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Old 03-19-2021, 10:16 AM   #1
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Shaping spray foam

After watching. Copius amounts of youtube it seems shaping the foam is the biggest challenge Has any body had luck with a hot wire cutter? How about a wire wheel on a disc grinder? Finally how about the Eastwood horizontal sander that can be fitted with a coarse wire wheel. Using a sawzall even with a flush cit blade or hand foam saws look likd a royal pita. Any success stories out there?
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Old 03-19-2021, 10:34 AM   #2
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Quote:
Originally Posted by Rivetboy View Post
After watching. Copius amounts of youtube it seems shaping the foam is the biggest challenge Has any body had luck with a hot wire cutter? How about a wire wheel on a disc grinder? Finally how about the Eastwood horizontal sander that can be fitted with a coarse wire wheel. Using a sawzall even with a flush cit blade or hand foam saws look likd a royal pita. Any success stories out there?
Joe
I've never shaped sprayed foam, but I've shaped other things.

The key is don't put on more than you need. The less overage, the less shaping.

Secondly, using a wide tool to shape with gives you a smoother (less dips) finished product.

Shape in the direction of least resistance. For a bus, I think that would be parallel to the side and roof ribs.

Wear the proper safety gear, respirator, eye protection are a minimum. You'll be covered with foam shavings.

Finally, keep a large shop-vac handy. I found it's the only way to clean up shaved foam remnants from my EPS rigid foam sheets.

Best of luck.
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Old 03-19-2021, 10:37 AM   #3
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I haven't tried it myself (yet), but I've heard people having success with a curry comb to manually scrape the foam down.

Google "curry comb" or "steel shedding blade" for examples.
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Old 03-19-2021, 10:38 AM   #4
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I've seen nothing but human misery as far as that task is concerned. It helped me go with foam board.

I wonder if something involving a long strip of bandsaw blade would work, like with handles on each end and two people could hold it taut and work it like a tree saw. It's very easy to cut through, you just need to be able to guide the cutting accurately.
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Old 03-19-2021, 11:26 AM   #5
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This is the tool I was referencing from Eastwood.
https://www.eastwood.com/paints/rust...s/removal.html
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Old 03-19-2021, 11:37 AM   #6
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I've seen nothing but human misery as far as that task is concerned. It helped me go with foam board.

I wonder if something involving a long strip of bandsaw blade would work, like with handles on each end and two people could hold it taut and work it like a tree saw. It's very easy to cut through, you just need to be able to guide the cutting accurately.
You know I just ordered a JET 14" metal wood bandsaw so I will me shopping for blades.. And they sell foam trimming blades and tree saws look like they might do some damage. But mother hunker chunker bunker that is way to much work. They sell a commercial tool I have seen on youtube but $3K is out of my budget. The Eastwood tool is similar to the 3K one, more of figuring out or field engineering a cutter for it.
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Old 03-19-2021, 12:36 PM   #7
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My bus ribs are about 25" on center apart.

Using the bus ribs as guides to lay a blade against will allow you to use a sawing motion to cut through the foam.

MacGyver a way to attach a fairly fine tooth yet wide blade that's say 30-36" wide to a stiff piece of wood or metal. Next, add two handles to the piece of wood/metal that allows you the most leverage for sawing side to side.

It may take a bit to fabricate, yet it should be more effective and faster overall.

Best of luck.
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Old 03-19-2021, 02:03 PM   #8
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My bus ribs are about 25" on center apart.

Using the bus ribs as guides to lay a blade against will allow you to use a sawing motion to cut through the foam.

MacGyver a way to attach a fairly fine tooth yet wide blade that's say 30-36" wide to a stiff piece of wood or metal. Next, add two handles to the piece of wood/metal that allows you the most leverage for sawing side to side.

It may take a bit to fabricate, yet it should be more effective and faster overall.

Best of luck.
Thanks Steve JB weld is always the answer...
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Old 03-19-2021, 07:41 PM   #9
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This is a horrible job any way you cut it
I trimmed my first bus. The installer said to use an angle grinder with wire wheel. It trims very well but it is MESSY! Think blizzard of static cling material. It gets everywhere. Doesn't matter if you masking off everything and wear a tyvek suit, goggles, respirator (and you will need to). It still gets everywhere. I sealed off everything with plastic and tape but the wire wheel would catch the plastic and get wrapped around it and rip holes.

My second bus I masked with tyvek left over from a project and that didn't tear or catch. This bus has ribs close enough so that the installer could use a big wire brush trimmer that rides along the ribs. That made it much faster but there's still a lot of hand work and and all the mess. I had driven to their shop for them to spray and do the big areas then I drove home in the sea of foam nibs to finish. That was crazy. The cleanup is more involved than trimming I think. After I cleaned up and stripped masking, there would be little spots that needed another shove here and there.

I found a serrated knife worked will for small spots as it created little mess. The problem with big blades is you have to have a flat spot on either side to slide the saw back and forth. When all the bays are bulging with foam, you can't lay a saw against the ribs.
By far, my least favorite part of the conversion to date. Good luck!
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Old 03-19-2021, 11:23 PM   #10
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If all the foam has been sprayed when you try and saw back and forth with a blade flush against the ribs, you will have bulging access foam on each side of what you're trying to stay flush against. Sounds like fun.
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Old 03-20-2021, 02:58 PM   #11
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Using xps foam I and others at Teardrops n Tiny Travel Trailers • Index page have made up Hot wire cutters. I would think the same works for spray foam. Certainly would be less of a mess. I just don't find the cut to be quick. You may need to experiment with temps/voltage to get something that works well for your needs.

Search for the wire cutters in the forum, ask some that have built them. Lot's of good folks over there that will help if they can.
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Old 03-22-2021, 09:57 AM   #12
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When I sprayed my house, I found an electric hedge trimmer to work the best. I removed one of the blades, pretty much turning it into a giant heavily serrated knife. The 4.5” angle grinder with a wire wheel was excellent for touch ups. A whole house wasn’t fun, but a bus sized project could be tackled in a weekend with this method.
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Old 03-22-2021, 10:04 AM   #13
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That sounds like a workable idea. How big of a hedge trimmer did you use? I also had a feeling that a cup wire wheel on a small angle grinder would do some damage also. Looking like i am going to hybrid my bus. Rigid foam for the walls and floor and spray foam for the roof. Thank you to all that replied. Joe
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Old 03-22-2021, 10:33 AM   #14
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A hedge trimmer with a coarse handsaw blade bolted on?
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Old 03-22-2021, 11:13 AM   #15
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It was a standard size electric unit, probably 18-22”. Nothing special. Mine was probably 80’s vintage, but a cheap harbor freight one would do the trick.

It was actually using the regular blade it came with. I wound up sharpening it and making the profile less aggressive as the day wore on, and that seemed to help it cut much better.

I probably should have mentioned- it really excelled cutting open cell foam. Closed cell was a challenge no matter which tool I used.
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Old 03-22-2021, 11:18 AM   #16
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Also, I found the flat braided wire wheel to be vastly better than a cup style wheel. The cup would tend to get caught in the material, the flat style was way more controllable.
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Old 03-22-2021, 12:06 PM   #17
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PHEW! I didn't realize the bullet I dodged there!



I think I'll just stick with my down sleeping bag. It's much colder on the top of a mountain in January with the wind blowing at 4:00AM than in my bus, and I'm OK up there.
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Old 03-22-2021, 02:15 PM   #18
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Now if only you could rent a 30" one.
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Old 03-22-2021, 03:27 PM   #19
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Now if only you could rent a 30" one.
Guess what I just found on EBAY? The knock off

https://www.ebay.com/itm/28414551761...fd551a4d6d764c
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Old 03-22-2021, 03:31 PM   #20
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It looks like it would bolt right up to a cheapo HF electric chain saw. Look hard and you can see the chisel teeth on the chain.
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