Different Wisdom

[somewhereinusa]

You sir, are a true craftsman.

[rlaggren]

I thought FRP = Fiberglass Reinforced Plastic = (common name) fiberglass...

GRP = Glass Reinforced Plastic = (common name) fiberglass...

Don't know what those 4x8 sheets at the box stores are made like. Maybe just grind a little, see how deep that smooth gel coat goes; normally when fabbing fiberglass you'd want to get beneath the gel and attach onto the "structural" glass.


Rufus

[Lostranger]

I'm to the point of installing a chimney for my wood stove. The stove takes 4" pipe. I'm looking at the Selkirk chimney parts recommended by Andrew at Navigator Stove Works, but I'm not sure about getting through the roof. The BCS Andrew suggested looks like it is for getting through a residential ceiling rather than a mobile roof. I'm planning on 12" of insulated pipe and a cap above the roof. I need something that's fire save, won't leak, and won't come apart at 65 mph. Any suggestions? I don't mind fabricating something out of SS, but I need some ideas.

Jim

[Lostranger]

After I posted the chimney question, I began having visions of a SS top hat-style thimble made of 8" tube. The "brim" and "top" of the hat would be SS plate at least 11g. All this would bolt to the roof, and a 4" SS tube would pierce the hat bottom to top. I'd fill the space between the tubes with something like vermiculite before welding on the top. What do you think, Jack? Anyone?

[Dusty]

Leave an air gap (1") between the inner and outer flue.

Have the outer go several inches below and above the roof.

I could take a pic of my finished instal if it would help.

[Lostranger]

Dusty, I'd love to see photos.

[Dusty]

Its a nice sunny day so I will do that now

[Dusty]

Hmmm ... it's amazing how bad this looks in the light of 20yrs of use and a couple of hasty repaints . LOL

However it never leaked.

I cut the roof and the inside lining for a tight fit with the outer flue , the outer roof hole is just a little smaller than the flue then gently hammered up a little to a curve so the flue just slides in with a bit of a bump with a block of wood . Then a quality sealer gooped around the edge. 2 pac paint over everything.

edit ; the top hat is just a saucepan lid



the riveted tabs are just to make sure nothing moved as the sealer dried . The tight fit seems to hold it all together, I know its not very flash , but it worked.







I hope that is of some use to you, I just know you will do a better job than that , eh.

[Lostranger]

Dusty, you're a prince, and you've given me much to work with. Thanks for taking the time to offer such help. Maybe we can get our busses together someday. I wonder what size pontoons it would take for me to make that crossing.

Jim

P.S. I'm going to try to post a photo of the stove in progress. For perspective, the bottom chamber is 10x10x15 inches, and the top part is 6x6. It will have a 4" flue.



And here's the original design:

[Lostranger]

And before anyone gets the wrong idea, this is not my shop, and I did not build the stove. My friend, Jason, designed it, and his high school welding students are building it. All I've done is procure some of the material.

But with that said, I'm already planning the next version. This stove is generating a lot of interest among preppers. Once we use it a while and correct any bugs, I'm probably going to set up to build a few for sale.

Jim

[Dusty]

That looks great , while you are considering improvements for the next version , consider a larger flue , you may well find that the 4" is forever getting clogged and needing sweeping .
My fire in the range is smaller than this and my flue is 6" . I still have to do frequent cleaning , mostly I think, due to the need to damp the fire down so I don't get too hot in the bus , this of course makes the flue run cooler , then the soot builds fast, and if a bit of gummy pine is inadvertently put on the fire ...........

Oh, and will you have enough room to put the kettle on the top ?

[Lostranger]

Oh, and will you have enough room to put the kettle on the top ?

Oh, yes, my friend. What good would a wood stove be without room for the kettle?

As for flue size, our inspiration for this baby is the cast iron "Little Cod" by Navigator Stove Works. The fire box is about the same size, and a 4" flue works great in them. I don't plan to throttle the stove excessively and go for long run time. Instead, I'll build several hot fires each day and let its considerable thermal mass do the radiant thing in between. I'm up a couple of times every night to deal with certain hydraulic issues, so tending the fire at night won't be a problem. I have plenty of dry hardwood available, and we'll refrain from burning any of the native conifers, even though I have lots of yellow pine on the place.

I'm sure the flue will need still to be cleaned a few times each season, but compared to most of the ones I've tended in the past, this will be a breeze.

Thanks again, Dusty, for your help. How's the motor swap coming?

Jim

[Stealth Camper]

A few years ago, I built a small trailer (20 ft) as a commercial kitchen with fryers, vent hood, etc. (Concession trailer). The vent duct required a fire proof insulation that I thought would be extremely difficult to build. Turns out, "they" make such a thing. Little pricey if you have to do very much, but the vent I made was only about 4 ft long and 16" x 16" square - I welded it up out of 16 ga SS sheet. (I think 16 ga was code at the time...) Bought the fire wrap at a local distributor and have been very happy with it. Rated to 2000 degrees or so....eases my mind!! When I do my next wood burning stove setup, this is what is going around the flue. Maybe a couple layers.

Wrapped the insulation around the duct and clamped it in place with long SS hose clamps. Overlapped with second layer where the clamps were.

They also made a little spike stud (about 2" long) that could be kind of riveted/staked on to the duct that would allow the insulation to be 'pushed' onto the stake and hold position while setting clamps. I tried a couple, but found it easier in my deal to just clamp it....leaving a very thin crushed spot that had to be covered.

This is the stuff I used...
http://firesafetyplus.com/firemasterfyr ... ation.aspx

This is the manufacturer - may be a better reference - the above link has a lot of other stuff. Interesting, but not necessarily pertinent.
http://www.fyrewrap.com/

[Lostranger]

Finally, I have a wood stove report:

Heat has been our top priority lately. Weather turned unseasonably cold in early November. We've had many nights with temps in the low twenties, and several in the mid teens. We've been heating with a couple of unvented radiant propane burners. We've not frozen, but we've been far from comfortable. Condensation has kept everything damp. Our bed is under an uninsulated section of roof, and so it rains on us all night while we sleep. Imagine how happy my wife is about that. To add insult, we've spent a small fortune on fuel and trips to the hardware store to have 20lb bottles filled, but that's changed now.

I've had the finished stove for almost a month. It's been set up under my open shed, and I've been learning to use it. I've also made a couple of technical improvements, but I'll get to that.

The problem, as I stated in an earlier post, was installing a safe and satisfactory chimney. Dusty's photos helped my thinking immensely. I'll walk through what I did in case it may interest someone else.

After figuring out where I could put the flue and measuring clearances, I started with an 8" section cut from an old oxygen cylinder. This is great tubing: seamless, 9" OD, 1/4" wall thickness.



Then I cut a 16" circle from 1/8" steel plate:



With a hole in the middle of the plate, the combo looked like this:



The roof slopes slightly, so I measured that with a level and a sliding bevel so I could compensate when I welded my new thimble together:





The primer is Duplicolor engine paint from a rattle can.

Until this point, I had planned to use 4" insulated chimney pipe sold by Navigator Stove Works in spite of the fact that the Canadian manufacturer of this pipe told me that it is not appropriate for mobile application. This pipe has a 6" OD and would have worked fine through my 8.5" ID thimble. What changed my mind was finding a more cost effective alternative. McMaster Carr sells a similar product, but they only stock down to 6". I checked with them and found that a section of 6" insulated chimney pipe has an 8" OD. Still a good fit for my new thimble. Last week I ordered an 18" section of pipe and enough related hardware to make a chimney. Here it is:



After this stuff arrived, I modified my plans slightly for the collars to close the top and bottom of my thimble. I started by making a pair of rings from 18g cold rolled. I sized these to fit snugly over the ends of the thimble. The strips I cut are 1-1/2" wide.



Then I welded a piece of 18g to one side of each of these rings:











With the purchased pieces in hand, I decided that the bottom collar did not need a second flange on the ID. I cut a hole to fit the new pipe adaptor and tack welded the collar to the bottom of my homemade thimble. This photo shows the result, but it's upside down for the picture:



For the collar on top of the thimble, I made a second flange to fit over the OD of the insulated pipe:



Here it is with the pipe in place and then a couple shots of mockup assembly:







Here's the place where the thimble will pierce the roof shown from the inside and then the thimble in place from above after I'd drilled the 16 holes. I figured the hole spacing by measuring the circumference of the flange and dividing by 16:





Here are a few more of the process, but I seem to have failed to get a shot of the final product from the outside:









And finally, that thing we'd been longing for, making this morning's tea:



Pay no attention to the temporary mount. It will be bolted in soon.

The stove has secondary combustion from a 3/4" pipe in the top of the firebox. This pipe feeds from an opening in the rear wall. This was a problem during the test runs outside because the secondary inlet poured smoke whenever the door was open. Jason, who designed the stove, thought that extending the inlet with a down turned tube would solve the trouble. I welded a 3/4" pipe nipple to the inlet and added an elbow and six inch nipple turned down. In case this was not enough, I screwed a brass ball valve to the lower end of the nipple. Jason thought it would be a good idea to have a way to regulate the secondary draft. These mods cured the smoke trouble. The stove will still smoke some if I open the door before the box warms up, but it's not bad, and it's manageable.

Stove did great on its first night. Easily burns for 3 hours on a load, and I'm always up again by then. It is by far the best thing I've done to the bus.

Hope the rest of you are staying warm enough — or cool enough as the case may be.

Jim

[ol trunt]

'Morning. I'll bet the tea hit the spot. Your new stove is elegant in its (seeming) simplicity. I look forward to seeing the exterior "top hat". Its probably just as well that you didn't use vermiculite because it is hard to tell if it is contaminated with asbestos, although it certainly is a good thermal block.

Questions: What do you use for fuel; What did you use as a sealing mastic; What are your plans for the final installation of the stove?
Jack