Cutting A Hole In My Deck/Chimney

[FamilyVan]

I am looking for pointers on running a chimney through my deck. I get the chimney part, it's well laid out in several manufacturers web sites. The problem is the hole.
There is an already existing chimney whole for a propane hot water heater that is being replaced with electric/cooling water. The inch there is 3 1/2 inch and in the right place (Or rather, I'm placing the stove beneath it). The Chimney hole I need is 5". So it won't be a new hole, just resizing and repurposing an existing hole.
The portion of deck that is being cut is on the coach house (there was no way I was touching my teak decks). It is 1 1/2 inch fibre glass with balsa core. I understand to finish the whole, I coat the core with 2 part epoxy, so I get that part.
The part I'm not clear on (probably because it's obvious to every one but me and is therefor not written down anywhere), is what tool am I using to cut the hole? Should I be getting myself a big hole saw?
Any other pointers are handy.The stove is a Pet Coal/Charcoal stove, 3" flu.
Thanks

[GordMay]

Yes, use a hole saw.
Fasten a piece of 1/2-inch plywood over the existing hole. Then bore into the plywood and through the hole behind it. The plywood will hold the pilot bit on track until the saw starts cutting.
Or you can use two hole saws on one arbor (telescoping hole saws). Use one smaller hole saw the size of the original hole and a larger hole saw the size of the new hole, with the smaller protruding at least 1/2" beyond the larger one.

[FamilyVan]

Perfect, Thanks. Can you think of any reason I'd want to use the Dickinson or other marine stove pipe, instead of the 3" Pellet Vent stuff from Home Depot (it's like half the price)?

[Cheechako]

making the 3.5 hole to 5 may be easier with a good sabre saw.... you're gonna need an expensive 5" hole saw and BIG drill motor to use the 5" hole saw.

[model 10]

Originally Posted by Cheechako

making the 3.5 hole to 5 may be easier with a good sabre saw.... you're gonna need an expensive 5" hole saw and BIG drill motor to use the 5" hole saw.

Yeah, unless you already have hole saw mandrel and a good 1/2" drill, a sabre saw will be a more useful tool to have around. The 5" hole saw will probably be a one time tool. There is no reason that you can't cut a nice hole with a good sabre saw. Especially with the core removed.

[roverhi]

Went with a hole saw to cut mine. Seem to remember it cost around $50. Couldn't use a saber saw because of stuff around the location on deck. Thought it would be one time use and then I'd sell it on Ebay but it's come in handy a couple of other times for cutting holes on and off the boat. You don't need a huge 1/2 inch drill but you do need one with an auxillary handle to counter act the torque of the drill motor. Used an old consumer grade corded 1/2 inch drill but have used a battery powered drill for slightly small hole saw cuts. Was surprisingly easy and quick to cut through the deck skins and 1/2" balsa core. You will need something for the pilot bit to bite into. Used scraps of wood cut so it could be jammed into the existing puka . Once the hole saw has cut into all sides of the hole, the pilot drill doesn't do much except tell you when you are getting close to going all the way through.

[robert sailor]

When you cut that hole make sure to remove a portion of the deck coring and fill it full of epoxy mash so that water can never get inside the deck core. Then install your deck cap etc.

[misfits]

Originally Posted by FamilyVan

Perfect, Thanks. Can you think of any reason I'd want to use the Dickinson or other marine stove pipe, instead of the 3" Pellet Vent stuff from Home Depot (it's like half the price)?

The pipe I've seen for pellet stoves (type L I believe) is double wall, looks like B-vent which is used for gas equipment. Using this for a charcoal/coal stove will put you in harms way.

[Mikado]

Harbor freight has an 18 piece hole saw kit for $15.00 including 5". If I were you I would go with Gord's recommendation and make sure you epoxy the exposed core to prevent water intrusion.

Carbon Steel Hole Saw Set 18 Pc

[mitiempo]

Originally Posted by Mikado

Harbor freight has an 18 piece hole saw kit for $15.00 including 5". If I were you I would go with Gord's recommendation and make sure you epoxy the exposed core to prevent water intrusion.

Carbon Steel Hole Saw Set 18 Pc

Looks like it will survive one hole.

[FamilyVan]

Originally Posted by misfits

The pipe I've seen for pellet stoves (type L I believe) is double wall, looks like B-vent which is used for gas equipment. Using this for a charcoal/coal stove will put you in harms way.

Could you expand on this please? I am not familiar with this language. In what way will it put me at risk?
The stove people recommend 3" flu.
I do believe I will go with the hole saw. I'm not going to buy anything, I'll borrow. I have the advantage of working with a half dozen marine engineers (unfortunately they don't have much advice on installing a wood stove on a sailboat).
Thank you all for the pointers, unfamiliar territory for me here.

Sent from my SGH-I547C using Cruisers Sailing Forum mobile app

[a64pilot]

Any chance of getting SS pipe? I know when you heat regular carbon steel for some reason it makes it very active for corrosion, I think regular stove pipe will be a mess of rust very soon.

Is the marine stove pipe SS?

[misfits]

Originally Posted by FamilyVan

Could you expand on this please? I am not familiar with this language. In what way will it put me at risk?

Flue piping is rated for it's intended application. Pellet stove pipe is not rated for wood, charcoal or coal. These fuels burn much hotter than wood pellets. If you think about pellet stoves, they have a blower on them to complete the combustion cycle & exhaust the flue gases. This blower keeps the temperature of the flue gas exiting the "chimney" lower when compared to a "solid" fuel. I'd hate to see someone use the wrong flue material due to price only to create a hazardous condition on their boat.

[ssanzone]

I know you are looking to repurpose an existing hole...

Have you considered that the wood stove will be exhausting soot and a lot more heat than the old diesel? Is the hole you are expanding for the stove vent properly placed for wood stove exhaust?

If, you choose to move the stove, cut the new 5" hole and from that cut a 2nd 3" hole and use the 3" hole to fill the original hole.

I have entertained the prospect of added a vented heating source (diesel / wood) but would have to vent just aft of my mast and I dont want to be discharging heat onto my wrapped up mainsail while not underway.

-steve

[FamilyVan]

Originally Posted by misfits

Flue piping is rated for it's intended application. Pellet stove pipe is not rated for wood, charcoal or coal. These fuels burn much hotter than wood pellets. If you think about pellet stoves, they have a blower on them to complete the combustion cycle & exhaust the flue gases. This blower keeps the temperature of the flue gas exiting the "chimney" lower when compared to a "solid" fuel. I'd hate to see someone use the wrong flue material due to price only to create a hazardous condition on their boat.

Okay, thanks, I'll stick to SS I think then.

SSanzone
Yes, I think the old propane hot water heater hole is well placed. It's well out board only about 12" aft of my mast, no sails should get close to the hot gasses.

However, this hole discussion might be going a new direction. I've recently discovered the Sigmar 190 diesel stove. It will fit nicely into the spot I need and is priced below $1000. It's 19000 BTU and I live aboard on the great lakes year round. Since I have a 500 litre (125 gallon) diesel tank, it is probably much more practical.

This still means cutting a hole in my roof though!