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Old Jun 24, 2012, 12:56 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
I finally maidened the wing!

Due to not really finding time to build a new fuse I decided to put it on my electric fuse. I did however do a total refit of the fuselage to reduce weight and fit the new F5J rules more nicely.
I used Hyperion DS11 mounted it the ruder for both elevator and ruder (instead of the 761 I had in previously), replaced the wiring and the molded ruder with a built up one for an additional weight reduction to accommodate the CG requirements with a smaller battery in the nose (4 cell 850 mAh).
I havenít measured ROC yet by I feel very comfortable with it (probably around 9 m/sec) and the all of weight is 2060 grams like my F3J Kevlar wing Gremlin which is really nice for an all-weather Gremlin.
If I build a lighter fuse with a lighter setup and some weight reduction is the tail, I could maybe build a slightly underpowered model at 1900-1950 grams but I probably wonít do it for a while, other projects first...
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Old Jun 24, 2012, 01:28 AM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,885 Posts
I think you will really like the DS11's, I do very much.
Sounds like an awesome plane.

R,
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Old Jun 24, 2012, 01:29 AM
Detail Freak
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Harbor City, CA
Joined Oct 2003
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Ooops, double post.
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Last edited by target; Oct 08, 2012 at 12:43 PM.
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Old Oct 04, 2012, 06:00 PM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
Had some time off today so got to fly my new Gremlin ST wing on my F5J fuse.
did about 4 flights on my 4 cell 850mAh batt without charging it and it isn't even empty

I've started playing around with the logging features of the F5J measuring device and so I recorded some flights.
The flights weren't against a clock but were just to push myself for some low starts to get more familiar with the system and the model before our next F5J competition in about two weeks.
After an initial climb to a "safe" altitude I would use my right slider to reduce the throttle for a medium speed cruise until I "hit" air. I would then circle it with my motor at low RPM to see if itís the real thing and then shut of the motor.

After I would feel I've "proved" to myself I could catch the thermal I was in and climb out and was able to come back with the wind and gusty conditions I would do some aerobatics and a nice high speed low altitude pass and start again from a low altitude. I caught thermals today from the 30ís, 40ís and 50ís (meters) which was very gratifying.

I'm amazed at how much better this wing feels with its lighter tips. The slightly larger rudder also helps with the "grip" in tight low altitude turns. The model feels lighter than it should in the air and is a true joy to fly.
My Gremlin is around 2.1 kg after some components upgrades (~74 oz) and with an area of 70 dm (1085 in^2) its wing loading is "conventional".

Attached are some figures from today
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Old Oct 05, 2012, 01:12 AM
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Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
2,449 Posts
Quote:
Originally Posted by roydor View Post
I'm amazed at how much better this wing feels with its lighter tips. The slightly larger rudder also helps with the "grip" in tight low altitude turns. The model feels lighter than it should in the air and is a true joy to fly.
My Gremlin is around 2.1 kg after some components upgrades (~74 oz) and with an area of 70 dm (1085 in^2) its wing loading is "conventional".
Nice to see the evolution on Gremlin

We often look at AUW while the better handling of less inertia is actually what we are looking at. Light wing tips combined with increased rudder area is a recipe for a plane that flies not only more easy, but also more stable, making flight more efficient.

BTW It is fascinating to see F5J planes coming down to conventional F3J weight. We are at point where electrifying a plane does not compromise its thermal flying performance.
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Old Oct 06, 2012, 09:17 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
Quote:
Originally Posted by Tuomo View Post
It is fascinating to see F5J planes coming down to conventional F3J weight. We are at point where electrifying a plane does not compromise its thermal flying performance.
My original F5J fuse was for an "unlimited" setup with a heavy motor and fairly large battery. because of all the weight of the equipment in the nose I didn't see a reason to save weight in the tail so I built it STRONG with a heavy tail boom, rudder and two 761 servos. It originally weighed 2.4 kilos with the old Kevlar wing.
When The F5J rules started to change I realized I could go with a much lighter motor setup so I dropped a couple of cells (from 6 to 2) used lower capacity cells as well and from a 1kW setup I went to a 400 watt setup with a weight save of 130 grams in the battery. To get the same CG I changed the tail servos to Hyperion DS11 and also the wiring. I reached a point where I can't change the motor to a lighter one because there is no more weight to take off the tail and with a lighter wing I'm where I am right now.

So, now I'm building a lighter fuse with a super light ruder and boom so I could use a 100 gram motor in the nose and drop an additional 150 grams (110 off the motor, 40 on structure) and by shifting the battery around I should be able to reach the correct CG so I should have an even lighter model in an F5J setup, around 1950 grams
I also plan to have a 500 gram provision for ballast in it.

The old fuse will go back to the old wing which should give a 2250 gram model for the windier weather.

In general, F5J models with a low power setup (enough for 200 meter in 30 seconds) can come to around 100 - 150 grams extra compared to F3J models assuming an F3J strength wing. If a lighter wing is taken into account (not capable of being towed in anything stronger than 2 m/sec wind) then the weight can easily come down to around 0-50 extras grams compared to F3J model of the same design. That is why I like the new F5J rules, no more "lead sled".
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Old Oct 08, 2012, 12:47 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
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Sounds well thought out.
I watched LJ's E-aspire and Ali Khani's E-Xplorer fly this weekend. Both are very light indeed, RTF.
They fly like a regular sailplane except for not needing a winch!

G/L with the rest or your building/developing.
Awesome pics.

R,
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Old Oct 29, 2012, 06:44 PM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
Had some success with the Gremlin during the last couple of F5J competitions we had here locally and I just LOVE the model.
At 2.1 kg it's a nice floater if needed and penetrates well for medium wind conditions.
I've made very little progress with the new fuselage, just the vertical stabilizer and the boom so far but they are LIGHT!
More when I get some more progress

A few pics and a movie a friend made of the last F5J comp is attached

F5J competition from my Naza eye (3 min 40 sec)
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Old Oct 30, 2012, 06:57 PM
Registered User
Sydney
Joined Apr 2009
716 Posts
Good to see that your F5J Gremlin is working well. It seems a great way to go. Good luck with it.
Not using the grass for your spot landings?
John
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Old Oct 31, 2012, 02:46 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
At the end of our summer it ain't grass, it's just some weeds several cm apart
The ground was very soft though.
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Old Nov 01, 2012, 09:50 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
Finished the new F5J rudder.
I built it out of Rohacell with light glass and some local carbon reinforcement for servos in the tail.
Final weight with two servos installed (Hyperion ds11) and linkage itís only 68 grams.
The built up ruder is slightly bigger than the original composite rudder and surprisingly strong.
The hinge is a peel ply hinge built in into the composite stabilizer and the buildup rudder is glued to it and had a balsa fairing for aerodynamic purposes.
With the new boom I made, I have around 40 grams saved in the tail in comparison to my current F5J fuselage so I can use a lighter motor then the one I have now.
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Old Nov 01, 2012, 01:17 PM
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Jyvaskyla, Finland
Joined Aug 2003
2,449 Posts
Nice work

Since the test flying I made in July, I have been playing with idea of building open structure rudder to Aspire. The idea is to dremel rudder off leaving maybe 1.5-2cm of material behind hinge line spar to work as a d-box for the structure. The new rudder would be about 2cm wider than the original.

Another possibility is to build whole new structure with rohacell core like Roy did, but is is much more work.
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Old Nov 01, 2012, 01:22 PM
mostly gliders
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SkellefteŚ, Sweden
Joined Sep 2003
965 Posts
Congratulations roydor! You've done a fine job with the Gremlin. I like to buy a model from you if you have one for sale? Actually believe that I asked you earlier to make a deal with you?

/Ville
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Old Nov 01, 2012, 03:32 PM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
866 Posts
liukku,

I'm afraid I don't build commercially and I'm not planning on selling one of my older ones at the moment. If something changes in the future I will let you know.

Tuomo,
the diagonal structure is extremely rigid for torsion because the ribs are covered with 0.2 mm carbon cap strips. It's so torsionally rigid that you don't need a d-box structure it support it. You can simply cut the skin 4-5 mm after the hinge and glue the built up stab to the skin (that’s what I did). My only recommendation is to build the rudder before you cut the existing one off, just in case you get in trouble with the build.
BTW, the rudder weighed around 7 grams before covering and took me about 3 hours to build
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Old Nov 02, 2012, 03:49 AM
Registered User
Italy, Emilia-Romagna, San Lazzaro di Savena
Joined Sep 2006
34 Posts
Quote:
Originally Posted by Tuomo View Post
Nice work

Since the test flying I made in July, I have been playing with idea of building open structure rudder to Aspire. The idea is to dremel rudder off leaving maybe 1.5-2cm of material behind hinge line spar to work as a d-box for the structure. The new rudder would be about 2cm wider than the original.

Another possibility is to build whole new structure with rohacell core like Roy did, but is is much more work.
Good idea for winter, Tuomo.
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