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Old May 02, 2013, 11:30 AM
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andrecillo76's Avatar
Heidelberg
Joined Oct 2009
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Build Log
Horten IV 1:4 Experimental

Hi,

as already mentioned in the "Show your Nurflügel" thread, I would like to post a post-maiden build log for a project that has been following me since October 2009: A wooden Horten IV in a scale of 1:4. Lothar and me did this together and used the extensive experience made with our Horten XIV (Video) and the small Schapel SA-882 (Video). I took the challenge of the aerodynamic design and analysis, whilst Lothar did the detailed engineering and milling of the parts. For many different reasons, we both left the project still for more than two years - equivalent to about five wooden flying wings (me) and several beautiful wooden skerry ships (Lothar). Anyway after Christmas at my parents, I made a New Years' resolution and decided to work again on the two half finished wings and to get the IV ready. The main reason is that I wanted to focus on a somewhat bigger project, the Snow White, and I needed thus to tidy up my humble "workshop". But this is another story for another time and thread...

We decided to make an experimental center section with an electric motor first. Then, after having confidence that the design performs well, we want to make a scale center section. The wings are as scale as possible, by the way. The experimental center section is a huge help when it comes to flying and testing, as no collegue is needed to aerotow.

Here's a short video showing yesterday's short maiden and below you find a picture of the plane before the maiden. For some reason it rained actually just a couple of minutes before the flight.

Erstflug Horten IV in Holz (4 min 32 sec)




We had a total of three designs before we started with millling and building anything. The final design "Final2" - yes, we had two finals - was ready for the CAD about March 2010. Soon a package with hundreds of pieces arrived from Bremen and I was able to start building. Lothar started at the same time with his.

The starting point is the mid rib of the center section. It's made of three layers of plywood, one birch and two popplar:



After that I had to make custom tubes for the joiners. For this I took paper soaked with 24h epoxy resin. Why paper, well because I had it here and after curing you can easily sand it, as the tube has to fit well into the ribs too. After curing, I had great assitance from two experts to test the result.




Selbstgemachte Steckungshülsen (1 min 35 sec)



Enough for today...
Cheers
Andrés
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Old May 02, 2013, 01:52 PM
I don't like your altitude
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Wow that is some rigorous testing regime you've got there
Laughed so much I ve got bellyache
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Old May 02, 2013, 08:30 PM
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United States, CA, Marina
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Jeez.....I could hardly believe my computer screen. Your thread is only a few hours old and it has 147 views already!

I too love building in wood, but that carbon joiner is one seriously beautiful bit of composite work. I haven't seen any thing like here in the US. Looks like your paper joiner tubes worked out well.

Kent
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Old May 03, 2013, 12:43 AM
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Heidelberg
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I love that video too, Stuart. The best thing is I had only to shoot the video. They decided themselves what testing procedure to take . My wive was impressed of how much they changed since then...

Kent, the joiner is a cross-wound CF-tube. With its diameter a must, else one could easily crush it. Sofar the tubes work perfectly. By the way, I used baking paper as a thin spacer between the tube and the carbon joiner. This paper is designed to have low adhesion and is perfect for this type of applications.

Andrés
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Old May 03, 2013, 06:59 AM
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Edgewood, KY (Cincinnati)
Joined Jan 2004
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Very nice Andres. I could not see that there was enough ground clearance for the prop. Watching your video, I waited to see how you would hand launch - possibly discuss launch? Then suddenly your ship lept off the ground!
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Old May 03, 2013, 10:25 AM
I don't like your altitude
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Happy,Dopey,Grumpy"................
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Old May 03, 2013, 11:36 AM
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Heidelberg
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Thanks Bruno! This size is not possible to toss with the hand. It's about 15 lb and you need a good minium speed. I use a rubber from EMC Vega (Scale rubber) pulling with about 50 lbs. In a slope its different: just throw down providing you have enough "cojones"

It's time for more pics. Having the tubes for the joiners, I was able to make the center section. In case you wonder, I actually showed the images for the wing-tube making and had already done the one for the center section. There is not much new in making this center section. The ribs are fixed into a jig, the joiner tubes installed and everything is glued together in place. After that, I went on to the planking of the top surface. I used 0,8 mm plywood for the center section in general, because it is one of the pieces subjected to the biggest stresses during hard landings.










The last picture shows the state in which the center section stayed since mid April 2010. It was like that on my table for about 3 years... Anyway, I moved then to the wings. First the 47 ribs were glued on a melamine shelf, which was supported with spruce strips below to create a stiff surface. So why exactly 47 risb? Because this is the scale amount: spacing was originaly 200 mm at a scale of 1:4 means every 50 mm a rib. Not more and certainly not less . After that the spar caps had to be made and installed into the structure. This needed a lot of choosing good material and many scarf joints!







Enough for today, it's dinner time

Cheers,
Andrés
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Last edited by andrecillo76; May 03, 2013 at 11:45 AM.
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Old May 03, 2013, 12:03 PM
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That's a clean build Andres.

Are those spar caps pine or spruce?

Kent
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Old May 03, 2013, 01:08 PM
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Heidelberg
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Thanks Kent. We have sometimes problems to translate the materials . I'm astonished how often the German language has very precise technical words difficut to translate into english - mostly because of lack of knowledge.

The spar caps are selected pine strips with high density of growth rings (about 8 per cm) and no obvious defects. The building shelf was supported with spruce (cheaper but softer). Birch and popplar plywood is used for ribs. We never use basswood (=Linde in German). For the Horten Ib I used birch strip material for the leading edge. Great wood, but hard to shape! Johannes used for the Beluga's leading edge oak strip material. That is really hard to shape but gives a great result!!!

Andrés
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Old May 03, 2013, 02:13 PM
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[QUOTE=andrecillo76;24896117]Thanks Bruno! This size is not possible to toss with the hand. It's about 15 lb and you need a good minium speed. I use a rubber from EMC Vega (Scale rubber) pulling with about 50 lbs. In a slope its different: just throw down providing you have enough "cojones" ....

Ah, I see. I watched the video again with the sound turned up louder. I could hear the motor turn on after she left the ground.

I'll be quiet now, and enjoy the thread!
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Old Jun 05, 2013, 08:33 AM
I don't like your altitude
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http://www.bbc.co.uk/news/world-europe-22767268

Hope you guys are ok.
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Old Jun 05, 2013, 01:23 PM
Hallo von Dresden
Joined Sep 2012
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Spent the day moving sandbags to the edge of the flood in the centre of Dresden ... not much fun and the damn water keeps on rising.


Nice thread though looks like another pretty wing.

Jens
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Old Jun 05, 2013, 02:32 PM
I don't like your altitude
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Good to hear from you Jens!Hope you'll get through this ok.
Regards Stuart
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Old Jun 05, 2013, 03:36 PM
Herk
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Virginia USA
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Hi Jens - I wondered why I have been thinking of you so much lately.

I do miss you on the forum -- my very best wishes --- Herk
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Old Jun 06, 2013, 03:13 AM
Hallo von Dresden
Joined Sep 2012
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I will be back upon completion of my new shop space ... but back to the thread ... this is Àndres and his new Horton time :-I

Jens
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