LA7flier

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I have built and flown my Vailly Hurricane about three years ago. I run a 3W-60 in it turning a 22x12 prop...weight is about 35 pounds. The plane takes off and flies beautifully but I cannot get it to land worth a damn! It simply will not flare. It either "balloons" up and stalls or mushes into the ground. I have another friend who also built and flew a Vailly Hurricane with the same characteristics. After about 5 flights and three ripped out gear, he gave up and sold his. After 6 flights and four wing spar repair/replcement, I'm debated whether to try again (and risk another broken wing) or simply sell the plane. CG balance is about 18% back from the leading edge and it doesn't exhibit any tailheavy symptoms. Some have suggested that it is nose heavy and others that the incidence is off.....anybody else flown this plane and can offer some suggestions?

Tmoth4

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I don't know about the Hurricane but my other warbirds (P47, Corsair, Dauntless) have the CG at about 25% back from the leading edge. 18% sounds pretty nose-heavy to me.

Jim

BobH

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If you are too nose heavy the plane will have a more difficult to flair on landing. Since the plane is balancing nose down (so to speak) raising the tail is harder. Try moving the CG back about 1/2-3/4 inch and fly it that way. There may be a little trial and error before you get it right.. BobH.

Ham639

My Feedback: (13)

LA7flier,
It sounds like a typical Hawker problem. On a smaller Tempest I built a few years a go it did the same thing you describe. After playing with the cg and Elevator travel. I finally added some expo (this was the only aircraft I flew with some expo) and this helped a bunch. I only Fly warbirds and this problem puzzled me. I believe it it because of the smaller horizontal stab and elevators than most other Warbirds. You need to keep the speed up and power to all you landings right down to the "Flare". With a little practice this should work. Your cg seems about right for the design. If this doesn't work, try about 2-3 degrees of down thrust. This should counter act the incidense problem. I am right now in the finishing stages of my Vailly Hurri and has questioned this same topic. I do have a few Questions for you. Did you set the incidence to the stab and wing according to Roy's #'s? What about Ballast, how much did you have to add. Best of luck.
Chuck

LA7flier

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Thanks for the advice to all....we have been fiercly debating the CG location for this plane....some said it was still too tail heavy and others said nose heavy and some said incidence....to be honest, I don't remember what I set the incidences to...I built the plane about 6 or 7 years ago....I usually like to set everything up on a zero thrust with the engine...that said, the plane flies beautufully while in the air and takeoffs are relatively nonevents as there is very little swing during acceleration. Remember, this is a 36 pound aircraft and so it is not small. I did have to put nose weight in.....on the order of three pounds of lead and that is after hanging a 3W 60 with Muffler out on the end of pylons and having all batteries and ignition in front of the CG. The elevator throws are a bit on the small side and I will try to get more out of them...not sure I want to dial in any down since the plane flies perfectly straight and takes off without any problem...the only problem lies in my inability to get it to flare during landing...I have already removed about 8 oz of lead and will rebalnce....If I could get this plane to land well, I would invest in some of daryl's hurricane gear since it is unique and I love the Hurricane...plus, it is, after all, the perfect stablemate to my Spitfire and Mosquito.

Ham639

My Feedback: (13)

LA7flier,
The added down thrust won't make that much of a noticable in the air. It will only help with the slow speed handling. Keep me posted of your results. I agree with Darrell's gear. That is what I have in mine. A notable Top Gun Pilot told me to balance my Hurri at about 17-18% of the cord, which is about an inch farther forward than the plan says. I was going to use that as a starting point. Dave Platt wrote a book about scale designing and such back in '77 (I was 12 years old then), about cg location compared with small stab designs (bf 109's, spits and Hurri's). Basically it said on these type of aircraft the cg would be around 15-18%! compared to 20-25% on Hellcats, P-47's and such. The smaller stabs need the further forward cg to keep the tail flying. Keep trying you will get it right. Let us Hurri fans know of your progress.
Chuck

LA7flier

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that's exactly why I balanced mine at about 18%. My buddy also balanced at about 18% and both planes (of nearly identical weight) exhibited identical landing characteristics. The only difference was he landed his with about 1/2 flaps and I landed mine with full 90 degree flap deployment. Didn't seem to matter as the planes exhibited a distinct tendancy to either balloon up when initiating a flare or mush into the ground when doing the approach at a slower speed. My hesitation to keep trying different balance points is that I am getting tired of repairing the wing after every landing.. I'm just completing the fourth wing spar repair which required a full re glassing, re finishing and re riviting of the affected areas...not an inconsequencial amount of work and my strong temptation is to take the plane and simply sell it while it looks good. My buddy sold his to a fellow who dropped more nose weight into the plane,(thinking it might be tail heavy) flew it and when it did the exact same thing, he sold it to somebody else. I was hoping there might be some experienced Vailly Hurricane pilots out there who have flown this plane without a problem and can offer a definitive solution. Very frustrating since I really love the looks of the plane and having flown it, love the flight characteristics...just not the landing.....my LA7 was a bear to land but if you knew what you were doing, it would flare beautifully and give excellent main wheel landings....if I could get that out of the Hurricane, I would be happy.....

Ham639

My Feedback: (13)

LA7flier,
Well let's hope somebody can chime in here and help you.
Chuck

FTT1967

My Friend has one which I fly a lot. It powered by a zenoha 38 and weight is 24Ibs. It flys very well and landings are very floaty with and without flaps. CG is around 20 to 25 % On my 1/4 scale hurricane we went back to at least 30%. The only problem I has at this c/g poss ion it is very floaty. The further back the c/g the slower it will fly.

Things you can try is reduce the pitch of the prop 12 is a lot use a 10 or 8 . I did this on my extra and it made a big difference on landing. I had a 24 x 10 which was OK but you had to watch the tip stall on landing change it to a 26 x 8 and no more tip stalls and is much floaty and now i can pin point it on landing.
Try different amounts of flap fore landing you may find small amount will help. you have a high wing loading. Full size uses a little on takeoff as well. this makes it float off the ground.

I hope this is of help

Richard

LA7flier

My Feedback: (1)

[quote]ORIGINAL: FTT1967

My Friend has one which I fly a lot. It powered by a zenoha 38 and weight is 24Ibs. It flys very well and landings are very floaty with and without flaps. CG is around 20 to 25 % On my 1/4 scale hurricane we went back to at least 30%. The only problem I has at this c/g poss ion it is very floaty. The further back the c/g the slower it will fly.

Things you can try is reduce the pitch of the prop 12 is a lot use a 10 or 8 . I did this on my extra and it made a big difference on landing. I had a 24 x 10 which was OK but you had to watch the tip stall on landing change it to a 26 x 8 and no more tip stalls and is much floaty and now i can pin point it on landing.
Try different amounts of flap fore landing you may find small amount will help. you have a high wing loading. Full size uses a little on takeoff as well. this makes it float off the ground.

I hope this is of help

That's interesting....I matched the prop to the engine....why would changing the prop pitch cause the plane to change it's landing flare? I'm glad that somebody has successfully flown one....I was giving up hope since I have never seen anybody but my buddy and mine's fly. I think I'll try to rebalance at closer to 20% and improve my elevator throw....24 pounds is very light for this airplane.....how did your friend get it built so light? I was hoping to get mine in under 30 but nose weight and detail work caused it to top at 36 pounds...thanks for the info

Tmoth4

My Feedback: (1)

A lower pitch, bigger diameter prop will help you slow down for landings. Top speed will be reduced somewhat. I use 24-8s on my G62 powered warbirds and they land really nice. I still think that 18% is awefully nose-heavy. I would try it at 25% and see how that works. Don't overdo it with elevator throws. It could cause stalls when you don't want them.

Jim

SpitfireMKI

My Feedback: (2)

Is it possible you are using too much flap ? I have a small P-51 that when the flaps are dropped it pitches the nose down. The airplane becomes very hard to flare. I don't think there is enough airflow over the tail at the point of flaring to overcome the flaps and I end up on the mains hard. And if you force it to flair, it balloons making for tense moments. I think the problem comes from the fact that it is a light plane and does not need the flaps to land.

On the other hand, my Vailly Thunderbolt flies like a truck (Is a tad nose heavy) when I land I have approx. 75-80% flaps down, 1/4 throttle to the threshhold, 1/8 throttle from here and fly it to the ground. I cut the throttle to idle only when I am about to start flaring which is maybe 10" - 12" off the ground. While doing this I can "feel" the loss of elevator air flow as the nose gets heavier and airflow over the wing decreases. I end up on the mains, close to three points but am "out" of elevator as I touch down. I think reducing the nose heaviness and maybe a little down thrust would cure the little problems I have.


I did experiment with changing the incidence on a hanger 9 p-51, reducing the positive on the main wing. This resulted in some similar problems as what you experience too.

I realize these aren't Hurri's but they might shed some light.

Funny, about using lower pitch props............seems to me the braking effect they have would increse the chance of a tip stall since your main wing airflow can get slower even though you have lots of prop thrust (Thrust being increased as pitch is reduced on the prop) across the elevator. At this point the main wing no longer wants to fly due to slow airspeed and you are using the elevator which is still effective due to the thrust to force the nose up. By forcing the angle of attack on the main wing past it's stall point you will induce a stall. Take an over powered cub off with insufficent air speed and you'll see what I mean.

S1

FTT1967

Having to much pitch on the prop will stop you slowing down. It keep pulling you along and there is only one way to slow it up is to get the noise up at this point it you have to hold the noise up a little to much to hold the speed off. That the wing tip is stalled. It takes time to fined the right propeller for a fighter as you are looking for top speed as well as slow speed. I tend to find that 10 pitch on the big model works well. Full size go's in to fine pitch to keep the draft of the prop as well as giving a brake effect when needed. we Dont have that. so we need to find a compromise. also a hurricane is not that fast a aeroplane.

Also what happens when you throttle back. dose the model dive when slowed up. this will tell you if the model is nose heavey.

Richard

SpitfireMKI

My Feedback: (2)

FTT1967,

You are correct about fine and course pitch on full scale. However, they also have airspeed indicators which allow them to keep the airspeed up for the proper glide path. This is the hardest part about landing models, you must rely on your eyes and feel of the sticks to know airspeed. I agree the larger diameter and lower pitch give better control of low speed. But I have seen guys get the planes slow enough for the tip stall to occur. It's a fine line and as you say, we are making a compromise. I don't believe this is the problem with the hurri, if he had an extreme prop choice like a 26 x 12 than yeah but......

If the plane drops the nose when you throttle back more than likely it's a engine thrust issue, needing more down thrust in this case.

In flight testing for balance seems to be very hard becuase there are so many variables, aerodynamics, thrust lines, airspeed etc. My observation has been that most nose heavy planes will drop the nose over in a banking turn. It's not a major out of control drop but a distinct nose down attitude which requires opposite aileron and a little more elevator to compensate. Aircraft lose altitude in a turn mainly due to lost lift but the nose should still stay some what level. Of course, if the tail drops it may be averse yaw.

Usually a plane landing nose heavy will want to set down demanding that you keep adding elevator, they usually don't balloon but may bounce a little becuase you didn't keep the airflow over the tail and the speed up. Tail heavy planes will ballon up and many times in extremes. require down elevator to land


I think in this case the Hurri is having several problems, balance, thrust incidence and wing/tail incidence. The degree of flaps may be aggravating the situation.

S1

JagBone

So what has happened??
A friend and I are currently framing up two birds (as of last weekend) We are scratch building. That was alot of ribs to cut and stringer notching till your red in the face!!!
Any other cautions we should be aware of in this endeavor? We are planning on MOKI 1.8's for power.
Let yo' opinions "fly"!!
Thanks.

JGrc

My Feedback: (29)

LA7,
sounds like you have nose heavy bird and/or you approach speed is low.

JG

Hal Ware

Had and flew a Vailly Hurr. for several years--3.2 Sachs on meth.--initial weight balanced at plans location was 28 lbs.--nose weight was gradually reduced to 26.5lbs. by flight experience to keep it from being tail heavy[if tail heavy the plane will climb as throttle is reduced or swoop upward on a quick power reduction to idle]--had much difficulty in the flare as described above--tried landings with no flaps,a lot of flap, a little flap and a medium setting with same result--for a while the only way I could land it decently was to come in with a low flat approach with a good bit of power and chop power with the wheels near touching and then feather with elevator as long as possible--even then it touched down faster than it should considering the broad chord and thick wing--after much discussion with club members and others it was determined that airflow over the elevators was being blocked or reduced so as to kill elevator response--I never solved the problem and sold the plane with advice about the above limitations--as it turned out, the problem was solved with a very simple solution by my friend--I had built the plane with what I thought was a large amount of elevator throw--my friend removed the elevator, re-hinged and increased my original throw by about 30% and the problem was solved--slow landings with good flare-----therefore, rig your elevator so that it has a high throw angle, much greater than you think is needed--if its then too much in the air for your comfort take off and fly on low rate and increase to high rate max elevator throw for landing--if you have any questions call me after 6 c.s.t. 225-629-4724--Hal Ware

LA7flier

My Feedback: (1)

great advice from all....I have not pulled the plane out of the rafters since my initial post because I have been up to my eyeballs in a 1/5th Spitfire for the Scalemasters competitions. I have always been concerned about the throw of the elevator combined with the 90 degree flaps. It may very well be that in this model, I am blocking the elevator with the flaps.....like you, my last landing was very fast and very flat with a last second chopping of the throttle...I still damaged the wing and broke a very stout retract trigger block...rebuilding the elevator may be the solution but that is alot of work...as soon as I get the plane airborn again, I'll report on my findings....I have removed about 8oz from the nose and I will land with less than full flaps and will try to get some more throw from the elevators..we'll see what that yields...

JET FX

Hi Guys I hope to put the maiden flights on my Vailly Hurri within the next week or two weather permitting? I still want to play with engine tuning a bit more before flight....
Some very good advice on this thread re-prop pitch especially, from my experiences with smaller warbirds I like to go for as large a diameter and low pitch as reasonable as this really helps slow model on landing. In my case I have a ST4500 with a 20x8 Dynathrust prop I hope will be ideal. I have also learned the best way to land my warbirds has seemed to be using a typical fighter approach eg curved descending base leg and final with lots of flap lowered as opposed to long flat finals and playing to much with the flaps, this tends to avoid the floaty long flare that can cause elevator authority loss due to slow air speeds, It has worked for me anyway! that said each model tends to be a bit different and has characteristics of its own and all seem to require a bit of trial and error before being able to nail the perfect approach and landing I also like the comment re- plenty of expotential on elevator this makes a lot of sense for the Hurri's small elevator. From experience all my warbirds I have noticed when full flap is extended tend to blanket elevator responsiveness as model slows, I try to raise flaps as soon as possible after touch down due to this reason to help keep tail down.
I will post my Hurri maiden flight report results as soon as I fly her...

Anyway, last weekend thought I would take some pre maiden pics. so I took time to pose her in a scale manner.... after taking the pics. and looking at them at home on the puter I noticed the pilot has an uncanny resemblance to Clark Gable

Cheers-