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Hangar 9 Warbird Elevator Reinforcement

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Old 01-30-2013, 09:43 PM
  #1
Rcflyyer1
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Default Hangar 9 Warbird Elevator Reinforcement

To start off, there are ALOT of people On RCUniverse and RCGroups telling how their Hangar 9 Warbird had horizontal stabilizer failure resulting in the inevitable. They say they were flying normal and not diving and others say, they dove at full throttle or over powered their model. In my Hangar 9 P-47 I have an ASP 91 Four Stroke which does not over power it at all.

So I already glued on my horizontal stabilizer on my P-47 60, in fact it is completely ready to fly. These horror stories are really scaring me alot!

Is there anyway to check if my H-Stab is strong enough and is there any way to reinforce it when it is already installed? It is epoxied in and would be a PAIN to remove. Thanks for the help and please tell if you have had any H-Stab incidents on the Hangar 9 Warbirds. I put a lot of work into this airplane and want to make it last. I am afraid I did cut a little bit into the underlying wood when I removed the covering on the Horizontal Stabilizer to glue it into place but the cut wasn't that deep.. Is there anyway to reinforce the Horizontal Stabilizer when it is already glued into place? I do have some spareCarbon Fiberto use on it.

I haven't maidened the airplane yet due to it being tail heavy and this Horizontal Stabilizer Issue.. Thanks for any help
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Old 01-30-2013, 10:38 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I have 3 of the H-9 60 models 2 I have flown and 1 in a box (a Corsair) the Mustang a "Marie" has quite a few flights on it and the tail is fine no structural weakness at all, I also have a P-40 with a little less wear on it and its in great condition also, both are powered by OS 91 Surpass engines and the performance and power of the engines is fine for the plane,

I have read about tail failure before and there are several threads that cover both these planes in detail as well as the P-47 but unless your going to really wring it out I wouldn't get all overly worried about it, truth is I would make sure the back of the firewall and tank compartment is coated with thinned out epoxy before adding weight and extra material to the tail.

that being said I will most likely sheet the tail surfaces with some 1/16 balsa if and when I strip the covering off them, but I have so many projects now I don't have the time or feel the need to bother with it
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Old 01-31-2013, 05:05 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

This is just my opinion, OK? But if you did cut into the balsa under the covering when you removed the covering, you have created a weakened spot there at that point. When ever I have to do that Iuse a little technique to prevent it. I first make a very small cut in the film and try to lift it enough to slip a piece of thin ply under it.. It may help to sand the ply to a thin edge to help with that. Then I work the ply under it film so I'm always cutting with thepoint of my blade on the ply rather than the balsa under it.

In my opinion, if you are concerned about having a stab failure, remove it. take off the covering and get some one ounce glass and reinforce the area where you cut into the balsa. Lightly sand it, fill it and sand it smooth, and recover it except where you need to re-attach it to the fuselage. Yes, it's a little work, but it will give you the piece of mind you are looking for.

Bottom line, never cut into the covering where you need to get to balsa for gluing without slipping something under the film to portect the skin. Even the slightest cut creates what engineers call a stress riser. Assuming the skin there is 3/32 and you only went in 1/32.. you have lost 1/3 of the strength where it is needed the most.

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Old 01-31-2013, 08:21 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

The most important area to reinforce - if you do it - is the bottom of the stab near the fuselage. This is because this will be the highest stressed area during normal loops etc. But if you like to do a lot of inverted maneuvers - especially inverted loops - then the top of the stab could be a concern. So when you cut the covering if you cut right att he fuselage then you can cause a weak spot. The last H9 plane I had was their yellow tail mustang, which was known to have stab failures, so I took off the covering, fully sheeted the bottom of the stab, and modified the fuselage to accept the sheeting.

Another way to reinforce the stab - if the stab is flat/not an airfoil shape - is to add triangle stock/wood where the stab meets the fuselage. Of course to do this you need to VERY carefully remove the covering from the fuse and stab there so the glue will get to the wood, glue some 1/4 triangle stock along the stab where it meets the fuse, and reapply covering there.

Good Luck and have fun flying your warbird!!!

Ed
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Old 01-31-2013, 08:42 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement


Quote:
ORIGINAL: rc34074

The most important area to reinforce - if you do it - is the bottom of the stab near the fuselage. This is because this will be the highest stressed area during normal loops etc. Ed
Sorry, Ed, but Ihave to disagree. The Stab is always pulling downward in level flight. This is to counter the lift being created by the wing being mostly aft of the CG. That is what makes the plane stable in pitch. Therefore, the top of the stab at the fuselage is in tension, and is where it will fail. The bottom joint is in compression and will almost never fail under compression. Pulling out of a dive in a high G manuver requires even more of a downward force on the stab in order to raise the nose. Even more tension. A High-G negative maneuver may put the lower surface joint in compression, andif that area is compromised it could fail.

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Old 01-31-2013, 09:08 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Dash, maybe I'm looking at this the wrong way, but it seems to me that if the horizontal stabilizer is pulling downward in flight, as you state, then the bottom of the H Stab would be in tension and the top would be in compression. With a downward force, the stab is pushed down. Since it is glued at the fuselage (the stab center), the rest of it is flexing up creating compression on the stab surface at the top and tension on the bottom. Since it will fail at lower stress when in tension compared to compression, the bottom should be reinforced.
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Old 01-31-2013, 09:24 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Quote:
ORIGINAL: edbu1

Dash, maybe I'm looking at this the wrong way, but it seems to me that if the horizontal stabilizer is pulling downward in flight, as you state,
The horizontal tail has to create a down force, and it's easy to see why.

The pitch of the airplane balances at the neutral point. Every one of our models has a CG. For almost every one of our models, the CG is ahead of the neutral point. The CG is a force pointing down and a force ahead of the neutral point. There has to be something behind the neutral point that counteracts the CG's downward force.

It's a see-saw. There is a kid on one side of the see-saw named CG. If he's the only kid on the see-saw, the other side of it will point to the sky. We trim our planes to fly level. When the see-saw is level, the kid on the tail side of the see-saw "weighs" as much as CG weighs. They both produce downward force.

If the plane is flying level, the down force of the tail equals the down force CG produces.
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Old 01-31-2013, 09:32 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Not sure what your point is, Rock. I agree that the horz stab is pushing down. My post is concerning the location of the compression and tension forces on the stab.
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Old 01-31-2013, 11:06 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement


Quote:
ORIGINAL: edbu1

Not sure what your point is, Rock. I agree that the horz stab is pushing down. My post is concerning the location of the compression and tension forces on the stab.
If the stab is pushing down, it would be like you pressing down on the stab tips, would it not? You would have to do that to cause the tail to go down. If you do, now which side is in tension and which is in compression? The top is in tension. Press hard enough and the stab will break off in a downward direction.

As for the down load equaling the CG,that is incorrect as well. Since the stab is furthur out on the end of that see-saw.the actual force required to off set the lift force behind the CGis much less.

Briefly, why this works to maintain stability is this. As the airspeed increases, the lift force increases and the wing would be trying to cause the nose to pitch down. However, the downward force created by the stab and elevator also increases. Being on a longer moment arm, it has more authority and lowers the tail, raising the nose again. As the speed decreases, the effect is greater on the tail again, the downward force decreases, and the nose drops. Left alone, the osilations decrease until the aircraft is level again (assuming thats where it was prior to any pitch change).

Dash
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Old 01-31-2013, 12:30 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Had to think about this for awhile. OK, Dash, you've sold me. Top is in tension and breaks first. Thanks for the enlightenment!
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Old 01-31-2013, 12:35 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I recently noticed flutter on my 3 year old H9 F6F about a month ago. Having gone over the plane today I discovered there was a lot of slop between elevator halves. Turned out to be the control horn side, after cutting the hinges the elevator slid right off the U joint connecting the two elevator halves, very bad. I'll be cutting new ca slots and re-gluing the U joint with gorilla glue. Hopefully will be back in the air this weekend for a test flight.

I was on a straight and level flyby when I saw the flutter on the right side stab. I'm amazed the stab stayed with the amount I saw, looked like about 4". I've done wing over diving strafing runs many times over the years so this must have developed recently.
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Old 01-31-2013, 02:32 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement


Quote:
ORIGINAL: Edwin

I recently noticed flutter on my 3 year old H9 F6F about a month ago. Having gone over the plane today I discovered there was a lot of slop between elevator halves. Turned out to be the control horn side, after cutting the hinges the elevator slid right off the U joint connecting the two elevator halves, very bad. I'll be cutting new ca slots and re-gluing the U joint with gorilla glue. Hopefully will be back in the air this weekend for a test flight.

I was on a straight and level flyby when I saw the flutter on the right side stab. I'm amazed the stab stayed with the amount I saw, looked like about 4". I've done wing over diving strafing runs many times over the years so this must have developed recently.
Edwin
You were very lucky! In many cases, the flutter just takes the surface completely off. Ask me how I know! Iwas flying an Acro Pro 180 powered by a Moki 180. I thought every thing was tight and I know it was well built. I had run about a gallon of fuel through it that weekend was was really enjoying the high speed passes. On the final flight for the weekend, I was coming out of a split-S when suddenly both stabs came off! Ididn't hear a flutter, it was so quick. I really can't say if Ieven had flutter, or the stab failedat the fuselage joint. In any case, is nosed over and went in almost straight down. The engine was compltely buried. The designer and kit builder was an aeronautical engineer and lived in my town. When Ishowed him my stabs, he said it was flutter.

Dash
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Old 01-31-2013, 05:23 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

To all, Thank you for all of the tips. Here are some pictures I took. Sorry for the blurry pictures, it was cold (In Florida!!).
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Old 01-31-2013, 05:53 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Will I`m not an aero dynam pro, but am I missing something ? I have not seen anyone mention the most important thing (IMHO) which is which way the wood grain is going in the stab. The grain should be running from stab tip to stab tip and NOT from LE to TE, which will cause a sure break to happen. You should really check this by lifting the covering. If the grain is running tip to tip then a thin piece of metal or carbon strip worked into the stab, (like a spar) through the bottom , say about 2/3s of the entire stab. All you need is a 1/4" wide metal running 2/3s of the stab and it will not break.
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Old 01-31-2013, 07:44 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I had a Hanger 9 Hellcat where the trim seemed to change mid flight. I flew gently and landed ok and found the leading edge of the left horizonal stab was cracked. I removed the top covering and put reinforcing gussets on all the joints and diaginal braces and recovered. Both sides. Seemed to fix the problem. 100s of flights without problems, until I flew it flew it into a high wire at full speed.
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Old 01-31-2013, 08:19 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I have and have flown the P-40 with saito.91, Corsair with saito. 91, Marie P-51 with saito 100, and Miss America P-51 with a os95 and have had no issues. Fellow club member had the P-40 with a saito 100 and had stab come off in flight, he had cut the wood a lil to much on assembly. He did call Horizon and they actually replaced the whole p-40 even telling them he thought he had cut the wood. Can't beat that
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Old 01-31-2013, 08:23 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Looks like the stab is flat so you can reinforce whatever way you decide to do it, my way or the other ways suggested. Still another way to reinforce it is to create a groove along the bottom and top of botht he leading and trailing edges of the stab and glue reinforcing dowels or carbon fiber rods in the grooves. You also might even put another groove from one side of the fuse to the other in the stab leading and trailing edges (you decide top or bottom or both and add more reinforcing rods to these grooves as well.

OR just fly it and watch it carefully for a while - don't fly too extreme just fly racetrack patterns etc. Then check the plane after you land to see if it the stab is failing.

By the way my plane lasted 5 years of full throttle flying with a G90 turning a 14-6 APC 11100 on the ground (unloading at least 1500 in the air) so the stab held up just fine, whether by my reinforcing or by the original construction I don't know or care .

When you apply up elevator to enter a loop the top of the stab is in tension but once you are in the loop the main/greatest force on the stab in a loop is the centrifugal force that puts the bottom of both the wing and stab in tension. Most of this centrifugal force is from the weight of the fuse but some is from the wings and tail. So the bottom of the stab has the most tension on it.

Ed
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Old 02-01-2013, 07:42 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I have had a P-40 and a P-47 from Hangar 9. I had no problems with my P-40, but the P-47 broke the stab.I was lucky it happened on the ground, during an engine test.I was holding the plane with my legs on the stab, as I have always done, when I noticed it was completely broken near the fuse.I fixed it inserting carbon fiber and epoxy from the underside.I’m planning on buying another P-47 from H9 because it flies and lands very well (my only complain is the landing gear).This time I’ll do the same reinforcement on the stabs before taking it to the field.
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Old 02-01-2013, 03:47 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

So does anyone think any reinforcements will have to be made in order to fly the airplane? I plan on maidening the airplane tomorrow since the weather will be good unlike Sunday. Any thing I should know about? Things that I should or shouldn't do? Thanks
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Old 02-01-2013, 11:05 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Go for it should be fine
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Old 02-02-2013, 12:06 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement


Quote:
ORIGINAL: Rcflyyer1

So does anyone think any reinforcements will have to be made in order to fly the airplane? I plan on maidening the airplane tomorrow since the weather will be good unlike Sunday. Any thing I should know about? Things that I should or shouldn't do? Thanks

I've got all the H9 60size warbirds. I've had the stab covering off 3 of them. The quality of the wood in every one was good enough that I never bothered to stiffen because it looked weak. I did put a diagonal rib in one of them. I'm pretty sure it was unnecessary.

Keeping the covering tight goes a long way to resisting stab flutter. With the covering tight, simply try to deflect the tip chord of the stab and you'll get a good feeling (pun intended) for how reliable the tail should be. Tight covering does much the same as sheeting. It's nowhere close to matching what properly done sheeting does, but loose covering does less than nothing.
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Old 02-02-2013, 05:25 PM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Well mine is fixed. I did three flights today, working up to a diving strafing run over the runway. No more flutter. Love to hear the engine unload as it comes over the runway.
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Old 02-07-2013, 07:15 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Hi all, so I am having someone glass the inside of my cowling with lead in order to reinforce it and also to add nose weight which was significantly needed. I plan to fly it this weekend but don't know how the weather will be, my weather channel is saying 20 mph N winds (crosswind) with 25 gusts so that may not be the best weather for a maiden.
I also ordered a valve adjustment kit from O.S. as my ASP FS91AR didn't come with any feelergauges. This is also my first four stroke engine so I don't have any tools for the valve adjusting. My O.S. valve adjustment kit should be in by Monday or Tuesday.
I suspect the factory setting for the valve is incorrect because the idle is really rough! Sputters after going below 3000 RPM. The engine has been broken in also. I've read that many people have bad idling ASP Four Strokes but have a great reliable engine once they adjust their valves.
The plane seems ready to go, I checked the whole airplane from nose to tail. The prop I will be using is a Master Airscrew 14x6 K series prop instead of the 14x8 I had originally planned to go with. I have decided to not reinforce my elevator as I probably haven't cut into the wood as much as I thought I did. I tried flexing my stabs and they seem really strong. I will tighten the covering and seal my hinge gaps as was recommended here.
The only problem I have now is the left retract wouldn't go all the way into the slot and my servo is a maximum travel before the EZ connectors hit each other which will just put load on my servo. The strut locks in position but just doesn't go in all the way. I may just fly it like that since it isn't a big deal. The retracts also make a creaking sound which I have seen on many other videos of the same retracts in action. I think it may be a normal thing.
I will try to update everyone on future events that happen (hopefully good ones).
Thanks Friends,
re"> Adam (Rcflyyer1)
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Old 02-07-2013, 09:07 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

Discard the H9 retracts. They will only give you headaches.
There are several after-market retracts, either mechanical or pneumatic, that will work much better in this plane.
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Old 02-08-2013, 10:15 AM
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Default RE: Hangar 9 Warbird Elevator Reinforcement

I did hear someone say that the epoxy should have filled the little gapes I made with my exacto knife and was wondering if my 30 minute epoxy would have filled the gap in the wood on my Horizontal Stabilizer and my Vertical Stabilizer. Hopefully that is true.
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