool shop tell them you are looking for hole saw kits or blades, tell them you want a 1inch. These are the same blades used to make door handle holes in your home.

Tape the area you want to drill off, then run the drill in reverse, let the drill do the work, don't press into it till its in the fiberglass. The Gell coat is very brittle and this is why you drill in reverse.

After your hole is don't peel the tape away and you should have a perfect non chipped hole.

something like this is best. http://www.automationdirect.com/adc/Overview/Catalog/Tools/Hole_Cutting_Tools/Multi-Purpose_Hole_Saws_%28HSS_-a-_Co_8%29_-a-_Accessories;jsessionid=5e30c825509570924afe23601c 4204c3a155?source=google&keyword=hole%20saw%20blades&type=search&gclid=COeDm7_jpKECFR5Ogwod2me3vw

I use blue painters tape. Normally 3 layers.

mmandley
04-26-2010, 01:27 PM
Forstner bits make very clean and crack and split free holes. You can also use a hole saw but you do risk the chance of gel chipping with the larger teeth of the hole saw. Just remember to take it slow and that regardless of what you use start from the outside with the bit/saw in reverse until your through the gelcoat into the fiberglass. You can then reverse it and drill forward until through. I've heard some say they drill in reverse all the way through but there's no benefit to that. Make sure to clean/chamfer holes on the exterior when done.

I haven't tried the forester bits yet. I have them. I was thinking with the 2 cutting edges as they spin it would be a bigger problem. I know it would cut faster then a hole saw bit. I need to cut 2 of these same holes in the boat still. Maybe ill try a forester bit next.

cab13367
04-26-2010, 04:19 PM
I drilled the hole below using a 4" hole saw run in reverse. I used two layers of regular masking tape on the gelcoat. Make sure you drill the hole perpendicular to the gelcoat so the holesaw hits it flush. Just take your time, and hold the drill square and plumb and you'll be alright.

I have two of those plastic drain fittings left over from when I replaced them with stainless so if you want them, they are yours for the cost of shipping.

Let me know.

Al

http://i250.photobucket.com/albums/gg276/cab13367/IMG_6373.jpg

Razzman
04-26-2010, 04:31 PM
I've got three of those black plastic thru hulls sitting in the garage as well now that you mention it.

wbarksda
04-27-2010, 09:02 AM
Thanks for the offer Al and Razz but I already have the pieces and got most of the ballast system done last week. I left the factory through hull but that was about it. We put in a new manifold and 3 reversible pumps for the new 750 lbs in the back lockers and changed out the factory pump for the ski locker as well. Now all we have left is to drill a couple vent holes in the sides. Thanks for all the info!

cab13367
04-27-2010, 10:33 AM
Could u pls describe ur ballast system upgrade in a litle more detail and post up some pics if possible?

Thx.

Al

ian ashton
04-27-2010, 10:53 AM
I'd go with the forrester bit as well, thats what I've used in the past without issue.

Hole saws scare me, haha.

jasonwm
04-27-2010, 04:45 PM
DO NOT USE A Forstner BIT!

They are great for drilling through non-brittle material like wood (which they're made for) and even work well for drilling through fiberglass, but are absolutely the wrong tool for drilling through gelcoat.

The correct item to use is a standard hole saw bit, just remember that it needs to be sized for the outside diameter of the fitting that will be installed (which is different from the marketed size). For example, most 3/4" thru-hull connectors will require a 1" hole be drilled.

Al's instructions are fairly comprehensive, although there's no reason to drill the entire hole in reverse. Once you get through the gel coat you can switch to forward which will significantly reduce the amount of wear your bit is subjected to.

Robin (wbarksda) worked with us to create a hybrid system to upgrade his GI factory solution to a new GIII setup with reversible flexible vane impeller pumps for all three bags fed from the factory thru-hull. If you want any additional information about the layout of the system I'm sure Robin can provide it, if not I'm happy to help out where I can.

Robin, did you guys decide to keep the factory thru-hull in place, or upgrade it with the larger fitting we sent?

How did the rest of the system go?

Razzman
04-27-2010, 05:09 PM
DO NOT USE A Forstner BIT!

They are great for drilling through non-brittle material like wood (which they're made for) and even work well for drilling through fiberglass, but are absolutely the wrong tool for drilling through gelcoat.

The correct item to use is a standard hole saw bit, just remember that it needs to be sized for the outside diameter of the fitting that will be installed (which is different from the marketed size). For example, most 3/4" thru-hull connectors will require a 1" hole be drilled.

Al's instructions are fairly comprehensive, although there's no reason to drill the entire hole in reverse. Once you get through the gel coat you can switch to forward which will significantly reduce the amount of wear your bit is subjected to.

Robin (wbarksda) worked with us to create a hybrid system to upgrade his GI factory solution to a new GIII setup with reversible flexible vane impeller pumps for all three bags fed from the factory thru-hull. If you want any additional information about the layout of the system I'm sure Robin can provide it, if not I'm happy to help out where I can.

Robin, did you guys decide to keep the factory thru-hull in place, or upgrade it with the larger fitting we sent?

How did the rest of the system go?

Jason, i have to agree to disagree. I'm not shy about drilling into a boat consequently I've probably drilled over two dozen holes through gelcoat in half a dozen different boats from new to old with a forstner through the hull, transom and deck without one issue. I could see a potential problem if you used a dull bit but then that would apply to ANY bit or saw. When drilled in reverse as ANY bit should through the gel a forstner drags it's razor edge across the gel to the perimeter of it's sharp radius blade, not biting into it.

But then this is what i do so if anyone is shy about drilling in the least then do your own thing or whatever makes you comfortable.

jasonwm
04-27-2010, 06:29 PM
I completely respect your opinion, and probably should have qualified my response a little more. For someone with as much experience as you I'm sure a Forstner bit is no problem.

I try to answer questions on the forum for the masses though, and for someone that is going to go out and buy a bit specifically for this reason a hole saw is absolutely the safest/easiest/best option. Because a hole saw bit scribes a circle in the gelcoat, there is virtually no chance damage will extend outside the diameter of the hole that is being removed. Additionally, the duller the bit the less chance of doing damage (which I think you'll agree is definitely not the case for a Forstner).

Anyway, if you're having success using a Forstner bit (or any other for that matter), I'm not telling you to go out and waste money on something else. If you need to drill a hole in your boat and don't have any experience or don't already own a bit, then the correct sized hole saw bit is what you want to go buy.

brain_rinse
04-27-2010, 06:38 PM
Thanks for the offer Al and Razz but I already have the pieces and got most of the ballast system done last week. I left the factory through hull but that was about it. We put in a new manifold and 3 reversible pumps for the new 750 lbs in the back lockers and changed out the factory pump for the ski locker as well. Now all we have left is to drill a couple vent holes in the sides. Thanks for all the info!

So why keep the factory thru-hull? Since it is only 3/4" ID I'd see that as a limiting factor in your system. Even if you didn't want to drill a new hole a 1" will fit without modification.

jasonwm
04-27-2010, 06:53 PM
If you remove the factory thru-hull you need to deal with the four holes left in the hull from the screws used to secure the scupper. A lot of people don't want to deal with that hassle (even though simply reinstalling the screws with some sealant is sufficient to prevent problems).

3/4" is right at the limit for a single Jabsco or Johnson pump, so that's an adequate installation setup, although 1" would certainly be a safer solution (we supplied Robin with a new 1" intake fitting if he chose to go that route).

Razzman
04-27-2010, 07:36 PM
I completely respect your opinion, and probably should have qualified my response a little more. For someone with as much experience as you I'm sure a Forstner bit is no problem.

I try to answer questions on the forum for the masses though, and for someone that is going to go out and buy a bit specifically for this reason a hole saw is absolutely the safest/easiest/best option. Because a hole saw bit scribes a circle in the gelcoat, there is virtually no chance damage will extend outside the diameter of the hole that is being removed. Additionally, the duller the bit the less chance of doing damage (which I think you'll agree is definitely not the case for a Forstner).

Anyway, if you're having success using a Forstner bit (or any other for that matter), I'm not telling you to go out and waste money on something else. If you need to drill a hole in your boat and don't have any experience or don't already own a bit, then the correct sized hole saw bit is what you want to go buy.

I'll concur with you there Jason, the hole saw is the safer method. A forstner does requie a bit of skill which i should have quantified as well. A pilot hole is also a must to prevent walking. Forstners will pull into the material and can be intimidating if you're not used to them.

So in reflection a hole saw is probably the better bet for the first timer hull driller.

brain_rinse
04-27-2010, 10:29 PM
If you remove the factory thru-hull you need to deal with the four holes left in the hull from the screws used to secure the scupper. A lot of people don't want to deal with that hassle (even though simply reinstalling the screws with some sealant is sufficient to prevent problems).

3/4" is right at the limit for a single Jabsco or Johnson pump, so that's an adequate installation setup, although 1" would certainly be a safer solution (we supplied Robin with a new 1" intake fitting if he chose to go that route).
It sounded like there was a manifold and 3 pumps all pulling from that intake though. I would think that would really hurt your flow.

wbarksda
04-28-2010, 10:01 AM
I am not Robin but his son. Jason, we just left the factory thru-hull on for now to see how it goes. If I remember correctly we should have enough flow to run two of the pumps at the same time without an issue. I tore my ACL a few summers ago so our boat has basically turned into a "surf" boat therefore two pumps at a time is all we need. For the occasional wakeboarding session it will just take a little longer to fill the third bag. Everything else went pretty smooth and took us most of Saturday and Sunday to do but we didnít want to risk the gel coat without knowing what to use to drill the holes.