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-   -   Skymaster Hawk Once Again (at least!) (https://www.rcuniverse.com/forum/rc-jets-120/3284481-skymaster-hawk-once-again-least.html)

jseppanen 08-21-2005 03:54 PM

Skymaster Hawk Once Again (at least!)
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Thought this should be The special moment to write my first post here...;)

Just had the maiden flight with my SM Hawk - it was a veerrrrrryyy GOOD experience!!! Also the second about 8min fligt almost right after!

Nearly perfect conditions; 21Celsius (70F), only a little (cros)wind, partly cloudy and not too many spectators!

Skymaster BAe Red Arrows Hawk, Jetcat P120. Dry weight ca. 11,5kg (25lbs), 2x1950FAUP 5cell receiver packs, standard Jetcat ECU pack, no additional weight needed for balance. Stock SM pipe, SM scale gear with Robart valve and UP valve for brakes. Jr 8511 in elevator (x2) and flaps, 9411 for ailerons and nose wheel steering, Hitec 225MG for rudder.

Ground handling was easy, take-offs effortless, handling in the air very smooth and landings uneventful - almost 3000ft tarmac field made it a lot easier for nerves.

CG at 180mm as suggested, about 10mm flap at takeoff - little under 30mm for landing. Elevator about 40mm each side, ailerons 16mm, rudder 30mm. Flap-Ele mix a little too much for my taste (linear Ele mix from 0 to about 15mm (Up) with flap - the plane wanted to stay in the air forever - had to push a little in aproach.

BTW these were also my first ever turbine flights...hopefully lots more to come!

Sorry no video - will try to get a clip or two of the next flights. Few images though...

jseppanen 08-21-2005 03:59 PM

RE: Skymaster Hawk Once Again (at least!)
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...and a few more...

jseppanen 08-21-2005 04:02 PM

RE: Skymaster Hawk Once Again (at least!)
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...and more

AirPac Models 08-21-2005 04:44 PM

RE: Skymaster Hawk Once Again (at least!)
Good Job Jseppanen!! You will enjoy this Hawk a lot. Welcome to turbine world.

Dave03B 08-21-2005 04:49 PM

RE: Skymaster Hawk Once Again (at least!)
Congratualtions! Great to hear it went well! Any inflight photos? :D



Q8SABRE 08-22-2005 02:16 AM

RE: Skymaster Hawk Once Again (at least!)
can you show me your nose gear door setup.
Did you have any nose gear door problems in flight?

Ali 08-22-2005 03:57 AM

RE: Skymaster Hawk Once Again (at least!)
Well done. The model looks great, and some really nice photos as well.
Feel free to move the Cg back a little at a time. Some people like the 180mm set up, and others have moved back 10mm I like the rearward CG, but it's up to you.
The 15mm up elv with flap is a little high I know ,but can come down a few percent at a time. I found that as the model slows down that the 15mm up stab makes for a nice model sit, but I agree if a too fast you have to hold some down in which can be strange on landing.
Anyway well done again, and I am so happy to see that customers are starting to fly and enjoy the Hawk.

David Gladwin 08-22-2005 06:02 AM

RE: Skymaster Hawk Once Again (at least!)
Glad to hear that your Hawk flights went so well but not at all surprised , this is a delightful model to fly. I see your elevator and aileron servo set up is the same as mine but I would encourage all Hawk fliers to balance the stab. or at least add SOME weight in the nose of the stab. This is a large tailplane and much of the mass is behind the hinge line and this mass must be balanced by the servos if the stab. is not mass balanced, the load increases with "G". I believe the easier one can make life for these servos the better it will be for their longevity and you will reduce current draw by them AND reduce the risk of flutter at high speed.

As Ali said the trim position of your stab. with flap will probably benefit by being reduced somewhat.

I added about two ounces in the nose of each stab., just fishing weights secured with epoxy.

Enjoy your Hawk, its a terrific flying model.


David Gladwin.

MNModels 08-22-2005 01:58 PM

RE: Skymaster Hawk Once Again (at least!)
Good job!! I am so glad that you show off that linkages. Any newbies should check it out. If the model is well linked up with good servo's it will feel solid in flight and will make flying that much better. Sometimes we rush to finish things and forget these vital elements(happened to me). Remember the weekest link...

I now also mass balance all my flying stabs! It can not do harm, only good! Takes only 5 minutes!

Congratulations again and many happy landings.


jseppanen 08-22-2005 02:54 PM

RE: Skymaster Hawk Once Again (at least!)
Hi again and thanks!

Three more succesfull flights today - really beginning to enjoy the plane! Allthough high up I dare to fly her really slow without showing any bad tendencies, down low at landing it's like twice as fast as Ali in the videos...[X(] - need some more practise (read: lots more).

to Dave03B; sorry, nobody with me to take the inflight photos. And besides, you would have needed some serious telescope to photo the plane in the first flight (you know - It's a bird! No, it's a stain in the lens! No, no, no, it really is my Hawk!!!)

to Sabre-RCU; have not installed the gear doors (yet). Also interested to hear/see some installations.

Ali, I will move the CG back some - first replacing the heavy ecu pack in front with some lithiums - should be a few mm's back with that. Did you or anyone else experiment with crow mix (AIL up with FLP down) for the landings? From my experience with heavy ballasted (not nearly this heavy!) F3B and F5B gliders the Hawk could - and i mean could - benefit from SOME crow mix. Though with very slow aproach speeds this is probably not needed (?).

David, yes, mass balancing of the elevators could not hurt if you can keep the cg at the ball park. Should be easily achievable. The plane is seeing some quite high loads in the air -my Schulze is constantly putting about 270-300 mAh to each receiver pack after only 8-10 min flight (the true mAh usage isn't this high ofcourse - don't know the real amp draws).

Today using the wheel brakes i noticed some asymmetry in braking power. Another brake contact plate (what is the word?) in the left brake had broken loose - mean the soft stuff (glued?) to the aluminium back plate. I have no experience fixing these, any suggestions?

Hopefully next flights in a couple of days...

rgds, janne

jeff sewell 08-25-2005 07:37 AM

RE: Skymaster Hawk Once Again (at least!)
I think it is really admirable that you take the time to tell others of your flight experiences with your new model. This kind of information is absolutely essential to anybody else (like me!) consideing buying one of these kits. Whilst I mean no disrespect to the various people who also happen to sell this model - nothing wrong with that - it is very good to get the subjective view of a 'normal' flyer. I wish you every success and hope to be re-joining jet flying myself soon...

F.Pock 08-28-2005 03:12 PM

RE: Skymaster Hawk Once Again (at least!)
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Hi ,

we are also flying the hawk in the last weeks. On our Jet meeting in Cologne this weekend we made flight 5 - 10. The model is very good in flying and on the field. It is very easý to handle at it gives a lot of fun. We are flying a same set up, but only 6mm elevator mix with full flaps, maybe we are to fast for more. but on our fild ( 260m grass ) it is very good to land. We are flying with a Jet Cat P120 and have many fun with it. Here are some pics of the installation.

RONW 09-07-2005 07:05 PM

RE: Skymaster Hawk Once Again (at least!)
Hi, Ron from New Zealand here and I am doing the Skymaster Hawk. I cannot find any previous posts on my query so here goes.

Ali or David I hope you can help.

I am concerned that the clunk may not be able to follow the fuel when inverted using the supplied Skymaster fuel cells.
My reasoning is, because the tank is more verticle then ordinary and the outlet is at the top I worry that the clunk will not be able to move to the (new) top of the tank when the model is inverted as easy as it would if the tank outlet was at center height.
The tube and clunk would have to bend a full 180 deg. to stay in the fuel when the tank is getting near empty.
I have watched Ali's clips of the model and it does not appear to suffer and problems when inverted so I would be pleased to learn if you have done anything special in plumbing the cells.


seanreit 09-07-2005 09:34 PM

RE: Skymaster Hawk Once Again (at least!)
Look up what a "UAT" is on RCU Jets section, and read all you can on what it does. Also, think header tank, and if you don't know what that is, ask your other jet buddies.

I don't know about your plumbing in a skymaster jet, but are you up to speed on header tanks?

Woketman 09-07-2005 09:49 PM

RE: Skymaster Hawk Once Again (at least!)
Sean is correct. So what if the main tanks are sucking air while inverted, the header should have enough reserve to continue an uninterrupted fuel supply, at least for a while. Just don't fly more that 10% of the time inverted!

That being said, I still try to set up the mains to use very flexible Tygon on the insides and use a heavy clunk to keep that clunk in the fuel, for insurance.

RONW 09-07-2005 11:09 PM

RE: Skymaster Hawk Once Again (at least!)
Thanks woketman this is what I thought. I realise the header tank would sustain fuel supply for a limited time but if the clunks in the mains are not in the fuel then the header will be filling up with air. If you have seen some of the photos showing the header tank also mounted vertical and I am not sure how they arrange the pickup in that situation. I will test the main clunk and lines before installing to see how far the Tygon will bend, at least Tygon should not kink if it bends that much.


RONW 09-07-2005 11:29 PM

RE: Skymaster Hawk Once Again (at least!)
How does the rudder feel with only a small power servo?
I notice that David Gladwin used an 8511 which is nearly 4 times the power.

jseppanen 09-08-2005 03:51 AM

RE: Skymaster Hawk Once Again (at least!)
Before dry testing I had similar doubts about the fuel tanks. BUT using flexible tygon lines and little adjusting I managed to set it up so that in both tanks clunk will go to every corner also inverted - and no kinks. Now after 18 flights no problems - no significant amount of air in UAT after flight (lots of rolls and some inverted flight).

About the rudder servo - I deffinately would have installed a more powerfull servo if only there was space! I tried jr9411 but it won't fit without modification. With Hitec 225MG I have at ATVs 140% both ways, shortest possible servo arm and long rudder horn. This way movement about 30mm (1 1/4 inch) each way. Prolonged knife edge and point rolls good, no signs of flutter yet...

Btw, increased flap movement to about 35mm with a little crow (about 6-7mm up aileron). Elevator mix with max flap about 10mm up. CG at 185mm. Very easy to land now.


David Gladwin 09-08-2005 04:06 AM

RE: Skymaster Hawk Once Again (at least!)
I shared your concern about the vertical tank . Although Ali says he has no problems, for the sake of confidence if nothing else I installed the tank FLAT under the rear radio tray and relocated the feed hole in the tank. Works perfectly for me and took very little extra time to do. You can use a UAT or just a simple header tank, 4 ounces or so, with a centrally located pickup, my experience is that both work equally well in a correctly plumbed and airtight system. I should add that after a flight including rolling manoeuvres there is almost NO air in the header and thats how it should be. Very much looking forward to doing a lot of flying with my Hawk this southern hemisphere summer as well as building my Airworld Hawk, being delivered as I write. Now that really is a superscale Hawk and full review coming in RCJI.

Yes I use 8511s they are hardly any bigger than a standard servo, cost only a little more and a strong, very strong servo is one of the best defences against flutter. I don't recall anyone losing a model because of a strong servo but know of many where a weak servo lead to flutter or degraded control. I should add that I installed the servo in the fuselage which allowed a concealed linkage as well as space for the 8511.


David Gladwin

RONW 09-08-2005 04:20 AM

RE: Skymaster Hawk Once Again (at least!)
Thanks for that information Janne and I will try your flap settings as well.
I was thinking of installing an 8411 or 8511 for the rudder somewhere near the elevator servos and setting a control rod into the rudder from the bottom and taking it through a matching hole in the fuselage to hook up to the servo.
I have not trial fitted it yet so I am not yet positive if I can get it all to fit or not. If I put one beast of a servo on the elevator it should make life a lot easier.

David I also had in mind to fit the UAT in the horizontal position for peace of mind.


jseppanen 09-08-2005 04:44 AM

RE: Skymaster Hawk Once Again (at least!)
I think David means he installed the front main tank in horizontal position - not the UAT. Best position for UAT is fill line(s) up (=tank tilted about 45 degrees) or vertical (=pump feed up). This way there is minimal amount of trapped air after filling. This is if you fill the main tanks via UAT...


Ali 09-08-2005 04:55 AM

RE: Skymaster Hawk Once Again (at least!)
Ron Hi,
I am on Hawk number 4 now (all 3 previous were sold on RTF) On hawk no.3 I had some real problems with flame outs after lots of slow rolls and inverted. The problem came from the clunk not following fuel around in aeros. I do use a UAT but the problem is that a UAT is quite small and it doesn't take long before the air build up was too great to allow the engine to keep running.
I was puzzled as I had never had a problem before, so I thought there must be something wrong. It turned out to be the fact that I had replaced the tubing that came in the kit for the tank install with original Tygon. The proper Tygon is thicker and less flexible which was not good for the Hawk tanks. Also I had pushed the tube through the fuel tank bung a long way into the tank. My thoughts were that I would have more tube for the tygon to rest on this reducing any chance of it coming off inside the tank. Again the problem here was that had made the tygo go through quite a sharp 90 deg bend to reach the bottom of the tank. Again reducing the flexibility of the clunk line. Once I changed the tygon to the original tubing and set up my tubes through the bung so that they were not all the way into the tank I added a lead washer to the clunk to increase the weight of it. This has now given me a air free system. After 12 mins of non stop areos including extended inverted my UAT has a tiny (and I mean tiny) air bubble.
As for rudder servo.
I have been using the Hitec HS 5125 Thin wing servo with good effect. My flights include some sustained knife edge and the odd flick at the top of a loop. At no time do I feel any rudder blow back or lack of control. Having said this my latest hawk has just been re-engined with a wren 54 and while I was there I decided to change the rudder servo. I was never happy with the amount of slop in the 5125 gears. It was always in the back of my mind and held me back from doing as much high speed stuff as I would like.
The problem I have is what servo to put in it's place. JR make the DS161 which from what I can tell is the same servo. But the 161 comes with a nasty plastic servo arm that has so much flex on it that I would be worse of than with the Hitec.
I am just waiting for a JR 3301 servo to arrive. If that fits easily I will give that a go.
I would love to put a 8411 on the rudder but I just dont want to add any more weight to the back end of this model, plus my linkage is already set up for a servo in the fin.
Janne: How did you mount the 225. Do you have any pics?
Hope this has been of help. Any questions please feel free to ask. Or you can email me direct on [email protected]
Regards Al

jseppanen 09-08-2005 06:25 AM

RE: Skymaster Hawk Once Again (at least!)
Hi Ali

Not everyone might like my method of servo mounting - lots of Hysol - quick, dirty and easy as he**. It is also possible to depart the servo afterwards with careful heating with a heatgun (softens the epoxy). You may brake the servo in process but I don't care, especially not with the 225.


john agnew 09-08-2005 08:14 AM

RE: Skymaster Hawk Once Again (at least!)

I have installed a Hitec 225 digital MG servo using the aluminium arm that comes with the servo. As you are no doubt aware this will not fit in the existing hole as the servo is proud of the rear of the opening in the fin. I have increased the length of the opening by about 20 mm and made a new 2mm plywood hatch to which I have glued / screwed beech blocks and the servo is screwed to the blocks. The servo is fitted as far forward as possible and the back end of the servo is still a tight fit under the cover but much better than the standard installation.The cover is screwed to the existing rear ply triangular plates and similiar new ones at the front end.

The cover is then painted to match the model. I have also increased the opening on the aileron servos to allow me to use the Hitec HS 5625 MG digitals the servos are screwed to beech blocks and glued to 2mm ply plates which are then glued to the upper wing surface using Hysol or equal., The flaps are similiar but using the supplied openings / covers.I am using one of the Hitec HS5998 TG giving 18kg at 6 volts on the elevator.

For tanks I have used two Dubro 32oz tanks mounted one on top of the other with fuel being drawn into the top tank from the bottom tank and then to a Graupner 6oz hopper with central pick up using an Orbit clunk, the main tank uses a felt clunk (weighted) on tygon, as the tank is shallow clunk movement is not a problem. 64oz should give a comfortable 8 minutes with the Wren Supersport.


Vincent 09-08-2005 09:37 AM

RE: Skymaster Hawk Once Again (at least!)
(2) 50oz dubros will fit as well.

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