Galaxy/Pegasus Hurricane

[Martin Harris - Moderator]

My old girl pictured in 2006 with a temporary engine - an old OPS60 that I bought for a never completed Mick Reeves 1/6 scale (80") Hurricane before I stopped model flying in favour of full size gliding.  Imagine expecting a 60 2 stroke to power an 80" warbird these days - but in 1977 it was a monster engine!  It was wearing both the Mick Reeves concealed "silencer" and an add on Pitts style in order to get below 82dB.  It just seemed the "right thing" to use the never flown OPS in a Hurricane while I was waiting for some bearings to arrive for the now venerable SC90FS  that powered it before and after to this day.  The weathering was originally faked but is now even more authentic!

 

 

I've taken another 4 oz out of the Hurricane’s nose, reduced the elevator movement a little and managed to squeeze in some 1/2” larger wheels while I was at it.  Hopefully taxying will be a bit better - and the stability won’t be too much affected…at least with a full tank!

 

I did try 3" wheels but they were too close to the leading edge for the depth of the wheels.  Did you use very thin ones Payneib?

[payneib]

7 hours ago, Martin Harris - Moderator said:

My old girl pictured in 2006 with a temporary engine - an old OPS60 that I bought for a never completed Mick Reeves 1/6 scale (80") Hurricane before I stopped model flying in favour of full size gliding.  Imagine expecting a 60 2 stroke to power an 80" warbird these days - but in 1977 it was a monster engine!  It was wearing both the Mick Reeves concealed "silencer" and an add on Pitts style in order to get below 82dB.  It just seemed the "right thing" to use the never flown OPS in a Hurricane while I was waiting for some bearings to arrive for the now venerable SC90FS  that powered it before and after to this day.  The weathering was originally faked but is now even more authentic!

 

 

I've taken another 4 oz out of the Hurricane’s nose, reduced the elevator movement a little and managed to squeeze in some 1/2” larger wheels while I was at it.  Hopefully taxying will be a bit better - and the stability won’t be too much affected…at least with a full tank!

 

I did try 3" wheels but they were too close to the leading edge for the depth of the wheels.  Did you use very thin ones Payneib?

Well I've finally seen a picture of one flying, that puts my mind at ease slightly! I had the same worries when I built the Galaxy Merlin. 😂

 

Just Dubro 3" treaded. There's not a lot of wing left around the cut outs. You can see on that mid-build picture of the underside of the wing, I cut a full depth (top skin to bottom skin) ply spar in to the wing joint, the width of the UC spread, then dug out the foam core, right through to the top skin. A two piece flat ply spar was glued in to the inside of top skin, again the full spread of the UC, then a ply web glued along the wing centre line, between where the wheels sit to stop the centre LE flexing. The rearmost hardwood UC mounts were epoxied in the right angles between the two ply spars. Once I put the wing bandage on, I wrapped a length of 100gr fibreglass around the LE from the top of the spar to the bottom of it.

 

Still crossing my fingers that the retracts won't punch straight through the top skin on the first landing. 

[Martin Harris - Moderator]

If mine survives the CofG experiment it will have flown in my care for over 21 years with no real handling problems in the air. There’s a lot of wing so hopefully it will carry the extra weight of your engine. 
 

There’s an outside chance of a wing drop with your higher wing loading so you might consider setting a little up aileron at neutral to provide some washout effect for first flights.  I did once manage to induce a spin off a turn at low level over trees in turbulence - a handily placed large blackthorn bush added some more weathering but saved the model from serious damage. 
 

P.S. Are you sure about the weight?  With your forward engine location and CofG in the plan position, I’m wondering where another couple of pounds has crept in?

Edited April 20 by Martin Harris - Moderator

[payneib]

29 minutes ago, Martin Harris - Moderator said:

 

P.S. Are you sure about the weight?  With your forward engine location and CofG in the plan position, I’m wondering where another couple of pounds has crept in?

25g fibreglass on the wings and about 60% of the fuselage, fabric and dope on the rear fuse and tail, including rib tapes/longeron tapes, two months worth of surface detail, 90% of a full cockpit interior, including sliding canopy, twin Rx batteries, ignition battery and ignition unit, 120 sized retracts, two extra servos (instead of the single torque rod servo on the plan), and about 6-10 cans of cellulose paint (depending how much actually ended up on the model). 

Edited April 20 by payneib

[Martin Harris - Moderator]

Surprising how it mounts up.  Hope all goes well when she takes to the air.  When do you plan to maiden her?

[payneib]

2 hours ago, Martin Harris - Moderator said:

Surprising how it mounts up.  Hope all goes well when she takes to the air.  When do you plan to maiden her?

Not sure. There's certainly no rush. When my DLE30 was new, every landing was a nightmare as the idle would creep up whilst it flew. It took most of season to run in, so there'll be plenty of ground running on this. Plus our patch is still pretty soggy. 

[Martin Harris - Moderator]

Wish my idle would have crept up...

 

Today's experiment was a bit of a mixed bag in a moderate to fresh gusting wind.  I taxied out without a moment of drama, turned into wind, started the take off run, brought the tail up, balanced nicely on the main wheels, came off into a steady climb out, raised the gear and found more performance than ever before, with half a pound of lead sitting on my workbench.  No sign of wing drops with tight turns, waffled happily at tickover with the stick hard back and still a reasonable push needed while in (non-scale) inverted flight.

 

Full of confidence, trundled down the approach, settled into the flare, waiting for the speed to bleed off and the engine cut...at the same time a crosswind gust hit and the model ballooned a few feet - with no energy reserve and no engine, despite immediate relaxation of the elevator the nose dropped uncontrollably and the poor old girl flopped onto her spinner, breaking the swiss cheese (from several engines over the years) engine mount (firewall seems fine) and hammering the undercarriage, popping the mounts out of the foam.  Nothing more and nothing terminal - unlike most ARTFs these traditional builds are pretty resilient - but annoying as all the comments from the peanut gallery were of how good she'd looked in the air and sounded amongst the plethora of electric models and EDF jets flown at our club today.  Maybe, given the earlier stall test, I'd overdone the elevator movement reduction but given the circumstances, probably a simple stall?

 

It was recorded on video but I'm not likely to get a copy before next week so further analysis will have to wait.

 

And Man City nicked a goal at Wembley...😢

[GrumpyGnome]

Oh no. She WILL fly again. Sounds like a simple stall based on your report... where's the cofg now?

[Martin Harris - Moderator]

An awful long way back - the engine's out!

 

More seriously, about 3/4 of an inch behind the plan point.   I don't think it had anything to do with today's hiccup - the rest of the flight was perfectly stable in pitch.

 

Hopefully I can find a compatible engine mount to avoid making more holes in the firewall.  Other than rewiring one of the retract units, the only other repair work will be the undercarriage mountings.

[Jon H]

a gusting wind can wipe out any model under the right (or wrong?) circumstances. My little hurricane got faceplanted into the runway once with a sharp downdraft despite full corrective action. But as you say, these traditional models can usually absorb the abuse and bent undercarriage was the worst of it. 

 

One other thing to consider though is the model is now a half pound lighter and will fly that bit slower. If your flare was at the normal speed you are used to you may have had just enough excess energy for the wind to really pick it up before dropping it back down. That said, it would probably have been a non event had the engine not decided to give up at that exact moment. 

 

In any case, retracts are always more prone to damage and I tend to hangar my warbirds in gusting conditions for that reason. Last weekend i took my sea fury to put some hours on the rebuilt engine. The first 3 flights were perfect with nice smooth landings. The 4th took me 3 approaches with 2 go arounds as i couldnt get it stable as the wind had swung to the north a little and the turbulence off some trees caused real problems. WIth the wind in that direction, 4 flights already and an undamaged model i decided to call it a day. 

[Martin Harris - Moderator]

I judge my approaches by attitude rather than (ground)speed but gusts in ground effect can add significant transient energy!  Flying today was probably my biggest error although conditions appeared reasonable enough for the flight.

[payneib]

She looked rather nice up the field today. The engine is running solidly after some tweaks to the top end, and now has enough compression for reliable hand starting. I reckon the idle is still going to take some settling. 

 

I took her for a little drive round the runway - very nose happy, even though the grass was cut this morning. The ground is still pretty soft, and the Club Press says it's not short-short yet, but I think I'll shim the UC mounts for some forward rake, and maybe consider a flight mode switch to give me full elevator on the ground. 

 

@GrumpyGnome gave me a second opinion on the CoG (a bit difficult in the wind), but we think it's about right, especially considering Martins experiments, and the 3/8" each way elevator. 

[GrumpyGnome]

Having the cowl on will, of course, move it forward......

[Eric Robson]

3 hours ago, payneib said:

She looked rather nice up the field today. The engine is running solidly after some tweaks to the top end, and now has enough compression for reliable hand starting. I reckon the idle is still going to take some settling. 

 

I took her for a little drive round the runway - very nose happy, even though the grass was cut this morning. The ground is still pretty soft, and the Club Press says it's not short-short yet, but I think I'll shim the UC mounts for some forward rake, and maybe consider a flight mode switch to give me full elevator on the ground. 

 

@GrumpyGnome gave me a second opinion on the CoG (a bit difficult in the wind), but we think it's about right, especially considering Martins experiments, and the 3/8" each way elevator. 

I just use high rates for taxi and take off, and low for normal flying depending on conditions. Don't think my brain can remember where all the switches are.😄

[Chris Freeman 3]

A tail heavy aircraft will show that it is very hard to trim in pitch and will tend to climb or dive. When I was testing the electric motors on the big stick the 50cc motor used 12 5000mah cells and the 30cc used 8 3800mah cells so there was a big difference in the  cg and as the motors were changed at the field it was a good way to see the effect of CG on flight performance. As the airframe is very stable and been flown a lot it was not a worry. The lighter 30 cc set up showed that almost no down was needed in the roll when inverted and on landing it was not as stable on the approach as it tended to want to pitch up. Trimming the elevator was not a cure as it was clearly a tail heavy situation. This tail heavy tendency is not what you want on a heavy warbird when test flying as a pitch up at low speed will lead to disaster or a very shaken pilot.

Dual Rates are very important in my opinion as you might need far less movement than what you expect but nice to have control if needed.  

[GrumpyGnome]

8 hours ago, Eric Robson said:

I just use high rates for taxi and take off, and low for normal flying depending on conditions. Don't think my brain can remember where all the switches are.😄

One of the reasons I don't use individual rate switches... Flight Modes on a singe switch for different rates, expo (if any), trims, some mixes. Takes a bit of initial setting up but nakes life easier in the long run...

[Nigel R]

2 hours ago, Chris Freeman 3 said:

A tail heavy aircraft will show that it is very hard to trim in pitch and will tend to climb or dive.

 

Which probably means a CG approaching (or even on) the neutral point. At this stage you will need to start trimming the thrust line to minimise pitch changes with throttle. Even then it might not be possible to trim out the desire to pitch up/down - it depends on the airfoil in use and how the centre of pressure moves with angle of attack. Lots of variables in play. (note, none of the preceding is getting into discussion of stall, or tip stall - still talking tendency for the airframe to start 'hunting' in pitch).

 

Symmetric airfoils display the least of effects.

Heavily cambered airfoils display the most.

Some airfoils have inherently unstable connection between the centre of pressure, and pitch; meaning with increased angle of attack they show an increased desire to pitch up (whereas ye olde Clark Y is the reverse, with more angle of attack, it tends to pitch down, and is inherently stable).

 

I am not an aerodynamicist, I may have very imperfect understanding of the above - take with pinch of salt.

 

Wikipedia link...

https://en.wikipedia.org/wiki/Longitudinal_stability

Edited April 22 by Nigel R

[Martin Harris - Moderator]

I’m waiting on a video of my experience on Saturday.  I’ve obviously got a significantly more rearward CofG than during my previous extensive flying of the model but the model showed no sign of excessive pitch sensitivity during the flight and inverted flight still required a positive push.  If it had been a model of unknown origin, I wouldn’t have had any concerns - and as I’ve done extensive test flying of clubmates’ models of all types and provenance over the years, I’m no stranger to flying models with rearward CofGs!

 

Was the response to the gust CofG related?  To be honest, I’m not sure and I’m hoping the video will give some clues.  What I do know is that conditions were deceptive and increasingly gusty for all pilots present that afternoon. 

[Nigel R]

If your Hurri wasn't 'hunting' or showing any kind of pitch oscillation during normal flight I'd be surprised if your landing issue was affected by the CG move. A fair sized push of down during inverted seems as expected - I'm assuming (always dangerous) the Hurri has a 'semi-symmetrical' or Clark Y type airfoil?

[Martin Harris - Moderator]

A thousand words…definitely semi symmetrical:

[payneib]

5 hours ago, GrumpyGnome said:

One of the reasons I don't use individual rate switches... Flight Modes on a singe switch for different rates, expo (if any), trims, some mixes. Takes a bit of initial setting up but nakes life easier in the long run...

Stick it all on the gear switch maybe? Wheels up - tiny elevator throws, wheels down - plenty of "up" available.

 

I'm not exactly a novice, but this project has produced more buttons, knobs, and switches than anything else I've done. 

[GrumpyGnome]

Why not?  Whatever works for you..... many many ways to skin this particular moggy - although I like to keep the actuation of gear isolated in case of issues....... which would allow for example, landing mode (lower idle + touch of up trim) if the gear is stuck up. And flaps,  to allow me to choose to use them or not, depending on weather conditions.

 

How to use the functionality of your radio is a VERY individual thing.

[Jon H]

On the climbing/diving thing i do not agree that it is related to c/g, at least within the realms i am on about. 

 

Its virtually impossible to get a scale model to be in trim through its entire speed range and certainly the full size is trimmed regularly. Even your basic cessna is constantly in need of trimming so if a model climbs with speed and falls with less speed i would consider this normal. 

 

My sea fury is the most neutral of my warbird fleet and its also the one with the thinnest and most symmetrical wing. My La7 and P39 really need a good shove of forward elevator at high speed. In the case of the P39 i have watched a number of those old WWII training videos for the full size and from many of the shots i can see my model behaving very much like the full size. In practice its not an issue and i just hold the nose down with some forward stick on fast passes. 

 

However, if a model climbs with power, that is another story and engine thrust lines should be investigated. Again i keep things simple these days with 0-0 on my up/side thrust and just fly the thing. I have not come across a warbird yet were this has been any kind of problem. 

 

The only tricky part is working out if the model is climbing with speed or power, but usually this can be tested by just opening and closing the throttle before the speed has a chance to change much. 

 

When it comes to rates, i have high/low set for ailerons and elevator on different switches. Generally i use high elevator low aileron for takeoff, and go to low elevator when in the air with the gear up. Landing is normally the same but i may use high aileron rate if the wind is choppy and i want more authority. 

 

Lowering flaps also enables my elevator flap mix to effectively trim the model for the landing configuration as the slow speed and drag of te gear usually makes the model want to bury its nose in the earth. 

[Paul De Tourtoulon]

Hi GG, I have put my VQ 161cm Hurricane with it's .90 OS 4-stroke engine in it in the car for an afternoon of flying,

do you want any information on it before or after I fly it ?.

[GrumpyGnome]

Hi Paul

 

It's not my Hurricane, I was asking for a friend (who is now a forumite - payneib). 

 

Having said that, I think the VQ ones are a bit 'lardy' - so all information will, hopefully, be welcome.

 

Cheers - have fun!