|Nov 04, 2011, 10:29 AM|
United States, NC, Lawndale
Joined Mar 2008
Not much difference
If you look closely at the pictures in the manuals of the parts laid out on a table you will see they are almost identical. The instructions are slightly different, the largest discrepancy is in the CG location. Probably the CG location in the Esprit version is the safer of the 2.
That being said, with the HL version you get the spoilers and motor/prop/esc. However motor/prop/esc is barely adequate. The motor esprit sells as recommended looks identical in the picture (and cost a lot more) different speed control.
That being said, IF I were going to buy one, the Hobby Lobby is the better value.
|Nov 13, 2011, 10:39 AM|
USA, NC, Hendersonville
Joined Sep 2007
Hello fellow Grob owners & pilots!
I'm just now nearing completion of my Hobby Lobby Grob. I had started it months ago and set it aside for another project.
As far as the kit goes, I've been pleased so far. The quality of the fiberglass fuselage and the wings are as good as Robbe and Graupner gliders I've built.
I used the Hitec 125 MG slim servos for the ailerons and the elevator. I found that they fit into the supplied plywood servo mounts fine although tight. Installing the elevator servo to be screwed into the fin did take some time. Mainly enlarging the hole at the top of the fin with a Dremel tool took the longest. The top of the fin is quite strong and after I had enlarged it still seemed strong.
When testing the neat electric spoilers, I had a Hobbico VoltWatch plugged to a fully charged 2100 mah RX battery. When I activated the spoilers the battery indicator lights went from Max to Low convincing me that I will run a separate RX battery. This should negate having to add lead to the nose for balance.
My canopy fit with no issues, however I cut it oversize and trimmed and sanded the tub and the canopy to final size.
I don't like the idea of put the velcro strips on the underside of the wingtips. I'll do it to help lower the stall speed as described in the manual.
Jon Barnes (RCG member Bajora) who does excellent reviews said that he got a Grob in for review but it hasn't been published yet. I really want to read his experience both building and flying this model.
This is a very nice looking model and the size of 2.8 meter is large without being cumbersome.
It's getting cold here in the mountains so I probably won't fly it until spring.
|Nov 14, 2011, 12:38 PM|
United States, NC, Lawndale
Joined Mar 2008
|Nov 30, 2011, 12:22 AM|
Queens, New York
Joined Dec 2004
|Nov 30, 2011, 10:58 AM|
I really like the physical set up of the xpower unit. However, I do think it's right on the line of what I think of as a power source for the Grob. But I'm not a glider guy.
I'm use to having lots of headroom in my set ups and typically use a ESC that will handle at least 25% more amp draw then my motor will pull. I also tend to over spec my motors so that I am only running them at about 80% of their rated power when I'm at full throttle. For example; Let's say I have a 10lb warbird and want 1,200watts of draw form the motor/prop set up. Then I get a motor rated for 1,400watts or more. But I choose the prop that will make it run pulling 1,200watts. I make sure I am well within the amp spec for that motor and not stressing my batteries. In this example I might see 50amps maximum at full throttle. So I get a 75amp or higher ESC.
Buy doing all of the above I always have a system that is never stressed and runs cool. I only have to worry about flight times due to normal battery drain when flying. Heat and over stressing my motor are not a concern....
Back to the Grob. In my way of thinking this power system is just enough. But as I said I'm not a glider guy and know just enough about flying them to be dangerous. If you fly the Grob like you would a standard sport plane or warbird then the stock system is lacking.
However, I am learning to realign my thinking when flying gliders.... They are, well........ Gliders !!!! The xpower system on the smaller prop mentioned earlier is plenty of power to climb to altitude. If you watch my video you can see how it pulled away nicely from George's hand when hand launched. The second flight was the same and George mention how he knew it would fly well as it was pulling hard at launch.
I got sick and the weather is now cold and messy here so I haven't flown it again. But from the flights on the day I maidened it, my plan is to do 4 pulls to attitude and hunt for thermals on the way down. If I need to add a little power once or twice for a very short burst to keep me in position so that I can approach our field from the correct direction I will have battery to do that with no trouble.
I'm running a BEC for the RX so no matter what I do I will have battery to fly with no worries about RX brown outs.
I felt my motor when I got down an it was just hot.... Not overly ouch kinda hot, but hotter than warm..... I also have a VQ KA-7 with a Super Tiger .15 electric motor. I thought that was too wimpy a set up and was getting short flights.
Thin I figured out that the KA-7 is a glider Climb to altitude(4 pulls), shut the motor off, thermal hunt, and land. The motor is perfect for that.
Sorry for the long post, but I'm finding I have to adjust how I think of power systems. I'm use to flying around with the spinney thing on the front making me go
If you want to fly like a sport plane (spinney thing working all the time) then this xpower is not what you want. But if you want to climb to altitude and hunt thermals then its good. My one caveat is we have a 400ft altitude limit at our field and I was only doing the maiden and some shake down flying. When I go to a field where that is not an issue I my only get two pulls to a higher altitude.
I'm using 2 3s 2100 Hyperion packs wired so that I have a 3s 4200 battery set up. This battery set up falls dead center in the space available for batteries when you CG the Grob at the 61mm mark.
I'm finding I don't need as much power as I think I do with gliders. If you like to climb like a hotliner, get a few more pulls to altitude, or fly like a sport plane hooning around all over then the xpower falls short.
One last thought. Remember you don't have down or right thrust so when you power up the Grob (and my KA-7) goes nose high and climbs on it own. You have to control the assent with down elevator. You can mix that in with your throttle which I've tired on my KA-7. I prefer doing it manually with no mix.... Anyway, if you are going to trim the Grob to fly straight an level at say 1/2 throttle or above like you would a sport plane then it's going to be much different when you shut the motor off.... I prefer it to fly good with the power off and trim for that. On the spoilers I set them up to a three position switch. 0 - fully retracted, 1 - Deployed about 1/3'd of their travel, 3 - Deployed fully. The landing you saw on my video was with the 1/3 deployment. Full deployment and the Grob descends really well. I like the 1/3'd for a nice feel till I need more.
Did I mention.... It's glider? Trim it to fly good with the power off and start from there.
If you fly like a glider and actually glide to let it stay cool, don't over use the battery available then it's great. Perfect no... but certainly good enough for a glider noob like me.
Hope this helps. I'm learning what works for me when coming from the world of normal powered sport flying. It took me realignment of my approach to things but I'm really enjoying it. So much so I now have a 3.4m Minimoa and a 2.6m ASK-21 that will be built next spring to join my little fleet of scalies. I have to spec the motor bit for those myself and I'm sure I will have more headroom in my set ups. But I need to get some advice from others here about how much power I actually need. The Mini just needs to get to altitude and the ASK will be closer to a sport plane but not need power for a full powered flight. I think....
I'll post a thread on those next spring when I get to them.
|Jan 14, 2012, 10:40 PM|
|May 10, 2012, 01:39 PM|
Any updates or tricks on any Grobs still flying ?
I flew mine twice yesterday. The air was kinda bumpy and higher winds than I wanted but still flyable.
The Grob chews up airspace quickly, yet even a sailplane noob like me could see it rising in lift. My spotter thought I was getting to about 500+ ft on some of my climbs. I'm settling into a 5 climb routine I think as my batteries started at 4.15 per cell and ended at 3.86per cell.
If I have fully topped off batteries I should be able to fly to my hearts content and know that I'm not over taxing the batteries.
I added a HK voltage alarm that beeps when you hit a preset voltage. I set it for 3.8v per cell. I never hit the alarm on my flights yesterday.
When I balanced my Grob I did it with the prop both on and off the plane at 61mm. So far I have flown it with the prop on and installed my batteries 1/2way in between
those two marks. So I'm nose heave just slightly at the 61mm mark.
Everyone that sees it fly says I'm in a good spot. However, I will get it into the hands of a good glider guy sometime this year to see if he'd move it at all.
With the high winds and bumpy air yesterday having the two 3s 2100 Hyperion packs 1/2inch ahead of the 61mm balance point worked very well.
I'm still not use to watching a sailplane at altitude so I have to work on keeping my orientation. Holding opposite sticks to the direction of travel for an extended time as the Grob gets pushed away from the lift starts to work on my head and I have to really think about whats it's doing at altitude. Cool, but different than I'm used to...
It was easier to do figure 8's to stay in the lift for me than trying to do circles. I was better at that then trying to keep the wings level against the lift. I still have a lot to learn.
I managed a 9+ minute flight. Longer flights are out there with practice.
Anyway, no signs of nasty tip stall. I did stall it at altitude a couple of times but not too bad. I just don't try to float it the closer to the ground I get.
Any others still flying?
|May 10, 2012, 04:00 PM|
|Nov 25, 2013, 03:38 AM|
Mount Juliet, TN
Joined Feb 2008
I know it's late chiming in on this thread especially since Hobby Lobby no longer sells this plane. Be that as it may.... Hobby Lobby brought one of these new in the box to the big annual swap meet in Nashville a couple weeks ago. I got the GROB and a spare fuse all for $125. It was something of a challenge to put together. I went off script on a couple things. For instance, I used flex cable for the elevator rather than to mount a servo in the tail. Without adding any weight and with a 2600mAh 3-cell, mine balances directly under the spar tube which is about 65mm back from the leading edge.
I also just happened to have a 10mm carbon tube which I've used to replace the steel bar. Fits perfectly. I was afraid the wall thickness was too thin. I also happened to have some 8mm carbon tube so I epoxied one into the other. So I have a perfect 10mm tube with a 4mm wall thickness. I'm totally sure it's tough enough. All up including 2600mAh battery, mine comes in at 4.9 lbs. The steel bar I replaced weighs nearly 1/2lb by itself.
The prop was badly out of balance, and I had to figure out a way to balance it. I ended up wedging some material into the folding prop so that it stayed in the deployed position. No flopping around. Then I carefully balanced it just like any other prop. Seems to have worked.
I also cut a couple small NACA ducts in the nose to allow some cooling air to flow through the fuse. I didn't cut any exits. Air will exit through the wheel wells and through the rudder push rod slot. That ought to be enough. The exit area is pretty close to the inlet area. If I still have bad overheating problems as has been reported here, I'll open up some more exit area. I will probably drill some holes aft of the wing on the bottom.
Mine was also very out of balance laterally. I had to glue in 1/4oz of lead in the extreme wingtip of the rh wing.
I guess we're well past the time of year for thermaling. But I will try to get in a test flight if we get a weekend with some sunshine and low winds. I'll post a flight report then.
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