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Old Oct 02, 2010, 05:31 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
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9 gram Fokker DR-1 Tripe

Here's my latest Tripe. This one has a span of 10-inches, has even more cartoon scale, and is about 9g. No landing gear yet till it's trimmed out. I've already cut out the motor and given it more down thrust. More trimming to do.

It uses a ZTRON 900mhz FH actuator receiver from BSD. Actuator is HingeAct. Propulsion is a 4mm watch gear drive that Ralph Bradley made me years and years ago. Battery is 30mAh Full River.

Weight is 8.7g, and with the landing gear after I get it trimmed it will probably be slightly over 9g. Wing loading is about 0.35 oz/sq.ft.

At present it can do circles in my family room. Turning leaves something to be desired. Maybe it needs a more force than the HingeAct. Anyway, more work to do.

Gordon
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Old Oct 02, 2010, 05:42 PM
Reduce the drama...
rick.benjamin's Avatar
USA, OR, Damascus
Joined Apr 2004
4,043 Posts
Gordon,
That is really nice work!
Isn't there some kinda rule against tormenting the less talented?
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Old Oct 03, 2010, 06:44 AM
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Ralph B's Avatar
Brandon Mississippi/Independence Kentucky
Joined Oct 2000
554 Posts
Gordon:

Nice work! If you are running the 3 inch prop you don't need more than a 20 MAH cell. That should save a little weight. I have flown a 10 gram model with that drive set up and a Full River 20 MAH cell. Duration was still very good.

Ralph
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Old Oct 03, 2010, 08:53 AM
Thanks for the Fish!
aerogel's Avatar
Land of cajuns
Joined Dec 2001
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looks sweet gordon your milling out your frames?
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Old Oct 03, 2010, 09:48 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Ralph, thanks for the battery suggestion. But, I don't have any 20's, so 30's will have to do.

Aerogel, I'm lasering the skeletons.

Gordon
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Old Oct 03, 2010, 05:26 PM
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West of California Speedway, East of LaLa, North of Disneyland
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Gordon,

That's remarkable. Congratulations!!

Add on to your living room!! Just kidding, but would aero balance on top and bottom of the rudder held in turning it? Might try a temporary tape job to see.

On the other hand, the HingeAct is a little weak. Time for a custom wind?
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Old Oct 03, 2010, 07:02 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
BSD is coming out with MicroAct's with high ohm winds for these RX's (they don't have FET's). I had though about Aerodynamic balancing, and probably should have. In the end I'll probably make a version two with a remote Act when BSD has them in the high resistance version. Weight will be a bit higher, but the additional force is probably worth it.

Gordon
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Old Oct 04, 2010, 09:46 AM
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bmutlugil's Avatar
Turkey
Joined May 2002
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Cute little model there.. I hope you solve problems..

Bulent
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Old Oct 04, 2010, 11:28 AM
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West of California Speedway, East of LaLa, North of Disneyland
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Quote:
Originally Posted by Gordon Johnson View Post
BSD is coming out with MicroAct's with high ohm winds for these RX's (they don't have FET's). Gordon
There's an alternative in that one could add an outboard FET switch circuit to handle the higher current of a lower resistance actuator. Weight gain would be minimal - FET's hardly weigh anything, power would come directly from the LiPo and the actuator weight gain is offset by fewer winds of slightly larger gauge wire. It's an alternative, but in your case, it's a lot more trouble than just substituting one actuator for another. (Besides, we all need to keep Bob and Janell solvent!!!).
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Old Oct 04, 2010, 12:37 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
There is another alternative as well. The ZTRON actuator RX does not have FETs. However Nick Leichty (MicroFlyer Radio) will make up his 900mhz actuator RX and add on from one to three FET's for an additional charge per FET. In the end I'll probably stick with this one and use the high resistance ACT's when BSD has them. Besides, the ZTRON RX costs about half what the Leichty RX costs.

Plus, I'll probably incorporate what I've figured out about down and right thrust (I've already cut the gearbox out of the fuselage once and increased the down and right thrust) and things like that in the second version. And, I'll probably add the aerodynamic balancing part of the rudder to help it turn sharper. I didn't mention it, but there are some differences between this Tripe and my larger 16-inch version so there are things to figure out and tweak.

The 16-inch tripe has its wings cut from 3mm foam and fuselage from 6mm foam. This one has the fuselage from 3mm foam and the wings from 1.1mm "Zepron". Zepron is a foam that a guy named Gabe used to sell through his company AeroDyne (if I remember the name correctly) before Depron could be purchased anywhere in the US. In this case 050 Durobatics was not stiff enough. But, I have Zepron in various thicknesses I could try. Zepron is not light. It's heavier at any thickness than equivalent thickness Depron. But, it's hard and stiff. Since I was doing a skeleton wing the weight of the foam is not as critical, but stiffness is. So, I made a few different wings from various thicknesses of Zepron till I figured the 1.1mm was about right in terms of tradeoff between stiffness and weight. Weight was about the same as 3mm Depron, but should have less drag since the leading edge would be much thinner. On a draggy plane like this powered with only a 4mm gear drive I figured I should do what I could to reduce drag, hence the use of thinner foam just stiff enough for the job.

The next difference is that I do not have a wing joint in the middle of the wings on this plane to give it dihedral like I do on the 16-inch tripe. I figured I could bow the wings up and hold them in that position with the CF wing struts. But, until I tried it I didn't know how that would work. It worked as well as I had hoped and you can see that in the curved wings rather than straight wing halves with a dihedral joint.

One final difference is I stretched the chord even more on this tiny tripe to increase wing area. And, On a DR-1 the lower wings are shorter than the middle wings which are shorter than the top wing. I reduced the taper from the bottom to the top wings, again to slightly increase the span of the middle and bottom wings, thus increasing the wing area to help get the lowest possible wing loading for this model.

The elevator is hinged, but has no actuator. Instead I glued short lengths of magnet wire on the underside running fore and aft across the hinge line. this allows bending the wire to adjust the elevator for trimming purposes.

All these differences plus the fact that it's a smaller span model makes trimming it more difficult and a process, probably leading to a version two of the plane.

Gordon
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Last edited by Gordon Johnson; Oct 05, 2010 at 11:40 AM.
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Old Oct 04, 2010, 08:26 PM
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West of California Speedway, East of LaLa, North of Disneyland
Joined May 2001
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Gordon,

What a coincidence, just a couple of weeks ago, I Googled any word or phrase I could remember for Gabe Baltaian's website - NYBlimps, Airdyn, etc. - and NADA!!! Just some really old posts in some of the forums from 2004, 5 and 6.

Oh, well, I have a small supply of .025 and .050 Durobatics left and some iFoam from Michael (epilot), plus my mushy 1, 2 and 3 mm Depron.
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Old Oct 04, 2010, 08:48 PM
Thanks for the Fish!
aerogel's Avatar
Land of cajuns
Joined Dec 2001
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ahh Zepron from aerodyne I use to mold and vac my planes out of it was one of the best foam materials I have found it was like virgin foam great for molds...anotner lost porduct..
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Old Oct 04, 2010, 09:17 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
It is good to have a collection of foams: Depron, Zepron, Gediplac, Wallfoam, Cellitac, Durobatics, wire cut blue foam sheets. Each one has its own characteristics/properties.

Gordon
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Old Oct 06, 2010, 11:00 AM
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Joined Oct 2002
232 Posts
Hello Gordon,

Nice semi scale airplane :-)

Do you have the plan of your micro fokker DR-1?

thanks in advance

Charles
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Old Oct 06, 2010, 11:36 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Sure, I can post the plan. It may be several days before I get time to make up a pdf file.

Essentially it's a scaled version of my larger Tripe which has its plans posted in this thread for that Tripe. What's different is the chord in the wings and changes in ribs etc to go with those tweaked wings.

Gordon
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