I want to fly an A-4 at Flite Fest...

[SlingShot]

Cradle: B-Fold. Then after you fold up the fuselage sides, you should see the set of slots the tabs fit into. One set is higher than the other, so it should only line up one way.

Inlet 'flaps': They should be scored and folded out into the nacelles - there is an angle gauge in the plans; it was meant to help set the angle they fold out to, but after building a few I've found that they need to be folded out a bit further. There should be some pics in the thread showing how they fold out.

Very good! Thank you. I've been crafting the pieces the last few days.

 

[Mid7night]

Very good! Thank you. I've been crafting the pieces the last few days.

Yeah...more and more I want to do a build video for this jet - it would make following along SO much easier for a wider audience... I just don't have the time right now. :-\ ...nor do I have a camera-person willing to sit with me for 4-6 HOURS!

 

[PsyBorg]

I use an old Drum cymbal stand that has a boom on it to hold any cameras I use for pictures or videos I do for here. I just took the end off a broken tripod that has the camera mount with the screw and rubber pad and modded the cymbal threaded shaft part so it fit down in the hole where the tube from the tri pod used to be.

 

[Mid7night]

Tripod mounts aren't really an issue, but I'd want more than a fixed viewpoint for some of the operations.

I'm just so swamped at work right now, I don't know how I even got THIS one done. ��

Lord willin" I'll maiden it after work today.

 

[SP0NZ]

Ben, in my experience, lots of pictures and some text describing how things go together are almost every bit as good as a video. On some of mine, I have pause to take pictures and write notes for every step. Yes, it makes the build process take a lot longer. But, it's pretty easy to make a build log/instructions that way too.

 

[SlingShot]

Yeah...more and more I want to do a build video for this jet - it would make following along SO much easier for a wider audience... I just don't have the time right now. :-\ ...nor do I have a camera-person willing to sit with me for 4-6 HOURS!

It's fine. I can see now that it fits together nicely. I just didn't see it until I started to fit the pieces together.

Did some folding, fitting and a little gluing tonight.

 

[Mid7night]

It's fine. I can see now that it fits together nicely. I just didn't see it until I started to fit the pieces together.

Did some folding, fitting and a little gluing tonight.

That's good to hear.

Yeah, it's definitely not an intuitive build to look at all unfolded... it once you start folding it up, you can see how it goes together.


I just flew my Jester today...and I'm pretty sure I smoked the ESC. 😬

I should be able to just remove the wing at the saddle and change the ESC, which has given me an idea; I think I might try and work out a semi-removable wing attachment, so it's easier to get at components when stuff like this happens.

Is hat something anyone else would be interested in as well?

 

[SlingShot]

A partial mock-up. Still have the fan and nacelle work to do.

 

[SlingShot]

That's good to hear.

I should be able to just remove the wing at the saddle and change the ESC, which has given me an idea; I think I might try and work out a semi-removable wing attachment, so it's easier to get at components when stuff like this happens.

Is hat something anyone else would be interested in as well?

I grew up with detachable wings on pretty much everything except the control-line models. They're convenient and they're great. On the other hand, it's foamboard so......

What happened to the ESC? Bad luck or abuse? Obviously you didn't lose the ship. That's good. I soldered up and test fired my unit last night. Had to be quick on the throttle as that ESC had a reverse throttle and started to run up on the bench!

Your basic high performance (I hope) foamboard type EDF setup. 1203 gms AUW with a 3300 50c 4S. I used a 60 amp ESC which was about 28 gms lighter than the 80 amp.

 

[SlingShot]

@CrossedUpChris

I'm 99% sure your plane was too heavy Mine at 1203 gms was too heavy and it still was when I got it down to 1180 gms. Taking a page from your book, I even threw it from the top of a 10 row bleachers or "stadium". Even hurt my arm slightly. Almost got it going. Just too heavy.

You can get some Flite Test from Graupner (you're in U.K. right). My foamboard runs 185 gms/sheet. I'm gonna have to slim mine down a lot. Pull off most of the inside paper and cut some lightening holes. Especially in the nose.

 

[Mid7night]

You guys must not be launching at full throttle or something ... my latest, Jester, flew as heavy as 61oz, or 1729g! To be fair, that IS the heaviest A-4 I've built/flown by far - the Dr.MadThrust all-metal-fan-and-casing is a lot heavier than the FMS plastic units, and the 61oz weight is mostly due to the Graphene 6000mAh battery - but it never felt underpowered or lacking for thrust. (at least, until the motor cut altogether )

I'm still not sure what went wrong with my ESC. I'm going to dig into it later this week, or this coming weekend; I've got an RC demo/showcase at work this Thursday, and I want Jester in one piece for show & tell.

As a point of reference, my previous, FMS-fanned A-4's all weighed at least 42oz, or 1200g, minimum.

So....why do you think your birds "feel" so heavy?

 

[SlingShot]

You guys must not be launching at full throttle or something ... my latest, Jester, flew as heavy as 61oz, or 1729g! To be fair, that IS the heaviest A-4 I've built/flown by far - the Dr.MadThrust all-metal-fan-and-casing is a lot heavier than the FMS plastic units, and the 61oz weight is mostly due to the Graphene 6000mAh battery - but it never felt underpowered or lacking for thrust. (at least, until the motor cut altogether )

I'm still not sure what went wrong with my ESC. I'm going to dig into it later this week, or this coming weekend; I've got an RC demo/showcase at work this Thursday, and I want Jester in one piece for show & tell.

As a point of reference, my previous, FMS-fanned A-4's all weighed at least 42oz, or 1200g, minimum.

So....why do you think your birds "feel" so heavy?

Dang......I'm gonna have to investigate a little. Possibly a bad ESC calibration? I dunno. But I will check to see if I can get the fan to turn higher. I've seen your launch. Mine should have got it going WITHOUT a motor.

 

[Mid7night]

Might be a bad calibration, or possibly wrinkles/kinks in your thrust tube? Sorry if it sounds elementary, but check that your intakes and exhaust are clean.

Also, check that your CG isn't too far forward. There is a range marked on the latest version of the plans.

 

[SlingShot]

Might be a bad calibration, or possibly wrinkles/kinks in your thrust tube? Sorry if it sounds elementary, but check that your intakes and exhaust are clean.

Also, check that your CG isn't too far forward. There is a range marked on the latest version of the plans.

My thrust tube is pristine. CG looks good. I had to put my battery all the way in the back of the compartment. I was looking at my radio (Futaba). There was something with the end points and servo tester that made me think possibly that I was only getting 84% movement on the throttle "servo". Over-driving the endpoint does not seem to have resulted in more thrust.

It feels good blowing out the back. An awesome leaf blower. I'm sure it would go if it could accelerate along the ground with landing gear. I cut off the nacelles aft of the intake flap and got back 20 gms.

I do have a building tip for the intake flap. On a future build I would leave it loose until after installing the nacelles. Then, I would use the "ship in a bottle technique" to apply glue and position the flap with a BBQ skewer.

I'm stumped. Yours practically flew out of your hand by comparison.

As to why it felt heavy, I just couldn't get it to accelerate and generate lift.

 

[DamoRC]

@Slingshot

Any chance you could check your static thrust? This is weird that you are having trouble getting in the air. For static thrust just stand it on its nose on the scale, tare the scale, and let her rip. Sure, you will have to hold it gingerly to keep it balanced and the reading will fluctuate a bit, but it should get you to within an oz or so of your result.

Although mine was a lot lighter (31 oz versus your 42), I could get it into the air on 3S power (although she flew quite slowly).

DamoRC

 

[Mid7night]

@Slingshot ... Another thing I just thought of: Which version of the plans did you build from? The earlier versions (before v4) had spec'd a too-small nozzle exit diameter. resulting in higher exit velocity but lower thrust.

What is your nozzle diameter at the exit? Mine is ~2.2"


That being said, my first A-4 flew adequately on the lower nozzle area, but not at the higher weights.

 

[SlingShot]

@Mid7night ver. 4 My exhaust is 2.x " slightly in excess of 2"

@DamoRC That type of static thrust test yields 475 gms

I did change the ESC timing from low (default) to high. It's a Turnigy 60 amp. That was after I tried to fly it.

So that number would seem to be the answer right? My "weight problem" is only with respect to my available thrust.

 

[Mid7night]

@Mid7night ver. 4 My exhaust is 2.x " slightly in excess of 2"

@DamoRC That type of static thrust test yields 475 gms

I did change the ESC timing from low (default) to high. It's a Turnigy 60 amp. That was after I tried to fly it.

So that number would seem to be the answer right? My "weight problem" is only with respect to my available thrust.

"Slightly in excess of 2in" - close enough to be right. You shouldn't be hampered by an over-constricted exhaust.

Your static thrust test is the answer: You're underpowered.

This jet doesn't need a thrust/weight ratio of 1 or better to fly, and fly fun, but it does need more than 0.5, and you're actually down at 0.4. That's a tough ratio to fly through with a dirty sub-scale RC plane. Real aircraft fly on less, but they have the benefit of high lift systems and long runways - we don't have either (usually).

You're using the same 70mm 12-blade FMS fan right? On 4s? If you can, I would consider doing a test with the 80A ESC, as opposed to the 60A you mentioned. The specs on the fan say it is capable of pulling over 60A. I've always run at least a 70A ESC on mine, and usually it was 85A.

The only time I used a 60A ESC, was when I tested the MotionRC 6-blade fan - but 50% less blades means lower power draw and higher RPM, which is why I could get away with a smaller ESC.

 

[SlingShot]

"Slightly in excess of 2in" - close enough to be right. You shouldn't be hampered by an over-constricted exhaust.

Your static thrust test is the answer: You're underpowered.

This jet doesn't need a thrust/weight ratio of 1 or better to fly, and fly fun, but it does need more than 0.5, and you're actually down at 0.4. That's a tough ratio to fly through with a dirty sub-scale RC plane. Real aircraft fly on less, but they have the benefit of high lift systems and long runways - we don't have either (usually).

You're using the same 70mm 12-blade FMS fan right? On 4s? If you can, I would consider doing a test with the 80A ESC, as opposed to the 60A you mentioned. The specs on the fan say it is capable of pulling over 60A. I've always run at least a 70A ESC on mine, and usually it was 85A.

The only time I used a 60A ESC, was when I tested the MotionRC 6-blade fan - but 50% less blades means lower power draw and higher RPM, which is why I could get away with a smaller ESC.

Yup. OK thanks brah.

I believe I'll cut out the wing and recycle it with a fresh fuse. I'm going to make a bench mount from the old fuse so I can do some better testing.

Out of curiosity, how much does a sheet of water-resistant weigh?

 

[Mid7night]

...Out of curiosity, how much does a sheet of water-resistant weigh?

Don't know the number off-hand, but it's the same or lighter than standard white Adams DTFB.