Ameyam,
If you can get your hands on the APC 12.34x3.75 I would try that. I used one of those for quite awhile in a 3D plane running the 55AX and it is a perfect prop for 3D with the 55. It spool up great and you get alot of thrust for pull out of a hover. I used it in a Profile plane and it would hover at less than half throttle and would accelerate straight out of a hover.

It is currently in the hybrid 3d-sports configuration. As I start trusting the engine more, I will starting 3ding. I tried it today, couldnt keep it vertical. I have currently put in a 13x4 MAS, will see on saturday. If it flies OK, I will retain it else I will put in a 13x6. The ultimate prop for this airplane was a 13x4APC 3D, but I have not opened it as yet because of the engine issues

Ameyam

But the big question is did it deadstick with that prop?

Yup... As I suspected it sounds like your engine was getting too hot with the 13x6.

So if you want to fly 3D stick with the 13x4.

Two increments down in pitch is about the same load difference as one increment down in diameter.

The engine will rev faster and in part make up for the slow pitch, but you'll get more thrust for 3D while still keeping the engine within operating temperatures.

Don't switch to the 13x6 as you KNOW that causes overheating.

Use the APC 13x4w instead. It's a wide profile prop that helps develop more thrust.

BTW: What is your flying altitude? The height of your airfield above sea level? As well as the weight of your plane?

I was never really pleased with how my 55AX ran with the 13x4 Wide blade prop from APC. I heard alot of guys using the 13x4 Sport prop wth good luck but I never tried it as I ended up using the 12.75x3.75 and loved it.

Yeah that sounds like a good choice.

I dont think the critical issue here was overheating (though I did not take an engine temperature reading, may be I should have). When I finished the fuel at the end of the day, the engine was at 60 deg after a minute of so of running, but that was mainly at idle . Note that he tightened the head bolts more. No idea how much that helped but it seemed to.

I noticed that even at 60-70% power with the 12x8, the hover could not be held. But she wouldnt climb either (if the power is sufficient, she should climb, shouldnt she?). Therefore will try a 13x4 on Saturday. I have also replaced the cowl. I am trying to lose some weight on her, will try 2.74" dubro diamond foam wheels, there is nowhere else to lose weight. Remember, I havent set the CG with this larger 320cc flexitank either, I just flew to check the engine

Ameyam

Not true....

You have

- No compression reported when the engine was VERY HOT
- Compression comes back to normal within seconds of it cooling off
- A Larger Prop
- Consistent "Deadsticks" with behaviour identical to heat issues.
- Switching to a smaller diameter prop ( less load ) solves problems

BTW: You still haven't told me your flying altitude nor plane AUW.

That pretty definitively points to overheating.

Again, what is the weight of the plane?

You may also have inadecuate cooling in the cowl.

Please post pictures of how you have cut out cooling holes in the cowl.

That could very well be the problem, particularly since the larger prop would REQUIRE better cooling.



You do have a .46 size plane right?

10oz seems a bit small for a .46.

Which one is it again?

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