Electric Wright Stuff B

[coachchuckaahs]

PS:

To measure pitch, we insert a metal pin (1/32 or 1mm steel rod) in the prop, then hold the tip of the prop against the edge of a protractor, and line the pin up with the scale to read pitch at the tip. Not as nice as a pitch gage, but our pitch gages are too bulk for such small props.

To repitch, we have had to add heat with a small heat gun. You can do some with just flexing it, but that tends to relax back out.

Coach Chuck

[jgrischow1]

PS:

To measure pitch, we insert a metal pin (1/32 or 1mm steel rod) in the prop, then hold the tip of the prop against the edge of a protractor, and line the pin up with the scale to read pitch at the tip. Not as nice as a pitch gage, but our pitch gages are too bulk for such small props.

To repitch, we have had to add heat with a small heat gun. You can do some with just flexing it, but that tends to relax back out.

Coach Chuck

Thanks for this and your last post. We will get back to the lab and work on things and get back to you!

[redscience]

Hi, we are looking for some help on our flights for Electric Wright Stuff. Our basic problem is that our plane is not able to fly for more than 20 seconds.

Here's some info on the plane:
JH Aerospace Zapper - https://jhaerospace.com/product/electric-wright-stuff/
Weight of constructed plane - 11gm
Capacitor : 2.7V, 5F
Wing span: 17.5inches, Chord: 3.5 inches
Stabilzer span: 11 inches, Chord: 2.5 inches
Propellor diameter: 2 inches
Environment:I Indoor Basketball court with clearance of 22ft.

We launch the plane at 45 degree angle. It climbs at 60 degrees for about 10 feet (15 feet above ground) and then sharply dips. Some times to a height of 12 feet, sometimes to 8 feet. Then it circles for about 2 rounds at max, all the while rapidly descending. We can see once in a while during the circles it drops suddenly by a few inches, like real planes do when they hit an air pocket.

Any thoughts or suggestions on increasing our flight times? Happy to provide any additional information.

[coachchuckaahs]

Need to know information about the setup of your plane, not the kit specifications.

Please include the location of you center of gravity (relative to the rear wing post is best), position of the wing (if a sliding wing setup), decalage (wing incidence, tail incidence. Measured as the height of the wing LE and TE from the motor stick, same with tail if adjustable), charge voltage at launch, or charge duration. Please use mm for your measurements if possible. A video of the flight linked would help as well. It sounds like your trim is way off. J&H provides some excellent videos, as well (I believe) as instruction in the kit, for getting initial trim correct.

Without these trim measurements, we would only be guessing at what the issue might be.

Coach Chuck

[redscience]

Thank you for your reply.

To provide more information you mentioned - the CG of the plane is 1143mm from the nose of the plane and 381mm from the rear wing post (in the picture in the shared link below).
The decalage for wing is 1mm (TE 68mm LE 67mm). decalage for stabilizer is zero (Picture of full plane in the link below).
Charge duration is about 20 sec using a 2 1.5V AA batteries.
Video of 2 flights in the link below.
First flight is about 20 sec (max we have achieved). As you can see the plane rises appreciably after launch, but loses height quickly after the first round and then does not turn as expected in the second round and crashes into the barrier. Other flights we have for 20 sec are similar, except that in those cases the plane descends rapidly while making circles.
Second flight is about 10 sec. As you can see the plane is launched and immediately dives towards the ground before stabilizing at about 5ft from the ground. Then it circles as expected, but rapidly descends to the ground.

Link to photos and videos : https://drive.google.com/drive/u/0/fold ... pMsXd1n_1A

Would love your help further on this. Happy to provide any other data as well.

Thanks

[coachchuckaahs]

The plane is definitely substantially nose-heavy. See the last few minutes of Josh's build instruction video at https://jhaerospace.com/product/electric-wright-stuff/, where he indicates the CG should be at or near the rear wing post. 5mm of change in CG is significant, and you are 381mm from the rear post.

Start with the cg at the rear post, or within 5mm. You can adjust this by moving the wing forward. It may need to be quite close to the motor. If you run out of adjustment, you can add a little clay to the tip of the tail.

Add incidence until you get a slight stall on the letdown, then remove a little incidence. You can add incidence by shimming the front of the wing slider mechanism.

Toss the plane lightly straight ahead or slightly up. It is not a rocket, nor a yard dart. It does need a slight toss, but not a strong toss, and not so steeply upward.

Coach Chuck

[bjt4888]

Redscience,

Of course, everything Coach Chuck recommends applies. One additional question/recommendation regarding correcting the center of gravity (the fore and aft balance point). It appears from pictures on the J&H Aerospace website that the capacitor should be mounted near the rear wing post. Watching your video, it looks like you have it mounted near the nose of the airplane just behind the motor. Recheck the plans and instructions and correct the location of the capacitor to help fix the balance point of the airplane. As the capacitor weighs about 2 grams (over 20% of the total airplane weight), it’s location on the airplane is important.

Great job building a nice kit and asking questions.

Brian T

[jgrischow1]

Yeh, fast and level probably means a trim issue. Step through trimming process (J&H should have video on that). Basically increase decalage until it stalls late in flight, then back off. J&H planes like CG around rear of wing. SMALL changes to CG will radically change flight, so be sure to take copious notes in your log (Hint: CG location is an important parameter to record, as is decalage).

About 1.5g over is a lot, but should still climb some.

J&H earlier motors were about 2-ohm, and climbed strongly. More efficient motor recently, about 3 ohms, will not climb as sharply.

But it sounds like you have trim issues.

Coach Chuck

Just to revisit this...my kids built a new plane with remaining components from their kit...lightened it from 10.95 to around 9.75 g. Moved the cg back to its specified location, got it all trimmed up, and now we ae getting fantastic times. Thanks to coaches Chuck, Brian, and Jeff, Josh Finn for the kit, and everyone else who helps out on here!

[coachchuckaahs]

Thanks for the feedback! It is always great to see improvement.

This post points out major issues we see over and over:

• Build light, try to build to weight
• Understand where the CG should be, and get it there. This year's planes really like the read wing post as a STARTING POINT. Adjust from there to optimize. Many planes we help are NOSE HEAVY
• Understand and set up basic trim. 3-6mm of wing incidence, no warps, 0.5 to 1cm tail tilt STARTING POINT.
• Every plane is different, but if you get these basics and then trim from there, 45 seconds to a minute is easily reachable, and then you can optimize for that winning flight!

Coach Chuck

[teehong]

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