Fellow hot wire foam cutters, please feel free to weigh in.

[wilmracer]

I found my answerer in your wing viseo #3.

Awesome! I have made some progress and hope to ramp back up in the next month or two.

 

[FlyingTyger]

This is all great info. I too have been thinking, for several years now, about trying a large scale foam build using a hot wire among other techniques. If anyone else is like me, and want to find as much info as possible, I have found these two books to be very educational.

The one by Keith Sparks is available from his website (parkflyerplastics.com). The other is older and you will have to do some internet searching to find it.
Also, the late John Morgan did some amazing foam builds over on RCGroups. His handle is J Morgan. They are worth looking at too.

 

[Taildragger]

WAY back @willsonman did a class at Fite Fest (they trialed a Flite Fest University thing in 2016 I think). I put together an article, available HERE: LINK on the bows that we built and used, including a materials list. I still use these bows and that charger to operate the hotwire and they still work great. Only had to replace the wire a few times, mostly when the bow sat unused for a long time and the wire corroded.

These are cheap, simple, and work great for cutting just about anything. The scroll-saw versions are really great too, particularly for cutting formers and pieces where you want a consistent 90* cut. I had a commercial one for a while that burned out. These days I just use a scroll saw and deal with the rougher edges and dust. I figure dust vs. fumes... its a toss up which is worse.

Also, while I like using solid cores there is another method (box method) that has some cool advantages.

This "Box method", can you explain it more? Based on the name it sounds similar to an idea I had a few days ago

 

[cyclone3350]

This is all great info. I too have been thinking, for several years now, about trying a large scale foam build using a hot wire among other techniques. If anyone else is like me, and want to find as much info as possible, I have found these two books to be very educational.
View attachment 216158
The one by Keith Sparks is available from his website (parkflyerplastics.com). The other is older and you will have to do some internet searching to find it.
Also, the late John Morgan did some amazing foam builds over on RCGroups. His handle is J Morgan. They are worth looking at too.

I had intended to order those books a few years ago. For what never reason, I forgot about it until U mentioned them. I've just ordered mine today.

 

[wilmracer]

This is all great info. I too have been thinking, for several years now, about trying a large scale foam build using a hot wire among other techniques. If anyone else is like me, and want to find as much info as possible, I have found these two books to be very educational.

The one by Keith Sparks is available from his website (parkflyerplastics.com). The other is older and you will have to do some internet searching to find it.
Also, the late John Morgan did some amazing foam builds over on RCGroups. His handle is J Morgan. They are worth looking at too.

I've got that one by Sparky and it is great. My P40 was built from his kit. John Morgan was a hero of mine as well. His builds were beautiful and he was a genuinely nice guy in person. @willsonman and I got to meet and fly with him a few times at SEFF

This "Box method", can you explain it more? Based on the name it sounds similar to an idea I had a few days ago

I cover the method in the video below. A lot of other folks have used this for a while so I take no credit for developing the method but it does work really well.

 

[FlyingTyger]

John Morgan was a hero of mine as well. His builds were beautiful and he was a genuinely nice guy in person. @willsonman and I got to meet and fly with him a few times at SEFFT

I never got to meet John in person. I discovered him when he was building his Helldiver and traded some notes with him from my build. Built from the same plans, his version ended up over 10 pounds lighter than my "per the plans" Beast 😲

 

[Taildragger]

Can anybody give some detail of how to make a fuselage with hotwiring methods? For reference the model I am trying to make is a Piper PA-12

Also @cyclone3350 @wilmracer is there a cost-effective (cheap) way to finish the bare foam so it is more durable and will take paint well?

Basically just what is a good way to make a tough but cheap hotwired plane using XPS (the pink stuff)?

 

[Taildragger]

t

I've got that one by Sparky and it is great. My P40 was built from his kit. John Morgan was a hero of mine as well. His builds were beautiful and he was a genuinely nice guy in person. @willsonman and I got to meet and fly with him a few times at SEFF



I cover the method in the video below. A lot of other folks have used this for a while so I take no credit for developing the method but it does work really well.

the "box method" I came up with is to make a box for each section of the fuselage and then cut away some of the outside to shape, if that makes sense

 

[cyclone3350]

t

the "box method" I came up with is to make a box for each section of the fuselage and then cut away some of the outside to shape, if that makes sense
View attachment 216431

Yes it does make sense. I came up with same idea & was going to try it with on my kinda sort of F-5 before I got hit hard with covid back in August & never got to it. The idea was to make a box with the pink stuff with lengths of about 6". Then I was going to pin formers on each end and follow it with a cutter. The method would pretty much be in line with this video.

Looked good an paper but haven't tried it yet. I have also experimented with this stuff once & found it to be very promising for use on foam.

I built this thing out of DTFB with the paper removed & used the hard coat to apply standard wrapping tissue from CVS. The paper method was such a hassle that I would classify it as not practical. However, the Modge Podge Hard Coat did make for a nice clear protective shell over the foam. The only draw back I found id that it does live up to it's name and therefore, not easily sanded due to it's hardness. It will sand to a very nice & smooth finish. If U look back @ my pattern plane, that was done by applying Eze-Kote over .75oz fiber glass & then I filled the weave by making a paintable paste mixing Lite spackle with the Polycrylic, brushed it on & sanded it down. This method will only take a WB paint. The Modge Podge Hard Coat will take Krylon with out letting it attack the foam. I say Krylon because I haven't tested it with Rustoleum, but I am sure that would work to. I have also used the Eze-Kote over .75oz fiberblass on this foam wing on my Pup. I used 2 brushes for this. One to apply the Eze-Kote, & a dry one to take as much excess as possible to leave the weave. This was to give it that WW1 fabric look. BTW, I didn't cut the wings on the Pup. It was part of an ARF that was molded with very nice rib details.

 

[Baron VonHelton]

Who's Sopwith Pup is that?

 

[Taildragger]

Yes it does make sense. I came up with same idea & was going to try it with on my kinda sort of F-5 before I got hit hard with covid back in August & never got to it. The idea was to make a box with the pink stuff with lengths of about 6". Then I was going to pin formers on each end and follow it with a cutter. The method would pretty much be in line with this video.

Looked good an paper but haven't tried it yet. I have also experimented with this stuff once & found it to be very promising for use on foam.

I built this thing out of DTFB with the paper removed & used the hard coat to apply standard wrapping tissue from CVS. The paper method was such a hassle that I would classify it as not practical. However, the Modge Podge Hard Coat did make for a nice clear protective shell over the foam. The only draw back I found id that it does live up to it's name and therefore, not easily sanded due to it's hardness. It will sand to a very nice & smooth finish. If U look back @ my pattern plane, that was done by applying Eze-Kote over .75oz fiber glass & then I filled the weave by making a paintable paste mixing Lite spackle with the Polycrylic, brushed it on & sanded it down. This method will only take a WB paint. The Modge Podge Hard Coat will take Krylon with out letting it attack the foam. I say Krylon because I haven't tested it with Rustoleum, but I am sure that would work to. I have also used the Eze-Kote over .75oz fiberblass on this foam wing on my Pup. I used 2 brushes for this. One to apply the Eze-Kote, & a dry one to take as much excess as possible to leave the weave. This was to give it that WW1 fabric look. BTW, I didn't cut the wings on the Pup. It was part of an ARF that was molded with very nice rib details.

View attachment 216458 View attachment 216459

that F5 drawing is amazing! and that high wing plane paint scheme reminds me of something...

 

[cyclone3350]

Who's Sopwith Pup is that?

That is an old Kavan 1/10th scale Pup. When I bought it, I found a superbly molded set of wings, quality hardwood inter plane struts and a scale bungee main gear set up. Everything else looked like a toy @ best. So, I used the parts as described & scratch built everything else around them. This one took me a very long time to do & will not do this on a small scale model ever again. Here R some examples of the stupid things I did to detail it out. The biggest regret I have is that this thing is too small to fly outside of the calmest days. That, & the fact that I went generic on the seat belt fittings verses doing a more authentic sutton type harness.

 

[cyclone3350]

that F5 drawing is amazing! and that high wing plane paint scheme reminds me of something...
View attachment 216468

Yeah, I don't know why I am partial to that scheme.

 

[Taildragger]

Yes it does make sense. I came up with same idea & was going to try it with on my kinda sort of F-5 before I got hit hard with covid back in August & never got to it. The idea was to make a box with the pink stuff with lengths of about 6". Then I was going to pin formers on each end and follow it with a cutter. The method would pretty much be in line with this video.

Looked good an paper but haven't tried it yet. I have also experimented with this stuff once & found it to be very promising for use on foam.

I built this thing out of DTFB with the paper removed & used the hard coat to apply standard wrapping tissue from CVS. The paper method was such a hassle that I would classify it as not practical. However, the Modge Podge Hard Coat did make for a nice clear protective shell over the foam. The only draw back I found id that it does live up to it's name and therefore, not easily sanded due to it's hardness. It will sand to a very nice & smooth finish. If U look back @ my pattern plane, that was done by applying Eze-Kote over .75oz fiber glass & then I filled the weave by making a paintable paste mixing Lite spackle with the Polycrylic, brushed it on & sanded it down. This method will only take a WB paint. The Modge Podge Hard Coat will take Krylon with out letting it attack the foam. I say Krylon because I haven't tested it with Rustoleum, but I am sure that would work to. I have also used the Eze-Kote over .75oz fiberblass on this foam wing on my Pup. I used 2 brushes for this. One to apply the Eze-Kote, & a dry one to take as much excess as possible to leave the weave. This was to give it that WW1 fabric look. BTW, I didn't cut the wings on the Pup. It was part of an ARF that was molded with very nice rib details.

View attachment 216458 View attachment 216459

So I could coat it with polycrylic/modge podge hardener and it would be even tougher than a molded plane?

 

[cyclone3350]

So I could coat it with polycrylic/modge podge hardener and it would be even tougher than a molded plane?

I would do an experiment with both. U can buy a very small can of Polycrylic from Wally Word for very little & Modge Podge can be bought from any craft shop & is dirt cheap. Apply both to scrap foam & see if that is the result U R looking for. Hmm. I am wondering how the Polycrylic would do over the Modge Podge. I found that Modge Podge is very hard & the Polycrylic would make for an easier sand finish. Keep in mind that Polycrlylic will only take a WB like latex paint.

 

[Taildragger]

So say I have the sections cut now... how do I join them together? (what glues, any pins, etc)

 

[Ketchup]

So say I have the sections cut now... how do I join them together? (what glues, any pins, etc)

If you aren't gonna try cutting through them again with the hotwire then gorilla glue will probably work real well. The bond would probably be stronger than the foam itself and pretty light. You might need tape or maybe a dab of hot glue to hold pieces together while they cure though. You could also use popsicle sticks stuck into the sections for lining things up and just tape everything real tight while the glue cures. There's a lot of options for holding stuff together while the glue cures tbh.

 

[cyclone3350]

I am with @Ketchup in that if U R not going to hot wire through it, then pretty much any foam safe glue will do. So far, my glues of choice have been Beacon's Foam Tac or Titebond Quick & Thick. For bonding foam together for cutting, I been using 3M 78 spray adhesive. I've been ordering it from Uline. It is kinda messy, but the bond is incredible & will hold up in the heat from direct summer sunlight & find it a non issue for hot wire. 3M 77 does great with cutting, but I don't think it will hold as well in the heat.

 

[Taildragger]

@wilmracer what glue did you use to build the boxes for the horizontal stabilizer?

 

[wilmracer]

@wilmracer what glue did you use to build the boxes for the horizontal stabilizer?

Gorilla Glue, used sparingly for the box. The hot wire has no issue cutting through it.