Strange Quark

[Futura57]

It's been raining hard most of the day so I made an initial sketch of my proposed Strange Quark model. A stealth EDF take on my Top Quark design. I have never owned, built or flown an EDF model, so it could all be a massive waste of time. But that won't stop me trying. I've seen plenty of examples over the years so reckon I could make a decent fist of it. I have a FMS 50mm 4S EDF unit to work around and a clean sheet of paper. The whole design is, of course, subject to change as I progress. But I will almost certainly construct a full size Depron prototype to assess the chuck gliding performance, establish an approximate CG and to drool over the aesthetics 🤣 Don't expect rapid progress as this will be a Winter project.

 

[Futura57]

Here is my first iteration XPS foam prototype. Profile form will be beefed up with fuz bottom, sides and main intakes. Will also box up the canopy and nose. Seems much larger than my Top Quark even though rear wings are identical and same wing stagger. Front wings are swept back more with root dorsal shoulders. I'm not entirely sure about the shoulders so may trim off later. Nose a little longer. Goes together quickly with a hot glue gun. All inspired by new Tempest jet. I'm beginning to think the 'production' model will end up as a balsa and foam board hybrid to keep the weight down for 4S 50mm FMS unit.

 

 

 

 

[Futura57]

I've been a busy boy on this wet and windy day. The Stealth Quark prototype is now fleshed out with foam and I am liking what I see. All ready to try as a chuckie when the winds abate. Cheat holes underneath double up as a hand launch grab point. But it's a bit narrow and needs opening up a little. The fuselage width is just about comfortable to hold it on the sides for a hand launch if it comes to it. The canopy area and turtle deck is easily made from two flat lengths of 3mm white foam which rest on the front wing and fuselage top edges and is guided over the canopy profile. I think I could turn this into an easy to build model. At the moment I am thinking balsa wings and fuselage spine/crutch. Then foam fuselage surfaces and fins. Apart from the wing outlines, everything has been cut on the hoof. So I will need to reverse engineer it for a plan. But I need to try the chuck glide first before getting carried away. Wish me luck.

 

 

 

 

 

 

 

 

 

[Futura57]

Following successful test glides of my XPS foam Strange Quark prototype, I’ve spent some time thinking about the materials I will use for my first powered version. I want them to be cheap and readily available if I’m to eventually publish a plan. Initially I was thinking of 1/4-inch-thick balsa plank wings and XPS foam board for everything else. But I want to try a slightly thicker wing with a more pronounced semi-symmetrical aerofoil section which is more refined than a plank wing. After much consideration I shall try something I’ve not seen anybody use, though it would interesting to know if it has been tried and failed before.

 

I want to make my wings from a sandwich of thin balsa or lite ply inside XPS foam top and bottom skins. Lite ply is much cheaper than balsa, but I need to get an idea of the weight penalty compared to balsa. XPS foam is easy to carve and sand to a profile and can be covered with cheap laminating film. I have already tried this on a couple of areas of my XPS foam chuckie. The results are encouraging because it goes on easily with my iron at around 100C. It tends not to wrinkle at this temperature and it adheres reasonably well to the XPS foam. Once sealed around the edges the laminating film can then be heated further to 120-130C to make it stick better. I’ve used matt laminating film which seems to have taken a coat Halfords white primer well, and hasn’t scratched or peeled so far.

 

The XPS foam I am using came from here XPS Insulation Board | The Underfloor Heating Store

 

As a crude experiment I made up four ‘wing slab’ samples of size 100mm x 200mm. 10mm XPS foam on the upper surface and 6mm XPS foam on the lower surface. Inside the foam sandwich I glued (using Titebond wood glue) different cores, and here are their overall weights.

1/16-inch balsa (23g)

1/8-inch balsa (32g)

2mm lite ply (42g)

3mm lite ply (49g)

 

As expected, the lite ply cores result in a slightly stiffer structure. I can’t be bothered to measure it scientifically so I just gauged it by hand. However, I believe the balsa cores are perfectly adequate for my purposes, so I will likely be pressing ahead with the 1/16-inch balsa option.

 

 

 

 

 

Trial of 38 micro matt laminating film on XPS foam board. Halfords white primer finish. See how primer has attacked the foam surface a little.

 

 

 

Edited November 16, 2023 by Futura57
typo

[Futura57]

Some progress yesterday and today with the front wings. After cutting a 1/8-inch lite ply template I cut four pieces from 6mm XPS foam and paired them up to make 1/16-inch balsa sandwiches glued with Titebond wood glue. After leaving weighted down flat overnight I set about rough carving and rough sanding, with 70grit, a symmetrical aerofoil section. A little more work is required to refine the finish; however, I am very pleased with the result so far. The balsa 'core' gives a nice straight leading and trailing edge which is tougher than the foam due to having soaked up the glue. The glue sands ok. Minor cock-ups, such as my Stanley knife digging in a couple of places, will require a little of that feathery light filler they sell in DIY stores. Eventually these foam wings will be covered in 38 micro matt laminating film. I have also started cutting some lite ply templates for the various fuselage parts and cut examples from 6mm XPS foam. There’s a little trial and error and improvisation going on, such as deciding I will add tabs and notches for more precise part location. The lite ply templates will be modified accordingly for cutting future foam parts. Each wing weighed 85g before I started carving the aerofoil, 70g after.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited November 18, 2023 by Futura57

[Futura57]

Too many domestic obligations today to get very much done. Made up the rear wings, again from 1/16 balsa sandwiched between 6mm XPS foam upper and lower skins. Carved and rough sanded. Then all wings sanded with 240 grit. I am happy with the results. Nice straight firm leading and trailing edges. The wings are flexible but I'm hoping the laminated film covering, closed triangular wing geometry and rigidly joined tips will give an acceptable structure. My only regret is not dropping in a 2mm carbon rod in each wing within the balsa layer to be on the safe side. I could maybe make a Stanley knife cut along the underside foam skin and push a rod in. Not sure.

 

[MattyB]

Just slice slots top and bottom, insert carbon strip of an appropriate size, then run in some (foam safe) cyano and a splash of kicker - should only take a few mins and work well (I’ve done this to reinforce many an ARTF, though with EPO models you can use std cyano).

[Futura57]

A little progress today. This is the front of the fuselage shown inverted. There is a lite-ply battery tray which will take sticky-backed Velcro and a Velcro strap for securing a 4S 2200 mAh Lipo. Two 9g servos side-by-side with snake links to elevons on the rear wings. The curved underside of the front fuselage will eventually be cut out as a large hatch for changing the Lipo. The servos are on a cradle which can slide out into the Lipo space for maintenance access through the hatch.

 

 

Front wings are glued to the front fuselage centre spine

 

 

Front fuselage sides will also form the inner surface of the air intakes, going under the front wing towards the rear mounted fan.

 

 

 

 

 

 

 

[Futura57]

I got the main fuselage sides on to form the intakes and the rear fuselage, which will house the EDF just ahead of the masking tape.

 

 

 

 

[Richard Harris]

That's coming together nicely Futura57, look forward to seeing it  completed. How does the foam your using compare to depron?

[Futura57]

4 hours ago, Richard Harris said:

That's coming together nicely Futura57, look forward to seeing it  completed. How does the foam your using compare to depron?

I prefer the XPS foam to Depron in many ways. It's firmer and much more resilient to being squashed and less prone to showing finger and thumb impressions, for example. It's also easier to cut with a Stanley knife without tearing. It is a bit stiffer too but slightly brittle so will snap / crack open if bent too much, rather than crease like Depron. You can bend it around curves but not quite as tight as the same thickness of Depron. The surface finish can be inconsistent such that there is usually one good side with wordworm like holes on the other side. Not a problem if you cover with laminating film or brown paper. Definitely worth experimenting with in my opinion. It comes in larger sheets than the B&Q 'depron'. I haven't compared the weight of identical thicknesses, though.

[Futura57]

Oh, and XPS foam sands well and without producing hundreds of statically charged balls.

[Futura57]

It's easier to cover the rear wings with laminating film before sticking them to the fuselage. First job though was to fix the elevons in place with film hinges using clear solartrim.

 

 

[Richard Harris]

On 22/12/2023 at 21:54, Futura57 said:

Oh, and XPS foam sands well and without producing hundreds of statically charged balls.

 Futura, thanks for the info.

Might give it a try in the New Year.

[Futura57]

 

The rear wings are now glued in place and joined to the front wings at the tips with 1/4-inch diameter hardwood dowels. With the 1/8-inch balsa elevon insets and the laminating film covering, I believe the wings are stiff enough without inserting additional carbon rods or strips. The rear fuselage formers are glued in place and the 50mm 4S FMS fan is spot-hot-glued in position. The outlet tube is 200mm long and made from 15 thou polystrene tube, fixed with tape and a zip tie. It reduces in area a little to a squashed oval at the tail end, where it is glued to the rear former. After running the fan at full power I reckon this thing will perform well. ESC location will be used to fine tune the CG. This may require wire extensions on the motor and battery side. My target all up weight is 800 grammes.

 

 

 

 

 

 

 

 

 

 

[Futura57]

Getting close to finishing my Strange Quark With EDF power. Still mostly bare foam (Depron and lilac XPS foam). Wings and fins covered with laminating film, though one wing was damaged by a dropped object 😣 Fuselage still needs covering.

 

The plan is to test fly before painting. Matt black or dark grey was my first thought for a traditional stealth fighter look. But I was also thinking orange with black tiger stripes. To be decided.

 

I'm already thinking version 2 will increase EDF from 50mm to 64mm and have full vectoring capability at the tail pipe exit. But I'm getting ahead of myself.

 

 

 

[Futura57]

With flying opportunities thin on the ground right now I've decided to paint my Strange Quark prototype before its maiden flight. I've chosen this CF-18 tiger scheme as the inspiration.

 

Edited January 21 by Futura57

[Futura57]

The paint job is progressing nicely thanks to some help from my cat Willow. She has recently had a hair cut due to unmanageable matting of her long fur each time she went out in the wet.

 

 

[john stones 1 - Moderator]

Nice work on the paint job, and Willow.

 

[Piers Bowlan]

If it flies as well as it looks it will be fab! Good luck with the maiden. A free plan in the mag soon?

[Futura57]

Just now, Piers Bowlan said:

If it flies as well as it looks it will be fab! Good luck with the maiden. A free plan in the mag soon?

Thanks. Yes, fingers crossed for the maiden. Next week hopefully. The construction needs a fair bit more development before I commit to a proper plan. I do have lite ply templates for all the major parts which are quickly and easily cut from foam sheet. But as it stands is only suitable for an intermediate to advanced builder to be able to improvise a little and fill in a few blanks so to speak.

 

My original propeller driven Top Quark design is all drawn up and a build article has been written. I just can't get any good flying shots otherwise it would have been winging its way to Kevin weeks ago. And he doesn't like content in dribs and drabs.

[Richard Harris]

Cracking paint job 

[Futura57]

Today was the maiden flight of my Strange Quark EDF design. Below are some short videos showing the first three attempts. You be the judge...

 

 

 

 

 

 

 

 

 

 

[Futura57]

Notes to self:

Launch on full throttle.

Launch on upward incline.

The model wants to roll to the left because of a warp in one of the wings. Some up elevon trim and considerable right elevon trim was added for the third attempt. Once the warp is corrected I will risk a right hand turn.

CG is about as far forward as I would want. Perhaps needs 10 or 20g weight on the tail.

Power is adequate rather than Stella, but should be able to gain height easily and exchange potential energy for kinetic and vice versa .

[Chris Walby]

Each to their own, but I launch left handed, TX on neck strap and right thumb on the elevator/aileron stick. Throttle hold on top right switch. Throttle up with throttle hold on, then when ready model in left hand, flick throttle hold off and launch with right thumb at the ready to get some input...does not always work, but better than watching it pile in while stabbing myself with a TX stick!

 

Looks to fly well, what's the low/high speed and stall like?

Edited January 27 by Chris Walby