Bowman Spatman

No! non no no non no no!

My last few foam wings and floats used nice soft 1/16" balsa sheet edge joined where necessary to get the width of the wing chord, but that option is sadly out until stocks are supposedly replenished at our balsa suppliers at some point!

Veneer seems to be hard to source these days. I used brown paper and it’s worked out really well. The paper I used was masking paper as used for painting and available at hardware stores. Sold in a roll. It’s strong enough and not too heavy. Used slightly diluted PVA as adhesive.

Good call Robert. I've got a huge roll of that paper that I use when spraying my models. I'd prefer to veneer and then film cover I must say, but if veneer is not an option then the paper would certainly be a new technique to try!

@ David, I’m sure that some versions had ailerons?

@ Robert & Alan, if not veneer then I will use laminating film, I use it on a lot of models and it is brilliant and adds quite a bit of strength.

Robert look like you’re papers covering has done a really good job. At least that’s one less thing I need to worry about.

Hi Ron,

I've never seen an aileron version - for me, there's something very characterful about rudder/elevator models, especially when the design is extreme (large dihedral, short moment arm) - there's something about the way that they fly, as opposed to 'bank & yank'. I suspect that an aileron version wouldn't work so well unless the dihedral is reduced, and I will look forward to reading about how such a version works, good luck with it!

Hi David. My plan was to reduce the dihedral from the 4” down to 1” for the aileron wing, but as I’m going to be cutting my own foam wings I also plan to make a standard one too, best of both worlds?

I'll second that! I always wanted a Mini Skyman.

Having recently acquired a G-Mark .06RC, which should be about right with small servos, I would love to have one. The closest I've found to the Mini Skyman, is the Scamp from Bowman's nemisis, Galaxy Models.

Galaxy Models Scamp

Well l think this is what Bob Ross used to call a 'happy accident ' l think it looks better now than the first paint scheme, hopefully next time it gets broken will be when I have crashed it LOL !

Now that does look rather nice Jeff, well done!

Well I've made a start on producing the foam wing

Not too bad

Ron, super results from your (gravity powered?) cutting bow. Any chance of some more details of how the weights are attached and more importantly how much much weight you apply? I have always been a hand-held bow cutter but I want better results.

I guess it might be useful to any other Spatman builders who want to cut their own wings too.

Will do Alan, I'll take some photos of the mechanism. BTW, not my idea but looked at a lot of Youtube vids!

Yes I have seen and read lots too, I'm just after some real world advice before I start! Do you have to alter weights and settings for different lengths of core.

Well my (limited) experience is no, the weight stays the same as it is a 'balancing' act between the pressure applied to the cutting wire and the temperature that is being generated from the wire. Different foams may mean an adjustment is necessary and that is why I can add or reduce weights accordingly. I'll get the photos for you later on this evening.

Thank you Ron, that is very interesting. look forward to the photos too!

OK, so here are some photos of my setup which copies things used by others that I found on YouTube. I made most of it from bits of scrap I had laying around, the only things I bought in were the main pulleys and the cutting wire (Nichrome 28 gauge).

The bow frame using a tourniquet for tensioning the wire. I started by using some elastic luggage straps but they didn't give it enough tension and the wire bowed when cutting.

When cutting the frame rests on the board so I made (3D printed) a couple of wheels so that it could move smoothly. I plan to surface the board to make it smoother.

On the end of the board are 2 plates on which are mounted the pulleys to route the pull cord down to the pivot weight bar.

I attached some swivel links to teh ends of teh pull cord so that they can be easily detached when I want to do 'free hand' cuts.

The next shot shows it rigged up with the frame fairly well back on the board. I need to make a hold back to retain the frame, a battery serves this purpose at the moment.

This is the pull cord weight which is adjustable. I can also separate the 2 pull cords to position them apart in order to carry out taper cuts.

the pull cord quick release attachments.

The bow frame running wheels.

When cutting an airfoil I put some lead weights on the bow frame arms to ensure that the hot wire follows the profile end plates.

My DC power supply.

I've tried different foams. The first I tried were odd bits of packaging, the white polystyrene type. This cut really well on low power settings and gave a nice clean cut. Off cuts from model 'plane kits (the leftovers from veneered foam wing!) cut really well as you would expect and again required low power settings and also less weight on the pull cord weight bar. Next up was some Kingspan insulation board I ordered from Wickes, oh dear what a mistake it will not cut and made a horrible smell! Lastly the grey foam board that I eventually cut the wing cores from, this was supplied by Bluefoam.co.uk and is a very dense foam which cuts really well but I had to up the voltage to 18v and I needed double the weight on the weight bar. I'm going to get some white polystyrene boards in to compare the finished article but it will have to go some to beat the grey board.

The interesting thing is that I was going to veneer the foam cores but the grey board is so dense and smooth that I'm going to use laminating film directly onto it. I tried it on a scrap bit of board and it can really take a lot more heat than white foam can and on my test piece I got no crock skin look. I'm going to glue on balsa leading edges although I could probably get away without them as the edges of etc foam are quite firm even before laminating them.

Bottom line is, this is an incredibly cheap form of construction which I think will be very strong.

Edited By Ron Gray on 25/11/2020 20:08:39

I forgot to take some photos of another bit of the hot wire cutting kit and that is a jig to ensure nice square and plumb cuts. I'll do that tomorrow.