|Jun 17, 2009, 04:12 PM|
Another little Arado 234 (50 mm EDF)
Just sharing this project with you.
I wanted a simple EDF and actually started out with a A-10 from RBC models, also twin 50 mm EDF. This is a wood kit though and I got stuck. I also got stuck on some other EDF projects (like the Me 262 and the Starfighter), didn't really finish these but some day I will.
The Arado project however took more easily off. It's a simple plane and it has an interesting story. Maybe the plane is a little dull looking at first glance, but knowing the background where the allies didn't discover this plane until early 1945 (according to some sources) it was a very succesful spyplane in German service. The allies were competing to get some samples for test after the war, the americans outsmarted some british..
I decided to build one using simple techniques, like vacuumbagging and castmolds. 1 meter span, 2 pc. 50 mm EDF from Wemotec and some 6000 rev/v engines.
Avoiding CNC drawings I just scaled some 3-views up with some software on my PC. After that some gluing and cutting of a4 paper and I got the contours.
Countours for the fuse and engine nacelles are made out of 2 mm plywood glued in 2 layers with 3M77 to be deattached later when casting the molds. The fuseplug were then built up with balsa formers and a lot of scrap blue foam in between. At last the scrap foam is of some use. I will spartle these plugs out later.
I will try molding the fuse and the engine nacelles in fibreglass+balsa+fibreglass. This will be an exciting experiment in molding light and strong. I haven't tried this before.
Wing is made of blue foam and will be vacuumbagged. Don't know what fibreglass I will use yet. Target weight for the wing around 150 grams.
|Aug 31, 2009, 04:21 PM|
A little progress
Had a long pause on this project. It was high summer, good weather, and I needed a DLG, so i built a SuperGee. Took me 4 weeks. Also had to built a CNC kit of a Sopwith Camel for display in our living room. But now - back to the Arado.
I ordered a pair of Hyperion Y22s-6000 for the Wemotec micro fans.
From the SuperGee project i found out that the cast I am using for moldmaking isn't stable enough and dentalcast is much to expensive. So now I am going for the traditional epoxymolds, which requires more work on the plug.
I started with the plug for the engine nacelles. The blue foam plug was first covered with 80 grams FG, after that epoxy-microballoons and sanding. Finish with some plasticsanding and paint and polished up with 400 grit sanding paper and wax. It is not overly glossy but has a very clean surface though. And it wasn't that hard. Now i just have to make the molds.
The tail fins was quickly done. Some pieces of 4 mm balsa, sanded in pattern and vacuum bagged with 49 grams FG with carbon rovings at the leading and trailing edges. Now - after bagging - I just need to trim the edges a bit.
I have mounted tubes for the servowires and powerwires for the engines. I plan to put the controllers (probably YGE 30's) with the Y22s for proper cooling. The powerwires will be a little long and maybe i will stabilize them with a big capacitor near the battery.
The wing is now ready for bagging, so the big hurdles left are the plug for the fuse - that will be a LOT of sanding and polishing, and making of the glassnose. The latter I plan to do with vacuumforming.
The weight budget:
Tail planned: 30 grams realized: 27 grams (w/o paint)
Wing planned: 150 grams realized: 70 grams (w/o FG and paint)
Fuse planned: 150-200 grams
Engine nacelles planned: 2x10 grams
AUW except gear: 350-400 grams
2x3S1600 lipo 240 grams
3x servos 24 grams
2xEDF+Y22 110 grams
2xYGE 30 50 grams
PCM Reciever 25 grams
Total Gear weight 449
Which gives a total AUW of 800 - 850 grams.
Powered with 400 W around 500-600 W per 1000 grams.
But lets see if I am to optimistic about the weight. But I think it would be able to fly at least.
|Sep 07, 2009, 04:03 PM|
The wing has now been glassed using the vacuum bagging technique. From the leading edge to the main spar I used 200 gr. UD carbon and from the main spar to the trailing edge I used 80 gr. glass. The trailing edge is reinforced with a carbon roving. Just to make it tougher.
The wing weighs 170 gr. against 150 gr. expected. I could have used a lighter UD-carbon, but I just took what I had on the shelf. And the 20 gr. ekstra is not fatal. It's not a DLG. The wing is extremely stiff and much stronger than you could build with traditional balsa/spruce at the same weight.
Now the wing needs two servos. I will use 2 pc. of Dymond D60. And some holes for the wing mounting bolts and the mounting bolts for the engine nacelles. Furthermore the ailerons must be cut loose. As hinge i bagged in som nylon (peelply ?). And finally paint all over with RLM 76 as base colour for the whole plane. I will use an acryllic paint, havent decided yet about using paint brush. After that the camo..
The mold for the engine nacelles is half done now, in fact more than half done. I wonder if I can pull the finished mold and the plug apart ? Thats exciting.
|Sep 13, 2009, 03:48 AM|
The molds for the engine nacelle is now ready to use. I am happy with the result. It is my first epoxy mold
The first layup consisted of 1x49 gr. FG, 1x160 gr. Kevlar and 1x80 gr. FG. Although the results is very nice it is much to heavy. 27 grams (almost 1 oz). I want it lighter, preferably 10 grams but realistically around 15-20 grams. In the latter case i will save 15-20 gr. total for two nacelles compared to the Kevlar layup.
Of course it is not necessary to be so focused on the weight here, but it is very easy just to mold a new nacelle and I want to try some different layups. It is cheaper to make test on a small nacelle than on a large fuselage, where the weight matters more.
The next nacelle will probably consist of 1x49 gr. FG, 1x0,8mm balsa and 1x49 gr. FG. Or maybe 1x25 gr FG, 1x200 gr. FG ? Thin Kevlar could also be the way, but I don't have anything on stock.
FG can be layed up much more dry than the thick Kevlar, which is difficult to wet properly out. The fabrics of the Kevlar necelle only weighed 6 grams, the filling of the corners (epoxy+tix+microballoons) weighed around 6 grams, so 15 grams is pure epoxy !! But on the other hand the Kevlar nacelle is almost bulletproof !
|Jul 27, 2010, 04:37 AM|
Have been stalled on the Arado because of other projects like DLG's and a huge CL-215 Canadair. But now on to the Arado.
The plug turned out to be a pain. The surface was to soft and I used to little fibreglass to stabilise it. It required a lot of filling, sanding, painting and so on. I wil use a lot more fibreglass to cover the foam next time, something like 2-300 gr. layup. And some hard coating paint like gelcoat instead of acryllic paint. Much easier to finish.
After that the moldmaking (first half) was easy but took a lot of epoxy and time for mixing..
I was worried about the paint. I choose the RLM 76/81/82 colorscheme, and it was easy enough to find spray cans at the hardware store that resembled the 81/82 colors, but their light blue cans were just to dark, and I couldn't live with that. But I found some spray cans for RC-cars at the local hobby which actually was light blue.
I made a test of the colors on the first engine nacelle that I molded. I found the color scheme satisfying. So now I am very motivated to have a full plane to paint.
|Jul 27, 2010, 01:52 PM|
I was inspired by your thread to update my own
It has a 1 m wingspan (40") and a fuselength of about 90 cm. (36") Trying to keep close to scale. It is easier to try new methods on building on a small scale model. If it goes wrong, then I haven't lost anything else but time.
The expected AUW is creeping up around 900 gr. now, because of heavier nacelles which leads me to expect a heavier fuse.
When I have a finished example I will make an undercarriage for static display
|Aug 15, 2010, 09:29 AM|
Finally I got the fuse molds done. A lot of work I must say.
The result is not perfect, but usable. There is a couple of scratches that I need to deal with before waxing and molding. No big deal.
I learned a few lessons doing this part of the project.
1. Make the plug out of a stable material. Foam easily gets dented and wavy in the surface if not covered with a lot of Fibreglass. I used to little Fibreglass for covering and used way to much time on sanding.
2. The paint must be 2 component and leave a hard finish. This is easier to sand and polish right.
3. Build the mold up with thin layers so it doesn't overheat. Overheating kan warp and give a wavy finish. The latter happened in this case, but not so much that I cant use the mold. I won't be painting in the mold anyway, and a little sanding one the molded result will probably hide this little mistake.
All in all I am relatively satisfied with the result, and glad that I chose a small model to mold. My next mold for a future project will be perfect, or at least better.
|Aug 15, 2010, 03:01 PM|
Hey they look pretty good from here..all the problems you describe can be fixed on the final product with only a small amount of work!..I will be very happy when mine is to this stage!
|Aug 16, 2010, 03:49 PM|
I think that the project will slow down a little over the next months. Started working again after the holidays ended
So I would like to see a lot of posting from your projects, so i can kill some time at work
Started on the finishing on the fusemold this evening. There is some work to be done, but the material is easy to work with.
|Dec 05, 2010, 09:37 AM|
At last I got to do the fuse molding.
As I mentioned earlier there were some scratches and waviness in the molds. I fixed this, but it demanded some work. And the time and motivation wasn't really there. And I wasn't very satisfied with the result.
But finally a couple of days ago..
This is the first molded fuse, just made very simple from 1.25 oz/50 gr. + 6 oz/200 gr. FG cloth and a little carbon.
I didn't mean it seriuosly, just wanted to try the mold out. This layup is to flexy and a little to heavy, but it is almost there. Didn't took me long to make. Weight of the fuse so far: 135 grams.
All the parts together in the mockup weighs 393 grams. Heavy but not way over the target weight. My target for the modelweight is around 400-450 grams, which together with the equipment gives 850-900 grams to a 400W setup.
I can save around 30 grams on a lighter wing, 10 grams on lighter enginenacelles and probably 20 grams on the fuse, but I wonder if I just should fix this one up to fly, 60 grams overweight or not.
Still need to do the glassed nose, installing equipment and a paintjob.
I saw a thread with AEO EDF40 8-blade and something like 3-400 W pr. unit and I am considering two extra engine nacelles with these. They sound better, look more scalelike with smaller intakes. Just an idea, but where do you get these units and which engines to use ?
|Dec 05, 2010, 10:49 PM|
Nice!! she is looking the part now...at that weight it will fly better than you think!..a C model would be cool also..I want to make that an option on mine..
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