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Post by Monte.C on May 5, 2022 14:43:11 GMT
Nerdnic calls it PVC on his blog. It's pieces cut from those black plastic trash cans next to your desk in the office. It's a similar compound to PVC but product descriptions call it Copolymer Polypropylene. Anyway, credit to Nerdnic on this idea. So I had to try it. I use two plates, one mounted to the motor, same as an X-mount, and one is the firewall mounted in the plane. I've been doing this with plywood. In this case I had planned to be using a deeper motor. This motor is quite shallow so I doubled up the mounting plate to bring the motor out a bit, give clearance for the prop to spin.   Findings: After a couple tests I haven't found an adhesive that sticks to it, so I needed to glue in these two wood rails - coffee stirrers - to hold the firewall in place. See in photo. It doesn't hold a screw as strongly as plywood does; it's easier to strip the hole in the firewall. In the future I think I'll be using a plywood firewall with a PVC mounting plate. This isn't as rigid as plywood either, bit it's not exactly flimsy. For the mounting plate I think it'll be fine. |
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Post by Monte.C on May 5, 2022 14:47:59 GMT
Also it cuts much easier than plywood. Just takes a couple firm passes with a blade. Easier to work with in general.
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Post by Burkeomatic on May 5, 2022 14:54:58 GMT
I used those before I started 3D printing mine. They can bend a little bit, but overall work well enough. Way better than making some wood mess and getting something that will crack. It works great for control horns too. I still have the $3 dollar (probably $6 now) trashcan that I had been chopping up to use for it. I used tin snips to cut it.
I sometimes go over the firewalls with tape to double secure it, but the only thing I have found that sticks to it is CA glue and gorilla glue. I'll hit it with 80 grit to give it some bite then go with it.
I posted something about that a couple of times (not in a dedicated thread) but everyone seems so fixated on the way FT does things, I don't think anyone noticed or cared.
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Post by Monte.C on May 5, 2022 15:04:20 GMT
I used those before I started 3D printing mine. They can bend a little bit, but overall work well enough. Way better than making some wood mess and getting something that will crack. It works great for control horns too. I still have the $3 dollar (probably $6 now) trashcan that I had been chopping up to use for it. I used tin snips to cut it. I sometimes go over the firewalls with tape to double secure it, but the only thing I have found that sticks to it is CA glue and gorilla glue. I'll hit it with 80 grit to give it some bite then go with it. I posted something about that a couple of times (not in a dedicated thread) but everyone seems so fixated on the way FT does things, I don't think anyone noticed or cared. Yeah I get it about tape. Those first couple planes where I built a power pod of one sort or another to nest inside the plane, I used tape. For all my planes since then I'd need to have the tape wrap around the outside of the plane, which I won't do if I don't have to. With a plywood firewall I pass a couple large size toothpicks through the firewall that get glued into the foam behind. These get CA'd to the firewall where they meet, then cut and sanded flush on the front side. Couldn't do this with the trash can material. Looking at what I have here (above) I couldn't tape anything anyway, with the fuselage sides protruding forward like that. |
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Post by Burkeomatic on May 5, 2022 15:08:56 GMT
Is the gorilla glue not working for you? That seems to be the only thing which works for me. I like the clear there so it doesn't foam and make a mess.
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Post by Monte.C on May 5, 2022 15:13:07 GMT
I did test a small scrap with GG and with Foam Cure. Didn't seem to hold. I'll need to test it again.
My thought is I need to test it smooth, not sanded, to see if there's actually a chemical adhesive bond and not just a mechanical bond into a roughed up surface. If it only works if the surface is sanded rough, I'm not sure I can bring myself to trust it for my motor mount.
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Post by ratcheeroo on May 5, 2022 20:16:41 GMT
I have done both ways , a good two way tape will work good on the PVC and if you used something like M3 nuts and bolts with some washers it will help hold the two pieces together as well as make your mount points stronger. I use 1/8 ply now with the nuts and bolts, a little CA to lock the nut in place , and use the tape too, that packing tape reinforced with the fibreglass strands
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