Tench745
Master member
See the above.^
I would consider not having the motor attached when binding in the future. I don't know if it's the right way or not, but I don't like to have anything hooked up that doesn't need to be when binding.
Refurbish of Carl Goldberg Sky Tiger (Build Log)
- Thread starter TexMechsRobot
- Start date
See the above.^
I would consider not having the motor attached when binding in the future. I don't know if it's the right way or not, but I don't like to have anything hooked up that doesn't need to be when binding.
TexMechsRobot
Posted a thousand or more times
What has me confused is that it was an immediate puff. The motor only pulls 60A max under a 13" prop at full throttle and the ESC was rated for 80A. I don't know how the setup I had could have pulled more than 80A and smoked the ESC that fast.
I'm nervous about buying another ESC until I'm somewhat sure what cause my issue.
I'm nervous about buying another ESC until I'm somewhat sure what cause my issue.
TexMechsRobot
Posted a thousand or more times
I bit the bullet and went for a higher quality ESC. I figured E-Flite would care about their product and my experience and so I forked over the dough for the 80A ESC they offer. I connected it all on the bench last night without a prop and after reading the ENTIRE manual that came with it. It worked flawlessly. But it cost me $100. The good news is I have an ESC that I can rely on and use in other projects that call for an ESC of that size.
I also put bondo in many of the seams and recesses and sanded it all smooth. I don't have any pictures of that since most of them weren't necessary anyway and I only did it because I care too much. The last thing to do is cover the fuselage with monokote and I'm still working out some of the color details.
Tonight I'm going to put the prop on and do a wattage test to see where I am. It's my first time using an inline watt meter so it's another learning moment.
I also put bondo in many of the seams and recesses and sanded it all smooth. I don't have any pictures of that since most of them weren't necessary anyway and I only did it because I care too much. The last thing to do is cover the fuselage with monokote and I'm still working out some of the color details.
Tonight I'm going to put the prop on and do a wattage test to see where I am. It's my first time using an inline watt meter so it's another learning moment.
The watt meters are very handy! I've saved a lot by NOT burning up my electronics thanks to the meter. It's interesting how something simple like changing the pitch of a prop can make a big difference in watts and Amos.
TexMechsRobot
Posted a thousand or more times
OMG THAT IS A LOT OF POWER!!!
All I can say is wow. I had to spend the last couple of nights soldering some connections since the watt/amp meter I bought came with bare leads. Took me a while because I changed my mind about the process when I was over halfway done. I then spent an hour or so reading online about how to hook it up and what to expect. I then triple checked everything and ran through what I would do if something went wrong (smoke, prop comes off, etc.).
Then I cranked her up. I started with about 1/4 throttle and ran it there for about 15 seconds. I then unplugged the battery and check the prop for tightness. I plugged the battery back in and slowly ran her to full throttle and man is that thing scary! I was giddy with adrenaline by the time I finished and almost forgot to look at the meter.
I only had the battery charged to about 3.9v per cell and it was pulling 512W at 35A. The motor is rated for 60A and the ESC for 80 so I have plenty of room to add more power if I want to just by adjusting the prop. I'm expecting the total weight to come in at about 5 lbs so 100W/lb seems likely which will give me a pretty gentle flyer with enough power to correct for the mistakes I will make.
The only things left to do is cover the fuselage, balance it all out, and then go for a maiden!
All I can say is wow. I had to spend the last couple of nights soldering some connections since the watt/amp meter I bought came with bare leads. Took me a while because I changed my mind about the process when I was over halfway done. I then spent an hour or so reading online about how to hook it up and what to expect. I then triple checked everything and ran through what I would do if something went wrong (smoke, prop comes off, etc.).
Then I cranked her up. I started with about 1/4 throttle and ran it there for about 15 seconds. I then unplugged the battery and check the prop for tightness. I plugged the battery back in and slowly ran her to full throttle and man is that thing scary! I was giddy with adrenaline by the time I finished and almost forgot to look at the meter.
I only had the battery charged to about 3.9v per cell and it was pulling 512W at 35A. The motor is rated for 60A and the ESC for 80 so I have plenty of room to add more power if I want to just by adjusting the prop. I'm expecting the total weight to come in at about 5 lbs so 100W/lb seems likely which will give me a pretty gentle flyer with enough power to correct for the mistakes I will make.
The only things left to do is cover the fuselage, balance it all out, and then go for a maiden!
Now you know why the 1600W setup in my giant scale P6-E Hawk scares me to death. That power transferred to an 18" prop is something I never mess around with. Be safe with the setup. You may also find with that large ESC that when you connect the battery after the ESC sits for a while, there will be a spark upon connection to the battery. That is an in-rush of current to the capacitors of the ESC. It is normal and nothing to be truly afraid of... just be cautious.
I see that spark with both my Pietenpol and the Astro-Hog when the battery is first installed. They're both running 5 cell 5000mAh packs. One uses a G60 and the other a G46 motor, and Willsonman is right, that power is something to be very careful with! Electric motors have a way of giving you a false sense of security when the motor isn't turning, but accidently bump the throttle and you may be seeing red. Lots of red...!
TexMechsRobot
Posted a thousand or more times
I'll definitely stay on my toes around this one. I had already noticed the spark when plugging in the battery but had read somewhere that this was normal.
The prop I was running last night was a 12 x 8. If I wanted to add more forward thrust, should I adjust the pitch or the diameter? Or both?
The prop I was running last night was a 12 x 8. If I wanted to add more forward thrust, should I adjust the pitch or the diameter? Or both?
Pitch will give more speed. Diameter will give more thrust. There is a difference. Generally a good balance of thrust and speed is a diameter : pitch ratio of 2:1. You are already in a pretty good place for that.
Examples of application:
Thrust
Lots of thrust is needed for WWI era biplanes as their tail surfaces are pretty ineffective at lower speeds. My 1/6 SE5a has a 13x4.5 prop so nearly 3:1. My O1 Tummelisa has a 16x6 prop so 2.7:1
Speed
Speed is needed for WWII era aircraft as they typically have more effective tails for low speed and provide better stability at higher speeds. Their wing loading is typically higher as well, which requires more speed to overcome. My P6-E Hawk has a 18x12 prop, or 1.5:1. My Bugatti build will have props at roughly 1:1 using 8x8 or 9x9 props. My AT-6 texan uses a 15x10 so again 1.5:1. My Pitts S2-C uses a 12x8 prop, again 1.5:1.
Hope that gives you an idea of what to expect. Lower ratios will cause the prop to stall at high RPM and low air speed so pulling out of sticky situations on landings may not be as ideal as a higher ratio prop. The trade off is that you typically have a little more torque sent back into the airframe with higher ratios.
Examples of application:
Thrust
Lots of thrust is needed for WWI era biplanes as their tail surfaces are pretty ineffective at lower speeds. My 1/6 SE5a has a 13x4.5 prop so nearly 3:1. My O1 Tummelisa has a 16x6 prop so 2.7:1
Speed
Speed is needed for WWII era aircraft as they typically have more effective tails for low speed and provide better stability at higher speeds. Their wing loading is typically higher as well, which requires more speed to overcome. My P6-E Hawk has a 18x12 prop, or 1.5:1. My Bugatti build will have props at roughly 1:1 using 8x8 or 9x9 props. My AT-6 texan uses a 15x10 so again 1.5:1. My Pitts S2-C uses a 12x8 prop, again 1.5:1.
Hope that gives you an idea of what to expect. Lower ratios will cause the prop to stall at high RPM and low air speed so pulling out of sticky situations on landings may not be as ideal as a higher ratio prop. The trade off is that you typically have a little more torque sent back into the airframe with higher ratios.
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TexMechsRobot
Posted a thousand or more times
That does help thanks! I'll stick with the 12x8 for now and then play with some different prop sizes after the maiden.
TexMechsRobot
Posted a thousand or more times
Covering the fuselage has started. I'm a little further along than this but I only took a picture of the first piece going on.
TexMechsRobot
Posted a thousand or more times
I finished covering the fuselage and I'm very happy with the results. Pictures to come later. I also glued the horizontal and vertical stabilizers to the tail. I used a 2 part epoxy and glued wood to wood to ensure a strong bond.
This dried and I feel like the join is too weak. It feels like the vertical stabilizer will just snap off at the first sign of yaw. If you look back at the original photos, you'll see that the vertical stabilizer does have two pieces that mechanically help it stay in place. One of them goes through the horizontal stab and the tail of the fuselage while the other goes only through the fuselage. My guess is that I should have used a little more glue in those holes to add some rigidity to the structure.
However, I think it is too late for that. No I'm trying to think of ways to strengthen it after the fact. My first thought is to cut small gussets out of 1/2" x 1/2" triangle stock about 2-3" long and glue them in the four corners: 2 against the vert and horizontal stab and 2 against the horizontal stab and fuselage. I'd remove some covering to get a good wood to wood joint when doing this. If it's all tight, would it be enough to keep it from moving or breaking loose in flight?
This dried and I feel like the join is too weak. It feels like the vertical stabilizer will just snap off at the first sign of yaw. If you look back at the original photos, you'll see that the vertical stabilizer does have two pieces that mechanically help it stay in place. One of them goes through the horizontal stab and the tail of the fuselage while the other goes only through the fuselage. My guess is that I should have used a little more glue in those holes to add some rigidity to the structure.
However, I think it is too late for that. No I'm trying to think of ways to strengthen it after the fact. My first thought is to cut small gussets out of 1/2" x 1/2" triangle stock about 2-3" long and glue them in the four corners: 2 against the vert and horizontal stab and 2 against the horizontal stab and fuselage. I'd remove some covering to get a good wood to wood joint when doing this. If it's all tight, would it be enough to keep it from moving or breaking loose in flight?
Can you put up a detail picture?
TexMechsRobot
Posted a thousand or more times
Yeah I'll do this in a little while. I'll show off my first fuselage covering job and get a few specific shots of the empennage issue.
TexMechsRobot
Posted a thousand or more times
First, pictures of the covering.
Here are the detail shots of the back. The vertical stab I'm holding is the one I took off and repaired. I used it as a practice piece for covering. The extensions on the actual vertical stab are about 1.5" long and not just the 1/2" shown.
Here are the detail shots of the back. The vertical stab I'm holding is the one I took off and repaired. I used it as a practice piece for covering. The extensions on the actual vertical stab are about 1.5" long and not just the 1/2" shown.
So the tabs at the base of the vertical stab stick down into the horizontal stab and fuselage 1/2" or more? Assuming the leading and trailing edge of the vert stab are single pieces of balsa it should work fine, but if you want to add some gussets at the base it wouldn't hurt as long as they're LIGHT.
TexMechsRobot
Posted a thousand or more times
I added 3" gussets. I think my issue was that there was a small gap (1/16") between the flat surface of the fuse and the main section of the vertical stab. I'd have to draw a picture to really describe it. I wasn't worried about the tail breaking because of those tabs stuck through (about 1" each) but that the glue holding the vertical stab on would break loose over time.
I have buttoned everything up and she's complete. All that's left is a balance test (and fix if needed) and a maiden.
I'm pretty happy with basically my first tries at everything. I've learned a ton about balsa building and can't wait to build one from scratch. The winter build along sounds perfect but I can't join in this time.
I'll video the maiden and post it when it's done.
I have buttoned everything up and she's complete. All that's left is a balance test (and fix if needed) and a maiden.
I'm pretty happy with basically my first tries at everything. I've learned a ton about balsa building and can't wait to build one from scratch. The winter build along sounds perfect but I can't join in this time.
I'll video the maiden and post it when it's done.
roversgonemad
Member
From the pictures your covering looks awesome! Nice work. I love balsa planes. I am also the guy at the field that usually gets the scraps when a plane goes in. I've got three planes right now waiting for reconstructive surgery.
Nice job! I'm sensing a Seahawks theme!?
Nice job! I'm sensing a Seahawks theme!?
TexMechsRobot
Posted a thousand or more times
Thanks! This was my first attempt at covering a plane so I took my time and did a lot of research. I made quite a few mistakes and learned a lot.
It is Seahawks themed
My wife is a big fan so she chose the colors.EDIT: I realized I didn't post the picture of the underside.
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