Flying Wing Plans for Hot Wire Cut Foam

[Chris King 3]

Hi,

I hope someone can help me. I've come back to model flying after some years and have had some fun refiting old models with brushless and lipo.

 

I want to kill a few birds with one stone if possible. I'd like to build something with a hot wire cutter but dont want the hassle of a fueselage so was thinking of a flying wing. This would also help with being able to fly in windier conditions which none of my exising models are particularly good at.

 

I was thinking of starting with something cheap and cheerful to prove the design like expended polystyrene covered with PVA and brown paper and then moving on to covering with glass fiber and maybe EPP.

 

So the question is does anyone know of some decent plans for a build your own wing using hot wire cutting? I'm looking for around 750mm-1M span and have 3S 1500mAH and 3S 2200mAH batteries kicking around but that isnt so important.

 

[MaxG]

Have you tried Googling for Zagi plans. There are plenty on the net which should be workable for foam cutting.

 

I have two Zagis both are foam covered with tape. One is EPP leading edge with white foam at the back and the other may in fact be EPP but it is so long since they were both built I am not sure.

The EPP/white foam wing is powered and uses a 1500 3S lipo.

If you cut a wing with all white foam then some spars should be used and it would be good to have some sort of wooden LE for strength and ding proof. Pine or the like from the local DIY place would be good or alternatively a Quadrant moulding set so the round part gives you a rounded shape for the LE without sanding.

Just a thought.

Maxg

 

[Eric Robson]

Look on the Flite Test website there is a lot of models which can be made of foam board  and do not need a hot wire cutter or the glue gun they use , I stick mine together with UHU por. 

[Chris King 3]

12 hours ago, MaxG said:

Have you tried Googling for Zagi plans. There are plenty on the net which should be workable for foam cutting.

 

I have two Zagis both are foam covered with tape. One is EPP leading edge with white foam at the back and the other may in fact be EPP but it is so long since they were both built I am not sure.

The EPP/white foam wing is powered and uses a 1500 3S lipo.

If you cut a wing with all white foam then some spars should be used and it would be good to have some sort of wooden LE for strength and ding proof. Pine or the like from the local DIY place would be good or alternatively a Quadrant moulding set so the round part gives you a rounded shape for the LE without sanding.

Just a thought.

Maxg

 

Thanks. Zagi's ring a bell from way back. I'll take a look.

[kc]

You might consider a Simitar design, not quite a flying wing but interesting.  See Outerzone for plan and articles.

[Chris King 3]

11 hours ago, Eric Robson said:

Look on the Flite Test website there is a lot of models which can be made of foam board  and do not need a hot wire cutter or the glue gun they use , I stick mine together with UHU por. 

I did build the Flight Test BushWacker which is foam board. Funnily enough I had trouble with hot glue on the wing section which resulted in the spar failing. Luckily fell into a bush so model was repairable with some carbon fibre to re-inforce the spar. Hot glue is too quick for some of the longer sections.

It's great fun but theres still quite a lot of time that goes into it even though quicker than traditional balsa.

I'm looking for an 'indestructable' fly anytime model and quite like the idea of hot wire cutting as I havent produced anythiing that way before.

I did see that FT have covered one of their foam board wings with fibreglass which looked interesting!

[Chris King 3]

Not sure if I need to start another thread for this but can anyone point me towards a supplier for EPP/polystyrene that will do small quantities and what density EPP I should be looking at please?

 

[Piers Bowlan]

Hi Chris, I bought some EPS from B & Q recently. An 8ft x 4ft sheet (50mm thick/2in) cost £17. I cut it onto four 4ft x 2ft pieces in the car park with a stanley knife! You can buy smaller pieces on ebay but the post and packing could make it a bit pricy. Some of the sheets are recycled and have 'black bits' in but the sheet I found in B & Q was pristine and cut beautifully with a hot wire cutter.

 

EPP is very difficult to get hold of these days, good luck.

Edited April 21, 2021 by Piers Bowlan

[Piers Bowlan]

Chris, there is some recent info on foam cutting from Ron Gray on the Bowman Spatman thread. Ron used A dence grey styrofoam from Bluefoam.co.uk. Very good results  from the photos. ? 

Edited April 21, 2021 by Piers Bowlan

[Chris King 3]

Perfect, thanks for the advice.

 

I think it will be off to B&Q for some EPS to practice with and maybe even for a prototype and then the grey styrofoam once thats working OK!

[Chris King 3]

Does anyone know how strong the styrofoam is from Bluefoam? I understand it's EPS (extruded polystyrene), just wondered how much stronger than XPS it is and is it anywhere near EPP?

 

 

[john davidson 1]

Don't know anything about XPS, but I have a large quantity of  4 inch thick blue foam recovered from  a demolished potato storage warehouse.   Insulated my shed with it in fact. Very handy, if i need some it is ready on the wall , It is very rigid and stronger than ordinary polystyrene foam , only  lacks the  rubbery impact resistance of EPP

Edited May 2, 2021 by john davidson 1
addition

[Chris King 3]

I finished my hot wire cutter today which works really well. Practiced on EPS and just for interests sake I stuck some laminate on one side. Its adds a huge amount of strength but when  you dent it it doesnt pop back like EPP.

 

[Mike Chantler]

Chris, I've been experimenting recently with hot wired EPS for a plank. I wanted something that would be a quick build as well. After messing around with a hot wire cutter for a while and different types of covering and reinforcement I've ended up with 3mm spruce or cedar LE, and carbon weave surface spars, top and bottom. I will likely cover in laminating film. Putting on the carbon weave is fast (use 3m77 on weave, leave to dry completely, cut, iron on to foam, wet with epoxy). The wing ends up light, reasonably stiff and ding proof. Yet to fly it though! 

 

I think hotwired EPS plus hardwood LE would be good for a zagi type wing ? 

 

Good luck with your experiments ?

Edited May 8, 2021 by Mike Chantler
Typo

[Chris King 3]

Thanks Mark. I like the look of the Plank. Certainly would be a good candidate for hot wire cutting. What would you make the fuselage from?

With the 3mm spruce/cedar do you wrape that around the leading edge and if so how far back?

Do you have to rebate it into the foam or just have a 'step' when it finishes?

Is a 'surface spare' just a strip of the carbon/glassfibre epoxied onto the surface of the foam?

Sorry to fire so many questions at you but you've piqued my interest!

 

I haven't found any wing palns that I want to build yet. Have been reading about some of the CrashTestHobbies wings and am tempted with their Pinata because a friend I fly with wants (needs!) something indestructible too but would prefer to build something myself tbh.

 

 

[Mike Chantler]

I just chop the first 3mm off the LE and then PU 3x9mm hardwood to foam with lots of tape. Then (carefully) microplane the hardwood to shape in place (you need one of those blue davids planes if you have not got one,  powesander will rip the hardwood off the foam). Section below is MH45 which I think is used on quite a few planks. For chevron you'd like be better with something else as you don't need the reflex in the TE. But anyhow- I'm chopping the TE off as well and fitting correx elevons.

[Mike Chantler]

This is a bit out of focus but it shows you  the LE shaped and the carbon  surface spar. The foam is EPS (from B&Q) as XPS and EPP is difficult to get. The LE is mainly to make the vunerable EPS less likely to collect dings.

 

For a Zagi type plane you probably don't need the surface spars - especially if you use some glass fibre tape.

Google sections e.g. https://www.rcgroups.com/forums/showthread.php?7994-Zagi-airfoil

 

My plank fus. is a 3D design and print by a friend I'm afraid.

 

Mike

 

Edited May 8, 2021 by Mike Chantler
typos

[Chris King 3]

Thanks Mike, much appreciated

[Piers Bowlan]

The CF tape looks a good idea Mike, simple, quick and strong. Where do you buy your CF tape by the way? With my Spatman wing I cut a slot and glued a thin ply (.5mm) dihedral brace in it with gorilla glue. The wing was then covered in brown paper using PVA. Once dry the wing was torsionally very stiff and quite ding resistant. I just used hard balsa for the leading edge, sanded to shape. 

[Chris King 3]

Its probably a question for another forum but does anyone know if you include the elevon when putting wing dimensions into a flying wing CofG calculator (if you are just adding them behind the airfoil profile)?

 

[Chris King 3]

Well I've been doing a lot more reading than building!

Had a good look at flying wings but theres lots of decisions to make there. Pusher prop, tractor prop and they look like they can be tricky to setup correctly.

I found plans for the Little Plank III which looks quite interesting.

Also came across the Simitar again which kc mentioned earlier on and I'd discounted because it looked to complex. Far from it, they are pretty simple and I like the fact that they were designed for foam core wings even though they cover with ply or balsa. The ability to fly in higher winds is what I'm looking for. Trouble is there's loads of variants to choose from! Only one was designed for electric and I saw somewhere that one wasnt the best flyer.

I'm also intrigued with the concept of getting some kind of flaps on a wing.