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Oct 22, 2006, 09:11 PM
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Myron's Avatar
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Discussion

Horton 9 v3/ Gotha GO 229 scratch build


Hey Guys,

I posted tidbits about this build elsewhere, but I was told this would be the best place. I decided a few weeks ago that I wanted to build a stand-off scale Horton bird. I chose the Horton IX V3. I ordered a couple of EDF's from HL. The units have a 5300KV brushless motor and the fan OD is 72mm with about a 58mm fan blade. I started by cutting a large ply center rib then two outer ribs per side. Using a hotwire I cut the foam blocks to taper down to form the center fuse section. I then cut the 62mm duct for the fans to fit snug in the center section.. I used some arrow shafts to beef up the wings and some ply for the center section... This isnt a great pic but you get the gist... The two EDF's crank out 495 Watts combined pulling 45 amps from a single pack, If I put them on seperate batteries they pull 286 watts each. Wingspan so far is 67" and airframe weight with motors is 1lb 6oz...

Myron
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Oct 22, 2006, 10:42 PM
Looks like you got that together pretty quickly. Seems like it far enough along that you could do some testing, instead of being like me, and waiting for all of the surprises at the end. With the fans installed, it could be tested for short powered flights with just throttle control. That would give some idea of the cg, and a bunch of other things.

The large wingspan should definitely give you a lot to work with. The 3sq-ft or more or area is nice. I'm slowly learning to increase wing area for reasonable wing loadings on EDFs. Reworked 3 so far, for more area.

Keep up the good work.

Bill
Oct 23, 2006, 09:12 AM
RCAPA #14
Myron's Avatar
Thread OP
Thanks Bill,

I am doing just that. I have the fans in there and I can do the old run and glide test.. Its a little nose heavy right now but not bad.. I think once I get the elevons on it she will be OK.. I will do that today and then start making the molds for the nacels and canopy.

Myron
Oct 23, 2006, 10:11 AM
Registered User
fuelsguy's Avatar
Nice work, this one is on my list too.
I've just worked up to trying a few EDF conversions of my pusher depron jets, so I've got lots to learn, so keep the thread going.
Ivor
Oct 24, 2006, 09:38 AM
RCAPA #14
Myron's Avatar
Thread OP

A little more progress


Hey Guys,

I put a little covering on this thing last night. I also added scale-like wing tips. The covering is an iron on silk span(had it laying around) and I figured if it doest fly right I will just paint it camo and hang it up. I will probabaly cover the bottom in packing tape before I spend more money on covering. After I get a few test flights I will work on cosmetics. If it flies well, I will change the control surfaces to operate more like the real one. I will also fly it as is before I go throught all the work of vacu-forming nacells and a canopy. As it sits right now with coveing on the top and with the elevons installed and a 5K battery is weighs 2lbs 9oz and spans 74".. I have yet to add 2 servos and ESC's and a rx battery and covering on the bottom. I would quess she will be a little less that 3.5lbs fly weight.. Shouldnt be too bad with almost 500 watts!

Myron
Oct 24, 2006, 09:56 PM
Looks good and you got there pretty quickly too! If it doesn't go perfect from the get-go, it will be worth sorting out. I've had a few that I almost gave up on, but were worth the effort after sorting them out.

Bill
Oct 25, 2006, 08:38 AM
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Myron's Avatar
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Hey Bill,

I am sure I will have a few bugs to work out.. My biggest concern is the wing being rigid enough for such a long span. It has 2 CF arrowshafts doubled up through the center section and it also has spruce spars, but there is some flex in the wings. I have built wings with longer spans that when you make the transition from down wind to into the wind, the wing would oscillate and in one case disintigrate!..

Myron
Oct 28, 2006, 01:03 PM
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Myron's Avatar
Thread OP
Hey guys,

Took it out this morning for a test run.. It flies!.. First toss I didnt have enough speed to make a safe turn and it went into slow flat spin-ish.. No damage and we added a little weight to the nose.. A good toss and she was off.. just a little down trim and minor aileron trim and I started making some circuits around the field.. At this point the fans were finally starting to dig in and it picked up a fair amount of steam..
I came around from a high speed down wind then turned up wind and she got the "wobble" and started oscillating from center to tip.. I chopped power and made a slow circle around and safely landed... Looks like it needs more beef in the wings!..

Myron
Oct 28, 2006, 04:36 PM
Maybe just embedding some CF spars or rods will do the job. I've done that after covering, and just patched the line with a small strip of covering. Good to hear its flying. Will be a real attention getter. We need more different stuff out there.

Bill
Oct 28, 2006, 04:47 PM
Living the dream
KiwiKid's Avatar
Anyone come across a flight sim download for a horten wing?

KiwiKid
Oct 28, 2006, 09:33 PM
RCAPA #14
Myron's Avatar
Thread OP
Hey Bill,

It already has two CF arrow shafts in it.. In our Flying wing UAV program, we have discovered that a single arrow shaft is sufficient for a small 48" wing that weighs about 2.5-3 lbs but anything bigger needs more beef! We have a unit that weighs 4.5lbs and has a two peice 54" wing.. We had to but in a pretty heafty aluminum wing spar to keep it from wobbling.. I will keep messing with it though... It is also going to take me some getting used to in flying the EDF's being they take a little longer to get up to speed...

Myron
Oct 29, 2006, 10:41 AM
internet gadfly
nmasters's Avatar
Your problem may be that the spar is too far forward, not too flexible. If the shear center is ahead of the local AC the tip will flex nose down and the spar will act like a torsion spring. This is called "aeroelasticity" and can be problem for any wing but sweep adds a pitch change to the mix which can lead to a peculiar flutter mode where the the wings flap and the nose bobs up and down. If this sounds like what you're seeing moving the shear center back by putting in an aft spar will add less weight than just beefing up the forward spar until it can resist twisting.
Last edited by nmasters; Oct 29, 2006 at 10:55 AM.
Oct 29, 2006, 11:59 PM
Quote:
Originally Posted by Myron
Hey Bill,

It already has two CF arrow shafts in it.. In our Flying wing UAV program, we have discovered that a single arrow shaft is sufficient for a small 48" wing that weighs about 2.5-3 lbs but anything bigger needs more beef! We have a unit that weighs 4.5lbs and has a two peice 54" wing.. We had to but in a pretty heafty aluminum wing spar to keep it from wobbling.. I will keep messing with it though... It is also going to take me some getting used to in flying the EDF's being they take a little longer to get up to speed...

Myron
Getting up to speed on launch is the only thing that keeps me from flying my AR234 more often. I'm tired of replacing nose glass pieces on it.

Bill
Oct 30, 2006, 09:58 AM
RCAPA #14
Myron's Avatar
Thread OP
Hey Guys,

Bill, it might be time for a bungee!.. Nmasters, do you any more info or tech papers on this "aeroelasticity"?. It certainly seems that the longer the span the more the problem exist.

Myron
Oct 30, 2006, 12:25 PM
internet gadfly
nmasters's Avatar
Sure I'll see if I can find some tech reports. I don't have any technical flutter material handy because all of my planes were chuck gliders so flutter wasn't something I've had to deal with much. If aeroelasticity is something you've never heard of the Wikipedia has a pretty clear definition . I'll work on getting you some info on designing spars for swept wings this evening.

BTW there's a new book out titled "Ho 229: Spirit of Thuringia - The Luftwaffe's Jet-Powered Flying Wing " I don't have my copy yet but I know the guy (8 years via e-mail) who wrote the introduction so I'm confident it'll be a valuable addition to my collection of Horten books

--Norm
Last edited by nmasters; Oct 30, 2006 at 12:26 PM. Reason: added sig


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