JH Hot Deamon - a true foamboard hotliner!


Free Flight Indoorist
My Speed Deamon project has hit nearly 120 mph in its current form without requiring speed wings, custom propellers, or any shenanigans, so I decided that the only thing to do is to blow it up to a much larger size!

Introducing the Hot Deamon - a foamboard hotliner for people who what screaming insane performance on a budget!

First, a comparison, little vs big:

I'm powering it with this:

Planned setup is that Turnigy 50-60 380 kv motor turning a GM 11x22 folding F5D prop on 8s. This should be exciting!

My only complaint is the materials went from a single sheet of DTFB to *SIX* sheets!!!
v2HotDeamon pts.png


Free Flight Indoorist
V1 plans here.

Ecalc simulations for hotlining setup (This is a hotliner, so we expect to open the throttle for only about 10 seconds at a time:

Hotdeamon sim.png

Ecalc simulation for speed setup:
Hotdeamon sim2.png


  • Hot Deamon Plans.pdf
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  • Hot Deamon Plyparts.pdf
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  • Hot Deamon sheet1.pdf
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  • Hot Deamon sheet2.pdf
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  • Hot Deamon sheet3.pdf
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  • Hot Deamon sheet4.pdf
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  • Hot Deamon sheet5.pdf
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  • Hot Deamon sheet6.pdf
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Free Flight Indoorist
Wing Span 64 inches
Length 57.5 inches
Center of Gravity 2.75 inches aft of wing root LE
Wing Area 736 square inches
All Up Weight 70 ounces
Wing Loading 13.7 oz. / sq. ft.

Skill required
Build skill level: 4 - Actual difficulty very low, but you better get it right the first time. You need to have built several models before so that you can fully evaluate the quality of your glue joints
Pilot skill level: 3 - You've mastered ailerons and basic aerobatics

6-7 channel rx
80A esc minimum, rated for cell count desired (4-8s)
Turnigy 5060 380 kv
RFM 18x19/GM18x23 (4s-6s) or GM 11x22 (8s) prop
5x MG90 servos
Transmitter capable of dual aileron mixing, crow, and camber
4-6s 2200 60C for hotliner
8s 2200 60C for speed plane

Recommended throws:
Ailerons: +/- 25̊ @ 30% expo, 15̊ up for crow, 10̊ down for thermal camber
Elevator: +/- 20̊ @ 30% expo
Flaps: 0̊ for cruise/climb, 10̊ down for thermal camber, 30̊ down for crow

With the recommended 6s and 8s setups, this is a very fast airplane that pushes the structural limitations of foamboard. It is capable of over 100 mph with both of the recommended setups, and foam wing spars cannot take the flight loads imposed by those speeds. Even without this powerful setup, foam cannot withstand the structural loads imposed by the heavy powerplant. A 3/8" carbon rod MUST be installed against the front of the foam wingspar shown on the plans. You may also use two wooden yardsticks stacked on top of each other, although these will not be as strong and will be heavier.

Build instructions, part 1:

Build instructions, part 2:
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Free Flight Indoorist
Six sheets of laser cut foamboard, coming right up!

This all led to quite a stack of foam. After a couple days I finally got my act together and started working in the fuselage. Each fuselage side is three pieces: two outer panels taped together for the full length, plus a side doubler. The top and bottom are the same way, and so you essentially attach the top and bottom and front and rear halves.

The elevator is made in one piece, with a fold over bottom layer for extra stiffness. After all, the elevator on this plane is almost as big as the wing on the Speed Deamon.

As per standard hotliner practice, the servo goes up under the elevator so a short, strong pushrod can extend through the open back into the elevator control horn. I used a Towerpro metal gear servo. Probably a bit minimalist of a choice, but the control loads are typically pretty light.

And so here it is all decked up with the servo enclosed. A pretty long extension is required, even with the receiver well behind the wing mount area. Quite a bit bigger than the Speed Deamon!

Caleb wanted a closer look:

Hope thinks I'm nuts. It's one big airplane!

With that done, I installed the aft top deck and glued on the 1/8" ply firewall which is then secured with fiberglass strapping tape in a crisscross pattern, then sealed up with packing tape for good measure. I also used a covering iron to seal up the fuselage seams in the nose before attaching the firewall so that I could fair everything in smoothly and reinforce all the seams with packing tape.


Well-known member
Can't wait to see this. Such a cool project. Love that you're not afraid to burn things up in the process.

I found the HJK Speedwings by accident a few months back. Beautiful birds but spendy for a greeny like me.

Downloaded the plans for the Speed Daemon. Watching your sweet build videos now. Thanks!


Free Flight Indoorist
Thank you for the support everyone! This is kinda how we do things at J&H Aerospace -- crazy, loud, and occasionally with severe carnage!

A note about the HJK models: they're very limited production airplanes designed for a very targeted audience--all out speed, and no compromises. They're the only outfit I know of selling airframes capable of 300+ mph without modifications. At least from the video they're claiming their new Micromonster is doing 250 mph, which is so much faster than anything else in its class as to be absolutely revolutionary. I'm pretty sure you could do 350 with the Bigmonster. If you've got deep enough pockets!

Made some more progress. The wing is a total of 6 pieces of foam, minus spars. I tape all of these together before beveling and such.

Unfortunately I was in a bit of a time crunch and forgot to take photos of the spar buildup. Basically it's just a larger version of the Speed Deamon spar. I put a really stout piece of carbon in there and it looks like it should be strong enough to survive. Time will tell. Anyway, here's the rather imposing result:

And just a reminder of how big of an upscale this is:

I couldn't resist taping some washers on the nose and giving it a test glide. Looks pretty good!


Free Flight Indoorist
Well I got the electronics installed...and then realized I don't have a series XT60 connector or the wire to make one. Well...ecalc says only 64A on 4s, so clearly a 4s 2200 should be fine. Yeah a small problem...it didn't balance. So I put two 4s 2200's in there at the wing trailing edge and it finally balanced around 25% of root chord. A bit forward, but it is a hotliner after all.


Even with an RFM 18x19 prop I wasn't expecting much, but boy was I in for a surprise! It took off with authority and just kept going straight up! What a ride! And it does glide very nicely. I'm quite pleased with the handling....only real problem is that it does NOT want to come down for landing even with full crow.

I'll try to get a 6s setup together and report on that tomorrow. Video will be forthcoming, and plans are available in Post #3.
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Free Flight Indoorist
I installed a GM 18x23 folding prop on this plane (available here: https://www.soaringusa.com/GM-prop/). Yes, that really is a $135 prop. I know that sounds insane, but I have to say that it's well worth the money. These really are the finest props available. We radared this plane on 1/3 throttle before chickening out due to the tight space for our radar trap, and it posted a speed of 96 mph, without really trying. Yeah, this bird really is that fast, and so far nothing is fluttering!