Parallax Foam Board Build Help?

[DamoRC]

So... being new to the hobby I’m not sure how to answer that. So I’m just going to list what I’m using and hopefully that will be enough.
- 3 cell 45C 850 mha
- 30A ESC
- Turnigy Air 3010C 1300KV 240W
- APC 8x6 SF prop

Do you have a link to the motor? The only one I can find says it's 420W not 240W. Was that a typo?

 

[sms021]

Do you have a link to the motor? The only one I can find says it's 420W not 240W. Was that a typo?

Yes, 420W. Sorry about that.

I believe it's this one: https://hobbyking.com/en_us/turnigy-l3010c-1300kv-420w.html

I get most of my parts from a local hobby guy, Gotta Know Joe RC (https://www.GottaKnowJoe.com/) awesome guy selling new and used, so due to my budget I typically go used and take what I can get. Awesome guy though!

 

[exnasaguy]

- 3 cell 45C 850 mha
- 30A ESC
- Turnigy Air 3010C 1300KV 240W
- APC 8x6 SF prop

I didn't see that specific motor in the eCalc database, but I found one that should be similar in performance. Based on that, you should produce just south of 200 watts with your setup...and that should be plenty.

FWIW - eCalc predicts your top RPM at 10,600. APC says the max RPM for slow-fly props is 65,000/diameter in inches. That works out to a max of 8,125 for an 8" prop. You may want to switch to a regular E-prop to be safe.

 

[sms021]

FWIW - eCalc predicts your top RPM at 10,600. APC says the max RPM for slow-fly props is 65,000/diameter in inches. That works out to a max of 8,125 for an 8" prop. You may want to switch to a regular E-prop to be safe.

Thanks for that, still learning what most of it means. Is there an easy guide or video around to understand the difference of a SF vs E type prop? Is it just the angle/pitch and how fast it cuts through the air?

 

[sms021]

Terry here. Your Parallax looks great! Good luck with the maiden. Let me know if you have any questions.

Terry,

Would it be alright if I re-posted my PDF of the foam board plans I created off your design?

 

[exnasaguy]

Thanks for that, still learning what most of it means. Is there an easy guide or video around to understand the difference of a SF vs E type prop? Is it just the angle/pitch and how fast it cuts through the air?

I don't know if there is a video to explain the differences. My understanding is that the SF props are thinner and undercambered to work best in relatively low-RPM/low-power setups. The standard E props are beefier and have narrower blades to handle more power. Nitro props are even more heavy-duty so that they can handle the vibration and stresses of an internal combustion engine.
APC has some basic prop design/safety info on their site: https://www.apcprop.com/technical-information/

 

[exnasaguy]

Terry,

Would it be alright if I re-posted my PDF of the foam board plans I created off your design?

The AMA said it's okay to post your version of the Parallax plans as long as you're not charging anyone for them.

 

[sms021]

The AMA said it's okay to post your version of the Parallax plans as long as you're not charging anyone for them.

Sweet! Thanks!

 

[DamoRC]

Yes, 420W. Sorry about that.

I believe it's this one: https://hobbyking.com/en_us/turnigy-l3010c-1300kv-420w.html

I get most of my parts from a local hobby guy, Gotta Know Joe RC (https://www.GottaKnowJoe.com/) awesome guy selling new and used, so due to my budget I typically go used and take what I can get. Awesome guy though!

In addition to what @exnasaguy said, it would be good if you could measure the current draw on the motor with that prop. Based on the HK reviews , you are significantly underpropped for that motor. This isn't a bad thing, it means you won't be pushing the motor hard and probably well within the limits for the ESC based on the 200 watt estimate. You should also be fine with the battery which has a theroretical 0.8 x 45 = 38 amp max draw. But the battery is a little on the small side for this motor so your flight time will be limited (2 mins at full throttle). For the first couple of flights keep a careful eye on your battery discharge and temperature.

 

[FoamyDM]

I just caught up with this thread... and I agree, It looks great !

I listen to both the FT and RC Roundtable podcasts and remember @exnasaguy talking all about it. I remember looking it up and thinking. It would be worth a build. I was suspecting i would have to do just what @sms021 did... thanks for that! Now I just get to build and have fun.

Question is... Did this ever get a maiden? I'm sure those watching would love to see it. (me included)

Also, as the CG is so Critical in all directions, Where is it?

 

[exnasaguy]

I listen to both the FT and RC Roundtable podcasts

Thanks!

Question is... Did this ever get a maiden? I'm sure those watching would love to see it. (me included)

Good question! I'd like to know too.

Also, as the CG is so Critical in all directions, Where is it?

CG location is a smidge inboard of the fuselage and a tad behind the spar. See attached.

 

[FoamyDM]

CG location is a smidge inboard of the fuselage and a tad behind the spar. See attached.

Perfect, Thank you. Have you messed with the Prandlt D Proverse yaw wing?

 

[exnasaguy]

Have you messed with the Prandlt D Proverse yaw wing?

No. Looks interesting though.

 

[FoamyDM]

I will be working on that here, but as you are an exNasaGuy (I get that it's a large org.) I thought I would ask.

@sms021 - good luck on the maiden.

 

[gadgetmann]

Terry,

Would it be alright if I re-posted my PDF of the foam board plans I created off your design?

Have you posted them? On flite test or somewhere else?