RE: FOX COMPOSITES Bae HAWK, Build thread
 

Great looking example of the Hawk again Paul. You flying with the sport wing yes? Slightly different in profile to the scale one?

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Hi Bob

I weighed everything in the kit, which is complete with all the retract mounts and bulkheads and various hardware and cockpit vacforms, and it came out at 6lb 12oz. That's actually with two lots of intake ducting included in the weight. I ordered my Hawk without the ducting fitted, but Jim still sent me the GDF intake ducts and the turbine intake ducts loose. I kept them both in there for weighing purposes because my own intake ducting will be longer than the glow ducting by an amount roughly equal to the turbine ducting.

I weighed the rest of the stuff to go in the model: 2lb 1oz for avionics, retracts and pilot; 2lb 2oz for a Schuebeler DS94 fan, Lehner 2250/15 motor and Schulze 40/160 esc (by itself 7.5oz); and 4lb 8oz for 2x6S 6600 Thunderpower Extremes. A pair of 6S 5000 Extremes would be 3lb 3oz so save 1lb 5oz but the experience of others has the DS94/Lehner drawing around 95A and I think that's too much for 5000s personally. Of course, Stu's fan only draws about 65A, so 5000s would be OK, and Stu's fan/motor and a Castle 110HV only weigh 1lb 11oz saving 7oz compared with the Schubi/Lehner/Schulze.

Overall, the weight of the Hawk with DS94/Lehner and big lipos looks like being 15lb 7oz with a power/weight ratio of 264W/lb , whereas with a Stumax SM110-52 and 12S 5000 lipos it’d be 1lb 12oz lighter at 13lb 11oz with around 218W/lb, which is still not so shabby! I too have a Stumax fan coming, and as I already have the CC 110HV I’m already thinking that I’ll fit Stu’s fan and try to be the first to put one in the air. Mine will have the 6600 packs whichever fan combo I use.

The EDF version of the Hawk as sold by Jim is basically the old glow version with the fan mounting over the wing, as in the first picture. As you can see from the videos that Paul has kindly posted, the plane does go well enough with this ducting, but my 12S lipo packs are made from 2x6S packs and not from 4 smaller packs, and will not fit like those the in the pic. My packs will have to go where I've drawn the yellow rectangle. I don't want to have to buy another bunch of lipos just so that I can fly this model [X(]

My revised ducting will look like that of the little 35in span West Wings Hawk which I’m test-building at present for the manufacturer. This is shown in the two other photos, and the motor/fan unit is in the more common aft EDF location, in this case completely behind the wing TE. The intake vertical splitter will be further aft in my case for more battery space. There’s a conveniently-placed bulkhead just aft of the wing TE in the Fox Hawk which will radially mount an EDF unit very nicely and the batteries will then fit between the ducting with loads of fore-aft movement available to achieve the required CG with any pack of any weight without having to make a special-to-type battery configuration for this one model.

Best regards

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Paul, thanks for posting the EDF videos. It’s good to see Mark's model going well, though I expect to have to get the flaps earning their keep!

Thanks also for your offer of help. There seem to be some pics missing from my instructions sheet ref the rudder servo installation, so I’ll peruse your thread again and maybe ask a question or two.

Best regards

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Dave
Yes it is the new wing and thanks ;)

Gordon

Thanks for the details...this EDF lark is heavy man!

Mine is about 13.5lbs on take off due to fuel so that is comparable to your second setup.

Help is always available Gordon...no problem. [8D]

This is the last video.

2nd sesion at the Nationals...passes getting lower.:D

Once again not using landing flap.

Paul

[link=http://rcuvideos.com/item/BHL29TP63Q3T4WDV]Hawk @ the Nats 2[/link]

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Hi Paul

I must admit that I was somewhat surprised by the weight I came up with, so checked back to your post #1

As you can see, my kit straight out of the box weighs 1lb more than yours did before any work is done on it. I guess that some of that could be attributed to the bigger wing, but if new production kits weigh what mine does, they're anything but lighter than the pre-production ones.

EDF'ers always do the sums first of course and I'd been banking on a final weight of about 14.5lb max with the heavy system Had I come up with an estimate approaching 16lb I'd have passed on this one. However, I'll just have to make the best of what I've got.

BTW, one thing that's missing from my instructions is the pic which is referred to in the text which shows the elevator setting wrt the fuselage, so advice on that setting would be handy please :D

Cheers

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Mmmmmm interesting!
Not quite sure what to make of that.

The wing is bigger but the weight remained around about the same if not slightly less than the original because lighter methods were used.

Dont know..odd..not a problem, but odd.[sm=confused.gif]
I did not include all the vac forms in mine (i did not have them), but they weigh very little.
You do have 2 sets of inlet ducting in with it.

I will have to think about that one. [sm=72_72.gif]

Paul

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Gordon
Are your stabs (tailplane) halves mass balanced?[sm=idea.gif]

RE: FOX COMPOSITES Bae HAWK, Build thread
 

I don't know Paul. I'll get 'em out of the box tomorrow and try balancing them on the pivot tube; I presume they should rest reasonably horizontal if balanced.

Thinks ... looking back at my photo in post #136 the tailplane is tipped backwards indicating no balance. Have you balanced yours?

RE: FOX COMPOSITES Bae HAWK, Build thread
 

I asked for non-balanced...I do not believe it is needed on this tailplane set up.
The mechanism is so good [sm=thumbup.gif]


The weight of the balanced tailplane is quite considerable due to the short moments involved.

I have flown mine now around 12 flights; the elevator is rock solid, no flutter, no issues, never a moments concern.

I have suggested to Fox Comp. that they don’t bother with it but I am not sure if yours has it or not.[sm=rolleyes.gif]

Paul

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Hi Paul

The tailplane on mine weighs 6oz including the dowels. I did a quick and dirty check on the weight needed to balance about the main pivot and it would be about 0.9oz in each stab half placed 1/2in from the root leading-edge, which doesn't seem worth bothering about.

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

So yours aren't balanced?

RE: FOX COMPOSITES Bae HAWK, Build thread
 

No, not about the main fulcrum anyway. I guess that for the small effort and weights involved I might as well add balance weights.

RE: FOX COMPOSITES Bae HAWK, Build thread
 

No point
Remember that is 2 oz at the rear, about 5 oz at the nose to compensate!
About 7 oz in total for nothing![X(]
They are just not needed

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Ah... but I have between 60 and 72 oz of batteries to move around so there will be no need to add more weight to compensate for the balance weights. I'll just shift the batteries forward a bit [8D]

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Fine

but they are not needed! so why fit them? Just a waste of energy!

RE: FOX COMPOSITES Bae HAWK, Build thread
 

It's only a small job that I could fit in whilst waiting for the epoxy to cure on the new ducting I'll be making;)

In fact the whole structure of the plane is rigid enough that I think your right and balancing isn't really needed.

Why did you bring up the subject of balancing Paul? I hadn't given it any thought before you mentioned it.

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

I was trying to track down where your extra weight had come from [sm=confused.gif][sm=confused.gif]

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Sneaky:D

The cockpit set which you didn't include weighs 5oz, and the two glow DF ducts weigh 4oz, which I presume won't be much more than the weight of the tanks you have instead.

Jim emailed me regarding the discussion on weight in this forum and was worried that I don't seem 100% happy with the kit.

So let me say right now that I AM 100% happy with the kit. There's no way I could make anything like this kit with all the detailed finish in a sensible timescale, get it right first time, and achieve a worthwhile DIY saving in cost on the full price which I paid.

Regarding the weight, I'm relaxed about that. On 5000mAh 12S lipos the weight would be about par for the course for a big EDF conversion, and mine will carry bigger than usual batteries (6600mAh weighing about 1 1/4lb more which at present fly around in another plane) so that they don't get caned by the current draw as much as smaller capacity ones, and I'll get longer flights as well from the 32% increase in capacity. Lots of big EDFs weighing around this figure are giving their owners lots of joy from flying them. I'll be one of those too eventually.

Gordon

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Gordon

Like Paul says no need to balance stab!

It's possible to reduce weight a little, but you need big savings to see a difference-my Spark is lighter than the Germans models and performance appeared identical!

We are going to do an EDF Hawk too so we can compare notes later.

At the JetPower show the Germans all looked at Jim's work and were impressed with the quality, we could have sold the Red Hawk kit we had 5 times over!

regards

Dave Wilshere

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Weight doesn't seem to bother jets much.

Just for everyone's convenience, I re-weighed the components separately and then all together.

I've emailed it to Jim so he can maybe look at production if necessary.

Here is the list:

Component weights (in grams) - Fox-Composites Hawk

Fuselage and nose door ..........765
Engine hatch……………………….…..75
Canopy and frame……….…...165
Turbine intake liner……..…45
GDF intake ducts………………….115
Nose bulkhead + Nose support rails + Ply engine mounts ..80

Fin and rudder + Carbon pins + Screw …150

Stabs (2) + Carbon pins (2) + Bearings (2) + Bellcrank ...185

Plywood servo mounts (6)……..30

Main gear mount plates (4)..90

Left wing & gear door………...535
Right wing and gear door…..525
grp wing joiner…………......………55

Screws.hinges/fences ……………..55
+ other minor bits

Cockpit vacforms (as it came and …...175
not cut out from backing sheet)

Total 3045g = 6lb 10.6oz


The weighing scales only read out to the nearest 5g, so the above individual weights are +/- 2.5g


Weighing everything in the above list all together at one go to minimise the +/- uncertainty on the same scales produced a weight of 3030g = 6lb 11.45oz

So there we have it.

Cheers

Gordon

edit. Hmm .. wish there was a way to display a table properly[>:]

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Thanks for that info Gordon.
As i said i did not have the canopy bits and other vac forms so that may be the difference.

Dave
Did you sell it 5 times??;)

RE: FOX COMPOSITES Bae HAWK, Build thread
 

I was the lucky one that bought the Hawk from Dave.

That's the benefit of going to jetpower at 9 o'clock friday morning, you buy everything you need before everybody else comes :D

Pics from when i got back home with the box.



regards

Zack

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Hi Zack

Fantastic looking box of bits...very complete kit isn’t it?
So nice to get the wing and body bags as well.

I hope you will send post some more photos as you build and keep us up to date on the progress [sm=thumbup.gif]

You made a good choice, I am very, very pleased with mine....just wish the weather was better [&o]

Paul

RE: FOX COMPOSITES Bae HAWK, Build thread
 

Hi Paul

Yes i am very pleased with the kit. When i bought it i didn't know about the bags so i was happily suprised when i opened the box.

I will post photos when i start the build.

Pack the hawk and come to cyprus to fly where the sun always shines :D



Zack

RE: FOX COMPOSITES Bae HAWK, Build thread
 

That explains it Paul.

Canopy and frame + cockpit interior + the GDF intakes which you also didn't have total just about 1lb.

With about 11lb thrust from 3kw into a new Australian SM110-52 110mm fan or about 14lb from 4kw into my Schuebeler DS94 120mm fan it ain't going to hang around when I firewall the throttle :D

Gordon