Home › Forums › Free Flight › Nostalgia Gas › Trimming High Thrust Line Models
- This topic has 13 replies, 4 voices, and was last updated 15 years, 4 months ago by Anonymous.
11/05/2007 at 4:16 pm #40722AnonymousInactive
I’m looking for help trimming a high thrust line (T-Bird) model. I’m new to power flying but have flown rubber the last few seasons. With rubber I flew right/left and I’ve been told left/left was “dangerous.”…presumably for the model not the modeler. I’ve also been told that right climb on a high thrust line model is hard to obtain. When rubber in a rubber ship winds down the model is flying approximately level and with R/L trim I can usually get a nice transition from power to glide.
When my T-Bird finishes the power run it is pointed nearly straight up and I loose about half of the original altitude.
So these are my questions:
1. Is L/L trim dangerous?
2. How do I get a good transition (power to glide) with L/L trim?
3. Are there better trim set-ups that would serve me better?
Stardust11/05/2007 at 7:20 pm #44853
Left-Left is the ONLY way to fly a High Thrust Line model. Go to the right, and you will re-kit the thing. I did it to three of them when I was a kid before some of the adults in the club got to me and explained things.
I fly my T-Birds L/L and they transition fine.
The CG is 80% with about 1-1/2 degrees decalage between the wing and stab. In other words, the stab has that much negative angle relative to the wing. A bit of left rudder tab, and a bit (1/8 inch on a 1/2A T-Bird) of washin in the left main wing panel.
That will get you started.
Launch vertical. Somewhere on the NFFS website under photos, there is a shot of Steve Bruno launching his yellow T-Bird 525. Shows perfect form. Adjust the rudder tab and wing washin such that it turns one 360 in 9 seconds. I have been working toward only a 180 turn and so far it is working. Turns waste energy. 😯
Trim the power with stab incidence, and the glide with CG shift. Without looking at yours fly, it seems like it is under elevated. Try 1/32 under the stab TE and try again. If that fixes the problem and the model stalls in the glide, move the engine forward with shims behind the radial mount. If it loops over the top, increase rudder tab. If after getting the power pattern set, it still doesn’t stall, begin adding weight to the aft fuselage until it does, then take off the last weight added. Don’t even bother hand gliding the thing. Set the CG and decalage and work on the power pattern first.
I went to “school” on T-Birds since 2004 when I converted from FAC rubber-powered scale models to Nostalgia Gas. I have compiled some notes and modifications to T-Birds which I can email you.
Send me your email address, and I will get them right out.
My email: email@example.com 🙂11/05/2007 at 8:54 pm #44854AnonymousInactive
Many thanks for taking the time to answer my questions. I think I have enough information to straighten up and fly right. Also, it is reassurning to see that you have confidence in the T-Birds. Someone reccomended them to me and I have build a 1/4a, 1/2a and have plans to build an A version. I see you left FAC scale to fly nostalgia. Last year I build two FAC moths and getting them to fly is driving me nuts. Our club has a number of FAC flyers and they can get them to work, but I’m a newby at model avaiton. It seems to me the smaller they are the harder they are to trim.
Thanks agin Dean
Earl Griffith11/05/2007 at 9:21 pm #44855
Dean has good advice on the T Birds. Launch them straight up. They MUST go left under power. Never launch it right to the wind.
Your transition is a decalage problem, so adding up elevator is the answer. Good lord, I hope that you’ve reinforced the fuselage athe the trailing edge of the pyln. If you haven’t, you will eventually. Most guys use carbon fiber strips inside the fuselage.
FA Moths build nose heavy. Add tail weight and shim uner the L.E. of the wing.
Earl, were you at the Perry, OK meet in September?11/05/2007 at 10:51 pm #44856AnonymousInactive
I was at the Perry meet. It was the fourth meet I’ve competed in. I’ve been to two Nats and the Mid America Meet in KC. I had planned on flying several events but, on the second round in Mulvihill some fool forgot to light the fuse and wouldn’t you know it I hit a boomer. Fortunately, I had a Walston transmitter on board so I was able to locate the model after I had; walked across a large soy bean field with some plants chest high, crawled through a hedge row, crossed a stream, walked across another bean field, crawled under a barbed wire fence (I’m 64 and 250 lbs) through some prairie and plucked my ship out of a Juniper tree. And then there was the return trip. When I got back to the flying site I found I was one second behind Bill Schmidt (Wichita KS) in the standings. Bill had all his flights in and I had one to go. Only one second separated us. You know, I was too freaking tired to put in the third flight.. just used up. What I took away from the meet is that more than one’s planes have to be in shape. I’m considering indoor.
Should we find ourselves at the same meet again please introduce yourself I would like to know you. I’ve read many of your post in this forum.11/05/2007 at 11:01 pm #44857AnonymousInactive
One more thing. On the T-Bird’s first two DT’s the tail boom broke off just behind the pylon. After the second breakage I added CF strips to the four corners of the tail boom and epoxied the whole works together. So far, no more breakage.
A second problem. I’ve broken a prop on every DT with the 1/2 A model. The first two were wooden. OK, I’v learned that lesson. The third was a Rev-Up nylon, broken on the first DT. I’ve ordered 6/3 APCs from the company. I would be glad to hear your comments.
Earl Griffith11/05/2007 at 11:14 pm #44858
Ok Earl, I thought that might have been you. I remember the mulvihill w/o a lit fuse.
Welcome to FF!
I’m the guy with half re, half blue planes. I tried giving directions to the mulvihill after one flight. Did not see you later on, but the plane was gone so I assume you got it. It’s a good flying plane, by the way.
Old nylon props can get brittle. solution— boil them for about 10 minutes.
APC 6×3 could work. The 5.7 x 3 is real popular, but alas, isn’t being made anymore. I don’t know if the 6×2 might be an option for the HH.
Amazing/amusing that you figured out the fuselage solution so soon.
Were you at MidAmerica this year?
Perry can be a tough retrieve.
Look for a private message11/05/2007 at 11:59 pm #44859AnonymousInactive
I was there. Saw a couple of amazing things. Bill Schmidt put up and early Nos 1/2a and for what ever reason the engine didn’t stop. One would think the timer didn’t get tripped, but I don’t know this for a fact. It was just wonderful watching that little 1/2a bouncing around up in the blue. Same could be said for Jim O’Rielly’s Jimmy Allen. Jim’s flying colors are red and yellow. I think he flys a BA cabin. Well, he got a string of thermals and that tiny bird was up and down and a beautiful sight against the blue sky. I was standing next to Jim and he was tickled and why not.
Don DeLoach beat me in Mulvihill by one second. However, it really wasn’t that close. It was the first round and Don maxed at 120 sec. and my flight was 119, bad prop fold which I have now fixed. This is the same plane you saw at Perry, my design, called the Copy Cat, because there is nothing orginal about it. This was the first round and I’m sure Don could have put up many maxes after that. I’m hoping to be more competitive in up comming seasons. I’ve got a lot to learn.11/27/2007 at 8:43 pm #44860AnonymousInactive
We built several a 1/2A, and 1/4A (TD .020) T-birds. Most flew right off the board. They go left/left. My 1/2A has a Space Hopper with a Windsor 6×3 prop, reworked tips. 3/16″ inch wash-in on left inboard wing panel, both tip panels have 3/16″ wash-out. Stab tilted just slightly less than inboard wing panel’s dihedral. No right or left thrust, but I needed about 1/8″ of left rudder tab as the plane would start to straighten out and go a bit right at about 9 seconds.
I put the GC right on the money according to plans, only a small amount of shimming the TE of the stab was needed to get the glide right. The transition was not really good until full power runs of over 6 seconds were used, but then it was fine. With the rudder tab set to give about 1-2 turns in the climb, it rolls out perfectly every time, unless you get a bad needle setting and slow power run.
We never launch vertically, or use javelin style launches, as it tends to upset the fuel flow, stalling the engine, and also could result in the wing or stab shifting off the keys with disasterouse results( need I say Lawn Dart?). If the engine should quit in the first few seconds after a vertical release it usually results in alot bashed balsa and ensuing expletives!!! We have found it much better to just release the plane at about a 20 degree nose up angle and let it build speed and ramp up into the climb at it’s own pace…..no surprizes or re-kitted planes are your rewards. This is most important while you are still trimming….spear chucking can come later once the ship is “locked in”, if you dare. If you do “spear chuck” I advise you run a bladder.11/28/2007 at 4:18 am #44861
If you do “spear chuck” I advise you run a bladder.
Actually, if you want to do anything with a Gas Free Flight (Always Capitalize), run a bladder. Any other fuel system will eventually cause problems, and the solutions to the problems make something simple really complex. A bladder allows total flexibility in launching and ensures, if properly set up (easy to do), steady needle valve settings and consistent engine runs.
You mention launching a T-Bird at a 20 degree angle. Probably you haven’t seen them lately. Straight up. If the CG is set properly, and in order to do this, you have to set the power pattern first, the airplane will go exactly where it is pointed. A 20 degree launch will equal a nearly 20 degree climb angle, the airplane will accelerate, and become nearly uncontrollable.
Trim the climb with stab angle and rudder tab, and the glide with CG. If it doesn’t transition, you have gone a bit too far back with the CG.
This is not the way we used to do this, but is the way we do it now.
Guess how I found this out 🙂11/28/2007 at 4:27 am #44862
T Birds. Straight up. They go where they’re pointed. If you’re gonna worry about what happens if the engine quits, make certain its not gonna quit. pressure systems solve a lot of problems.11/28/2007 at 2:53 pm #44863
One other thing I forgot to mention. 😳 Short DT.
This is the salvation of many a Free Flight Gas model on the first nerve-wracking first flights. JMendoza mentioned the possiblity of the lawn dart effect after a vertical launch and a short engine run. Well, that is a distinct possibility. How to get through these first flights successfully is the challenge.
The answer is the Quick DT. You want the stab to pop about 2 seconds after the engine cuts. This is on a 3-4 sec engine run. Impossible with a fuse DT rigged in the conventional position on the aft fuselage, but easy if you have a fuse system on the forward part of the fuselage, or a viscous timer, either with a DT line holding the stab TE down.
I prefer viscous timers. They are a pain to set up, but once done, are quicker than a fuse, and much more dependable. Either way, the Quick DT can be set up by bypassing the snuffer tube or the viscous timer and using the engine timer to trigger the stab.
You are using a Texas Mini timer aren’t you? If you are making do with an old Tatone or KSB unit, put it on eBay and get you a decent timer. Hank Nystrom (no relation) puts out an excellent line of products and his website, http://www.texastimers.com, is a wealth of information. Under “Helpful Hints” you can look at a couple ways to easily rig a Quick DT system.
I set my Quick DT line to run one thread on the timer scroll behind the trip wire. It lets go about 2-3 seconds after the engine cuts. That will save a model if it gets its’ nose down early in a power phase, or save one that cuts in an extreme nose high attitude.
They usually don’t get turning satisfactorily for the first few seconds.
Trim for the 6 second engine run, and it should be OK for the 9 second run. 8)
One other thing I forgot to mention. Sometimes, with the iron-on coverings, the washin that you put in the left (for a high thrust) main wing panel won’t stay in. I have now changed to using a bit of TE stock, reversed to give a roll input, glued to the left TE at the polyhedral joint. If it rolls too much, you can cut some off, if not enough, you can add some. When it is right, you can paint it to match the airplane, cover with tissue or appropriate transparent covering, or like me, leave it bare balsa so it will look like Luddite Dan Berry’s airplanes. 🙂 🙂11/28/2007 at 3:43 pm #44864
Hey Hey Hey
My planes look great, at a distance. In fog. A couple beers help, too.
Get ’em up fast. I might have noted a plan to use a prop backwards. Don’t do it. All to the wall.11/28/2007 at 7:03 pm #44865AnonymousInactive
My T-Bird doesn’t know what year it is, even though things may have changed in the way people do things now, and therefore continues to fly great inspite of that!!! 😆 Please, don’t tell my T-Bird. 😛
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