Large Skymaster Hawk build
 

Hi Guys

I've just started putting one of these together for a customer, if anyone's building one feel free to jump in and share your experiences.

The model is a Hawk T2/100 in RSAF markings, the same as shown in the picture. Power will be a JC 160SX, power box and JR radio. Drop-able ordnance with some scale additions will hopefully really bring this model to life.

Cheers, Alex

RE: Large Skymaster Hawk build
 

Looking forward to seeing the progress.

Thanks
Rick

RE: Large Skymaster Hawk build
 

Here's a few pics of the kit. There are a few little things that need sorting but when isn't there? It's one of the most impressive ARTF's Ive seen, paint finish, gear door fit, mouldings all to a very high standard and did I mention those oleo's...........................The only big thing wrong with the model is that it's not mine :(

The first thing I did was take the gear out as this needs to be painted, I'm also going to replace the tiny main gear door cylinders with some heavy duty one's and then repaint inside the gear doors to match accordingly.

Cheers, Alex

RE: Large Skymaster Hawk build
 

sweeet[8D]

RE: Large Skymaster Hawk build
 

Also looking forward to the build.
I have just placed an order for one and some waiting to do...

RE: Large Skymaster Hawk build
 

SAP_2000, which scheme did you get?

RE: Large Skymaster Hawk build
 

It's been a slow start with this one, just Needed to sort out a few issues with the kit first. I don't believe these problems are representative of this model generally. The reason I say that is thus particular model has been on display in various places, packed and unpacked a few times with the inevitable dinks and people handling it where it shouldn't be handled etc... It was also one of the first large hawks to be produced.

I set about dismantling and degreasing the oleo's and wheels. These really are a work art better than anything else Ive seen from these eastern manufactures infact I think the machining is better than the Sierra stuff I have.

I wanted to start on the wings which is where I discovered the first little problem. The flap hinges have had their slots pre cut. In this case the slots are perpendicular to the trailing edge which is wrong. (The pics in the instructions show the slots cut correctly) They need to be in line with the aircraft's longitudinal axis. If I were to install them in the pre cut slots they would all be angled out board. The first two pictures Ive attached should explain things. The slots have been filled with a epoxy/micro balloon slurry ready to be wet sanded flush and new slots cut. Once the hinges are installed I'll touch up the paintwork visible when the fairings are on. The flap hinges were missing and are being sent but as I said this things been all over the shop so it's not surprising things are missing. I then moved onto the ailerons..........Ideally I would like the linkage perpendicular to the hinge line but because this is faired it's not possible so I'm awaiting some heavy duty ball links so there will be no binding with the linkage off set slightly.

RE: Large Skymaster Hawk build
 

The drop tanks supplied will be made droppable, Ive used a BVM EZ drops and adapted the pylons and drop tanks. The pictures should explain things. Ideally I would have had the EZ drop in the centre of the pylon. Because of the internal structure I had to move it forward. I devised a system where you slot the tank in and push back thus fixing the tank in place. Its held like this by the airflow when dropped it just falls and pulls itself out of the rear lock.

There will be four airlines exiting the wing so 4 BVM EZ airs will be used making rigging a breeze.........

RE: Large Skymaster Hawk build
 

The elevator servos are mounted at the very back under a shroud. Currently there's no support for the servos just the 0.5mm or so of glass. Using some ply I made a plate that's epoxied under the area the servos will be mounted. I've also added some carbon sheet to stop the L brackets digging in which could alter the geometry creating a small amount of binding. Overkill I know but I would prefer it this way especially on the stabilizer! plus I'd run out of G10 so carbon it was.......

With this done my attention turned to the stab bearing block. I've replaced the bolts with high tensile steel and used aeronuts as these are far more tolerant to temperature. (The pipe sits near to these fixings) I've used carbon sheet on the inside to avoid the washers pulling into the ply and creating slop. The fittings for the stab were again changed to high tensile steel...........

There's lots of hardware missing so I'm using my own nuts and bolts linkages etc... as I said this model had previously been unpacked and put together for static a few times so probably why some bits have disappeared....

Cheers, Alex

RE: Large Skymaster Hawk build
 

Final job for the night was to install some larger rams for the main gear doors. The provided rams were too small for this sort of application....

Alex

RE: Large Skymaster Hawk build
 

Hi, Dubd

see the attached picture that SAP_2000 asked this color scheme ,,

Best regards

Anton

RE: Large Skymaster Hawk build
 

Hello !

Anybody who knows the dimensions of the tub dimensions for the cockpitset fot this BAe Hawk large ?

Any info preciated :-)

Peter B

RE: Large Skymaster Hawk build
 

Hi, Alex48

Thank you for your commented, Sorry for my workers made this mistake, the flap hinges slots was wrong. I just check my first products , the flap hinges slots was correctly, So, I will ask my workers for modify these slots again,

Best regards

Anton

RE: Large Skymaster Hawk build
 

Wondered how long that would take ;)

Now to find an equally rare scheme for my Tomahak Hawk.....

RE: Large Skymaster Hawk build
 

Hey Alex, it looks to me like with your pylon dropping mech you will end up ruining either your pylon or you rear tab. I am assuming that the airflow is in the direction of the blue arrow. When you release the tank it is going to want to pivot on that rear hook and the drop tank will be pushed up int the pylon (yellow arrow). I would think you would want the hook farther back (red circle), no? I am just thinking that with all that leverage on the tank and pylon, one of them is going to give, especially at 100+ mph.

RE: Large Skymaster Hawk build
 

Hi Anton, no worries regarding the flaps, its good to do builds on here as the manufactures get to see the little problems with the kits. Good to know your watching and making alterations to the production models........

Hi Ianober, I wondered if someone might comment on that. Your right in what you say it would be better to have the slot further back. I'll post some more pictures when I get home (In Germnany atm) that should show things a little better. The back part of the tab on the tank is round as is the slot in the pylon (when looking from the side). The slot is much deeper than the tab too. It has enough room to pivot slightly from the very back of the pylon and then fall away even with pressure on the tank. Ive also built a weak point into the tab so if it did hang up this would just break leaving the aircraft flyable and the tank needing a minor repair. The pylon and tank were not designed with this function in mind so I'm working around thier internal structures and trying to make use of what's already there. Thanks for commenting on it, any help is very welcome....

Hi Marc what about painting your new Hawk red ;)

Cheers Alex

RE: Large Skymaster Hawk build
 

Hi Peter will measure those when I get back for you...

Alex

RE: Large Skymaster Hawk build
 

Does anyone have a good picture of the retractable landing light in the nose wheel well? I have a few from the front but I#m after a view of it from behind.

Thanks Alex

RE: Large Skymaster Hawk build
 

Hi Alex, one pic nose landing gear light

http://data3.primeportal.net/hangar/...8_20_of_29.jpg

RE: Large Skymaster Hawk build
 

Thanks, some good pictures there........do you guys think the light is attached to the right gear door? I was going to make it retract from the top. I'd like it to be as scale as possible.......................

Cheers, Alex

RE: Large Skymaster Hawk build
 

This is big.....:)

RE: Large Skymaster Hawk build
 

Right then................Ianober's post got me thinking so I made few calls and managed to get 30 minutes wind tunnel time late this evening. Couldn't take any photo's or Videos due to security (more likely he didn't want his boss to find out what the tunnel had been used for tonight lol....), shame they would have made interesting watching.

My system worked up until 110mph then it just broke the weak link I'd made, we tried three times 110 was definitely the magic number. So I'll have to do a little bit of redesign to the pylon and tank then make the rear lock position as was suggested. This is what happens when you try and avoid a bit of work you just make more for yourself........anyway thanks for the prod!

Cheers, Alex

RE: Large Skymaster Hawk build
 

WOW, Impressive!
I cant say I have ever had a builder test one of his ideas in a wind tunnel! I hope thats not going on the bill :D

RE: Large Skymaster Hawk build
 

Hi Al

lol........I wasn't going to but now you've mentioned it......................;)

Hi Pete those tub dimensions are 5" deep 5.5" wide and 10" long these are maximum dimensions as the tubs taper in.

Cheers, Alex

RE: Large Skymaster Hawk build
 

Hi Alex:
I am about to maiden mine. Great kit. No complaints. Paintwork is outstanding.


In reference to your observation regarding the angle of the flap hinges (slots pre cut perpendicular to the flaps), I observed same thing on mine.
Now, be aware that there is almost no clearance between the flaps and the ailerons and fuselage. Also, the flaps are in close contact with the fuse and the ailerons during almost its entire deployment. I simulated the deployment of the flaps with the hinges aligned with the fuse centerline, and they wouldn't move unless you shorten them big time.
Also, the servo to flap linkage will have a side movement that will require ball links (I am not sure if they will fit). Same concept applies to the aileron linkage if you align it with the fuse centerline.
I am not saying it can't be done as you are suggesting. Just try it before doing anything permanent.
I ended up installing them as they came. Works great. The fairings orientation does look weird, but only when you peep underneath..... LOL.

(Probably on the full size the hinges are perpendicular with the flaps, and the fairings are somehow aligned with the centerline (just guessing)).

On another subject: each wings is held in place by a screw that joins the fuse with the root rib. The main gear is massive, and when dropped tends to pull the wings outwards really hard (by inertia, when the gear stops suddenly in the down position). This outwards force is transmitted to the screw. My suggestion is to reinforce the fuselage with 1/8 ply at the screw location; and reinforce the root rib with 1/4 ply joining the upper and lower skins with the rib at the nut location (glued perpendicular to the rib). To visualize what I am saying, drop the gear with the wing installed without the screw, and see how the wing gets shot out....

To avoid the gear to drop so hard, and since I am using the EV5UPRO valve (no individual air flow control), I did the following:
-Install a check valve in the gear down line, oriented so that it stops the flow of air towards the gear cylinders.
-Bypass the check valve with a Dreamworks flow control valve, and adjust the flow to the minimum necessary for gear deployment.
-At the gear up command, the cylinders pressure will return via the check valve.
BTW, I understand you need over 110 psi to get the gear up in flight!!! I will let you know soon.

Last for now: if you are going to work or assembly the plane on a cradle, reinforce the area of contact with the cradle with carbon cloth and 1/4 ply. The bottom front part of the fuse is very soft and will deform and crack.

I almost forgot: "Reinforce the area of the canopy frame that receives the locking pin". On mine, I am sure is was going to pop out on the first flight. Pin was held by about 2mm of fiber, at the most.


Good luck
Jack

RE: Large Skymaster Hawk build
 

Hi Jack

Thanks for the heads up, I'll get onto it.................funny you should mention the wing roots, I was just looking at these thinking they need some reinforcement. I've also just installed some extra BVM canopy hooks but will reinforce the area you suggest too. I'd love to see some pictures.................

Good luck with the maiden! I'm told they fly very well.

Thanks again

Alex

RE: Large Skymaster Hawk build
 

I just wanted to mention a problem I had with mounting the stabilizer bearing block. I noticed the sides of the fuselage were bulging out close to the bearing block. A little investigation discovered the aluminum bearing support was digging into the fuz. i didn't notice this problem when I first attached the stab because there was no compression of the glass, It may have had a small amount of glue supporting it and the constant bolting/unbolting must have dislodged it. When I checked the structure I made certain there was a 1/4 inch ply plate bonded into the structure at this position. The problem is that the ply hasn't been glued flush with the fuz. The forward holes are fine but when I opened up the rear mounting holes I found there to be a 6mm gap between the top of the ply and the start of the glass fuz. To solve this I used 3 large penny washers ontop of the ply so the stab has something solid to bed down onto. While I was working on the stab I carefully checked the geometry of the servos and linkage with a laser and finally bolted the 8711's down.

The touching up on the paintwork was done by SM, it's a bit messy yet to sort it out......just thought I'd mention it in case you thought I was getting messy.

Cheers, Alex

RE: Large Skymaster Hawk build
 

some pics

Jack

RE: Large Skymaster Hawk build
 

Great Job..........[sm=regular_smile.gif] Like the color scheme too!

Cheers, Alex

RE: Large Skymaster Hawk build
 

I also hate that the slams up and down. On some planes you almost expect the gear to come up through the wing as it slams so hard. Can't be good for the gear mechanism or the gear mounts in the wing.

To solve this I restrict the airflow of the exhaust port on the valve. It is much better (IMO) to restrict the exhaust flow as it makes the gear go really slow and smooth, but still with great force so it almost looks hydraulic. When you restrict the in airflow the gear tend to move irraticly and with out force.
On the jet-tronic valves for instance, I blind off one of the exhaust ports and install a festo fitting (M5) in the other. Insert a short piece of festo tubing in the fitting and slide a M3 wheel collar over the tube. Now you can control the flow and make the gear go as slow as you want by turning the wheel collar screw.

I'm sure there is an an exhaust port on the EV5, but you may have to thread it to install a fitting, or glue an air nipple in place with epoxy.

I have used this method on all my planes for many years, and even big heavy gears come up in a slow nice manner.

Looking forward to getting mine[8D]

RE: Large Skymaster Hawk build
 

No engine in there? [:-]

http://image2-5.rcuniverse.com/e1/fo...63/Tn32095.jpg

RE: Large Skymaster Hawk build
 

Staale, I agree with you in restricting the exhaust flow of air instead of the in airflow.
That is what I do in most of my planes.
The problem with some planes (and, according to Ali, this is one of them), you really need to slam it "up" with lots of psi (about 120), or they will not retract in flight.
In other words, you want "Unrestricted" flow going up. So, I needed to slow down the "down" part of the cycle only. And what I described was the only way I could figure it out (using the airpower valve) Any ideas??


Anyway, I will know when I fly it. Depending on the required pressure to retract, I may change things around

Jack

RE: Large Skymaster Hawk build
 

Staale, the engine was installed and ready to go.........(Jetcat 160)

I did't forget it ...LOL

What I forgot, was to "tighten the fin screw". And to do that you have to take the engine, bypass and pipe out.

At least I am glad I remembered that, before going to the field.

Jack

RE: Large Skymaster Hawk build
 

Just wanted to make sure you did not try to maiden it without the engine:D:D

I think that enough pressure is the key to safe retraction. If it does not retract well @ 120psi, the cylinder/ geometry is not right IMO.
I use 120 psi in all my planes and like to use large and maybe even 2 large air bottles so the pressure does not drop that much when retracting.
I always test the system @ 140-150 psi regulary so I know it will hold up and use 120-130 psi normally.

To have induvidual exhaust flow control, the UP valves all have it. I am going for an UP-3 mechanical sequencing valve in my Hawk.
If you don't like the UP valves, you could also go for the normal red Robart valve that also have seperate up/ down exhaust control and a sequencer.

Robart valve: http://dreamworksrc.com/catalog/prod...roducts_id=746
UP-3 valve: http://dreamworksrc.com/catalog/prod...roducts_id=740

http://www.up-1.com/images/pgTW_VALVEthreeINFO_19.gif

RE: Large Skymaster Hawk build
 

The issue with the gear on this model is as follows.
First off the main door rams are just too thin and weak. I replaced mine with a pair of Jet 1a big boys which work great.
Then the actual gear itself was a pain to get retracted, even though on the ground they worked fine. I sort of cured this by doubling up on the large air bottles for the gear only ( Increase volume of air ) and ran 130 PSI This worked better but still had the odd issue in the air.
What it turns out to be is the speed at which you are flying when you cycle the gear.
I found it on the big Skygate hawk. If you left it too long after take off and the speed built up then no matter what pressure you had the mains would just not go away. Even flying inverted ( Which normally gets any troublesome gear away ) did not help. I think the slightly outward facing doors attached to the main gear cause so much drag that as the speed builds up the restriction is too much. So now what I do is take off, as soon as I am off I throttle back a bit, slow down and then cycle the gear. Hey presto 110 PSi and it works every time.
Hope this helps?
Regards Al

RE: Large Skymaster Hawk build
 

Hi, Jack

Thank you for posted these pictures,

i saw you used the 2 x L elevator horns for 2 x elevator Pushrods is better than the Single L elevator horn, I also used this way for my prototype,

I will ask the Morne for modify our manual for this way, Thanks a lot for the remind,

Best regards

Anrton

RE: Large Skymaster Hawk build
 

Re Ali's comment on speed above. All full size have an airspeed limit for retracting the gear - for instance the Jet Provost has a limit of 125 knots for raising the gear, but once down the limit becomes 140 knots. The Lightning (250 retraction and 280 with it down) nose wheel retracts forwards - if the gear is not selected up quickly enough the airflow prevents it from retracting, and you zoom skywards with the nose wheel sticking down - this always leads to ribald comments from any mates who happen to witness the event! Perhaps we are asking too much of our model systems (flaps also are limited to avoid airframe damage and having too great a pitch reaction), and we should make selection of the services at more modest speeds?

RE: Large Skymaster Hawk build
 

Colin, Just out of interest. Did this ever damage the gear on something like the lightning if it were to hang down?

RE: Large Skymaster Hawk build
 

That does look a better set up than one L bracket. I only had one included though so did as the manual suggested.

Alex

RE: Large Skymaster Hawk build
 

Hi Ali, No you just had to slow down to about 220 knots, and the nose leg would pop up. It was just air pressure overcoming 3000 psi of hydraulic pressure. I suspect that the doors and leg might get damaged if the speed was allowed to increase too much. I think there is an example on U-Tube of a four ship take off from Wattisham where one of the aircraft's nose legs sticks down.