My F3J project - takes flight - Page 4 - RC Groups
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Jan 09, 2010, 03:24 PM
or GPS, F, J, K, or even TD
FLY F3B's Avatar
Awesome job Roydor. Fun to follow your progress here too.

Cheers, and happy flying.

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Jan 09, 2010, 07:13 PM
F3B and F3K
RetoF3X's Avatar
Congratulations Roydor!

Awesome work and thanks for sharing.

Jan 10, 2010, 05:29 AM
Registered User
isnt it amazing what really hard work and committment will produce.
We are all delighted for you and that it has fulfilled expectation.
Jan 10, 2010, 02:31 PM
Hot Dawg Glider Pilot
schrederman's Avatar
+1 for what Ian said... Makes me think that I should at least try it...

Jan 10, 2010, 07:59 PM
Registered User
Congratulations Roydor. Thanks for all the info.
Here's to many happy hours of flying.
Jan 13, 2010, 06:32 PM
In F3J size does matter!
roydor's Avatar
Thank you everyone for the kind words.
As I get more flying experience time with the Gremlin I'll post some more info.
I thought I'd post some part weights:
left wing - 677.8 grams
Right wing - 677.3 grams
joiner - 78.8 grams
fuse - 549.7 grams
elevator - 39 grams
total weight - 2022.6 grams

I couldn't believe the weight difference between the wings, unreal...

My electro fuse is nearly complete, I've finished the rudder and installed servos in it and already attached it to the tail boom and pod.
The motor, a Hacker B-40, is installed and I plan to run in on 6 cell 1100 mAh battery.
The battery is put together from two 3 cell Hyperion batteries and weighs only 200 grams. With a 16x10 prop I get about 900 watts out of it and used it on my Perfect getting a nice 11 m/sec climb. I should get a slightly quicker climb in the Gremlin with an all out weight of about 2.3 kg.

The rudder came out kind of neat, I laid some glass fiber in the mold and trimmed it into a servo cover the shape and size I wanted and glued it back in the mold with some 3M spray. I then waxed the mold and molded a rudder. Once I removed the rudder I also removed the servo cover, cleaned it and got the most perfectly and tightly matched servo cover you have ever seen!
You can barely feel the seam and it actually snaps into place, I put some double sided tape just in case but it could have flown without it.
The elevator servo (761) is screwed in place through the hatch opening and then the rudder servo is put in place (a reused Hitec 125). It is actually held in place by only one screw while the other side is inserted into a slot in a glass epoxy reinforcement on the web before the hinge. A very tight install but everything fits under the cover.

Iíve ordered a regulator to use in parallel to the speed control, this way I can save the weight of an extra battery and my speed controller doesnít have a BEC. I think I will use a AR 7000 as I have plenty of room behind the joiner.
Attached are some pics of the rudder, enjoy.
Jan 13, 2010, 08:14 PM
Registered User
Hi Rydor

Hello from Down Under. Great work. It takes a high level of dedication to complete a project to this level.

Will I get to see you in France for the WC? It would be great to catch up and discuss yor projects.

David Hobby
Jan 14, 2010, 12:20 AM
In F3J size does matter!
roydor's Avatar
I'm afraid not, I will not be attending France this year as I messed up during team selections. I was running pretty high in the league all year long entering the team finals in second place but made a series of mistakes that sent me into fifth place right at the last round of the finals...
Maybe I'll go for a eurotour competition this year instead, haven’t competed internationally in awhile it's starting to itch...
Jan 14, 2010, 07:51 PM
Registered User
That's a shame. Our team selection is only one event so it is really important to have a reliable setup.

There is a chance I will be in Europe for 2 months after the WC, so long as my work does not get in the way. We might meet then.

David Hobby
Jan 14, 2010, 07:52 PM
Registered User
Well good luck with this model for the next selection trials.
Jan 14, 2010, 08:39 PM
Challenge is rewarding
djklein21's Avatar
Originally Posted by roydor
I'm afraid not, I will not be attending France this year as I messed up during team selections. I was running pretty high in the league all year long entering the team finals in second place but made a series of mistakes that sent me into fifth place right at the last round of the finals...
Maybe I'll go for a eurotour competition this year instead, havenít competed internationally in awhile it's starting to itch...
holland glide is the week after the WC right? BTW, I'll be in Europe at that time.

I'll come by the WC during the first few days, then it is off to Kulmbach for the B Eurotour event there. Then I'll be back in Northern France until the 19th of August. If anyone wants to fly B during that time, I'll have my Targets with me.
Jan 15, 2010, 01:10 PM
In F3J size does matter!
roydor's Avatar
Went flying the Gremlin again today and all I can say is WOW!

Launch, thermal, cruise and speed are trimmed rather well and either I’m getting better in trimming models or that this is a really forgiving model which is not that sensitive to setting, because after just two flying sessions I feel I could go competing with it…

Conditions were light with a some light wind, about 5 m/sec (10 Knots) so not too much. Light thermals, nothing really booming but if you were persistent a decent altitude could be attained.
Got the launch trimmed pretty close to optimal, still needs a bit of work but not too much. The Gremlin builds a lot of tension in the tow and the zoom is quite spectacular.
The interesting thing is that it needs quite a bit of down trim in the launch, much more then my modified Perfect, so getting the elevator to launch camber mix setup took a few launches. My methodology is to trim the model in launch camber for best glide (L/D max) at all camber settings as I tend to manually reduce the camber during launch using the slider, I start with about 12 degrees of camber and reduce it as the tension builds up to trade it for a little speed up the line. I Usually reach the dive in point with 6 to 10 degrees of camber depending on the wind, 6 for stronger winds (Usually so I don’t break the line) and 8 to 10 for light to no wind conditions. This is of course an approximation as I change it manually to what seems appropriate depending on the conditions.
After I get the elevator to launch camber trimmed, I move the hook to the position that gives the best tension without tip stalls or pop off’s.
After getting off of the line I use the slider to move into reflex and have some down trimmed in to prevent the plane from pulling up during the zoom, just enough for it to go straight up without having to fight it.
The problem I was getting was that without the mix, the fairly large amount of down elevator (1.5 mm) caused the tension to drop when I reduced the launch camber ( without changing the elevator) and then too much down for the zoom, after some trimming and mixing and a couple of launches, the plane was pulling HARD and zooming well. Unfortunately I had two line breaks (I told you it builds a lot of tension) so I couldn’t get as much Zooms as I wanted and this is something that I probably can still improve on, but right out of the hand it’s stable even at cross winds and the tow seems really good.

Penetration is good in reflex and the plane slows down well in thermal mode and interestingly enough it responds well to large amounts of camber, can’t say if it’s better than the normal 2-3 degrees I use on the perfect but the Gremlin is more tolerant to different camber settings making it easy to fly well without having to set it just right.

The large trim I needed in the ailerons has been reduced to about half as I changed the incidence of one wings by about half a millimeter, I’ll change the other wings incidence for next time to get rid of the trim completely, thought I needed to when I redid the incidence for the first one but I didn’t want to overdo it without checking first, this should fix the incidence mistake I made on the fuse.

I just have to add that the Gremlin fly’s VERY similar to my modified Perfect, the resemblance in flight behavior is incredible, the performance, floating, agility, penetration, launch and especially feel is nearly identical and since my modified Perfect has better handling and penetration than the original Perfect this says allot (I have a lighter fuse and reduced cross section in my modified Perfect). Changing between models should be transparent. I am very happy with the result.

djklein21, I’m thinking of several possibilities for a Eurotur, Bulgaria sounds interesting and should be fairly cheap, Italy and Holland sound nice too and of course if there is an open competition before the worlds in France that should be a very interesting competition (even though it won’t be a Eurotour one), Turkey is also a great competition (one of the best) but having been to Turkey several times before I wanted to take the opportunity to check other venues this year.
Jan 15, 2010, 01:43 PM
Detail Freak
target's Avatar
Hi, Roydor-

I have a question for you:

With a two-piece wing, such as you have, and a rectangular joiner, how do you change the incidence of the wings relative to one another??
Do you have to sand the joiner a bit to allow the pins to "twist" the wing angle??

Target, perplexed.
Jan 15, 2010, 05:46 PM
In F3J size does matter!
roydor's Avatar
No, I don't need to sand the joiner, you see, the joiner has about 0.1 mm difference in size then the joiner box or else it wouldn't fit. So, 0.1 mm over a 27 mm wide joiner are equel to 1 mm of twist in a 260 mm wide wing.
The thing is I must have made a small mistake in the master for the pod and forced the wings to this twist and now i'm actually setting them back.
Jan 15, 2010, 08:18 PM
Detail Freak
target's Avatar
I see. Very good information to know.
So you worked just on the pins on the wing or wins to correct the issue then.

Will you add a tape wiper to the rudder of the electric fuse, or some other type of wiper, or none at all?

Last edited by target; Jan 15, 2010 at 08:27 PM.

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