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Old Aug 02, 2006, 03:25 PM
Scale nut
jimhorner's Avatar
Santa Clara, CA, USA
Joined Apr 2001
477 Posts
Congratulations Edi. I'm happy for your success.

Now there's two of these Albatros Triplanes patrolling the skies. Yours seems to fly much like mine does. Neat to see two different implementations of the same bird.

According to the Albatros Experimentals datafile, the full size bird suffered from being tail heavy. I don't know if that means that the CG was really off or if the incidences weren't correct. Hard to say.

Just for kicks:

The DVa was 2017 lbs according to this link http://www.oldrhinebeck.org/collecti...s/albatros.htm. If you assume (wild guess here) something like 150lbs for a pilot, and maybe another 150lbs for the extra wing, then you get 2317 lbs. Not sure if the 2017 is with ammo or gas, but lets round up to 2400 lbs in fighting condition. The tripe's full size wing area is something around 29.53 ft2. So, the wing loading of the full size might have been around 81 lbs/ft2. That works out to 9oz/in2 which is a little more than 1/2 of my tripe's wing loading. Should be fine.

The Electric Motor Calc web page gives a Watts out calculation for my power system (Mega 16/15/7, 9x3.5 hand-carved wooden prop, TP 2100 3S) of 119 Watts. With the mass of 25.7 oz, the power loading of my model is 4.6 Watts/oz. If you assume the full size was putting out 160 HP, then its power loading would be (160*745.7)/(2400*16) = 3.1Watts/oz.

So, the wing loading of the full size is better, but the power loading is a bit worse. I agree with you, it should have flown better than it did. Wanta build a replica full size and prove it? (That would be fun wouldn't it?) Perhaps they didn't see enough of a performance improvement that it wasn't worth further development.

One other thought is to see what the full size should weigh if the model weight is scaled up. The scale up factor should be model scale cubed. My model's weight is 25.7 oz and the scale is 1/9, so applying the math would give a full size weight of (25.7oz / (16oz/lb)) * 9^3 = 1171 lbs. Maybe that's the issue?

Who knows. The models certainly fly well, and that's good enough.
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Old Aug 02, 2006, 03:47 PM
edi
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Elstertrebnitz, Germany
Joined Aug 2004
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Very interesting data, Jim.

According to "Triplanes", the speed of the original was over 200 km/h. Kurt and I thought that maybe the main goal of the triplanes was improved responsiveness and climb rather than top speed, so perhaps the Germans didn't regard the Dr.1 as a significant enough improvement to be worth the additional hassle of a third wing and four more ailerons. And certainly they didn't care for a fighter to be cool looking in the air and on the ground.

Thanks to everybody for keeping fingers crossed. Especially to Kurt, of course, but also to you, Jim, since your marvellous build (especially the videos) made me talk Kurt into spinning a Dr.1 off his D.Va.
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Old Aug 02, 2006, 08:33 PM
The Hun in the Sun
vonJaerschky's Avatar
Canada, BC, Comox
Joined Nov 2003
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Edi, that is just too cool. What a great model of a rare bird. And the icing on the cake is how well it flies! Congrats on your accomplishment.
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Old Aug 03, 2006, 03:23 AM
edi
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Elstertrebnitz, Germany
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Meanwhile, the video is ready, as always unedited

http://www.bengco.net/guest/videos/albdr1maiden.mpeg
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Old Aug 03, 2006, 11:50 AM
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Rekitter's Avatar
Oakland, CA
Joined Nov 2002
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Hi Edi:

Congratulations on the madien. You did a fantastic job on this build. Good to hear that it flies so well. Regards,

Alex
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Old Aug 03, 2006, 12:26 PM
Scale nut
jimhorner's Avatar
Santa Clara, CA, USA
Joined Apr 2001
477 Posts
Quote:
Originally Posted by edi
Very interesting data, Jim.

According to "Triplanes", the speed of the original was over 200 km/h. Kurt and I thought that maybe the main goal of the triplanes was improved responsiveness and climb rather than top speed, so perhaps the Germans didn't regard the Dr.1 as a significant enough improvement to be worth the additional hassle of a third wing and four more ailerons. And certainly they didn't care for a fighter to be cool looking in the air and on the ground.

Thanks to everybody for keeping fingers crossed. Especially to Kurt, of course, but also to you, Jim, since your marvellous build (especially the videos) made me talk Kurt into spinning a Dr.1 off his D.Va.
I'm having a hard time believing that the original speed was over 200km/h. According to the web site I referenced above, the DVa's speed was 172km/h, and that third wing would have added quite a bit of additional drag. I wonder, sometimes, where these references get their info. The "Fighting Triplanes" book by Haddingham (sp?) even gives the serial number for the DV fuse upon which the Dr-1 was built. I certainly can't see that in either of the two photos I've found, and I can't find any references either. Of course, this sort of speculation and research is part of the fun of these birds.

Nice video, looks like it's got plenty of power. Now you need to work on long, slow takeoffs.
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Old Aug 03, 2006, 01:37 PM
edi
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I am certainly in no hurry to repeat that take-off when I needed every bit of that power! But I have learnt to do long, slow scale-like takeoffs only when it's *really* calm - due to the bushes along the road cutting our runway you get crosswinds channeled, extremely local but stronger than in the open. Those have eaten more than one plane in our club, and they have often upturned my planes after the landing.

BTW, this evening would have been ideal for flying, but I had no time
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Old Aug 04, 2006, 02:56 PM
edi
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Second flight today. The wind got nasty, so the landing was bumpier than hoped for, but other than that it was fine - I think the video is better than the first one. You'll find it on

http://www.bengco.net/guest/videos/albdr1-20060804.mpeg

Have fun!
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Old Nov 30, 2007, 02:41 PM
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Washington State
Joined Oct 2007
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Thought I'd resurect your thread, edi!

I'm building an Albatros right now myself. I'm trying to figure out the spinner. Did you have any balance/vibration issues with your spinner? I don't know if I missed it or not, but I didn't see you write up much on how you made it, and attached it. Kinda self explanitory with your pics, but if there's anything you could expand on, I'd love to hear it.

Here is mine...
http://www.rcgroups.com/forums/showthread.php?t=763111
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Old Nov 30, 2007, 03:13 PM
edi
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Elstertrebnitz, Germany
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Nothing really. Since it's sitting in the middle and the polystyrene is light, too, I didn't experience any issues. On the other hand, I have never flown her without the spinner, so I cannot compare.

Good luck with your Albatros!
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Old Nov 30, 2007, 11:32 PM
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Torrance, CA
Joined Sep 2004
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Although somewhat off-topic, I would like to comment on jimhorner's post 121 above.

There is a very interesting article in the January 2008 Smithsonian Air and Space Magazine that I just received in the mail. The article discusses recent computer modeling/analysis of World War 1 fighters. Definitely a good read.

http://www.airspacemag.com/issues/20.../red_baron.php

The Fokker DR1 was summarized among others, and showed that the middle wing provided minimal lift (their term was "nearly worthless") due to the proximity of the adjacent wings. It's high rate of climb appears to be due to the props pitch at the expense of top speed. The high maneuverability is due to the rounded leading edge and thick airfoil providing greater lift, novel at the time. The maneuverability of the plane is apparently directly related to the lift of the wing. These features may or may not be represented correctly in the models we fly.

The point of all this is that the models we build today do not use scale airfoils, use lighter stronger building materials for the model's weight than the originals, have extremely light weight and efficient power trains and our propellers don't come close to representing the scale ones used. I believe comparing the performance of our models to that of the originals is a very complex problem that would require a detailed computational analysis of the model and the original. One that I sure am not capable of performing. Not sure I would even want to go back to college to learn how.

The fact that edi has built a beautiful, solid performing tripe may have less to do with the design of the original than edi's building skills and Kurt's great kit design.

This line of thought is definitely a fun and challenging, however. I agree that we will just have to build a scale replica to find out how the original flies compared to the model. Anybody got the original engine lying around and an empty hangar they would like to donate in the name of science.
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Old Dec 01, 2007, 03:48 AM
edi
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Quote:
Originally Posted by Jeff in So Cal
The Fokker DR1 was summarized among others, and showed that the middle wing provided minimal lift (their term was "nearly worthless") due to the proximity of the adjacent wings. It's high rate of climb appears to be due to the props pitch at the expense of top speed. The high maneuverability is due to the rounded leading edge and thick airfoil providing greater lift, novel at the time. The maneuverability of the plane is apparently directly related to the lift of the wing. These features may or may not be represented correctly in the models we fly.
I think I can confirm some if this and add a few more thoughts: My Gordon-Sellers Quadruplane has wingerons (second wing) which need a surprising large through and a bit of leaning on the stick to provoke aileron reaction. She *is* a very stable flyer, but still I think this is due exactly to the fact that that wing doesn't produce a lot of lift anyway (and then, on a four-winger one-wing wingerons use "only" 25% of the wing surface).

Maneuvrability is not only an issue of wing load and weight/lift ratio, but also weight distribution. Planes like the Fokker Dr.1 or, even more so, the Wight Quadruplane have all the mass close to the center of gravity. This makes them more responsive to control input, and, as a model bonus, easier to transport and less prone to take damage.

Especially on the Wight Quadruplane, you find that not only the empennage, but also about 50% of the wing surface are in the airscrew slipstream. (To a lesser degree, this is also true for all my three- and four-wingers.) This will improve lift and reduce minimal airspeed.

Quote:
Originally Posted by Jeff in So Cal
The point of all this is that the models we build today do not use scale airfoils, use lighter stronger building materials for the model's weight than the originals, have extremely light weight and efficient power trains and our propellers don't come close to representing the scale ones used. I believe comparing the performance of our models to that of the originals is a very complex problem that would require a detailed computational analysis of the model and the original. One that I sure am not capable of performing. Not sure I would even want to go back to college to learn how.
Obviously, these comparisons are not to be taken seriously. For modelling, an important question is always "Will this be a cool plane to look at?". For a fighter, this is a complete non-issue. Clearly, the larger and more scale a model becomes, the more likely it is to inherit bad habits from the original. Our models taken as *airplanes* are designed from scratch based on our experiences. (This is why I find license issues so absurd.) Only the *outlines* resemble the original.

Quote:
Originally Posted by Jeff in So Cal
The fact that edi has built a beautiful, solid performing tripe may have less to do with the design of the original than edi's building skills and Kurt's great kit design.
I just had to quote this ... just made my day!
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