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Post  OVERLORD Sun Sep 29, 2013 9:21 am

This is how I found the wing after cutting open the covering:

Repair of the JR SATAN Imgp4817

After removing the bits, this is what was left of it:

Repair of the JR SATAN Imgp4819

In order to do some damage analysis to check if the construction could be improved or find out how it broke, I puzzled it all together again. You can see 3 impacts on the leading edge where the tree hit the wing. The leading edge broke in way of the rib notches.

Repair of the JR SATAN Imgp4824

Repair of the JR SATAN Imgp4820

That were the weakest points of the LE, but why? The ribs were not glued properly to the LE. I used CA glue after assembling LE and ribs and thought the capilary action would take care of the rest. Not quite!!No! The ribs were only glued at their surfaces and in the corners where they meet the LE, so no penetration at all! The forward rib edges are mostly still in 1 piece.

Repair of the JR SATAN Imgp4821

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Next thing to do is getting new balsa to start repairing!

Lieven
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Post  ian1954 Sun Sep 29, 2013 9:46 am

Hi Lieven,

I have had a close look it the pictures and the way the wing has broken. Although I wouldn't expect a model to fare well after hitting a tree - It looks as if the balsa, particularly on the leading edge, is soft. The grain or figure looks soft - not the best choice for a leading edge especially if you have cross cut part way to accept rib.

Here we have hard, medium and soft balsa.

Repair of the JR SATAN Balsa_10

I would always suggest hard balsa for the leading edge and medium for ribs. Hard balsa can be over 4x the weight of soft and medium over 2x. Also a lot of sheet balsa varies in the sheet itself.

Rgds,

Ian
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Post  roddie Sun Sep 29, 2013 11:02 am

Lieven, Don't forget... hard balsa and excess glue add weight! Your building skills are incredible. I believe that if you had a hard balsa leading edge, there could have been more serious structural damage that "might" have even been hard to detect. It's fairly plain to see that the damage is localized to that area.

In my opinion, your wing "as built" had the perfect "crumple-zone" for such an impact. The spar looks undamaged... and that's really the only part where you want the most strength in a wing. The replacement L/E could be joined near the root, with a short (1") piece of aluminum tubing roughed-up and "dowelled" in, for support. Keep your repairs "A"-grain lightweight balsa. On internal structures that have broken or need strengthening; I cut small patches of fiberglass window-screen mat'l. and bridge the joint/break... "tacking" with CA... then brushing-on epoxy using a short-bristled plumbing flux brush. It forms a lightweight and very strong patch.

Here's a photo that shows a joint that I chose to strengthen in this way.

Repair of the JR SATAN <a href=Repair of the JR SATAN Dsc06714" />
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Post  Cribbs74 Sun Sep 29, 2013 3:24 pm

It looks to me that the leading edge notches were cut a little deep. It may just be the picture though.

The good thing is it's a quick repair.

Ron
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Post  ian1954 Sun Sep 29, 2013 3:42 pm

It seems that me and Roddie have opposing views on builds. Roddie prefers crumple zones and I prefer aeroplanes that will bounce of the ground.

My favourite control line, apart from "Blue Pants" was the "Dominator" - the Dominator was a survivor. Definitely hard balsa leading edge! Although some used soft balsa at the front of it because it was easier to sand but only for the rounded portion. You can see this in the contructor's link below.

http://www.flyinglines.org/kb.dominator.html

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Post  duke.johnson Sun Sep 29, 2013 6:18 pm

Ken is one of the guys we fly speed and combat with. Most of the combat guys around here fly the dominator in D-bat. they are very tough.
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Post  roddie Sun Sep 29, 2013 9:07 pm

ian1954 wrote:It seems that me and Roddie have opposing views on builds. Roddie prefers crumple zones and I prefer aeroplanes that will bounce of the ground.


Wow... c'mon Ian... I had 2 gigs this weekend, and I'm tired. I looked forward to coming home to our beloved forum I.S.O. some "Love" lol!
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Post  OVERLORD Mon Sep 30, 2013 9:13 am

Cribbs74 wrote:It looks to me that the leading edge notches were cut a little deep.

Ron
Ron, That's because the piece of balsa I used was wider than the leading edge on the drawing while I left the ribs the same size. That's also the reason why there is a flat part on top and bottom. The centre sheet of wood should in fact butt against the back of the leading edge with a rounded flare. Because the LE is wider, I glued the centre sheeting on top of the LE and sanded it.

Repair of the JR SATAN Imgp3311

When I bought the wood to make the model in Jan of this year, I was still the unexperienced balsa buyer: as long as the dimensions were ok, that "wood" do for me. Later, by reading other plans and posts, I realised that the LE wood was indeed soft but light. So that's the way it went.

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Post  Cribbs74 Mon Sep 30, 2013 9:55 am

Lieven,

I hope you don't think I was criticizing. You did an excellent job with the build. Much better than I can do. I was just trying to figure out why the wood gave way so much.

In reality you hit a tree and even hard balsa would snap given the same scenario. Here's to a quick rebuild!


Ron

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Post  OVERLORD Mon Sep 30, 2013 10:54 am

No, you weren't criticizing, the grooves are deeper indeed. I think the whole would have been a little stronger if the ribs were properly glued into the grooves, but would that have resisted the tree, no, I don't think so. I just wonder, to avoid such things again, how do you stay on the same spot while turning round and round and round?

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Post  roddie Mon Sep 30, 2013 11:27 am

OVERLORD wrote: I just wonder, to avoid such things again, how do you stay on the same spot while turning round and round and round?

Lieven
Hi Lieven, I used to have to fly 1/2-A in a small side yard. I had about 60 ft. to work with... between the house, a stone wall, shrubs and a tree-line. I measured-in 30 ft. for the center of the circle, where I used the "lid" of a 5 gal. pail with hole drilled through the center to accept a long (8") aluminum gutter nail. Hammer the nail through the lid, into the grass/dirt... and you have a reference point to feel with your foot. It takes a little getting used to at first... but soon becomes second nature. I used 25 ft. lines... and although there "were" times I got a little dizzy, I never hit anything... because I always had a 5 ft. "safe-zone" to work with. Maybe that's a little "tight"... but it worked for me.

If you paint the lid "green"... you can leave it in place and just trim around it when you do your lawn-mowing. That way, it isn't real noticeable... and you don't have to measure-off every time.
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Post  Cribbs74 Mon Sep 30, 2013 12:03 pm

Lieven,

The dizzies go away after a while. In your case you had multiple problems as the plane wasn't flying right so you were spinning and fighting at the same time.

Roddie's suggestion about marking the center is a good one. Some use a rag or other things. I use a paver stone as it doesn't move.

Once you stop getting dizzy you don't move much off of center anymore.

Ron
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Post  RknRusty Mon Sep 30, 2013 3:07 pm

I use a big square piece of white sweatsuit material. It stays put, and after I do a wind dance, I can see it out of my peripheral vision and work back to it. If I can't see it, I know I'm right there.

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Post  OVERLORD Thu Oct 24, 2013 2:02 pm

OK, I'll make myself an artificial spot to use as a reference, and even better, choose a place without trees. Below some pictures of the repairs still going on.

After cleaning the bits out, I shaped the edges of the LE flat and square and glued in a new piece of balsa. I cut out the rib parts, beginning at the spar up to the LE, cut out the holes for the lead outs and glued the ribs in place with brackets on both sides for reinforcement. The broken parts behind the leading edge will be filled in separately.

Lieven

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Repair of the JR SATAN Imgp5210

Repair of the JR SATAN Imgp5211
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Post  roddie Thu Oct 24, 2013 3:34 pm

Glad you're fixing her up Lieven... Looks real good!

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Post  OVERLORD Fri Nov 15, 2013 11:46 am

The woodwork is finished. I'm waiting for the Oracover to arrive. I've also cut out a bit of the elevator hinge material as this is rather heavy piano wire. After cutting, I put the pieces on the scale but that indicated 0. It must have some effect, I think.

Lieven

Repair of the JR SATAN Imgp5611

Repair of the JR SATAN Imgp5710
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Post  roddie Fri Nov 15, 2013 2:34 pm

SUPERB Lieven!!! Clapping The lap-joint on the l/e must have taken some time. It all looks beautiful!
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Post  Cribbs74 Fri Nov 15, 2013 6:06 pm

I like it!

Now cover and fly!!!!
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Post  OVERLORD Fri May 09, 2014 9:27 am

The Jr Satan is repaired and covered. Last time when it came down after hitting the tree, I found that the engine crankcase bolts were loose. I fixed everything and did a test run with the 8x4 prop: all went well. I hope to fly  soon.

Repair of the JR SATAN Imgp8914

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Post  getback Sat May 10, 2014 8:20 am

Nice repair work Lieven , looks good and strong... I am using chalk for line refill to mark my center .. so far I only need it for the 42' circle but I am thinking I can fly up to 54 ' were I am at in the back field behine the house! what are your line length ? Getback Biplane
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Post  RknRusty Sat May 10, 2014 9:17 am

That Satan is bigger than 1/2A, so probably 52'. I'm looking forward to seeing it fly again. Getting through the launch is the hardest part with those. If it goes straight up, just let it go and back up. It'll probably tighten up and fly.

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Post  Ken Cook Sat May 10, 2014 10:06 am

One thing I would do due to earlier problems. Tape a quarter on the outboard wing tip with clear packing tape and add 1/2Oz. of nose weight. You could always remove these but it will keep down the sensitivity issues until you get used to the plane. Ken
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Post  roddie Sat May 10, 2014 12:01 pm

Lieven, now I can see why you and Ken were so interested in my Voodoo. The Jr. Satan is a very similar design.. a little smaller?

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Post  OVERLORD Sat May 10, 2014 1:33 pm

My lines are 15 meters I think. I prepared already a 15g, which is near 1/2 oz, and also a 20g weight to fix to the nose. I'll tape some coin on the wingtip too. I also binned my self made handle.

To me, both Satans and the Voodoo are very good looking. I don't know why but they seem to look much better than other combat planes. The Jr Satan has a 29' span. You can find the drawing on Outerzone. That's where I got my plan from:  http://www.outerzone.co.uk/plan_details.asp?ID=1816

I'm gonna give it a try as soon as the weather gets better. We have rain and a lot of Wind at the moment. I hope I can fly across the road instead of my neighbours garden. At least there are no trees that can move into my way. I maybe have to wait until they cut the grass 'cause that's rather high at the moment.

Repair of the JR SATAN Imgp8915

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