DerJet Hunter here!
05-09-2016, 05:51 AM
#76
Dave,
Have you ever dis-assembled the main gear? I noted that my mains do not fully extend (see in-flight gear-down picture above). Are they just spring gear, or something different? If a basic spring, I'm assuming the Tygon tube trick would work again.
Paul
Have you ever dis-assembled the main gear? I noted that my mains do not fully extend (see in-flight gear-down picture above). Are they just spring gear, or something different? If a basic spring, I'm assuming the Tygon tube trick would work again.
Paul
05-09-2016, 06:48 AM
#77
Thread Starter
Dave
05-15-2016, 07:07 PM
#80
Some photos from a jet meet in Texas this last weekend. Came away with the Best Military Jet award, and lots of very positive comments on the Hunter.
Tygon tubing in the nose gear spring helped with the rotation - looks much better and reduced the 'launch' effect.
One word of caution - DO NOT stall the plane, especially with the flaps and gear down. I tried it deliberately at altitude, and although I was high, I was only just high enough. Everyone that saw it thought it was the end.
Whilst it will fly slow, once you get too slow, it will start to wallow, and then BAM! - the nose pitches up and over onto its back and into a vertical dive. Even with full nose down elevator, immediate gear and flaps up and full power, you will lose a huge amount of altitude in the recovery.
It caught me on a go-around on another flight, by not adding enough power, and it started to wallow, but I powered out of it before it really bit hard.
Later, on reading the Pilot's Notes from the Full-Scale, it states (my highlights in red);
So it appears that the model exhibits the same characteristics as the full-size, except we modellers can't feel the buffet stage, and only the pre-departure looseness is the key to getting too slow.
A characteristic to learn and respect, but otherwise a wonderful model with lots of presence. The Merlin 140 is a perfect match for huge effortless aerobatics. 8 minutes on 3600mL of fuel plus about 1000mL of smoke.
Looking forward to more flight soon.
Tygon tubing in the nose gear spring helped with the rotation - looks much better and reduced the 'launch' effect.
One word of caution - DO NOT stall the plane, especially with the flaps and gear down. I tried it deliberately at altitude, and although I was high, I was only just high enough. Everyone that saw it thought it was the end.
Whilst it will fly slow, once you get too slow, it will start to wallow, and then BAM! - the nose pitches up and over onto its back and into a vertical dive. Even with full nose down elevator, immediate gear and flaps up and full power, you will lose a huge amount of altitude in the recovery.
It caught me on a go-around on another flight, by not adding enough power, and it started to wallow, but I powered out of it before it really bit hard.
Later, on reading the Pilot's Notes from the Full-Scale, it states (my highlights in red);
NOTE-Because the rate of descent is very high and because it is possible to induce an inadvertent spin when the aircraft is fully stalled, stalling practice is not to be continued beyond the buffet stage nor below 25,000ft.
(i) Although the aircraft must not be deliberately fully stalled in flight, the characteristics are described here to assist pilots who inadvertently enter the fully stalled condition
(ii) If the control column is held back after the buffet stage is reached,a nose-up change of trim will occur, and though it will vary in degree from aircraft to aircraft to counteract it may require full forward stick movement. Either wing may tend to drop but can be controlled by the ailerons. Relaxation of the forward pressure on the control column at this point will lead to a further reduction in forward speed accompanied by a very high rate of descent. In this condition the elevator is relatively in- effective and response is slow. If extended wing leading edges are fitted there is less tendency for either wing dropping or yawing to occur.
(iii) A spin or spiral may develop, and in any case considerable height will be lost. Large deflections of the ailerons near the stall will cause the aircraft to yaw in the direction of the downgoing aileron and will increase the possibility of a spin or spiral developing.
(i) Although the aircraft must not be deliberately fully stalled in flight, the characteristics are described here to assist pilots who inadvertently enter the fully stalled condition
(ii) If the control column is held back after the buffet stage is reached,a nose-up change of trim will occur, and though it will vary in degree from aircraft to aircraft to counteract it may require full forward stick movement. Either wing may tend to drop but can be controlled by the ailerons. Relaxation of the forward pressure on the control column at this point will lead to a further reduction in forward speed accompanied by a very high rate of descent. In this condition the elevator is relatively in- effective and response is slow. If extended wing leading edges are fitted there is less tendency for either wing dropping or yawing to occur.
(iii) A spin or spiral may develop, and in any case considerable height will be lost. Large deflections of the ailerons near the stall will cause the aircraft to yaw in the direction of the downgoing aileron and will increase the possibility of a spin or spiral developing.
So it appears that the model exhibits the same characteristics as the full-size, except we modellers can't feel the buffet stage, and only the pre-departure looseness is the key to getting too slow.
A characteristic to learn and respect, but otherwise a wonderful model with lots of presence. The Merlin 140 is a perfect match for huge effortless aerobatics. 8 minutes on 3600mL of fuel plus about 1000mL of smoke.
Looking forward to more flight soon.
05-16-2016, 11:21 AM
#81
Some photos from a jet meet in Texas this last weekend. Came away with the Best Military Jet award, and lots of very positive comments on the Hunter.
Tygon tubing in the nose gear spring helped with the rotation - looks much better and reduced the 'launch' effect.
One word of caution - DO NOT stall the plane, especially with the flaps and gear down. I tried it deliberately at altitude, and although I was high, I was only just high enough. Everyone that saw it thought it was the end.
Whilst it will fly slow, once you get too slow, it will start to wallow, and then BAM! - the nose pitches up and over onto its back and into a vertical dive. Even with full nose down elevator, immediate gear and flaps up and full power, you will lose a huge amount of altitude in the recovery.
It caught me on a go-around on another flight, by not adding enough power, and it started to wallow, but I powered out of it before it really bit hard.
Later, on reading the Pilot's Notes from the Full-Scale, it states (my highlights in red);
So it appears that the model exhibits the same characteristics as the full-size, except we modellers can't feel the buffet stage, and only the pre-departure looseness is the key to getting too slow.
A characteristic to learn and respect, but otherwise a wonderful model with lots of presence. The Merlin 140 is a perfect match for huge effortless aerobatics. 8 minutes on 3600mL of fuel plus about 1000mL of smoke.
Looking forward to more flight soon.
Tygon tubing in the nose gear spring helped with the rotation - looks much better and reduced the 'launch' effect.
One word of caution - DO NOT stall the plane, especially with the flaps and gear down. I tried it deliberately at altitude, and although I was high, I was only just high enough. Everyone that saw it thought it was the end.
Whilst it will fly slow, once you get too slow, it will start to wallow, and then BAM! - the nose pitches up and over onto its back and into a vertical dive. Even with full nose down elevator, immediate gear and flaps up and full power, you will lose a huge amount of altitude in the recovery.
It caught me on a go-around on another flight, by not adding enough power, and it started to wallow, but I powered out of it before it really bit hard.
Later, on reading the Pilot's Notes from the Full-Scale, it states (my highlights in red);
So it appears that the model exhibits the same characteristics as the full-size, except we modellers can't feel the buffet stage, and only the pre-departure looseness is the key to getting too slow.
A characteristic to learn and respect, but otherwise a wonderful model with lots of presence. The Merlin 140 is a perfect match for huge effortless aerobatics. 8 minutes on 3600mL of fuel plus about 1000mL of smoke.
Looking forward to more flight soon.
Danno
05-22-2016, 12:14 PM
#82
Thread Starter
Matt got to solo his Hunter this weekend and managed to put in some good flights even on the 'rained off' Saturday
Few pictures from today before it rained again!
Few pictures from today before it rained again!
07-25-2016, 03:45 AM
#83
Advisory - Exhaust Pipe Failure.
I was doing some work on my Hunter and noticed a defect inside the exhaust pipe. After removing the pipe, I found cracks in the inner pipe at 2 of the 4 locations where the inner/ outer spaces were welded onto the inner pipe.
The model has 28 starts and 17 flights on it, with no hot starts, just normal operation. The engine is a Merlin 140.
DerJet suggested that this was caused by an installation error, with incorrect engine/ pipe distance. I have the Merlin 140 mounted with a pipe gap of 25 mm, although I did notice that the fuselage got very warm during initial ground runs, and I added insulation just behind the engine. Gaspar quotes 25-75mm pipe gap for the 140.
I am going to replace the pipe with a Tamjets pipe, but advice on if the engine/ pipe distance is incorrect would be appreciated.
Thanks
Paul
I was doing some work on my Hunter and noticed a defect inside the exhaust pipe. After removing the pipe, I found cracks in the inner pipe at 2 of the 4 locations where the inner/ outer spaces were welded onto the inner pipe.
The model has 28 starts and 17 flights on it, with no hot starts, just normal operation. The engine is a Merlin 140.
DerJet suggested that this was caused by an installation error, with incorrect engine/ pipe distance. I have the Merlin 140 mounted with a pipe gap of 25 mm, although I did notice that the fuselage got very warm during initial ground runs, and I added insulation just behind the engine. Gaspar quotes 25-75mm pipe gap for the 140.
I am going to replace the pipe with a Tamjets pipe, but advice on if the engine/ pipe distance is incorrect would be appreciated.
Thanks
Paul
03-06-2017, 07:26 AM
#85
Thread Starter
The thread starter Hunter is finally ready to fly. Andy Rann has finished the build and we hope to test fly it in the next few weeks-once the weather settles in England, and we have airfield access. I have just completed the first run and final set up. Balance needs adjusting from the figures he got with the 'chocolate tea pot' electronic balance machine, manual checking shows it out buy over an inch!
JetCat P-140Rxi, JR 28X radio.
JetCat P-140Rxi, JR 28X radio.
03-06-2017, 11:15 AM
#86
Hi Dave
you are not the first one that found that with the electronic C/G try this I find it very accurate
http://rudolph-modellbau-design.de/p...e22d93faf51384
cheers
Andy
you are not the first one that found that with the electronic C/G try this I find it very accurate
http://rudolph-modellbau-design.de/p...e22d93faf51384
cheers
Andy
03-06-2017, 11:57 AM
#87
Dave,
Can you take a photo of the main gear from directly behind. My main legs are splayed out 6degrees. I mentioned it to DerJet and they just said I should have built it per the instructions, even though they installed the gear.....
Retracted position is fine. Looks like it needs an 89deg retract, not the 95 degrees as supplied.
Also, the mains are marginal on retraction power - they take at least 80psi to lift the main leg when on the bench, and they fail to retract in flight at over 125psi unless I bunt over to negative g at the same time. I have plenty of air capacity.
I'm working with Darrell at Sierra to get a new set of retracts that puts the main legs perpendicular to the ground and with bigger rams.
Paul
Can you take a photo of the main gear from directly behind. My main legs are splayed out 6degrees. I mentioned it to DerJet and they just said I should have built it per the instructions, even though they installed the gear.....
Retracted position is fine. Looks like it needs an 89deg retract, not the 95 degrees as supplied.
Also, the mains are marginal on retraction power - they take at least 80psi to lift the main leg when on the bench, and they fail to retract in flight at over 125psi unless I bunt over to negative g at the same time. I have plenty of air capacity.
I'm working with Darrell at Sierra to get a new set of retracts that puts the main legs perpendicular to the ground and with bigger rams.
Paul
Last edited by JSF-TC; 03-06-2017 at 12:22 PM. Reason: Added picture
03-06-2017, 12:44 PM
#88
Thread Starter
Andy
You would never catch me using any electronic balancing machine! People waste so much time pin pointing a balance point only to find it does not fly the way they like.
I get it somewhere near and fly it to see what it needs.
Paul.
Andy has taken the model home, but I can say for sure the wheel is not angled like that. Can you show a picture of the wheel/leg joint.
The Miss D model has the gear going away at 110psi. Like any scale model with big doors they are speed and g limited. If you climb and retract they will never go away.
what valve are you using?
Dave
You would never catch me using any electronic balancing machine! People waste so much time pin pointing a balance point only to find it does not fly the way they like.
I get it somewhere near and fly it to see what it needs.
Paul.
Andy has taken the model home, but I can say for sure the wheel is not angled like that. Can you show a picture of the wheel/leg joint.
The Miss D model has the gear going away at 110psi. Like any scale model with big doors they are speed and g limited. If you climb and retract they will never go away.
what valve are you using?
Dave
03-06-2017, 01:05 PM
#89
Dave,
I'm using a UP-3 valve. I have even drilled out the nipples on the UP-3 (after removing them from the valve!) to get more flow through it.
Not sure what you mean by the wheel/ leg joint, the bottom of the oleo or the retract trunion area?
I have a picture of the frame, plus a picture if the trunion (ignore the crack - DJ replaced it as it arrived cracked through being over-tightened)
Paul
I'm using a UP-3 valve. I have even drilled out the nipples on the UP-3 (after removing them from the valve!) to get more flow through it.
Not sure what you mean by the wheel/ leg joint, the bottom of the oleo or the retract trunion area?
I have a picture of the frame, plus a picture if the trunion (ignore the crack - DJ replaced it as it arrived cracked through being over-tightened)
Paul
Last edited by JSF-TC; 03-06-2017 at 01:36 PM.
03-06-2017, 01:09 PM
#90
As for c.g., I'm flying it now about 10mm in front of the recommended most-forward position from the manual. It is much more solid on approach and it does not pitch up rapidly on take off, just a very smooth rotation. It does need a fairly positive pull to flare though on landing.
It does fly about 1" aft of the most-aft position, but not well, and not for the faint-hearted......!!!
c.g. determined by feel and flying it with progressive lead removal, but validated via the electronic chocolate tea-pot!
Paul
It does fly about 1" aft of the most-aft position, but not well, and not for the faint-hearted......!!!
c.g. determined by feel and flying it with progressive lead removal, but validated via the electronic chocolate tea-pot!
Paul
03-06-2017, 01:43 PM
#91
Thread Starter
Having found a picture of Matts Miss D they look similar to yours! (he was also using chocolate tea pots at this time)
UP valve never needs drilling out, you opened the needles to get a 'snappy' retraction?
UP valve never needs drilling out, you opened the needles to get a 'snappy' retraction?
03-06-2017, 01:49 PM
#92
Yes, UP-3 needles opened almost all the way - nothing snappy about the mains retracting, but they come down positively. They struggle to get past the 45deg position on the way up.
They've been taken apart and cleaned and lubed with teflon dry spray to help out.
The nose slams up well though.
Paul
They've been taken apart and cleaned and lubed with teflon dry spray to help out.
The nose slams up well though.
Paul
04-02-2017, 09:46 AM
#95
I received the custom gear back from Darrell at Sierra Giant Scale, less than 4 weeks from my initial call to him about the possibility of making custom retracts to fix the extended angel error.
Very sturdy units, utilizing the original trunion from DerJet, but everything else is Sierra's, including a larger internal diameter air ram. These units now retract at around 50psi on the bench, compared to 80psi for the original units.
Very reasonable price too, especially considering these were custom built, not off the shelf.
They were a drop-in fit for the original units. They arrived last Thursday, and I spent less than an hour installing them and then loaded up for the Bomber Field jet event that evening. I put 12 flights on them over 2 days and they were faultless. The jet rolls better on the ground now the wheels are perpendicular. Everything I expected.
If you want a set, give Darrell a call and mention the DerJet Hunter retract units.
Paul
Very sturdy units, utilizing the original trunion from DerJet, but everything else is Sierra's, including a larger internal diameter air ram. These units now retract at around 50psi on the bench, compared to 80psi for the original units.
Very reasonable price too, especially considering these were custom built, not off the shelf.
They were a drop-in fit for the original units. They arrived last Thursday, and I spent less than an hour installing them and then loaded up for the Bomber Field jet event that evening. I put 12 flights on them over 2 days and they were faultless. The jet rolls better on the ground now the wheels are perpendicular. Everything I expected.
If you want a set, give Darrell a call and mention the DerJet Hunter retract units.
Paul
10-07-2017, 06:45 PM
#97
Had 3 great flights today at the local club field (Fort Worth Thunderbirds). Weather was perfect. The runway is not overly large for a heavy jet (480'x40'), but the Hunter handled it just fine - the take off is more 'committed' than the landing. Stopped in half the length with the aid of the drag chute.
The Hunter and the Merlin 140XBL running perfectly. 56 flights on it so far.
Paul
The Hunter and the Merlin 140XBL running perfectly. 56 flights on it so far.
Paul
08-12-2019, 05:07 PM
#99
I just ordered a white, red & green LED from Unilight, along with a retractable landing light. The lights show up well in daylight.
I think I have the 4W nav lights.
https://www.unilight.at/navigation-l...-light-4w.html
Paul
I think I have the 4W nav lights.
https://www.unilight.at/navigation-l...-light-4w.html
Paul
10-30-2019, 02:13 PM
#100
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Nice! I was considering getting a set for mine (Love the drop down landing light!) for my one. I'd be really keen to see your installation on this as well.
ALSO! wondering if I could reach in regards to the cockpit in the Hunter. I don't suppose anyone could give me some measurements of the cockpit itself? I have a TOPRC Hunter and the cockpit is...well a little average. I reached out to DerJet asking if they have some in stock (DerJet HH and TopRC HH are similar sizes) But before I pull the trigger I wanted to see if the unit would actually fit.
I hope someone would be able to assist. Thanks in Advanced!