For a while now I’ve been toying with the idea of a really crash-able but reasonably lightweight plane for indoor flying that could be used for combat, pylon racing and other fun flying. There are lots of EPP planes around but none of them really did it for me, providing crash-ability with easy building, great agility and good handling.
I built a prototype a couple of months ago and a few friends liked it and did the same. We had 4 of them in the air together on Monday for some indoor combat (with and without streamers) and we're all agreed it's great fun! Lots of collisions, lots of streamer cuts, lots of fun and no significant damage.

The idea was to design something suitable for one-design combat, pylon racing, limbo, etc, that could take pretty severe knocks without needing to be re-built after every outing. It had to be:

• easy to build
• able to handle lots of abuse
• cheap to build
• very agile
• fun to fly!

Unfortunately I lost the CAD file for the latest version due to a computer problem but I'll redraw it and post it here in the next few days. In the mean time I thought i'd share some pictures and video.

Hope it's of interest

Aidan

It's built entirely from 6mm EPP (grade 20L – this is the soft stuff) and a little 3x0.5mm carbon strip. The prop's in the middle and it's got a big, blunt, bouncy nose.
It's virtually immune to head on collisions with walls, floors and roof beams (we've tested this several times now!). There's no landing gear or other breakable bits sticking out (but it can still take off easily from a smooth floor due to the new fuselage shape).

The prototype shown weighs 130g. You should have no problem getting a similar weight with similar equipment.

Hardware
Motor: Infinite A1705-2250 (17g)
Battery: 2s Rhino 360mAh lipos (21g)
Prop: GWS 6x3DD
Servos: Waypoint W-060BB (6.6g)

If you fly indoors you’ll probably have suitable cells, ESC and servos already. The motor is a little more critical because you need to end up with the right size prop for the slot. I think this Infinite motor is a very good copy of the Hyperion Z1705-11. There are other motors that will do the job but I suggest keeping motor weight below 25g. Thrust available from my setup is a little over 200g which is plenty for the 130g plane.

Below are some construction pictures. It's an easy build. The only part that takes any real time is cutting out the parts.

Aidan

Here's some video.

This is from the start of our Monday session before we cracked out the streamers. These 3 are all the previous version which has a slightly more swept delta. I'll add plans for this version too it also flies great and some people may prefer it. I think the new one holds speed a little better in tight pitch manoeuvers.
They will happily slow down to a crawl but it's mostly fast-ish flying in this video. They're a little noisy because of the slot but not as loud as the camera makes them seem.

No video of some of the more lively stuff later in the session - I was too busy flying!

Indoor RC Combat using the Imp delta (0 min 49 sec)

A scaled up version might be good for outdoors.
Good video and the plane certainly seems to be very controllable.

I have no indoor flying venues near me so outdoors is all I fly.

John

Originally Posted by jclassic1

A scaled up version might be good for outdoors...

You could certainly tweak the design for outdoor use. I've flown the indoor version outdoors and it does a lot better than most indoor planes but you would still notice the breeze.
For dedicated outdoor I was considering scaling it up about 10% to 15% to maybe 800mm (32") span and fitting a suitable 150W motor. The spars would need to be re-designed to stiffen up the wing for the extra power.

Aidan

A slightly scaled up version or maybe a lower Kv motor would make this a good candidate for E Fest in Feb. The new combat rules require full throttle from launch w/800 mah pack. What's the wing span on this version?

Nice job Adian.

Azarr

700mm if I remember correctly.

The enclosed prop is specifically intended for crash protection. That's probably a bigger factor indoors than out. That feature might be a bit of a disadvantage outdoors against conventional front prop designs if you were streamer cutting but would still be perfect for impact combat.

Aidan

Originally Posted by Aio_1

700mm if I remember correctly.

The enclosed prop is specifically intended for crash protection. That's probably a bigger factor indoors than out. That feature might be a bit of a disadvantage outdoors against conventional front prop designs if you were streamer cutting but would still be perfect for impact combat.

Aidan

E-Fest is indoor full contact. Looking forward to the plans. Personally I think full throttle from launch is a recipe for disaster but they seem more interested in cutting duration, we're looking at lower Kv's to make the flights manageable at full throttle since there are usually ~ 40 planes involved.

Azarr

Originally Posted by Azarr

E-Fest is indoor full contact.

Well in that case it might work very well. What sort of planes will everyone else be flying?

Looking forward to the plans. Personally I think full throttle from launch is a recipe for disaster but they seem more interested in cutting duration, we're looking at lower Kv's to make the flights manageable at full throttle since there are usually ~ 40 planes involved.

I definitely don't like the full throttle from launch idea, especially for indoor flying!
I'd be interested in taking a look at the rules for this if you can point me in the right direction?

Edit - Nevermind, I found the website

So 10oz max, 800mAh and no touching the floor.....it doesn't say how the winner is judged. Is it simply last up wins? It also doesn't say if 3s packs are allowed. If they are you get an extra 50% available energy - just need to spec the motor and prop to match.

I presume you'll want to weigh nearly 10oz so you have the inertia to hold your own. You could remove the "chin" if you want since touching the floor isn't allowed so a take off skid is no use.
As it's not a one design competition and is going to be very aggressive it might be better to go with the previous version. It's got a smaller span but similar wing area. I think it's just a little bit more robust and will be easier to beef up. It's not quite so good on pitch response but I don't think that's as important for full contact as for streamer cutting. It would also be wise to put a strip of carbon along each LE and maybe in the fuselage too for protection.

Aidan

Cute plane - looks fun. Could you post the main dimensions ? Wingspan, root & tip chord, fuse len / height & CG would be great, if you have time. Thanks!

Aidan,
Looks like yall were having a blast! Can I ask a question about your elevon pushrods? They look very light. I also see an extra piece just before the servo heat shrink. Does that piece make them adjustable? I have thought about going light on some builds but have had concerns about not being able to fine tune elevons/alierons (after crashes). Thanks

[QUOTE=Aio_1;17021226
I presume you'll want to weigh nearly 10oz so you have the inertia to hold your own. You could remove the "chin" if you want since touching the floor isn't allowed so a take off skid is no use.

Aidan[/QUOTE]

There's no limitation except the 10oz and 800mah. In the past I've been using the Firefly on 3S. This year I'll run 4S if I can find a low enough Kv motor. It's basically a fly what you brung, with the MS Composit Swift and Leadfeather's Firefly being pretty popular.

In the past it's been last man flying wins. Unfortunately that means both surviving and having duration. Hence the quest for low Kv motor on 4S. There have been some proposals to change it from a duration finish, but the management is being mum. I wouldn't be surprised to see a change at the event.
Azarr

Originally Posted by dstrout

Cute plane - looks fun. Could you post the main dimensions ? Wingspan, root & tip chord, fuse len / height & CG would be great, if you have time. Thanks!

I'll try and pull the plan together tonight if I can but if not I can definitely give you a sketch of the wing and dimensions as it's all straight lines. The fuselage is the tricky bit to re-draw accurately.

Originally Posted by Bhamflyer

Aidan,
Looks like yall were having a blast! Can I ask a question about your elevon pushrods? They look very light. I also see an extra piece just before the servo heat shrink. Does that piece make them adjustable? I have thought about going light on some builds but have had concerns about not being able to fine tune elevons/alierons (after crashes). Thanks

The yellow piece before the heatshrink is a length of tube I slid over the pushrods when I was making them up to be used as part of pushrod supports. The ailerons don't need it so I'll cut those off again. The rudder is borderline so I'll attach the tube on the rudder pushrod to the fuselage with an EPP spacer about half way back. I've been doing carbon pushrods this way (but with 1mm rod) on indoor pattern aerobatic planes for a few years and it works great. As you say there's no adjustability in the linkage, that bothered me at first but I haven't found it to be a real problem in practice. It might be more of an issue for combat planes. If it turns out to be an issue I'll look at other options on future builds but so far so good.

Aidan

I've attached a plan for the previous version of the Imp. This is the one being flown in the video and it flies great. It took a while to get this one laid out properly and the newer one will take longer so no chance of getting it tonight I'm afraid (it's 2am!). I'll be away from home for the weekend so it'll be early next week before I can get the new one up.

Aidan

dstrout,

The latest version is quite closely based on the "Pre-Imp" above but it's been modified as follows:
Span goes from 629mm to 706mm
Root chord reduced to 385mm (measured nose to aileron rear)
Nose to hingeline distance reduced from 295mm to 282mm
Fuselage is stretched 10mm longer (same height)

Aidan