Jump to content
Sign in to follow this  
SlopeMe

MDM FOX (again)

Recommended Posts

Some may recall my 4 metre Fox about 3 or so years ago? I built it to fly off the slope at Raglan, heavy and strong.  The theory was that it was to be a strong wind aerobatic glider but Raglan turned out to be the wrong slope for this model. In retrospect, what was really needed was a more "powerful" slope, higher and with better lift generating winds. This model was too difficult to launch on my own at 8.5 kgs and struggled to aerobat in anything under 25 kts, which I never actually got to fly it in.

Sadly, I sold the model after investing quite a lot of time and $$$ constructing it. But the other day I spotted an unfinished kit on TM, a 3.5 metre Fox from a Chinese manufacturer. So I drove to Tauranga and bought the kit. A very nice glass fuselage, canopy and cockpit with sheeted and covered wings, rudder and tailplane, a spare canopy and bag of hardware bits and pieces. The fact that the projected flying weight is 4.8 kgs made it a nice replacement and the slightly smaller span seemed a more manageable size...I thought it will be perfect for Raglan.

There are a few quite nice features such as airbrakes with integrated servos, so you don't have to buy and install separate servos, the wing sheeting seems to be 2.5mm instead of the usual 1.5mm. The wing joiner is a hefty 16mm solid steel rod weighing in at 1 kg.  I don't mind this as the overall flying weight is still quite light and it certainly simplifies and speeds up rigging at the slope. The fuselage already has a very large cockpit frame and several formers to strengthen down the tail moment.

At the moment, after spending about 20 hours, the model is almost finished. Another 2 or three hours will sew things up and then of course the wind won't play ball for three weeks.

A few photos to follow.I usually put the Wog in these photos for scale, but she would not cooperate, that's her in the first one... ( no it's not my Great granny's hat ! )

_PAU2580.jpg

_PAU2581.jpg

_PAU2582.jpg

_PAU2584.jpg

_PAU2586.jpg

_PAU2587.jpg

_PAU2588.jpg

Share this post


Link to post
Share on other sites

Cool bananas Paul - I actually thought of you when I saw that model on TM and wondered if you had pinings:-D

Chris is very happy with his one and it seems to be strong enough with the sheeted wing.

Looking forward to seeing it grace the Raglan slope in the near future.

I have a boxed up 3M one that I REALLY must get to.

 

Share this post


Link to post
Share on other sites

Fox all finished and ready to go!  I beefed up the forward end of the fuse with chopped strand mat. Nose weight ended up at 514 gms for a CoG of 26% at the root.

It feels a bit over the projected 4.8 kgs but I guess we all know they under estimate these things on the box. Will probably do a weigh-in just to satisfy my curiosity. Looks like the wind's won't be anything near a westerly until middle of next week at least. I'm going to maiden her in a different spot to normal; I don't trust our usual spot these days, too much gorse and rotor now.  I drop her off the cliff near the surf club, Daryl, you will know where I mean, go straight ahead at the roundabout and park before driving down to the car park. There's a steep cliff next to the picnic table and seat. Will have to walk back quite a way to land, or down to the beach.

 

Share this post


Link to post
Share on other sites
2 hours ago, SlopeMe said:

Hey Daz, which Chris do you mean?

Oh, Chris from Cambridge - "ducatikid". I mentioned him in a recent post in the "Hand launched" gliders thread which relates to the ESM gliders at RCBandit.

Here's his electrified ESM Fox: http://www.rcgroups.com/forums/showpost.php?p=32549400&postcount=29

He took the swirly bits off and gave it a bit of a makeover.

Share this post


Link to post
Share on other sites

Just a thought Paul - it might be an idea to have a word with Chris and see how the stock CG worked out on his Fox. I know the CG quoted by HRS for the Ka-6 is a mile out. Do you still get the Flyers World? If so, Chris's contact details are listed as the contact person for the Cambridge Club in the club listing pages.  

http://www.rcgroups.com/forums/showpost.php?p=32966515&postcount=35

Share this post


Link to post
Share on other sites

I maidened the Fox yesterday at Rags. Arrived at 11am to a SSW of 15 kts so it was too south to risk but the wind was due to move around to a SW anytime so I drove over to town for lunch.

I sat at the airfield and watched the wind sock and before long it had swung around a bit to the west by 20 odd degrees, so time to get back to the slope. By 12.30 it was flyable and I decided to launch from our usual site but from down 8 metres or so to the very edge where the gorse has grown. This was to move out of the dead zone that has been created by the new gorse and weed growth. (We must have a little working bee soon and clear all this crap away so we can restore our normal launching spot to the top again).

The launch was excellent with no sign of any of the stalling problems encountered at the top, the Fox climbed away nicely but needed an urgent thumb to the elevator trim as she was very much up-trimmed and required many clicks of down. I may have to move the stabiliser dowell position further up.  She also required three or four clicks of right aileron, due to the less than perfect balsa kit ailerons supplied which are slightly warped. After these adjustments the model flew nicely. I tried only one gentle loop, as I noticed my elevator clevis required a squeeze with the pliers which I had neglected to bring and I didn't want to risk it popping off (er... not very nice having no elevator....!!!). The wind direction was not ideal but at 17 kts the lift was adequate and without too much turbulence. I had programmed the model with more than the "normal" control movements and with plenty of expo to ensure it would complete manoeuvres quickly if required. Not strictly scale, but more exciting to fly.

I climbed away and tried a few rolls which were pretty axial and then I tried inverted flight which was excellent, due I think to the airfoil which is pretty nearly symmetrical, but on close inspection actually has a more rounded underside towards the trailing edge (I don't know what to call this but I assumed it was to improve the inverted flight characteristics) and it seems to work as the model flew surprisingly well upside down.

After 20 minutes or so the wind direction seemed to improve a little more and the lift got better, allowing plenty of height to be gained before walking back to the hang gliding paddock to land. I thought this to be the best option on the day. The approach was fine even though the airbrakes provided only minimal slowing of the model, as they do not rise all that much. The landing was also good except for the wheel coming off, breaking the plywood frame inside the fuselage. A typical sign of Chinese lack of attention to strength. So this area will need to be beefed up a bit.

All in all a pleasing first flight, especially knowing I will be able to launch this model on my own, unlike the bigger 4m Fox. I feel it won't be worth trying to fly it in anything less than 17-18 kts as it won't be capable of any manoeuvres worth doing, but in 20 kts plus, she will be loads of fun and looks great in the air, as it's a very pretty looking plane ( well just my personal opinion).

Maybe I'll get photos next time or whenever I have some company.

Share this post


Link to post
Share on other sites

Good stuff, Paul.

re: no elevator, i had a mid-air once at the Nats which took out my elevator, but it stuck in the hard up position, and the thing eventually just looped its way to the ground and in a happy coincidence, it looped nicely onto its belly without any further damage. Mid-panic i threw my transmitter at Joe W, and he tried to see if he could do anything - he couldnt in the final few seconds, but didnt matter in the end.

However, he did share with me a nice peice of advice (or several actually).

  • If you loose the elevator, then he says to roll it upside down, and pile in some reflex into the wing (only really works if you have full-moving trailing edge) so as to turn the wing into a stable foil (akin to a flying wing) and then you can actually fly it using reflex trimming in place of elevator. He *has* done this before.
  • If your elevator gets stuck up/down, then roll it over and enter a sharp descending turn - or as he puts it: "its doing the yanking, you do the banking"... again he has done this, and would have helped my incident if he realised what had happend early enough.

Nuts... Doubt, i would be thinking that clearly and calmly in any of those situations...

Share this post


Link to post
Share on other sites

Hey Paul, I'm thinking of acquiring an ESM Fox.  Is that what you've got, or is it a different manufacturer?  The ESM model is 3.5m and 4.8kg spec.  I'm keen to hear how it works for you, in particular which bits need beefing up.  Have you tried much hard aerobatics yet?  Presumably if the wings fell off, you would post!

Cheers,

Peter (Chch)

Share this post


Link to post
Share on other sites

Hi Peter, I'm sorry about this very late reply. Yes, I think mine is the ESM Fox. It has the heavy steel wing joiner which I wanted to replace with some other much lighter one but have not done so to date. After today, I feel this to be unnecessary, as the model really needs the added weight IMO, in order to assist momentum through aerobatics.

 

Today I went out to Rags as it was predicted to be 16-18 kts Westerly and this proved to be correct, only if anything it was a little stronger which was superb for the Fox.

I had no issues launching, as I stepped down the slope about 3 metres or so to overcome the nasty little rotor that has developed (Rags guys will know what I'm talking about). The first thing I noticed was my modification to the stab incidence was pretty good. The Fox was still climbing ever-so-slightly but 3 clicks of down took care of this and she cruised around nice and level. The lift was excellent today and so permitted any aerobatics I wanted to try. She does shed off speed quite easily, as you might expect from a scale machine, but I'm used now to slippery F3B ships and so I was happy to make allowances.

I'm pretty happy with this plane as she looks good in the air although does not have quite the presence of the 4 m version, which as I've discussed earlier, was not the right ship for this slope and so I've sold it. This 3.5 m version however seems about right for our Raglan slope and is quite manageable for me on my own.

I had two flights today and the first landing was quite a hard one, as I was fast approaching a fence and had to decide whether to attempt to fly over it or land heavily before it. After the maiden landing several weeks ago, the landing wheel and molded housing required a small repair plus beefing up. The beefing up paid off today with the heavy landing as there was no damage at all. The second landing today was way better; one of those landings you wish your mates were watching.

She assembles quickly at the slope and the wing retention bolts which screw the root to the fuselage are a good idea. I have given the elevator a lot of extra up-throw and controlled this with exponential function, so the model can be flaired quite well just prior to touch down. But it's still not an easy thing to achieve in practise when landing towards yourself in long grass. 

Daryl, if you're reading this, I texted you the other day, but no reply...

Share this post


Link to post
Share on other sites

sounds great Paul. Nothing like getting a session in on a school day. Perhaps we will get to see it fly at the 2017 slope fest :) 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×