Flight B/C

[jgrischow1]

welp i went from having way too fast of a climb to struggling to get a good climb at all
plane suffered a major break but after fixing it (even with the same prop, cg, pretty much everything) its been kind of struggling to climb

on the kind of bright side, the plane maintains altitude strangely well. it gains maybe 2 meters but can stay at the same height for like 1:30
could be because under powered; i switched from .94" to 3/32" rubber, but I feel like that change is way too small for a major impact like this

if any of the coaches or anyone has theories to why this is happening thatd be great

3/32=.09375~.094

[Astronomyguy]

welp i went from having way too fast of a climb to struggling to get a good climb at all
plane suffered a major break but after fixing it (even with the same prop, cg, pretty much everything) its been kind of struggling to climb

on the kind of bright side, the plane maintains altitude strangely well. it gains maybe 2 meters but can stay at the same height for like 1:30
could be because under powered; i switched from .94" to 3/32" rubber, but I feel like that change is way too small for a major impact like this

if any of the coaches or anyone has theories to why this is happening thatd be great

1. Provide videos to the coaches if you haven't already so that they can best diagnose your problem. It's much more useful to have them look at your video firsthand rather than reading your secondhand account of the flight, and they'll get a lot of the answers to the questions they'll ask about your flight without you even needing to type a word.

Here's what I would suggest:

1. Get rid of any pitch on your propeller if you have any. The point of having pitch is to reduce the efficiency of the propeller so that it doesn't climb too high at the most optimized CG/decalage settings. Seeing that your plane maintains height very well, you've already got that down.

2. Get more launch torque on your rubber, if possible. This means less dewinds, or more winds if you aren't dewinding. If this causes a roll inwards, add more washin or tilt the plane slightly outwards when you launch it.

3. Increase your decalage. This might result in a stall, but you can resolve it with changes in your CG. This results in a greater angle of attack (the air is being pushed more downwards), which will increase the rate at which the plane climbs.

4. If you're in Division C, this year's planes fly better with a slight bit of stall. I would push your plane to the point of stalling, then back off a bit until it looks like it wants to stall in the descent phase but can't really get to it. You want to adjust your decalage to the ideal amount first, then move the wing forward (which moves the CG backward) until the plane starts porpoising or has a big stall, then move the wing back incrementally.

Hopefully all of my information it correct!

[randomdogonapc]

So, I’ve been shaping and forming a bunch of different propeller blades, but for the shafts of the propeller, I was wondering where to get the wire insulation used to cut Teflon washers from. Could anybody help me out? Thanks.

[bjt4888]

So, I’ve been shaping and forming a bunch of different propeller blades, but for the shafts of the propeller, I was wondering where to get the wire insulation used to cut Teflon washers from. Could anybody help me out? Thanks.

Here you go. Slice your own from this. Make them thin; like 1/32” thick or less.

https://www.seemecnc.com/products/small ... g-per-foot

Or, Indoor Free Flight Supply sells Teflon washers in various sizes.

[pumptato-cat]

Unfortunately, I can't do glide tests in my house without crouching and releasing the plane at almost knee height. When releasing at knee height, it turns to the left... When releasing any higher(shoulder height ish) it begins turning right. I'd do more testing and change wash-in, but it's crashed twice pretty nastily into chairs, lamps, and more...
Any ideas on why it might change direction depending on what height it's launched at? I'll try changing wash-in when I get back to my flying site, but as of now, I'll have to settle for my hazardous glide tests.

[bjt4888]

Unfortunately, I can't do glide tests in my house without crouching and releasing the plane at almost knee height. When releasing at knee height, it turns to the left... When releasing any higher(shoulder height ish) it begins turning right. I'd do more testing and change wash-in, but it's crashed twice pretty nastily into chairs, lamps, and more...
Any ideas on why it might change direction depending on what height it's launched at? I'll try changing wash-in when I get back to my flying site, but as of now, I'll have to settle for my hazardous glide tests.

Cat,

This makes sense. It takes a moment for the airplane to build up speed (higher launch height). And washin has greater effect at higher speed.

Brian T

[coachchuckaahs]

welp i went from having way too fast of a climb to struggling to get a good climb at all
plane suffered a major break but after fixing it (even with the same prop, cg, pretty much everything) its been kind of struggling to climb

on the kind of bright side, the plane maintains altitude strangely well. it gains maybe 2 meters but can stay at the same height for like 1:30
could be because under powered; i switched from .94" to 3/32" rubber, but I feel like that change is way too small for a major impact like this

if any of the coaches or anyone has theories to why this is happening thatd be great

You indicate several changes, including repairs, change of rubber (width and batch likely). While the rubber "width" appears small in change, there could actually be a substantial change in linear density. That is why Coach Brian and I consistently push for students to express their rubber in g/in, or loop length if you consistently have 2g loops (consistent tying with no extra tails and right at weight). This could result in under powering the plane during the climb.

While we tune decalage and CG for letdown, small errors can also impact the climb. After repairs, did you re-optimize the decalage? Increase decalage until a stall is apparent (low power, cruise/letdown), then back off a bit. Verify with stopwatch.

Is the wash-in the same as before? The tail tilt, the rudder offset? All of these will affect circle and climb, especially wash in.

Is the plane rolling inward (left) more than it did before? Wash in allows you to trade roll-in for climb, at the expense of drag late in flight. So wash in amount is another optimization.

All of these factors impact the flight, and interact with each other. After a major crash, you are starting over with your trimming, though your prior experience should guide you quickly to a decent solution. For example, your log should precisely tell you what CG location was optimal (at least best so far). Given a CG location, then slow flight trim variables are reduced.

Also, inspect your prop shaft. Did it get bent at all? Did the prop pitch change (check your pitch against your log entries). Are the washers or beads still in place? Are there any cracks in the prop, especially hidden where the blade meets spar? IF a plastic prop, did a blade get bent near the tip? The tip does a lot of the work, so damage here is critical.

Coach Chuck

[epicSus]

Hey there,

My name is Justin and I've been following this forum for the last couple months and it's really an awesome environment.
A little about my flight: Stinger 2023:
Old plane was in trim but wear and tear led to propellor cracks and other such things. It was overweight (10.8 grams) but still scored ~1:30 at comps.

Info: ~1000 turns, mild AC, 25 ft ceiling, shim 3/32 inch

New flight: I bought (another) JandH stinger kit and I built it as light as I could but the weight still came out to 9.1 grams (with ikara prop assembly) + super ultra mylar

Current performance: (this is gonna get a little confusing)
New fuselage + new wings: < 30 seconds
Currently, it is stalling really bad at like 2 seconds and then diving down. We tried cracking and re-gluing the nose to get down thrust and turn (2 degrees left + 2 degrees down) like our other planes, but it made no difference. We did stab tilt (maybe 15-20 degrees) and it boosted the performance slightly (30 seconds) but still had the gist of stalling and diving.
Visualization of our flight: It takes off, climbing (pretty well) for 2 SECONDS!!! Then it slows down A LOT and front wing height increases over back wing A LOT, then it falls. If it doesn't hit the floor the first time, it will continue swooping for 10 seconds.

Old fuselage + new wings: ~1 min
When we tried with our pre-trimmed fuselage from the old kit, (which is overweight + prop cracked in every direction possible), and also added the stab tilt (15-20 degrees) and it did a little better.
However, I really don't want to be using my old fuselage and optimizing it because I know that we can do a lot better with a new fuselage and prop.

A couple quick questions:

1. Will increasing the height of the front wing (leading and trialing edge) by 0.5 cm have a profound effect? When assembling the plane, I made the front wing height higher for experimental reasons and can't figure out if this is making it stall.
2. Should I apply washin or washout to make it stop stalling? I felt like by making the leading edge lower than the trialing edge should make it not lift so much and hopefully control the plane.
3. I have tried using no shim as well, and still stalls and dives repeatedly, so if you know how to fix this, please let me know.
4. Should I try increasing the length of the front wing to maximize performance?
5. Should I sand down the fuselage a little to try evening out the weight?

I have another plane left in the kit, so if there is anything I should do differently when I built it next, please let me know.

I would appreciate any help, thanks so much!

- Justin

[poonda]

thanks for all the help everyone

issue was rubber density and possibly prop pitch
(i forgot to mention during repair i fixed all my measurements to stay consistent)

also was unwinding with a broken torque meter so it was somewhat underpowered
i may try to build a simple digital torque meter for a replacement, if i can get it to work ill document it here

poonda

[coachchuckaahs]

thanks for all the help everyone

issue was rubber density and possibly prop pitch
(i forgot to mention during repair i fixed all my measurements to stay consistent)

also was unwinding with a broken torque meter so it was somewhat underpowered
i may try to build a simple digital torque meter for a replacement, if i can get it to work ill document it here

poonda

If you have a gram scale, you can make a simple torque meter as shown in the latest posts to this thread: https://www.hippocketaeronautics.com/hp ... =26767.125

If you make the arm length (from pivot to contact point on scale) 2.835", then set your scale to grams and the readout will be oz-in*10. I believe Tom's version has a string (Kevlar fishing line) form the shaft to the back wall, and a simple hole in the front wall for a bearing. The string takes up the thrust load without adding friction.

If you search the Hip Pocket forums for torque meter you will find a build of a 3-d printed version, but that is not a quick and easy route.

Coach Chuck