Fellow hot wire foam cutters, please feel free to weigh in.
- Thread starter cyclone3350
- Start date
Off-topic jes
Elite member
hows this one going friend?
cyclone3350
Master member
Everything is still in boxes. Sold the house in Illinois & move to Georgia. We R in a tiny apartment until we find a house. Hopefully another 2 months before I get back to building.
Off-topic jes
Elite member
well good and bad for you, i hope you get back to it friend!
Off-topic jes
Elite member
building is a grate outlet to
danskis
Master member
Below is the story of my newbie hot wire foam cutting journey along with all my mistakes and recommendations.
The bow was just thrown together out of 1"X2" lumber. It doesn't have to be a work of art for it to work (as you can see). Mine has a 26" cutting wire from Jacobs online. Its Renee wire 27 gauge, I would recommend it. The wire needs to be really taught so you need to put a lot of pressure on it. My first mistake was to put the wire holding screws through the side of the legs so the wire attached with a 90 degree bend to the metal through bolts. With the 90 degree bend the wire broke too easily. I switched it so the bolts go through the face of the legs and the wire just wraps around the bolts with no bend. This allows you to get the wire really tight without breaking it.
My power supply is pretty straightforward and didn't cause me any problems. I used the wiring diagram from Jacobs online. I've got an inline on/off switch and push on/off/rheostat switch. The diagram strongly suggests you use the hot lead to go through the switches - I found that it didn't matter. Jacobs also suggests that you need an indicator such as a light to let you know when the power is on. I found that there is a slight vibration in the wire and its easy to tell when the power is on or off because the bow vibrates a little. I put the power supply/switches on the floor and just use my foot to switch the rheostat on and off. The switches are in a plastic construction box from Lowes. Power is 16V 3A.
Nichrome Wire Power Supply Design (jacobs-online.biz)
The bow was just thrown together out of 1"X2" lumber. It doesn't have to be a work of art for it to work (as you can see). Mine has a 26" cutting wire from Jacobs online. Its Renee wire 27 gauge, I would recommend it. The wire needs to be really taught so you need to put a lot of pressure on it. My first mistake was to put the wire holding screws through the side of the legs so the wire attached with a 90 degree bend to the metal through bolts. With the 90 degree bend the wire broke too easily. I switched it so the bolts go through the face of the legs and the wire just wraps around the bolts with no bend. This allows you to get the wire really tight without breaking it.
My power supply is pretty straightforward and didn't cause me any problems. I used the wiring diagram from Jacobs online. I've got an inline on/off switch and push on/off/rheostat switch. The diagram strongly suggests you use the hot lead to go through the switches - I found that it didn't matter. Jacobs also suggests that you need an indicator such as a light to let you know when the power is on. I found that there is a slight vibration in the wire and its easy to tell when the power is on or off because the bow vibrates a little. I put the power supply/switches on the floor and just use my foot to switch the rheostat on and off. The switches are in a plastic construction box from Lowes. Power is 16V 3A.
Nichrome Wire Power Supply Design (jacobs-online.biz)
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danskis
Master member
I made some jigs to cut the block of foam to the outline of the wing. I use these for vertical cuts.
I had a hard time telling how far each side of the wire was through the cut when I was using the airfoil templates so I marked the foam in intervals. The wing is a little over 6 inches
I had a hard time telling how far each side of the wire was through the cut when I was using the airfoil templates so I marked the foam in intervals. The wing is a little over 6 inches
danskis
Master member
This is my first really successful cut. I made the airfoil templates out of hobby sheet brass. I originally didn't put a "tail" on the templates but found that the "tails" are essential. I later epoxied some "T" pins to the back of the templates which worked well. They sure do help start the cut. I'm planning on covering the wing with 1.5 laminating film.
So what is it? A 60% Kwik Fly pattern ship.
So what is it? A 60% Kwik Fly pattern ship.
cdfigueredo
Elite member
Very good job on that cut. Yes, tails are essential to get a precise cut, yours is really good. Covering this with a 1mm basa sheat will make them strong as hell
FlyingTyger
Elite member
I found this good video by Keith Sparks today showing how he cuts is own foam sheets.
Interdimensional Aircraft
Member
I have a youtube live stream that often showcases 3d printed foil covered template making as well as manual hot wire foam cutting.. next time I cut some wings I'll throw the live stream/clip here. I use EPP which is a very different animal than any other foams. I'm not very smart or rich so its probably the dumbest and most cost effective way to make quality cut EPP cores with some practice. EPS and other foams are another story, much easier to deal with. I played with a lot of different power supplies and concluded, after destroying two DIY power supplies despite some successful cuts, that this was the most reliable and cheap option: https://www.amazon.com/dp/B076Y2XHRS/?tag=lstir-20
Out of touch old timers will tell you to go pick up an old train transformer as if its still the 1990s and they are just laying around. Save yourself a headache and just grab that variac I posted - the other thing you're gonna see are jenky setups on plywood with switches and fuses and blablabla, forget about it. If you want to go the extra mile get yourself a good DC $200 power source with all the bits and bobs and call it good.
Then you just need a strong frame, a strong spring, and some conductive wire that won't stretch to make your bow. Everyone says nichrome I say bullshit, that stuff sags and lags like crazy. If you want to do a good job, get some Inconel 600 wire available on Aircraft Spruce, or some Rene wire.
I think above all the most important part of the manual wing cutting process is having a perfectly straight and flat building surface to work with that does not flex. I use a piece of glass, but tuned granite, or a torsion/tension table, etc. will work great too.
Please observe the perfectly razor sharp trailing edges on these wings.
Out of touch old timers will tell you to go pick up an old train transformer as if its still the 1990s and they are just laying around. Save yourself a headache and just grab that variac I posted - the other thing you're gonna see are jenky setups on plywood with switches and fuses and blablabla, forget about it. If you want to go the extra mile get yourself a good DC $200 power source with all the bits and bobs and call it good.
Then you just need a strong frame, a strong spring, and some conductive wire that won't stretch to make your bow. Everyone says nichrome I say bullshit, that stuff sags and lags like crazy. If you want to do a good job, get some Inconel 600 wire available on Aircraft Spruce, or some Rene wire.
I think above all the most important part of the manual wing cutting process is having a perfectly straight and flat building surface to work with that does not flex. I use a piece of glass, but tuned granite, or a torsion/tension table, etc. will work great too.
Please observe the perfectly razor sharp trailing edges on these wings.
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danskis
Master member
@Interdimensional Aircraft - thanks for the post and I'm looking forward to your future posts. I'm just getting started so I'm basically just practicing to see if this is something I want to get into further.
Where do you get your EPP foam?
Where do you get your EPP foam?
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Interdimensional Aircraft
Member
windcatcherrc.com for the EPP.. might have to send them an email they are sold out. they also have depron which is basically a higher quality paper-off foam board suitable for more detailed or high performance indoor stuff. shipped very fast last time I ordered. practice with regular foam first (EPS) EPP is expensive stuff and usually difficult to obtain in small quantities
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danskis
Master member
@wilmracer - I'd like to try the box method on my next build. I was wondering what glue you used to glue the box together?. It seems like if you use the wrong glue the wire will hit those spots and slow down the or snag and ruin the cut.
Sorry... I've been off the forum for a bit. I use a light layer of gorilla glue. Go slowly with the bow and the wire will pass right through it without any issues. You can always go back and add additional glue to the joints in the panel if they feel flimsy after you cut the airfoil.
Off-topic jes
Elite member
I didn’t notice you’ve been gone for a while good to have you back friend
Thanks! Hoping I can get some hobby time back. Fingers crossed.
I stumbled across this guy. Has anybody built one of his machines?
Looks like he has taken hotwire cutting to the next level, CNC controlled.
https://rckeith.co.uk/
Looks like he has taken hotwire cutting to the next level, CNC controlled.
https://rckeith.co.uk/
FlyingTyger
Elite member
Finally got around to putting my bow together. I tried to keep it as simple as possible.
The wood pieces are yard sticks from Menards, 4 total. The tensioning cable is left over 1/4 scale flying wire cable and a 4" turnbuckle. I have small eyelets at the end of the arms for the cutting wire. The wire just loops through and is wound around itself. For cutting wire, I found some 26g nichrome wire on Amazon.
I still need to assemble the electronics. I am hoping to start test cutting some Wilmracer style box wings in the next week or two.
The wood pieces are yard sticks from Menards, 4 total. The tensioning cable is left over 1/4 scale flying wire cable and a 4" turnbuckle. I have small eyelets at the end of the arms for the cutting wire. The wire just loops through and is wound around itself. For cutting wire, I found some 26g nichrome wire on Amazon.
I still need to assemble the electronics. I am hoping to start test cutting some Wilmracer style box wings in the next week or two.
cyclone3350
Master member
I like it!
. I built a fancy looking one from Jacob's online (see post#1 this thread) & it has some drawbacks. The wire length has to be just right to when replacing & is cumbersome to do so as it uses the stiffness of the PVC pipe for the tension. The tension is adjusted via eye bolts & U have to undo & then retighten 2 nuts per bolt. It is also limited to one size length. The one U have has a wide adjustment for what length of wire U can use and the turnbuckle makes for easy and precise tension adjustments. I think I will go this route for my next bow.Similar threads
