flyinfool1

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Well a workout it did get.

13 flights burning 5 gal of fuel.

I did not count how many different people got there first turbine flight, but I am guessing it was close to 20. There was even one heli pilot that never flew an airplane before.

Everything work perfectly without any issues at all. The only complaint was when I had stop to recharge batteries after every 3rd flight.

JohnVH

My Feedback: (38)

The block of wood in the fuse that the wing bolts go into, one of the holes is finally stripping out, any problems putting a blind nut on the top of it? Thinking that would be a pretty permanent cure.

Also, what are you guys using to hold your wing on? I have two metal bolts as I couldnt find any nylon ones long enough.

highhorse

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It's been a while since I have away my Reaction, I can't remember how long the wing bolts were? Dubro and others sell 3" 1/4-20 bolts. Mcmaster Carr is a good source for aluminum bolts (in case yours are steel) which offer ridiculous strength for a negligible weight penalty.

BruceTharpe

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The kit comes supplied with 3" aluminum bolts. John, shoot me an email if you need some. Blind nuts should be okay if you can fit them in there. Might have to shave portions of the flanges.

JohnVH

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no biggie, the steel bolts seem to be fine, I got this bird used and didnt get any wing bolts so I guessed they must have been something other than plastic. I did shave some off the blind nuts, will test fit and install tonight, then its ready to rock again!

Thanks!

flyinfool1

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I also bought mine RTF.
When I got it it had 3" nylon bolts and the wood was just drilled and tapped for the 1/4 - 20 thread.
I was not going to try to hang well over 100 lbs on a plastic bolt.

I used 1/4-20 x 3"long steel socket head cap screws. I have a fender washer under the screw head and a nylon fender washer under the steel one.
With the changes I made to my mounting block I had to go to 3-1/2" long steel socket head cap screws with the same washer setup.
I tried to get blind nuts in there but they were just not cooperating.
For my blocks I drilled and tapped to install 1/4-20 heli coils with the full depth of the blocks and the ply floor having a heli coil thread.
I also have 4 8-32 screws holding the blocks to the ply former in addition to the epoxy.

I did test it with some significant negative Gs. all is good again.

xxq111

http://www.youtube.com/embed/8WeuWssWLZE?feature=oembed


Not my model. It is another pilot in Norway who built it and fly it.

bobparks2

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Well, lets just look at that…

First, some typical nylon bolt strength measurements:

http://www.plasticnutsandbolts.com/mechtech.html

An 8-32 nylon bolt threaded into a steel nut to maximum torque is good for a bit over 100 lbs. The 1/4-20's used in a Reaction are good for 300 lbs each, 600 lbs total.

Next, some measurements on the wing.. the root chord is 23" and the bolts are 15" back from the LE. Since the wing is pretty much unswept on the quarter chord line, and the airfoil is pretty much symmetrical, the lift load can be considered to act 23/4" aft from the LE, or 5.75". In negative G, the lift load is shared between the LE dowels and the bolts. Its just a simple lever setup, so 38% of the load is on the bolts, 62% on the dowels. That means the bolts themselves are good for about 1500 lbs of load on the wing to body joint. If your R54 is flying at a weight of 21 lbs (with fuel) as you pull that outside loop, and lets say the wing is 6 lbs of that (I never weighed just my wing.. its a guess), thats 15 lbs of body weight getting carried by the wing to fuselage attachment. So, in nice, round numbers, thats 100 G's

The total wing lift would be 2100 lbs. That means stalling the wing at something over 300 mph. A nice, tight 100 Ft diameter loop at that speed. Its just not going to happen.

BUT… lets look at the other part of that attachment. 2 dowels in shear, 1/4" birch. I did not find any conclusive data on that (in a 5 minute search, most shear strength is given parallel to grain, and we have cross grain shear). But 2000 PSI is probably a reasonable number. The cross section area is about 1/20 sq in, so 100 lbs each, 200 lbs total strength at the LE. Thats 322 lbs of total wing lift or about 21G's limit there. Unlike the bolt numbers in back, there is a lot more uncertainty here. If you really cared, it would be worth just doing a quick test of a sample dowel into plywood joint to see how good it really is.

So, those nylon bolts that you don't like are about 5 times stronger than the dowels at the other end.

I did some quick structural strength analysis on the R54 wing a while ago. I think I posted the numbers here, but, as I recall, it was good for around 45G's before the spars would fail. (really rough numbers, and could be higher than that if built well.)

OTOH, if you look at what the aero loads COULD be.. at the 150 mph typical of an R54, if you pulled (or pushed) hard enough to stall the wing, its going to be about 250 to 300 lbs of total lift. If that was a push, then you are close to the limit strength of the dowels…. but nowhere close to the strength of the bolts. BUT, I really doubt an R54 has enough elevator power to come anywhere close to stalling the wing at that speed. Thats about a 200 ft diameter loop, about 3 seconds, so 120 degrees/second pitch rate. The R54 is a pretty short tail moment but the elevator is a small fraction of the total tail area. I could go figure it out, but thats more work than I feel like doing right now.

Suffice to say, that its probably just not possible to break a well built R54 in the air by pulling G's from level flight. Maybe if you did a long full power dive first.... But the weakest areas are probably the dowels and the threaded wood blocks in the back.

BTW, your helicoils are better than threaded wood, particularly in wear, but they only enlarge the diameter a bit and are still just threaded into wood. So SLIGHTLY stronger than freshly threaded wood. Gluing them in would help. Blind nuts would be a lot better.

Bob

BruceTharpe

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xxq111 - Great video! Congrats and thanks for sharing. I am sure you are learning that your landing approaches need to be a little lower and flatter. If you are diving for the runway, even with flaps down, you will end up floating a long way. Hope you get lots of enjoyment from your new R54.

Bob, thanks for the analysis. Provides a lot of comfort! You wrote, "probably just not possible to break a well built R54 in the air". As the designer and kit producer, the key phrase there is "well built". Every glue joint becomes incredibly important when you are yanking around what is basically a balsa wood structure through the air at 150 mph. One area that needs emphasis is the difference between pulling positive and negative G's with this plane. When you are pulling positive G's, the wing is more or less retained by the fuselage. I would expect the actual loads on the dowels and bolts to be relatively minimal. However, when you go negative, the wing is only held on with those dowels and bolts. The dowels are retained by a multi-layer lite-ply bulkhead, and the bolts are retained by a small plywood block. That plywood block is glued into the boat tail which is arguably the weakest link in the whole system, and it's definitely an area that needs to be well built. With all this in mind, when flying I am definitely less aggressive with outside maneuvers

highhorse

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Well, one could write a plastic bolt thesis (excellent work above) or...just test them like I did.

I screwed just one through a metal bar and into an overhead 2x4, then hung my 175lbs from the bar. There was minor deformation at the threads, but no stripping etc. If there'd been two bolts, as on the Reaction, there'd have been no effect in either bolt whatsoever.

I think that aluminum bolts are totally unneccesary, but one should can't be criticized for making a jet too strong ;-)


Don.

BruceTharpe

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Ahhh, my kind of testing. I like it!

bobparks2

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I have never really looked at the performance of the airfoil, but its not really symmetric, and its probably going to make a bit more lift upright than inverted. So there is more margin there.

And, its REALLY not "jet like" to do these itty bitty outside loops anyway! And, somewhere in the high G range, servos probably start having issues, and you could well blow the engine bearings. I have asked a couple of engine manufacturers what pitch and yaw rates their engines are rated for at full throttle, and the result is a "Huh??". But the gyroscopic precession loads on that shaft with blobs of weight on each end, spinning really really fast are significant. (I once blew the bearings in an OS .91 ducted fan engine by doing a rather energetic outside snap roll into an inverted spin while at full throttle.. and it was only doing 22,000 RPM)

I agree that the strength of the boat tail area might be the real limit here, particularly since a lot of folk (me included) cut notches in the boat tail to clear the engine starter. I did add some fiberglass to that area to help get the loads around the cutout.

All that said, I do tend to do some occasional very high G loops.. just because I can. (but I cut throttle first.. )

Bob

Ron Stahl

My Feedback: (12)

I can attest to the strength of the Reaction 54 kit if built as designed. Mine is over eight years old and has never come close to ever having a wing attachment issue or any other issue that wasn't my fault. However one of the not so locals built one after seeing mine fly years ago that we have nicknamed nine lives and started putting black cat stickers on for every time he should have lost the plane. I landed it once with no elevator control when the push cable solder joint failed. The wing has come off three times when we would never expect it too; first when we were moving the plane in the pits because it started raining. He didn't follow the directions when he first built it and he pulled the blocks out of the fuse when he tightened them up with a power screwdriver earlier in the day. He then had the wing come off during a bad landing, the wing and fuse separated at FIF this past spring. He did a poor repair and the bolts didn't shear the blocks pulled out again. In August he dodge the bullet again when I refused to test fly it because I saw how poor a job he did on that repair. Since it was windy we went and got some new wood, fashioned new blocks and tied them in so he would disembowl the plane to have them pull out now. I told him when we get to eight on the cat stickers it's time to sell it lol.

bobparks2

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I am sure Bruce has his stories too on this, but about 20 years ago, I did a kit design for a company, and all of the "difficult" tech support calls got forwarded to me. It was amazing how much people can screw something up! The kit had a foam wing and needed to have balsa skins applied. The instructions told how to do it with epoxy and vacuum bag or a bunch of weights. The instructions were very similar to what Bruce does.. lots of details, photos etc. They SPECIFICALLY said not to use CA glue near the foam (this was before foam safe CA existed). So, I get one call from a hobby shop owner. His customer used CA to try to glue the skins on. Melted the cores down to nothing. I sent the guy new wing cores at no charge. So..he used epoxy the next time, but glued the skins to the foam cradles, not the cores. I told him to just try again and glue the skins to the cores next time… so he glued them to the cores AND the cradles. I finally just bought the kit back from him (at full list) just so he wouldn't be out there trying to fly it and giving the plane a bad reputation.

NOTHING is idiot proof… ever.

OTOH, and I am SURE Bruce can attest to this.. For every total idiot, there were a half dozen calls from people saying how much they liked the plane.

So Bruce, I know I said it before… The R54 is AWESOME! The kit, the instructions, the flying, everything! THANK YOU!

Bob

Woketman

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Hey Bob, post some photos of the skins bonded to the cores AND the cradles!!!! That is hilarious!!!!!

causeitflies

I'm glad I wasn't drinking anything when I read that!
That's as bad as the guy who showed up at the field and didn't know how to secure the RX in his plane. So, he just drilled a hole through the center of it and bolted it in.

bobparks2

My Feedback: (1)

Sorry! Never got any. That was before digital photos and almost before the internet..

Bob

flyinfool1

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xxq111
Great flight, was that the maiden?

Bob
While all of the theory sounds good, I have seen many 40 size low wing trainers break two 1/4-20 nylon bolts on a rough landing.

I am not saying you are wrong, I am just saying that I am not wrong either.

Per all of your specs, that 300lbs per 1/4-20 nylon 6/6 bolt is the failure point. On a critical structural part, I like a 5:1 safety margin. NO ONE designs to have the working load at the failure point. So based on all of your numbers the nylon bolts are good for a working load of ~20 Gs with a safety margin, but you calculated that 21Gs is realistically achievable. Those specs are also for a fresh, new, dry, nylon bolt, age, moisture content and wear will take a toll. This fits right in with my desire to use steel bolts.

The R54 has the gear spaced well apart for great ground handling, BUT when you stick a main gear into a hole in the grass at speed there is a huge shock load on the wing bolts, I really do not want to take the chance of the wing coming off or stressing a plastic screw and have it fail on the next flight. Can you calculate the instantaneous shock loading on the bolts when the plane is traveling at 35-40 mph at touch down, or lift off, and a wheel drops into a hole in the ground?

My wing dowels in the front of the wing are not 1/4 inch, mine are 3/8 inch. and there is an extra layer of aircraft ply in the front mounting of both the fuse and the wing.
With my new blocks that I have, there is 3/4 inch of heli-coiled thread engagement, (there was just no way to get the blind nuts in there with out major surgery) the blocks are now screwed to the fuse and not just glued. I broke the rear wing mount once, it will not break again.

I bought my R54 second hand RTF, there are many things that were not built right and had to be reinforced, or redone. To strong (to a point) is far better than not quite strong enough. Remember I already broke the stock setup once.

I have no interest in scale like flight, I fly very aggressively. How many Gs am I pulling? No clue. But it is a lot. Definitely a lot more than any other jet pilot that I have met.
100 or 200 foot loops, why make them so big? Yes the small elevator does have enough authority to stall the wing coming straight down at ~3/4 throttle. ( the down legs of square loops or square fig 8s).

When I added 3 lbs of smoke system (including oil), the wing loading did not change by much, barley noticeable in the air.
Bottom line is the extra 1 oz (maybe 2 oz) in weight penalty for the the steel bolts and bigger dowels makes me feel a lot better even if the math says it is not needed.

bobparks2

My Feedback: (1)

Thats probably a shear load, not tension. Whole different problem. OTOH, what I have normally seen is a pile of rubble surrounding intact bolts.

That was yield, rounded off. But ultimate was not that much above yield for those.

Why don't you go read what I actually wrote? The yield load number for the bolts was 100G, it was the 1/4" dowels that were a mere 20 G's. When designing a structure, yes, you figure out expected loads, apply a safety margin and design structure to meet those margins. When you have existing structure, it is just as valid to figure out the load carrying capability, then compare that to expected loads with the result being the real margin, which is exactly what I did. And these were all for OUTSIDE loops.

FWIW, structural parts on aircraft normally get a 1.5:1 safety margin, with 2:1 for small fittings. I would like 5:1 too… but I just don't get to design airplanes that way.

Depends on how fast its really going, The higher the speed, the more elevator it takes to stall the wing. I kinda doubt its the 300 mph I mentioned Are you doing outside square loops? It would be interesting to put in some telemetry and an accelerometer and see what its really doing.

Sure. Depends what you want to do. But I fly nylon bolts on mine and will continue to do so. Ages ago, when nylon bolts first started to replace rubber bands for holding on wings, the idea was that in crashes or snagged landing gear cases, the bolts would shear to minimize damage to the rest of the structure. In many cases that I have seen, the bolts are often the only intact part remaining after the crash. But, I have seen a few cases where the bolts really did fail when they should, leaving a plane that is easily repairable. Take your pick.

Bob

Woketman

My Feedback: (6)

Boy, sure am glad you did not work on Shuttle! We would have NEVER left Pad 39A or 39B!!!!!

svennoe

Hi!

I have been building a Reaction 54 for 6 months, and I had an fantastic maiden flight just two days ago. Its the best kit I have ever build, and as you all know, it flies like a dream!! Im using a VT80 turbine witch has a lot of power and Lado retracts. It flies surprisingly fast and it really slowes down on landing.
A friend of mine filmed all three flights, and made a video..its quite long, but I hope you like it.

Best regards from Svenn, cold Norway

http://www.youtube.com/watch?v=8WeuWssWLZE

BruceTharpe

My Feedback: (1)

Hi Svenn, welcome to RCU, and CONGRATULATIONS on your new Reaction 54. I liked the video very much - it was actually posted a few days ago. Maybe it was the cameraman? Anyway, I hope you get a lot of exciting flights on your R54. It would be interesting to see some pics of your VT80 installation and Lado retract installation.

Dr Honda

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I REALLY want an R54... but I know if I buy a kit... I won't ever find time to build it. (its hard to find time to fly sometimes)

flyinfool1

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The R54 can be flown with skies, check my avatar and post #1946 and #1948 in this thread.



it is a different problem but not one that can be discounted in this case.

I did reread what you wrote.
Your calculations were based on the lift load, I could be wrong here, but once the wing is stalled it is no longer making lift, the airfoil does not matter, it might as well be a sheet of plywood, do you not have to use the center of pressure for the wing which would be near the 50% chord point, that would move the fulcrum much closer to the bolts and take load off of the dowels.
Actually now that I think about it, in this case the lift of the wing is irrelevant in an outside maneuver. It is the weight and center of gravity of the fuse that needs to be considered, that is the load on the screws and dowels in an outside maneuver, not the center of lift or the center of pressure of the wing. The fuse is trying to be pulled off of the wing not the wing trying to be pulled off of the fuse.

I guess we have different backgrounds, I never did design work for anything fragile. My background is to get as close to indestructible as possible and heavy is a benefit.

I am willing to bet that I am no where near 300mph even full throttle on a vertical down line.
I do all elevator maneuvers both inside and outside. My square figure 8s usually have one half of the maneuver as outside. It is always a crowd grabber for those that do not know me to see the plane coming straight down and expecting a pull to upright to finish the square loop and the gasps as it goes to inverted to complete the outside half of a square 8.
I would love to get an accelerometer in there. I thought about buying one a few times.



I guess I remember it the other way around, rubber bands were used on trainers to let the wing pop off, and nylon bolts were used on higher performance models to ensure the wing always ended up in the right place and did not move under the aerodynamic loading.
I agree completely, we can each take our pick of what to do to satisfy our own preferences, that is why we have choices.

But at least some people including me are learning some things from this discussion, so all is good.

We have learned that mathematically and realistically the nylon bolts are plenty strong.
We have also learned that I practice overkill in much of what I do ........




No i did not work on the shuttle, but my dad did. But only since you brought it up in this context, maybe if the shuttle had higher safety margins we would not have lost 2 brave crews.

Woketman

My Feedback: (6)

You CLEARLY did not understand the failures in both Shuttle accidents.

Challenger was caused by a cultural need to keep flying and stick to the schedule. They ignored the warning signs from the SRB O-rings. They conitinued to blow vent holes in the field joint insulating putty despite evidence that the O-rings were getting singed.

Columbia was a similar failure of management to ignore debris damage issues until too late.

Pre-calculated safety factors were irrelevant.

And Bob (as usual) is correct about the nylon bolts. And way back when we were always told to use the nylon bolts cause they would shear off easily and save the wing, like rubber bands.