GP Reactor 46- Nose keeps dropping in hover
 

I have a GP Reactor 46 with a OS FS55AX engine flying a 13x6 prop. Last week I tried (to correct engine problems I had) witha a 12x8 prop. It was good but couldnt hold the hover.

This week with a 13x6 prop the airplane hovers for a second and then drops the nose even on application of power and full elevator. I am already at the full 3D throws. I dont apply full throttle, just about 80% in the hover. I figure that the engine should have some left to pullout if I get into trouble. Another issue is that in high-alpha nearing the hover, the airplane seems to have a lot of wing rock.

When I checked the CG, the thing is just a bit tail heavy at the recommended CG. Problem is even with a CG machine, it drops the tail if the tail is lower and the nose if the nose is lower at the recommended CG, so I guess I am somewhere close to recommended. I have a larger than stock 320cc (14oz) Sullivian flexitank in the airplane, most of the time when I hover, I have a good amount of fuel (I usually land with 1/8 tank of fuel after a 10 minute flight), so in that configuration it should be nose-heavy.

I tried a 13x4 prop also, the engine overheats and there is really no airspeed in that prop.

Please suggest what I should do in this case?

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

ameyam,

Are you new to 3D are is it just this plane? Are you sure you have your engine tuned properly and you have enough power to hover your plane? I'm running a Saito .82 with an APC 14X4W prop and it does fine. Try using more than 80% of power while your hovering. How much expo are you running?

RE: GP Reactor 46- Nose keeps dropping in hover
 

I am not new to 3D, I have been 3ding a Twist for a couple of years now. Engine issues on the twist earlier and even ths Reactor has prevented me from trying the other 3D moves, mainly hovering, flat spin and high alpha is what I do. Harriers were possible on my Twist but not on this Reactor.

My engine is tuned ok. Initially I did it and when in my second flight I heard the engine struggling in mid air, I had one of the experienced members tune it. Set it 1/8 turn back from max RPM with the nose held vertical.

Thats the point I am asking. Everyone had recommended that 81 size 4c is the right engine for this airplane. But 4c engines are not too popular at my field and 75ax is too big so my mentor suggested a 55ax. What I do want to know is whether the 55ax is powerful enough for this airplane. At that time the 61FX was not available and it is too heavy for its power. Now the 65ax is available and I am told its quite strong. The 81A is just too expensive. After haveing the LG break of recently in a hard landing, I reinforced everything, so it has gained a bit of weight from stock, may be 150-200 grams or so.


None, I am ok with the response curve being straight

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

I would try a larger dia prop with less pitch. It sounds like you need to get more prop wash over the tail. I am a little concerened about your fuel as well. What are you using and how old is it? What I mean by fuel age is how long ago did you open the bottle and when in storage is it 100% sealed so no air can get to it.

RE: GP Reactor 46- Nose keeps dropping in hover
 

I have worked through all those variables. Remember, I said I had engine problems? I did check just about everything to get them resolved.

I dont think I should put a 14x4 on this engine. Witha 13x4 I noticed that after running for sometime, the compression gets very soft as the engine overheats (compression comes back when engine cools for a few seconds). A 14x4 is likely to make it worse

The fuel I am using is klotz100 based with 10% nitro and 20% lube in the mix. Its only a couple of weeks old and the main can has been mostly sealed. I carry around a litre of fuel, thats all I need for one day's flying

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

A prop does not provide cooling. Airflow during flight and fuel is what provides the cooling. When swithching to a prop that will rev a bit higher, you need to needle the engine accordingly.

RE: GP Reactor 46- Nose keeps dropping in hover
 

Done that. Also, I am flying without cowl

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

Ok, had 4 flights on the Reactor yesterday and 2 today. In all of them I had only one goal- to make the thing hover. Started with a 13x4 which I could hear was over-revving and gave me the soft compression problem again when hot though it didnt cut. Then used a 13x6 which was much better but still couldnt hover. Today, I tried a 12x6. Also Last week I already tried out a 12x8. In the hover, even at 100% throttle and full rudder and elevator throws, the plane could hover for a second or so before falling nose down. It fell nose down everytime, did not slide backward or left or right. Today I even got a buddy to make sure I was at full throws and full throtthe when that happened and he confirmed it. And it happened with every prop

I have already checked the CG and its ok if not a bit tail heavy. I flew today with a much lighter 1300mah LiFe battery under the tank to make it tail heavy.

That settles it. The 55ax with whatever prop doesnt have the power to 3D the Reactor, atleast not with my reinforcements. It just lacks the last 10% of power. So while I resolved the engine issue with a 12x8, the engine just doesnt have enough grunt, even with 10% nitro. It is great for pattern flying but not for 3D

I am contemplaing which engine to put in

1) FS91SII- I have this engine in good condition on another airplane. Rather than keeping it unused, I would like to use it on the Reactor. Total weight is 24.2oz (686g) with muffler and that is comparable to a 65ax and is lighter by 2.26oz or 64g than the 75ax. This would be the economic way to go

2) 75AX- had issues on another airplane but those may be due to tank height problems. Has a lot of power by is heavier

3)65AX- has only marginally more power than the 55ax. Is a bit heavier too. I dont have this engine though

Please Suggest

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

ameyam, what kind of rpm reading are you getting, 13x4 prop should not be puilling to many rpms. What is AUW of your plane?

RE: GP Reactor 46- Nose keeps dropping in hover
 

My thoughts, definitely before considering a new engine:

The .55AX should be more than enough power for the .46 Reactor. The .55 was designed to fit in .46 planes to give them more power. As others have mentioned, 2-strokes need more throttle (rpm) to hover a plane than 4-strokes with their increased throttle response and torque.
-I think 13x5 would give good vertical performance on that engine in that plane. I have a 12x8 in mine for aerobatics.
-I did notice in the GP video they are flying the 4-stroke .70, but the .55 should give you more power, just with more RPM.

I would try more nitro (15-20%) and less oil (18%).
-2% more oil means 2% less fuel.

I wonder if the problem lies in the engine tune. Hovering is probably the hardest thing on an engine - high power, no air flow, and demanding fuel vertically against gravity.
-Check the tuning of the idle valve; most people seem to try to attack tuning with only the HSN, but it is a 2-part system. You're getting hot and lacking power, sounds like fuel draw is an issue in vertical attitude.
-Run the engine on the ground. Advance to full power, drop to idle, and watch your RPM. They should stay constant for a good 20 seconds. If you see a gain in RPM, your idle valve is lean. If you see a decrease, your idle valve is rich. Adjusting one means you have to go and check the other; it is an iterative process.
-Check your fuel system for leaks. Close off the vent, disconnect the engine, and pressurize it over night (by mouth). Or if you want to do a more thorough check, pull the system from the plane, pressurize it, and dunk it in water to check for bubbles.

Check the balance of the plane in the air, not on the stand. The stand gets you close, all adjustments to be made by flying. Fly straight and level at 3/4 throttle, pull to 45 degrees, roll inverted and let off elevator. What happens? If you are concerned mostly with 3D, the plane should continue straight, or even gain a touch of altitude. "Neutral" will have a very slight decrease in altitude.
-Don't forget that balancing on the machine is without fuel, and if you're flying 10 min and landing with fuel in reserve, that's a bunch of extra weight in the nose.

Hope this helps. Good luck!

RE: GP Reactor 46- Nose keeps dropping in hover
 

Though it was designed for a 46 engine, that would only give sufficient power for sports flying. The FS72A wont be any better, it would give the power of a 46 size 2C (2/3 SIZE)

I noticed with the 12x8 that aerobatics were quite good and the engine was running well. With a 13x4, the engine did not have compression after running a few minutes. It did not have the airspeed for any pattern flying either. When I landed I found that the engine could turn over without any perceptible compression. After it had cooled a bit compression was back. This happened repeatedly even with the 12x6. I presume engine is overheating. I have the engine tuned ok, half turn rich from max rpm. I didnt however tach or check the temperature


It it overheats at 10%, it will have more problems at 15-20. I dont want to put that much nitro in it anyway



My LSN is a bit rich but not by much, may be by 1/8th or 1/16th turn. In any case, I dont think that will affect the hover. If I need to put in 100% power just to hover, where is the spare for pullout?


Already done that


Didnt do the in air test. I did balance without fuel. I dont think the reserve fuel is that critical to balance In any case, that reserve was for when I start getting more comfortable with the setup, I had two timers one set for 10 and the other for 12 minutes. So if I do a lot of hovering, I will fly for 10 and if I do more pattern, I will fly for 12mins.

Some weeks back, I had a hard landing after the engine quit in flight and broke the LG. When I repaired, I added more ply and tristock everywhere. I also added 1" wide birch wood to the LG Block so that it would take harder landings. Consequently, the airplane has become slightly heavier. Note that I do have a FS72A. I just dont want to open it as if it doesnt have sufficient power either (which is likely), I will have another unused engine. I have already run in the 91 and it would be better to keep it operating instead of idle

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

You keep saying the engine is "overrevving" with a 13x4 prop.Then you want to switch to a smaller prop??
Put a 14x4 prop on it!! If that don't work try a 15x3!

RE: GP Reactor 46- Nose keeps dropping in hover
 

Just a minute, KB9STD. I put in a lower size prop with a higher pitch. I went from 13x4 to 12x8 to 12x6. I had similar problems with the 12x6 and 13x4 but the engine was quite happy with 12x8. However, I couldnt 3D that prop

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

RICHEN it up off of the high RPM the AX likes a little rich mixture .Get a good stream of smoke and it will be a happyer eng. Use 15% for more power.

RE: GP Reactor 46- Nose keeps dropping in hover
 

I think he is leaning out and has weak fuel..
if not the OS` 91 should give the punch and torque he is looking for

RE: GP Reactor 46- Nose keeps dropping in hover
 

Here's the plane hovering just fine on an OS .70 four stroke:
http://video1.hobbico.com/gallery/gp...021-deluxe.mpg

All this stuff you're talking about with the engine sounds like you're missing something with the tuning and setup (temperature, compression, lack of power). I don't think the problem is the plane or motor.

Go to the RCU Ratings page:
http://www.rcuniverse.com/product_gu...fm?kit_id=4630

Everyone else is happy with the 55AX. Some people are using a smaller prop (12.5x5 or something like that).

RE: GP Reactor 46- Nose keeps dropping in hover
 

So what changed?? The work on the landing gear? Is it balanced different? Different throws? Change radio settings?

RE: GP Reactor 46- Nose keeps dropping in hover
 

My persistance in hovering, thats what changed. At the time I wrote that, I was not much used to the airplane so I would hover only for a few seconds and the 55AX was able to hover that time. I still does hover for a few seconds, but when I persist, it stalls out. Further, I landed hard and broke my LG sometime back. When I reinforced it, I added additional ply above the LG Block and 10mmx25mm birch wood below the LG in two rows along the fuse width with the 25mm pointing towards the LG. I also added a lot of ply and tristock along the side walls of the fue to make it stiffer so that it could take harder landings.

It worked- in the week after the repair I had a deadstick and with no where to go and no air speed and pointing downwind, I landed in area with a lot of rubble. It threw up so much dust, the others thought I had totalled it. But there was no damage whatsoever, just a very dusty airplane. A slower landing in the same gravel broke the MUCH stronged LG Block on my colleague's Phoenix Yak 60" (with a 120ax, so it was heavier, it stalled at head height with no engine)

Probably I have added some weight or may be I am having engine problems. Engine problems cant be diagnosed on the net, my mentor and some other members at my club seem to have given up. So I am better of installing an engine that I know works well instead of extending the 2 month long trial-&-error session. Will replace the piston and liner in that engine later

I have the following lightening plans to help reduce the weight and hence wing loading.

1) Since the 91 4c is a big engine, I will be using Dubro antivive beam mounts to lessen the wear on the airframe. I will be using the 50-75 2c variety as that is the lighter (and I have it at hand). I wont use the GP adjustable mount unless you guys suggest otherwise.
2) The LiFe battery will go into the tail to balance the airplane.
3) I will also be putting in 2 3/4" foam wheels from Dubro
4) I am considering replacing the stock aluminium 15mm dia wing tube with a CF tube if I can find it.

There is little more in the airplane to lighten

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

As I've pointed out repeatedly.... means the engine is lacking sufficient cooling airflow...

Remove the cowl, then try the same thing again with the wider prop... even try the 13x6 prop too.

As said, this engine is more than enough for that plane.... so something is very wrong with the setup.

RE: GP Reactor 46- Nose keeps dropping in hover
 

Opjose,

the only thing I didnt try is 14x4. Otherwise 12x6, 12x8, 13x4, 13x6- tried them all. I accept the 55ax is good enough for this airplane- for pattern. With a 12x8 the airplane flew with authority. I did all the pattern moves I am familiar with and very well. Evn with the 12x6 (on Sunday) and 13x6 (on saturday), when I had concluded it couldnt 3d, I had the confidence to demonstrate the rest of the flying at high throws (triple rates were set in my TX) to some aerobatic beginners. In fact I was confident enough to fly upside down, do the slow roll, knife-edge- usually moves I dont even contemplate on my airplanes on a Saturday when I am lacking practice. But it couldnt hover, harrier, flat spin, waterfall etc even at 3D throws.

Like you said, there is something wrong with the 3D setup... or this specific engine doesnt have the power for 3D

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

Perhaps it will help if I post pics of my airplane. It is now sitting on my loft without the prop. As you can see, I have already opened up the cowl all I can.

Now please dont say that irrespective of how open it is, it required more cooling. Remember, I have tried it out without the cowl.

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

Great now we can see what you've done.

Some would argue that there is not a cooling hole, but there is enough of a cutout over the head that you should not be having problems.

So it's back to what is causing all of the heat issues...?


What is the ready to fly weight of the plane?

You may have posted it before... but if you would please post it again.

RE: GP Reactor 46- Nose keeps dropping in hover
 

What are you using for a glow plug??

RE: GP Reactor 46- Nose keeps dropping in hover
 

Weigh the plane and let us know. My Reactor originally had an older OS50FSR with a Mac's tuned pipe. It weighed approx 5lb 10 oz with that setup. Best prop was a 12x4 Xoar, but even then, it wouldn't hold a hover for long. From all accounts, the 55AX is a fair bit stronger.

I switched to a Saito 82 with a 14x4W and had plenty of power for hover. All up weight was almost identicial, as I lost the weight of the tuned pipe setup. If your plane is over 6lbs, you're asking too much of the 55AX. A 4 stroke .91 would be good; you're going to have to juggle setup (battery location, etc) to keep if from being too nose heavy.

RE: GP Reactor 46- Nose keeps dropping in hover
 

As far as your CG is concerned.... you're probably nose heavy. The only TRUE indication of nose/tail heavy I have found is to fly the plane inverted, hands off - in my experience. The plane should be able to fly level, or VERY near it without losing altitude when upside down at normal cruising speed. The CG tools have only gotten me in the ballpark so it isnt a disaster at takeoff.

Once I started flying 3D, no matter how perfectly I might have set everything up, the true tests and adjustments come after flying.

RE: GP Reactor 46- Nose keeps dropping in hover
 

You have to big of a prop with a 12x8 LOL try the 12.5x3.75 wide prop but is a heavy prop. also to hover a plane or do 3D stuff the plane needs to be light and have a light wing loading. get rid of that 14 ouncs tank for starters.
Do you have a big exit hole for the air to leave the cowl? i also bet that since you are over proped you are trying to get every bit of rpm out of the engine and it goes lean during your hover and loses power.
also if havent yet remove the baffle in the muffler.

try a 12x4 or 13x4 prop also.

for most planes in this size range a four stroke engine is best.

RE: GP Reactor 46- Nose keeps dropping in hover
 

I will weigh the airplane and report. Dont have a weighing scale myself, I will need to borrow someone's.

When I was flying inverted, I had to give a touch oof elevator to hold level. But it was no so much that I noticed while flying, it was more of a bit of reflex, if at all. I know because I was rolling, bunting, split-S-ing etc from inverted.

With regards to the weight of the airplane with the 91, it will gain 100 odd grams in the nose 5.68 oz (161g) in the nose. Moving the battery back was making the airplane tail heavy with the 55ax but it should help with the 91. I am also considering lightweight faom wheels (2 3/4" Dubros) and a CF wing tube to replace the aluminium one if I can find it in the require dia 15mm x 47.5mm size

Using a #8 plug, already tried a Ftype, there is a lot of preignition at WOT

Airraptor,

you have covered all the bases:):)

I put in the 14oz fuel tank to resolve the engine issues earlier. Now with a 91 I will need the additional capacity

With a 13x4, the engine sound was much harsher than a 13x6. Some at the field remarked that it may be over-revving and the soft compression may have confirmed that. After my final flight with a 12x6 when I was cleaning up, I noticed a lot of black residue on the ground and on the tail of the airplane, if that is some indicator. Though I didnt get it again when I was finishing of the fuel at home

I am not running it lean, I set the needle with someone holding the thing vertical. Looked for max rpm, then turned it back quarter turn or so towards rich side.

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

What's your current setup? Servos, Rx pack size, etc. I'm asking because you're talking about cutting weight, and several have given tips that will help. You will not need a 14 oz tank for a .91 4-stroke. I put the .82 Saito that was in my Reactor in a Yak 55 profile, and it has a 6oz tank. I still get 8 minute flights! Less fuel weight, less tank weight with a smaller tank. The Reactor was designed for mini servos: I used Hitec 225MG's, though they've fallen into disfavor with me, as several have died on me. I just bought two Spektrum A5040 mini digitals and put them in my Reactor Bipe. Flew it two times yesterday; I like them better for their accuracy: my 225's had different travel/endpoints, even after setting the mix and endpoints on my Futaba 10C. They didn't seem to "travel together" accurately; the Spektrums eliminated that problem. I also used a micro servo on the throttle of my Reactor and also in my Yak55. If you're using full size servos, changing out the servos as I've recommended will save a minimum of 5oz, more than a carbon tube. While on that subject, I believe a carbon tube is available from Graphtech...

RE: GP Reactor 46- Nose keeps dropping in hover
 

55AX, original tank was 10oz (240cc, not stock), Futaba 3010 servos all round except throttle (3004 for that), 6008HS RX with both evevators and ailerons on different channels. I tried botha 5c Hobbico battery and then a 2c LiFe Battery to reduce weight on the weekend. GP nylon spinner with aluminium backplate I think 2.75" dia.

That tank was put in to eliminate tank issuse earlier. I started this thread coz the engine wouldnt remain running and I was getting blcak oil in the exhaust. After tightening the head bolts, it now keeps running, even when the compression goes soft. Due to the reincorcement, I doubt the stock tank will go in. I have to either put this one in or a 240cc 10oz one. Lets see

I had ordered 225MGs for my Reactor. But we chickened out when one of then jammed even before we had put the model together. Thats when we put the 3010s in. Though I have burned-in the servos and they are now more reliable, I dont want to replace the servos. Not only because my model is already drilled for the servos but also, the larger engine will need more torque and relaibility (I should have asked Tower to replace the one 225 that failed, considering what else they have replaced subsequently). I am holding back the 225MGs for my Reactor Bipe. They are the only minis I have

I need to source the CF tube locally, getting from abroad is just too expensive. What I wanted to know was the characteristics of the material. If it shatters or cracks easily when loaded, I am better off with the aluminium one

I am currently using GP 2.75" rubber wheels but have 2.75" foam wheels from Dubro in stock and they are much lighter. I also wanted to know whether I should put the foam ones in.

I have spent so much time getting the setup right on this airplane without much joy, sometimes I feel I should give up on it and open up my Phoenix Extra 330 60" with the 120ax reserved for it

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

Well, I did weigh it. The scale I am using isint very accurate (it doesent have markings between 2 & 3 kgs) but the weight minus fuel and prop is 2.6-2.8 kgs which is 5.7-5.9 lb. So I guess it a bit heavier than stock.

I am posting pics of my repair (it has the effect of birch beams or I beams under the LG. Yes, I am a mechanical engineer). I am proceeding with taking off the engine though. Havent installed the wing bolts when taking this pic

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

A .46AX may not be enough for a 6lb plane to hover it as you want.

4-5lbs is OK, but that extra pound makes all the difference.

RE: GP Reactor 46- Nose keeps dropping in hover
 

Well, I took out the FS91SII from the donor (sad time. That engine made that airplane so happy, especially after I had the time with the 75ax) and was somehow able to open up the muffler. I couldnt get the nut on the extension to rotate, however, it will take more trained hands than mine. I also took the 55ax aoff the Reactor.

Big cricket match tomorrow, no one will want to help put the airplane together. I will take her to the mentor's workshop on Thurday evening and finish the setup on Friday. Then Sunday is test flight day

One doubt- the original FRP mount (GP's adjustable mount) weighs only 120gms. Whereas the one I am considering (Dubro's 75-1.08 2c antivibe aluminium beam mount) weighs 195grm and the actual one that should be used (80-91 4c antivibe aluminium beam mount) weighs 215 gms. I am still not sure whether I should use the 2c one or get a 50-75 one and use it. In either case, it will be a (161+125) 286 gms gain in nose weight. That is why I was pushing for a weight reduction elsewhere

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

I don't think there's anything wrong with using the nylon mounts like the Great Planes or Dave Brown ones for 4-strokes. I also have a Kyosho Flip with a Saito 100 and a Dave Brown nylon mount; it is plenty sturdy. I would not use the anti-vibe mounts precisely because of the weight gain. As mentioned by myself and others, to fly 3D as you seem to be wanting to do, you can't necessarily built for durability or toughness. You are looking for as light a wing loading as you can get. If you use full size servos, over-size tank, heavier engine mount, etc, it all adds up, and you are thus fighting a losing battle of bigger engine to hover, heavier servos, heavier mount, etc, and end up on the heavy end of the scale. It will be a fine sport/pattern flying plane, but not a 3D one...

RE: GP Reactor 46- Nose keeps dropping in hover
 

It certainly seems you have tried everything without success. Conclusion: engine worn out. My Reactor is one of my favorites and hovers great. Howsever, I have a Saito 82 in it and it's a perfect fit.

RE: GP Reactor 46- Nose keeps dropping in hover
 

The GRP mount I have is a GP 40-70 mount. Can it take the 91? I think I will take both mounts to my mentor's workshop and we will see then & there if the GRP one is OK. If so, I will use it

Another question would be, should I open up the 72A, will that engine be able to pull 5.8-5.9lb into a hover with pullout to spare?

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

At the weight your at (almost 6lb), I think the .91 would be the better choice. Another club member here had a Showtime 50 with a similar OS91, and it flew quite nicely on that...

RE: GP Reactor 46- Nose keeps dropping in hover
 

Gave my Reactor for fitting the 91 yesterday. Wanted to do it myself under my mentor's guidance but they were more interested in the cricket yesterday:)

Ameyam

RE: GP Reactor 46- Nose keeps dropping in hover
 

You've got to got to got to go large diameter and low pitch for 3d'in. Your trying to hover in 5th gear instead of 1st gear. Higher pitch doesn't not have the throttle response needed to control the plane in the hover.

RE: GP Reactor 46- Nose keeps dropping in hover
 

Well, turns out the 91 is too long to install the cowl. That leaves me with the 72A and the 75ax. Either way, looks like sunday flying seems difficult[:o][:o][:o]

Anyway, do you thing the 72A will have sufficient muscle to hover the 5.8lb airplane?

Ameyam