HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 10, 2011, 10:49 PM
Registered User
Highfly!'s Avatar
United States, CA, Cameron Park
Joined May 2007
1,259 Posts
Thanks for the Fox pointers. I will run the numbers individually just to make sure the CG is about right. First observation is that it has a high wingloading which should be fine for how I plan to fly it.

Some of you were complaining that the supplied motor is not providing sufficient climb power. What are the numbers on a 3S pack and which props have you been using besides the supplied one?

Thanks!
Highfly! is offline Find More Posts by Highfly!
Site Sponsor
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 11, 2011, 07:18 AM
Registered User
United States, NC, Lawndale
Joined Mar 2008
181 Posts
Quote:
Originally Posted by Highfly! View Post
Thanks for the Fox pointers. I will run the numbers individually just to make sure the CG is about right. First observation is that it has a high wingloading which should be fine for how I plan to fly it.

Some of you were complaining that the supplied motor is not providing sufficient climb power. What are the numbers on a 3S pack and which props have you been using besides the supplied one?

Thanks!
Highfly,
The problem was not the motor/prop did not provide sufficient climb. The problem is the motor/prop combo pulls so much power that the motor/esc will burn up. We had no way to measure watts. we used the scientific method of touching the battery and motor breifly, (way to hot to touch) and smelling burnt windings on motor, to determine the combo was pulling to many amps. That is why we used a smaller prop, 13X6, on the new motor which still provided sufficient climb but did not heat up as much. Still get pretty warm but not smokin warm.
Tabasco is offline Find More Posts by Tabasco
Reply With Quote
Old Oct 14, 2011, 01:50 PM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Hey Guys,

Well I'm getting ready for my trip to the slope and found another build thread on the Grob. Here's the translated version of that thread.

http://translate.google.com/translat...7m-arf-10.html

In this thread they say they are flying at 61mm CG. I may re-balance my plane tonight..... I'm at 47mm and it just seems a little too far forward.

I'll re-read that translation then decide.

In that thread there are a fair number of links to videos. You will have to bring up the same page without Google translating to get the links to work.

More news as I progress.

Joe
Joespeeder is offline Find More Posts by Joespeeder
Reply With Quote
Old Oct 14, 2011, 02:28 PM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Videos....

Here's the Topmodel/EcoTop/Hobby Lobby Grob flying with a 61mm CG.


Grob G103C Twin Acro (3 min 55 sec)



Same Grob landing using a 61mm CG... Look at 2:40 for the landing.


Acromodèles 44 : Dimanche 29 Août 2010 (4 min 15 sec)




You've seen this video before but now we know this plane is flying on 61mm CG.

GROB TWIN III ACRO (2,77m) (0 min 19 sec)




So there it is.... 61mm which is well ahead of the Hobby Lobby Spec. I can't argue with the videos above. In reading the translated version of that build thread, I get the sense they are having motor overheating issues if the motor is used for more than climbing at about 45degrees then being shut off and allowed to cool.

They all mention adding 20-30g of weight to get the Grob to balance. Since 30g is about an oz that's not too bad. I had to add more to get to my 47mm. I'll strip out some lead and rebalance tonight. Winds are predicted for 12-16mph at the slope this weekend. Zoooooooooom

At the end of the thread there is talk about the same set up in the Fox. So the motor is for burst to altitude then off.

Joe
Joespeeder is offline Find More Posts by Joespeeder
Last edited by Joespeeder; Oct 14, 2011 at 02:37 PM.
Reply With Quote
Old Oct 15, 2011, 08:04 PM
Registered User
United States, NC, Lawndale
Joined Mar 2008
181 Posts
Quote:
Originally Posted by Joespeeder View Post
Thanks Tabasco,





I will keep you guys posted.

Joe
Any new news!!!!
Tabasco is offline Find More Posts by Tabasco
Reply With Quote
Old Oct 15, 2011, 08:30 PM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Packed, battery's charged, leave for the slope tomorrow at 7am.... 4 hours to the dunes.... Hopefully there aren't any Sandworms there, alas I don't think there are any spice mines close...

I rebalanced to 61mm.

Both the Windrider Habicht and the HL Grob are ready to be chucked off the dunes into the great abyss above Lake Michigan. The wind speeds are going to be 18-21mph.

Both of these will be maidens and my first time at the slope!!

I am going with a group, some of which have completed the LSF levels including the long 8 hour flights so I have lots of help.

Here's the view from where we are going. First up will be the Habitch.

The sands shift from day to day so landing zones vary form day to day. If the sands are in a bad place then I'll maiden the Grob here with no wind later in the week.

RC Slope Soaring at Sleeping Bear Dunes (12 min 9 sec)



Joe
Joespeeder is offline Find More Posts by Joespeeder
Last edited by Joespeeder; Oct 15, 2011 at 08:37 PM.
Reply With Quote
Old Oct 16, 2011, 09:01 AM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
2,473 Posts
I've flown those dunes in a Hang Glider for many years. When its good its really good.
Gary Evans is offline Find More Posts by Gary Evans
Reply With Quote
Old Oct 16, 2011, 09:31 PM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Hey Guys,

A quick update since I know you're waiting....

We left here are 7am and arrived at the dunes at 11:00. It was windy in the parking lot.... We got ready and I thought I'd come back to the car for the Grob after flying the Habicht.... Well as we walked to the slope (about 3/4 of a mile or more) it was apparent we were dealing with 25+ mph hour winds.

As it turned out this was the SLOWEST wind speed we saw all day !! It was stupid windy. Gust to 35+ mph

We flew and crashed some planes, but it was too brutal to even think about throwing the 7+lb Habicht off the slope. The Grob wouldn't have made to trip to the slope without folding its wing. In the valleys of sand walking out there seemed to be a venturi effect and the wind speeds were well over 40. I could barely carry the Habicht without it being ripped from my hands.

We lost a full balsa V Tail off a plane just walking back to the car due to the winds. They just ripped the tail from its mounts.

I can't even describe the winds we saw today so that you get a sence of things.

We threw some sticks toward Lake Michigan that were bigger than an inch around and two feet long. They went about 6 feet forward then CLIMBED about 12 feet vertically, then went behind us about 25-30 yards!!!

Windy......


I'll maiden the Grob in normal quiet air.... Today was insane. But we had a great time laughing and flying foam till it was dead.


Whew..... back to normal flying, flying fields and no sand blasting your face at 25+ mph !!! Stay tuned.....


Joe
Joespeeder is offline Find More Posts by Joespeeder
Reply With Quote
Old Oct 17, 2011, 07:24 AM
Registered User
United States, NC, Lawndale
Joined Mar 2008
181 Posts
Sorry you made the long trek to the dunes with those conditions. Where on Lake Michigan are those dunes? Give me a nearby town name and I will google.
Mike
Tabasco is offline Find More Posts by Tabasco
Reply With Quote
Old Oct 17, 2011, 08:19 AM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Hi Tabasco,

We had a good time but not what we expected. John has flown there many times and has never seen it like that. wooooosh....

We were near Empire but the closest major city is Traverse City.


Here's the Dune
http://maps.google.com/maps/ms?msa=0...09339,0.022724



I centered the map on where we were.
http://maps.google.com/maps/ms?msa=0...04669,0.011362


Joe
Joespeeder is offline Find More Posts by Joespeeder
Last edited by Joespeeder; Oct 17, 2011 at 08:29 AM.
Reply With Quote
Old Oct 19, 2011, 12:57 AM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Hey Guys,


Taaaa Daaa.... Did the maiden tonight + an additional flight. I'm VERY happy

For me 61mm was the sweet spot for the CG at least till I can fly it some more but it flew great there with no hard tip stall. So here's my mini review below. I'm NOT a sailplane guy and I'm use to H9 sized warbirds in the 10lb range so you might disagree or adjust your Grob but I can recommend the 61mm as a starting point for a stress free maiden.

First I didn't put any fake wash out in the ailerons buy raising them 1mm like some like to do. I don't believe that helps with tip stall. Any time you raise a control surface on a wing that wing drops. Why would I do that to a wing tip? You are speeding up the air over the top of the wing by doing this and no matter what an incidence meter says I believe this to be a false reading. Do what you want, but if raising the aileron reduces lift in every other movement/function like spoilers, ailerons, including differential ailerons why would I raise it to "help" generate lift in the one instance where it works the opposite in every other instance ?

My ailerons are set level with the trailing edge of the wing. I was careful to cut and place the turbulence generators on the wing so they are about 1/8inch wide and spaced about an inch apart so that they disturb the air in a controlled fashion. The strips act as a rough fence. I cant prove it but I think it's important to cut and place these fences carefully for them to work well.

The Grob is like my KA-7 in that there is NO down or right thrust built in to the motor. I expected it to go nose high when I throttled up so I was ready for it. I had to hold down elevator to control the climb at high throttle settings. Everyone reported the power train was too light for the Grob. I agree. It climbs like a home sick angle but I used the motor only to blast up to altitude then shut it off to cool. I tried not to use the motor too much other than to climb and when needed to maneuver a little bit when low. It was hotish to the touch when I got down both times. Not outrageous but if I had spec'd the parts I would have put more power into the Grob and used the parts at much below their rated specs. I think we are at the high end of these parts specs. I got he ESC to program the brake and it worked perfectly.

I didn't allow the Grob to slow too much but it didn't need to scream around. It flew at what felt like scale speeds. Fastish but very resonable. It's not a floater like a Radian. Don't try to float it.

I set the spoiler to deploy about 1/3'd of its travel on the middle position of my flap switch with a little slowing of its action so they just don't pop out. Then full deployment on the bottom position of my flap switch.

The spoilers are VERY effective. As I turned final, I came in at what felt like high and deployed the spoiler to the mid position. The Grob dropped it's nose and started coming down. I controlled the decent with the elevator but didn't allow myself to try to fly level to much. I let it descend to the runway and played with flair til it landed. It was sinking nicely so I never went to full spoiler.

On the second flight I came in hotter and from higher up. When I got within a foot of the ground I was still traveling at a good speed so I went to full spoiler and the Grob settled in nicely bleeding off the speed. Be ready to flair when you go to full spoiler as it will come down quick. Really fun.

Finally, I can see where this would have been a tough flight if I hadn't rebalanced to 61mm. The rearward CG HL recommends would make for a touchy maiden when you combine that with a motor set up that doesn't have any down or right thrust. Those two factors would have made it act very tail heavy if you weren't ready for it. 61mm and holding down elevator made the Grob a happy camper in the climb.


To climb I just throttled up and waited a second the Grob pointed it's nose skyward and took off for the clouds. I held down elevator to control it's accent and pushed the nose down when I throttled down to keep it from trying to stall or drop altitude by running out of energy. Once the Grob was level it started its scale glide slope and I worked it till I was close to our tree line then repeated the climb.

I have the maiden on video and will post it as soon as I can. Hopefully I can get it to You tube tomorrow ... Watch for the video here.

Everyone at the field enjoyed my flights and gave me the airspace to fly the first flights on the new Grob. We have a 400 foot altitude limit but the Grob will be going to another field where I can stretch it's legs and try to find some thermals.

I really enjoyed my flights !!!!

Joe
Joespeeder is offline Find More Posts by Joespeeder
Last edited by Joespeeder; Oct 19, 2011 at 01:34 AM.
Reply With Quote
Old Oct 19, 2011, 12:18 PM
Registered User
Cliffside Noth Carolina
Joined Jan 2011
21 Posts
Job well done Joe , looking forward to see the video , the weather has been rain and wind here hopeing to try to fly my Grob this weekend , keep us posted
Ric
Rick Cromer is offline Find More Posts by Rick Cromer
Reply With Quote
Old Oct 19, 2011, 05:20 PM
Registered User
Joespeeder's Avatar
Davison, MI
Joined Sep 2007
1,226 Posts
Hey Guys,

Here's the video


PMAC - Hobby Lobby Grob G103c Maiden Flight (5 min 5 sec)





Joe
Joespeeder is offline Find More Posts by Joespeeder
Reply With Quote
Old Oct 19, 2011, 06:11 PM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,394 Posts
Quote:
Originally Posted by Joespeeder View Post
Hey Guys,

Here's the video


http://www.youtube.com/watch?v=-zsPLbT5b7o




Joe
Thank you for sharing your iMovie! Wonderful flying too, the Grob looks great in the air. You need to send this movie to HL and have them update their notes section.
studioRS is offline Find More Posts by studioRS
Reply With Quote
Old Oct 19, 2011, 06:28 PM
Registered User
USA, NC, Hendersonville
Joined Sep 2007
71 Posts
Nice video and flight!
RCForever is offline Find More Posts by RCForever
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Careful! The Phantom Order from Hobby-Lobby tolladay Vendor Talk 19 Mar 08, 2011 12:18 PM
Sold New in box hobby lobby F-86 lovetoflyjets Aircraft - Electric - Jets (FS/W) 7 Mar 07, 2011 12:31 PM