Difficult Cutting Problem - What Tool Would You Use?

[CatBuilder]

My dagger boards have a big cut out near the top to save weight and put your uphaul lines in, as seen in this picture of a sistership. The dagger board is that yellow thing sticking up near the boom with the big hole in it. (Don't mind the nudity - it's the only picture of the board on my designer's site):



The part of the board where the cutout is is about 5-6 inches thick, so I can't cut it with a jigsaw. No blade on my circular saw will reach. In fact, nothing will reach through, except a Sawz-All.

I made one of the cut outs yesterday using a Sawz-All or reciprocating saw like this:



However, the blade of the Sawz-All bent on one part of the cut, making a good cut on the side facing me, but a cut that was 1-2" off on the side facing away from me. It's way too big of a cutout on the side facing away and now I have to stick the foam back in with bog and do a repair on the glass to get the hole back to the right size on the "bad side."

My question is:

Is there a better tool???

How can I cut out a hole in the center of a fiberglass and corecell part that is 5"-6" thick?

What tool would you use to do it?

Is there some special tool I can buy?

This is the only cut of its type on the whole boat build. The rest are through 1" or 2" thick material.

[Wingandaprayer]

Once you have a starting through cut with the Sawzall, switch to a Japanese hand saw. They cut on the pull, not on the push and are not subject to blade bending such as you have been experiencing. Also, with the thin blade on Japanese hand saws, you are cutting less material and therefore need less effort to get where you are going. Only drawback is that you'll basically have to throw the saw away after cutting that much glass.

~~ I hate being right all the time, but what's the alternative? ~~

[BATAAN]

Cut using the Sawzall at such an angle that it is inside the line on the back side of the board, then cut again on the other side. Sawzalls don't do very well at trying to cut thick stuff precisely since they only have one guide, so you make an intentional error into the waste material the first time through getting the bulk of the hole cut, then go back and cut the rest away from the other side to its line.
A hole saw worked from both sides through a pilot hole will do the rounded corners of the cutout best.

[Scrumble]

For acuracy, use a Bosch multitool and cut from both sides. See my use on my blog, use the metal blades through epoxy and glass.

[Sand crab]

I'm a home builder and have used this method for cutting beams especially when the cut will be seen. It takes 2. One is running the sawzall and the other is holding the pliers on the other side to keep it tracking straight. Set the pliers or Channelocks so it is just wider than the blade and hold from the back of the blade. These act as a guide similar to what's on jigsaws and bandsaws. Practice on scrap first but almost no learning curve. Really fast easy and cheap. BOB

[rberrey]

Buy a cutting dic (matavo) for your grinder, your mini grinder might not cut though 5"so a big grinder. Place painters tape on the area your going to cut , mark your line on the tape, cutting though the tape will reduce chipping.

[BATAAN]

Originally Posted by Sand crab

I'm a home builder and have used this method for cutting beams especially when the cut will be seen. It takes 2. One is running the sawzall and the other is holding the pliers on the other side to keep it tracking straight. Set the pliers or Channelocks so it is just wider than the blade and hold from the back of the blade. These act as a guide similar to what's on jigsaws and bandsaws. Practice on scrap first but almost no learning curve. Really fast easy and cheap. BOB

That is a very nice example of thinking in a direct fashion and getting the job done, thanks. There's always a different way, if you have a good helper. It looks like the cutout in the daggerboard behind the naked people has radiused corners so what works for cutting a beam straight might not for what's ideally a bandsaw job. I'm not familiar with the new tools like the Bosch which seem to do some difficult jobs easily, so cannot comment on them. The usual shipyard approach if you don't have the right tool is ask the boss to buy it, when he says no you go ahead and hack it out with what you have (and hurry up!), being quite careful to err on the side of the waste material, then using whatever's necessary to finish, which for glass over foam is abrasive things. Oh and your helper is busy helping haul out a big awkward sailboat on the decrepit old marine railway and you have to do it alone (why aren't you done?!). I'd probably get it close to the line with holesaw from both sides guided by a carefully squared pilot hole in the radiused corners, removing the bulk of the waste with the sawzall but leaving some fudge factor room , at least .25 inch of safety material, at the line. Then use a beefy stiff fairing block with 60 grit glued to it, working from both sides inward (don't strip lam from foam) to a high point at the foam, getting the glass skins right to the line and leaving some foam till the last thing, then carefully using the block, and round ones for the corners, to square things up last.
Not the way a machinist or a well equipped yard would do it, but I'd be done in a couple of hours and we could move on to glassing while the machinist was still trying to build a jig for his router to achieve a job that would be maybe 5% more 'perfect' in the end.

[Charly]

Use a circular saw! cut the radii with a hole saw first, then flip it over

where do the uphaul lines go?

[CatBuilder]

Thanks for all the ideas. Seems I'd make a make a great shipyard boss on this project because I keep thinking and saying all the things BATAAN wrote in his post! (hurry up! too expensive!)

I'll probably pick BATAAN's way, since this is the only cut to make like this and I'd like to use the tools I have (too expensive!) and get it done tomorrow (hurry up!).

One thing I'm using is a belt sander inside the hole to square up the cut and take it back to the line. Works great.

And, yes... the cutout has rounded corners that I also tried with the Sawzall. Big mistake there too.

I'll just have to fix the bad cuts and use a hole saw on those corners.

Good advice!

Originally Posted by BATAAN

That is a very nice example of thinking in a direct fashion and getting the job done, thanks. There's always a different way, if you have a good helper. It looks like the cutout in the daggerboard behind the naked people has radiused corners so what works for cutting a beam straight might not for what's ideally a bandsaw job. I'm not familiar with the new tools like the Bosch which seem to do some difficult jobs easily, so cannot comment on them. The usual shipyard approach if you don't have the right tool is ask the boss to buy it, when he says no you go ahead and hack it out with what you have (and hurry up!), being quite careful to err on the side of the waste material, then using whatever's necessary to finish, which for glass over foam is abrasive things. Oh and your helper is busy helping haul out a big awkward sailboat on the decrepit old marine railway and you have to do it alone (why aren't you done?!). I'd probably get it close to the line with holesaw from both sides guided by a carefully squared pilot hole in the radiused corners, removing the bulk of the waste with the sawzall but leaving some fudge factor room , at least .25 inch of safety material, at the line. Then use a beefy stiff fairing block with 60 grit glued to it, working from both sides inward (don't strip lam from foam) to a high point at the foam, getting the glass skins right to the line and leaving some foam till the last thing, then carefully using the block, and round ones for the corners, to square things up last.
Not the way a machinist or a well equipped yard would do it, but I'd be done in a couple of hours and we could move on to glassing while the machinist was still trying to build a jig for his router to achieve a job that would be maybe 5% more 'perfect' in the end.

[rberrey]

A sawzaw is not used often for finish work, it,s to hack somthing out that you cant get to with a skillsaw or other cutting tool. Step by step would be to drill the holes in the corners, cut your stright cuts from both sides , use your jig saw in the corners both sides. Rember the painters tape , just like you use cutting a counter top. Rick

[CatBuilder]

Originally Posted by Charly

Use a circular saw! cut the radii with a hole saw first, then flip it over

where do the uphaul lines go?

That could work too. Hole saw to cut the radii, then draw lines between the circle tangents in each corner. Simple!

But... neither the circular saw nor the hole saws can go through 5-6" of foam core. Just whack that out or cut it with a hacksaw blade then?

Do we have the same foil plan, Charly?

If so, there is a stainless eye bolt bedded into this cutout (into the core at the bottom of it) with structural bog. Then, as you seal up the core, you glass over the bog holding the eye bolt. This is your uphaul. I am assuming the line for it lives in that cutout area.

[CatBuilder]

Originally Posted by rberrey

A sawzaw is not used often for finish work, it,s to hack somthing out that you cant get to with a skillsaw or other cutting tool. Step by step would be to drill the holes in the corners, cut your stright cuts from both sides , use your jig saw in the corners both sides. Rember the painters tape , just like you use cutting a counter top. Rick

A little voice in the back of my head kept telling me that too, as I was cutting. It felt wrong.

I don't need that painter's tape in this case because I have to glass back over the newly exposed core, bringing it around the edges. That'll take care of any stray glass filament that might catch a blade.

[Charly]

Circular saw set at the deepest cuts 2-1/2 or so inches. should be close enough to just cut the middle with a handsaw or something.

I understand the bog anchor embedded in the foam part, but I have been wondering what to do with the uphaul line itself after it exits

[BATAAN]

Use as fine toothed a skilsaw blade that will work, not a coarse general purpose blade. Some carbide blades intended for cutting aluminum work very well in finish work on other materials. Did all the finish work for a whole bookstore once in oak shelving, about 1000' of highly finished shelf, using a chop saw with a 144 tooth aluminum cutting blade and the edges were very smooth with no tear out. I suppose a circular saw will work fine but remember it's pulling up and trying to peel the glass from the foam, so use fine teeth and go slow and let it cut.

[BATAAN]

Originally Posted by Charly

Circular saw set at the deepest cuts 2-1/2 or so inches. should be close enough to just cut the middle with a knife or something.

I understand the bog anchor embedded in the foam part, but I have been wondering what to do with the uphaul line itself after it exits

goes to a fixed block that turns it parallel to deck and through stopper to winch.