CARF Skygate Hawk in the house !
08-25-2016, 08:26 AM
#1201
Thanks, Marc, it was a VERY near disaster. I certainly endorse your idea of the carbon plate over the pushrod area, as a minimum. I have a carbon plate going from the base almost to the top of the fin sternpost AND a doubler over the cutout area .
I never did put a baffle in your big tank , but so far so good.
The Hawk is ready to go again, but spending too much time fiddling with my Mig. 29 , using up valuable flying slots, (everything working well) and Eurosport, which also suffered rudder flutter last Sunday. That now has a very strong and stiff fin!
David.
I never did put a baffle in your big tank , but so far so good.
The Hawk is ready to go again, but spending too much time fiddling with my Mig. 29 , using up valuable flying slots, (everything working well) and Eurosport, which also suffered rudder flutter last Sunday. That now has a very strong and stiff fin!
David.
Last edited by David Gladwin; 08-25-2016 at 08:31 AM.
08-25-2016, 09:33 AM
#1202
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Question guys
apart from the small air ram which Marc used on the small front gear door what else has everybody tried too over come this problem?? I'm trying to keep as scale as possible thanks in advance
Regards
apart from the small air ram which Marc used on the small front gear door what else has everybody tried too over come this problem?? I'm trying to keep as scale as possible thanks in advance
Regards
08-25-2016, 11:22 AM
#1204
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Bill,
I might be able to assist here.
The tank I made for this conversion is large, its a good shape for a clunk but nonetheless when it starts to get empty fuel will naturally flow to the front or back, the back is fine, the front is not so good for any clunk system.
The Hawk tends to like a steep final which means that fuel can accumulate at the front of the tank and during this prolonged time frame air can be drawn into the pickup line and depending on the amount cause issues with the bubble trap capacity (if used) and hence possible flame outs. Talk has been around inserting baffles in the tank to help prevent this but personally I've not seen anyone post any info on how they have done this, and indeed how the clunk/pickup works inside a baffled tank. I did make suggestions to incline the tank and mounts so that on finals the tank remains closer to the horizontal, I do believe some have done this mod. A friend in NZ is toying with an idea I suggested to add a bulge on the base of the tank so it works as a reservoir holding fuel in a place where the clunk can collect fuel when low. Another option is to add a header tank with a simple fixed central pickup to act as an air accumulator.
There are loads of these tanks fitted in SGH's so maybe others who have them might chime in here and let us know what they have or have not done.
I'va a drawing of an idea I had using the main tank (with a mod) to perform the role of two tanks, if you want the info let me know, it should be achievable with minimal work and a little glass cloth resin work.
marcs
I might be able to assist here.
The tank I made for this conversion is large, its a good shape for a clunk but nonetheless when it starts to get empty fuel will naturally flow to the front or back, the back is fine, the front is not so good for any clunk system.
The Hawk tends to like a steep final which means that fuel can accumulate at the front of the tank and during this prolonged time frame air can be drawn into the pickup line and depending on the amount cause issues with the bubble trap capacity (if used) and hence possible flame outs. Talk has been around inserting baffles in the tank to help prevent this but personally I've not seen anyone post any info on how they have done this, and indeed how the clunk/pickup works inside a baffled tank. I did make suggestions to incline the tank and mounts so that on finals the tank remains closer to the horizontal, I do believe some have done this mod. A friend in NZ is toying with an idea I suggested to add a bulge on the base of the tank so it works as a reservoir holding fuel in a place where the clunk can collect fuel when low. Another option is to add a header tank with a simple fixed central pickup to act as an air accumulator.
There are loads of these tanks fitted in SGH's so maybe others who have them might chime in here and let us know what they have or have not done.
I'va a drawing of an idea I had using the main tank (with a mod) to perform the role of two tanks, if you want the info let me know, it should be achievable with minimal work and a little glass cloth resin work.
marcs
10-03-2016, 01:20 AM
#1207
After my near disaster with the fin failure, my Hawk with the fin repaired as described in RCJI made three more certification flights yesterday. Rudder travel, flaps up, was limited as suggested , four point and slow roll flown using the full travel of the reduced rudder deflection, a full power fast flight showed no sign of any flutter and the new dummy trim tab stayed attached. All went well. (but I will be using stronger rubber bands to hold the nose hatches closed !)
Pitch response was was very good, perhaps too sensitive, with the stab pivot moved to the scale position (allows scale covers on the pivot point) and the low current drain suggests the two JR 6311 HV servos are not working very hard even at large deflections. The model was stalled with full stab deflection as part of the certification flights, totally docile, with a clean break at the stall with not too much wing drop so no nasty tendencies.
Current drain remained remarkably low ( Weatronic data) and the Powerbox Lipo gave a very steady 8 volts, so no switchover to battery 2 on any flight.Weatronic users may like to know that rx status remained at 8 in flight showing the high gain patch antenna really do work well.
It goes into the hangar now for a full internal inspection, activation of the smoke system and the alternate gear extension system, although the Intairco selector valves show zero leakage in one month.
Lots of of pictures of it on the Long Marston thread, many thanks to Alistair Powers.
David.
Pitch response was was very good, perhaps too sensitive, with the stab pivot moved to the scale position (allows scale covers on the pivot point) and the low current drain suggests the two JR 6311 HV servos are not working very hard even at large deflections. The model was stalled with full stab deflection as part of the certification flights, totally docile, with a clean break at the stall with not too much wing drop so no nasty tendencies.
Current drain remained remarkably low ( Weatronic data) and the Powerbox Lipo gave a very steady 8 volts, so no switchover to battery 2 on any flight.Weatronic users may like to know that rx status remained at 8 in flight showing the high gain patch antenna really do work well.
It goes into the hangar now for a full internal inspection, activation of the smoke system and the alternate gear extension system, although the Intairco selector valves show zero leakage in one month.
Lots of of pictures of it on the Long Marston thread, many thanks to Alistair Powers.
David.
10-03-2016, 01:41 AM
#1208
Good news David,
On the pics it seems that you had a camera mounted on the fuselage aimed at the left side of the fin/rudder; any video?
And I'm curious to the stabilizer throws you have used as I've made the same Stabilizer pivot point mod on my Tomahawk Hawk (ground part of certification done last weekend).
Did you use any expo? And are you changing the throws?
On the pics it seems that you had a camera mounted on the fuselage aimed at the left side of the fin/rudder; any video?
And I'm curious to the stabilizer throws you have used as I've made the same Stabilizer pivot point mod on my Tomahawk Hawk (ground part of certification done last weekend).
Did you use any expo? And are you changing the throws?
10-03-2016, 07:57 AM
#1209
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Hi david
im also doing certification flights useing Olympus HP my hawk weighs in at 25.5 kilos then 6.5 litres of fuel, I'm thinking on a larger engine right now what's your thoughts
Regards and happy landings
im also doing certification flights useing Olympus HP my hawk weighs in at 25.5 kilos then 6.5 litres of fuel, I'm thinking on a larger engine right now what's your thoughts
Regards and happy landings
10-03-2016, 09:56 AM
#1210
Good news David,
On the pics it seems that you had a camera mounted on the fuselage aimed at the left side of the fin/rudder; any video?
And I'm curious to the stabilizer throws you have used as I've made the same Stabilizer pivot point mod on my Tomahawk Hawk (ground part of certification done last weekend).
Did you use any expo? And are you changing the throws?
On the pics it seems that you had a camera mounted on the fuselage aimed at the left side of the fin/rudder; any video?
And I'm curious to the stabilizer throws you have used as I've made the same Stabilizer pivot point mod on my Tomahawk Hawk (ground part of certification done last weekend).
Did you use any expo? And are you changing the throws?
I will use it on next flights.
Not much negative G but the PST bubble trap has only a small bit of air in it, so no signs of cavitation or leakage from Tygon or Festo fittings !!
I used 25 % expo , then increased to 30% on pitch but it's still a little twitchy so Iwill limit the throws ( initially as per original ) as I gain experience. My aim is to make it handle exactly as per my Airworld Hawks which are just right for my flying style which emulates the way a real Hawk is flown, no hotdogging or knife edge. (Yuk! ) aileron throws were perfect, even with just a little gyro gain.
Can't see any reason for using a bigger engine than an Olympus. My jet takes off, zero wind in about 60 yards, and has more than enough power for aeros. In fact I am considering putting a smaller engine, JetCat 220, in it.
Lovely model but handling the size and weight is a hassle on my own.
David.
10-03-2016, 10:07 AM
#1211
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Hi david
i couldn't agree with you more ,I thought the Airworld was a absolute corker as I've owned the 1/4.5 and 1/4 and too be honest I thought you wouldn't come no better , but the skygate all I can say is wow! It's in a class of its own, I was warned by several people not too even try and get it out light , so I bought just about every extra from uk jets including full bypass and larger tank, she came in at 25.6kg dry and at that weight I will also agree on your own it's a handful!! But on the other hand even risking a hernia it's worth it �� All I need too get now is a high flow valve for retracts ,
i couldn't agree with you more ,I thought the Airworld was a absolute corker as I've owned the 1/4.5 and 1/4 and too be honest I thought you wouldn't come no better , but the skygate all I can say is wow! It's in a class of its own, I was warned by several people not too even try and get it out light , so I bought just about every extra from uk jets including full bypass and larger tank, she came in at 25.6kg dry and at that weight I will also agree on your own it's a handful!! But on the other hand even risking a hernia it's worth it �� All I need too get now is a high flow valve for retracts ,
10-03-2016, 10:35 AM
#1212
My Feedback: (6)
Hello David ,
speaking from experience these Hawks fly great with P-180RXs and will pull any maneuver in the book .,
scale competition pilots fly these throughout the routine , knife edge and all .,
true these are all under 20kg . But still with lots to spare .
After almost two years mine is finally ready , finely got my ducks in a row , right tail number matching the crew names who flew it . XX322 :-) ....
more updates soon
speaking from experience these Hawks fly great with P-180RXs and will pull any maneuver in the book .,
scale competition pilots fly these throughout the routine , knife edge and all .,
true these are all under 20kg . But still with lots to spare .
After almost two years mine is finally ready , finely got my ducks in a row , right tail number matching the crew names who flew it . XX322 :-) ....
more updates soon
10-03-2016, 10:52 AM
#1213
My Feedback: (6)
Just a note to all seeking to build a competition scale model of the Red Arrows from the skygate /CARF models kit , this hawk is an Mk66 of the type delivered to the Swiss Air Force and differes from the one used by the Britush aerobatic Red Hawks team in several areas most significant at the very rear end of the fuselage above the exhaust pipe as well in other areas .,.
10-03-2016, 03:46 PM
#1214
Just a note to all seeking to build a competition scale model of the Red Arrows from the skygate /CARF models kit , this hawk is an Mk66 of the type delivered to the Swiss Air Force and differes from the one used by the Britush aerobatic Red Hawks team in several areas most significant at the very rear end of the fuselage above the exhaust pipe as well in other areas .,.
This is by far the best flying scale bird on the marked if built right. I will out fly a lot of sport jets in it's size category.
If you are into must have perfection on scale then maybe another model but for shear fun and being able to fly at war bird, scale events you want beat it.
JMHO
10-04-2016, 03:16 AM
#1215
The dummy trim tab was cut away from the rudder to look exactly scale and mounted with polyply tabs, but glued to the top of the tab cutaway to lock in place.
My suggestion of the sequence of events is that the tab fluttered (judging by the damage to the trailing edge of the tab cutaway.
This flutter caused the rudder to flutter overloading the fin which then failed longitudinally just above the mounting tube.
I belive the tab separated, stopping the rudder flutter and saving the fin from total failure.
My suggestion of the sequence of events is that the tab fluttered (judging by the damage to the trailing edge of the tab cutaway.
This flutter caused the rudder to flutter overloading the fin which then failed longitudinally just above the mounting tube.
I belive the tab separated, stopping the rudder flutter and saving the fin from total failure.
As suggested this may have been the "root cause" all along.
My SG Hawk has had hundreds of flights. Its an original kit with the only modification (to the horizontal stab), being an additional grub screw on the spar. JetCat P-200SX and a dry weight of 25 KGs.
Perhaps some are being too HARSH on the original design.
10-04-2016, 04:40 AM
#1216
Darryl,
Having carefully looked at the at the structure of my original SkyGate fin after the failure, I still feel that the original design was poor with shortfalls in load paths and distribution. The bending moment is concentrated at the top of the fin " tube" with not much above it.
I feel that my modification, ie the carbon plate sternpost with a doubler at the pushrod cutout plus cf cloth inside is worthwhile, substantially improving strength with no penalty and is easy to incorporate. The weight increase was about 100 grammes which meant I could remove 100 gm of tail ballast which served no structural function. The ballast required on my machine was about 700 gms.
Anyway, all was well on the last three flight!
David.
Having carefully looked at the at the structure of my original SkyGate fin after the failure, I still feel that the original design was poor with shortfalls in load paths and distribution. The bending moment is concentrated at the top of the fin " tube" with not much above it.
I feel that my modification, ie the carbon plate sternpost with a doubler at the pushrod cutout plus cf cloth inside is worthwhile, substantially improving strength with no penalty and is easy to incorporate. The weight increase was about 100 grammes which meant I could remove 100 gm of tail ballast which served no structural function. The ballast required on my machine was about 700 gms.
Anyway, all was well on the last three flight!
David.
10-04-2016, 08:45 AM
#1217
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Hi guys
for my two Penith I got to go with David, not that I'm taking anyone's side!! Thing is as I see it you build the model lite it looks crap in the air and you can't get a scale landing let alone flight! As I said before I was told not too even try and get it out lite and at the same time after a couple of issues I've heard with fins cracking I made the decision too cloth the inside and strengthen post, as I see it the model is slightly heavier as I said 25.6 dry but having now eliminated the fin risk I will say it's probably one of the best and most solid planes in the air there's absolute no two ways about it, so at the end of the day trim tab no trim tab if you want too risk 15k and you got money too chuck away don't strengthen nothing , myself personally I listen too other people's problems and experiences and do my best too keep my jet safe ��Thankyou too you all
Regards and happy landings
for my two Penith I got to go with David, not that I'm taking anyone's side!! Thing is as I see it you build the model lite it looks crap in the air and you can't get a scale landing let alone flight! As I said before I was told not too even try and get it out lite and at the same time after a couple of issues I've heard with fins cracking I made the decision too cloth the inside and strengthen post, as I see it the model is slightly heavier as I said 25.6 dry but having now eliminated the fin risk I will say it's probably one of the best and most solid planes in the air there's absolute no two ways about it, so at the end of the day trim tab no trim tab if you want too risk 15k and you got money too chuck away don't strengthen nothing , myself personally I listen too other people's problems and experiences and do my best too keep my jet safe ��Thankyou too you all
Regards and happy landings
12-10-2016, 01:18 PM
#1220
My Feedback: (6)
I've finally done my maiden on my Hawk yesterday plus another three sorties .
absolutly stunning as I've witnessed quite a few of these fly in past years since Stefan Wolker completed his very first one .
The hawk flown right has a beautiful scale like non steep approach ( proper energy management ). I've added another 1.5l of fuel to the existing fuel tank allowing a comfortable 9min flight duration with my P-200RX .
the model is a bit over 22 Kg . Had to add 750g of ballast to the tail due to my overloaded high scale cockpit I built for it .
Got a scale functioning smoke pod carrying 2.5l of smoke fluid .
Absolute joy to own and fly one of these ... Thank you Stefan !
absolutly stunning as I've witnessed quite a few of these fly in past years since Stefan Wolker completed his very first one .
The hawk flown right has a beautiful scale like non steep approach ( proper energy management ). I've added another 1.5l of fuel to the existing fuel tank allowing a comfortable 9min flight duration with my P-200RX .
the model is a bit over 22 Kg . Had to add 750g of ballast to the tail due to my overloaded high scale cockpit I built for it .
Got a scale functioning smoke pod carrying 2.5l of smoke fluid .
Absolute joy to own and fly one of these ... Thank you Stefan !
12-12-2016, 02:31 AM
#1225
Glad to see all went well. Mine is flying again and handles beautifully, although rather sensitive in pitch, c of g will be moved forward a little and a little more expo used, currently 30 %
I have received a new a new fin from CARF and the main tube is smaller than the original. I have used a combination of CF tubing to make things fit.
I looked carefully at the at the latest fin structure and frankly it's not that much different to the original. As the model needs tail ballast, I will incorporate carbon fibre cloth in the lower are of the new fin and a cf sternpost as I described in RCJI. I will not cut out the dummy trim tab ! As the small weight of these mods. replaces structurally useless lead it is more insurance agains any possible failure.
Over the Christmas holiday I will split the fuselage and inspect the engine mount etc to see that all is wel, then ready for the new season next spring!
Superb model, particularly at weights higher than 20 kg. !
Regards,
David.
I have received a new a new fin from CARF and the main tube is smaller than the original. I have used a combination of CF tubing to make things fit.
I looked carefully at the at the latest fin structure and frankly it's not that much different to the original. As the model needs tail ballast, I will incorporate carbon fibre cloth in the lower are of the new fin and a cf sternpost as I described in RCJI. I will not cut out the dummy trim tab ! As the small weight of these mods. replaces structurally useless lead it is more insurance agains any possible failure.
Over the Christmas holiday I will split the fuselage and inspect the engine mount etc to see that all is wel, then ready for the new season next spring!
Superb model, particularly at weights higher than 20 kg. !
Regards,
David.
Last edited by David Gladwin; 12-12-2016 at 02:34 AM.