Kind of inspired by this thread and some other attempts at hotwire rail band tools I made this:
The angle of the wire is 10 degrees. It could easily be made adjustable by adding another eye screw. I designed my cross sections in boardcad, then printed them. Then I marked on the prints where a 10 degree cut would tangent on the cross sections and measured where this would be on the top of the blank and marked this on the blank. Then I connect and blend these markings with an outline template a good bit longer than the board template since the rail band width taper towards nose and tail. Then it’s just a matter of following this line with the rail band tool, matching the two markings on the toll with the markings on the board.
I got some unevenness and a gouge or two, but it cleaned up quite nicely with a hard sanding block. It looks worse in the picture than it really is. For the next cut use a tangent to the crosssections at 20 degrees and measure where it intersects with the first cut, put the marking on the already cut band, connect and blend and let the hotwire tool rest on the first cut band. Sorry, no pictures of the second cut.
Pros:
Less dust
Surprisingly accurate
Cons:
Slow
I think this may be a viable option for the hobbyist that can give you very accurate results. Every rail band will be the same angle and, if you mark it well, the same width. It also cuts down on dust which is a big plus for me. For the professional with a powerful planer that does deep cuts I guess the power planer will be faster. Controlling the power to the hotwire is a good thing or you will get smoke on the narrower parts of the band, I got a variac off ebay for a few dollars.
FWIW your rail bands are much cleaner than mine while attempting to use a similar device. I figure the depth of cut on most planers is such that to remove as much foam as you did with one pass of your hot wire would require dozens of passes with the planer.
I might route some slots in the end piece and use wing nuts for some depth adjustment?
I made similar tools and they worked well, but slow. I made three with different angles. I never measured the degrees, just eyeballed them. I went back to a planer, probably because I am so ADHD. Even if it actually takes more time, 5 passes with the planer are better than one pass with hotwire with my attention span. When I cranked up my variac, I could go faster, but I kept breaking wires. For the patient, meticulous (spelling?), perfectionist person, it works great. I first tried to use the shapeable wires that I saw on a foam cutting website. Mold the rail off existing board, then run it on the blank. I could not get it to work, it was a disaster for me. It might have worked for someone with a lot of patience.
I made similar tools and they worked well, but slow. I made three with different angles. I never measured the degrees, just eyeballed them. I went back to a planer, probably because I am so ADHD. Even if it actually takes more time, 5 passes with the planer are better than one pass with hotwire with my attention span. When I cranked up my variac, I could go faster, but I kept breaking wires.
I’ve yet to break a wire, but my wires are 0.6 mm, rather thick. It does make alot of smoke if it gets too hot though, most likely very unhealthy. I agree, it’s not for the impatient.
Try getting a bevel guide for your planer. That may help. Also are you using nichrome? Try stainless leader wire from a fishing shop if you are. Works quicker and much harder to break.
I made a small hot wire cutter and have done some experimenting with cutting rail bands and also cutting outlines. Your cuts are much cleaner than mine. For me it’s a hobby. Anything I can do to cut down noise and dust are good things. My small hotwire is about ten inches…
Which is why I use a planer with a bevel guide. Still nice and accurate, but much faster.
Sounds like a good idea for accurate rail band angles, but how do you use that? Make the initial band at correct angle, then remove the bevel guide and deepen/widen it? The first cut in this case is wider than the width of the planer blade. In addition I’ve cut the outline 3/4" from the final outline to allow room for balsa rails, otherwise each cut would have been 3/4" wider.
here is a photo of the planer and bevel guide I am using. You may be able to pick out the slide on the bevel guide that lets you adjust the width of the cut. I can cut quite far into the board if need be. This is the best bevel guide I have ever used for a planer. It’s a Bosch 1594k as well.
How about using a pair of tape lines along the rail to guide the hot wire and keep you from going too deep. I bought one of those cheap hobby hand held hot wires a while back and never got around to using it, but was to be my plan.
I used masking tape as a guide. Messed around with doming the deck. I’m just experimenting with the concept. Maybe tighter wire or more heat would help. I’m not sure…
I have 4 boards almost ready to glass so I won’t be playing around with the hot wire for a few months. Sure would be interesting to see what you guys come up with.
I use two layers of masking tape and a hand held wire for rail bands . Tried one only and burned through. Two really makes for a lot of tape use. Sometimes I can reuse the tape, sometimes it just doesn’t stick enough again.
Haavard’s Rail Band Tool has got me thinking…Could you have two or more wires all at once? You could heat both wires and cut two bevels at the same time. I guess the thing for me is the outer rail where the balsa goes. I tend to use that as my control elevation. I keep that face a certain height for gluing up. The nose and tail area still get the old eye ball blend in the last foot.
Maybe the board cadd makes it easier.(?)
Haavard, can I see a pic of the outer rail? Is it consistently the same width?
Haavard’s Rail Band Tool has got me thinking…Could you have two or more wires all at once? You could heat both wires and cut two bevels at the same time.
I actually had the same idea with three wires and that’s what I made first but scrapped it. First of it’s more complex (my first try was stupidly complex), secondly since the second bevel may not be the same distance from the first bevel at nose and tail you can only get close (like an oldfashioned profiler I suppose). Sorry I didn’t take any photos of the second cut.
Ya know, using a planer takes a lot of practice. Maybe we need to really focus on the hot wire rail band thing. Give it the same amount of practice we so eagerly gave to the planer. The hot wire thing is just so unforgiving compared to a planer.
