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Old Dec 10, 2012, 06:00 PM
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Finding the optimal decalage angle for your desired CG is easy if you do it empirically. If you want to adjust your decalage to zero out trim for your favored CG location:

First adjust your CG to your liking. Once you think you have it, test this setting on windless days (!!!) and make sure you test at least a half a dozen or so flights to confirm the setting.

When you are sure of your CG location, fly the plane and adjust the trim for the desired cruising speed. Land without touching anything.

Carefully measure the elevator angle in degrees. Then calculate how much you have to alter the stab angle to achieve about 1/3 of that angle on the whole stab. Do the decalage mod, moving the stab to that new position.

I have flown Radians with and without the mod. It is a purest sort of thing. Yes the plane flies a little faster with the mod, but all the decalage mod does is eliminate trim drag. That is really important in competition or if you are flying one of those $1000 dollar carbon birds. Of course most of those have full flying stabs so it wouldn't matter anyway.

What is really important is getting that CG back. Focus on that first. Then look at the new trim required. Maybe you will decide you can live with it.

Cliff
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Old Dec 10, 2012, 06:19 PM
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Went to 4 stores today including 2 sporting goods stores and no one had single arrows for sale let alone any CF ones. However I do have some 12" hardwood 1/8" dowels here at the house. Do you all think gluing one of those in on each side of the fiberglass spar in the last 12 inches of the tail boom would do the trick? Or I also got some 2.0mm carbon rod I could cut into 12-14 inch lengths and glue 2-3 down in per side.

Right now the tail boom seems pretty straight. I layed the carbon wing spar up against it and its straight from the end up to the point that the belly of the plane starts curving down. All in all I'm not really wanting to change any angles of anything, just get rid of the flex in the end of the tail boom. It trimmed out nicely the way it was yesterday and was gliding straight.
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Old Dec 10, 2012, 06:50 PM
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United States, MA, Southbridge
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Originally Posted by campbellj View Post
Went to 4 stores today including 2 sporting goods stores and no one had single arrows for sale let alone any CF ones. However I do have some 12" hardwood 1/8" dowels here at the house. Do you all think gluing one of those in on each side of the fiberglass spar in the last 12 inches of the tail boom would do the trick? Or I also got some 2.0mm carbon rod I could cut into 12-14 inch lengths and glue 2-3 down in per side.

Right now the tail boom seems pretty straight. I layed the carbon wing spar up against it and its straight from the end up to the point that the belly of the plane starts curving down. All in all I'm not really wanting to change any angles of anything, just get rid of the flex in the end of the tail boom. It trimmed out nicely the way it was yesterday and was gliding straight.
Personally, unless you do a full boom replacement spar, i don't see the last 12" doing anything other than shifting your CG rearward. You are just moving the flex point further forward on the boom. You could put a properly sized dowel inside the FG tube (full length) that is there now to stiffen it further. Look up archery supplies in the yellow pages and call them.

YMMV
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Old Dec 10, 2012, 06:51 PM
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The thing about arrow shafts that makes them so amazing is that archers are just as fanatic as we are when it comes to weight/stiffness ratios. A 6 dollar arrow will blow away any wooden dowel or CF rod and will be about the same weight as the fiberglass spar that you remove. Maybe you could get a hold of an archery club and somebody would be glad to sell you one, or give you one that has a broken end. Another possibility is fishing supply stores where somebody might have a broken fishing rod. (Another source of high-quality CF tubes). Have you tried checking with a gun-shop? They often sell archery supplies as well.
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Old Dec 10, 2012, 06:52 PM
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Originally Posted by Jovanx View Post
The thing about arrow shafts that makes them so amazing is that archers are just as fanatic as we are when it comes to weight/stiffness ratios. A 6 dollar arrow will blow away any wooden dowel or CF rod and will be about the same weight as the fiberglass spar that you remove. Maybe you could get a hold of an archery club and somebody would be glad to sell you one, or give you one that has a broken end. Another possibility is fishing supply stores where somebody might have a broken fishing rod. (Another source of high-quality CF tubes). Have you tried checking with a gun-shop? They often sell archery supplies as well.
If there is a kite shop locally, they use CF tubes for keels and spars
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Old Dec 10, 2012, 07:34 PM
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Maybe you could get a hold of an archery club and somebody would be glad to sell you one, or give you one that has a broken end.
+2.
At our archery club there's a trash barrel full of arrows that are slightly damaged or were found in the woods. They'll be happy to give you as many as you want. You could also post on CL. Most archers have a few lying around.
Don't buy one unless you have to. They're @ $10. If you have to, go to Walmart or K-mart. They're crappy arrows (not as perfectly straight as good ones) but will be fine for this purpose.
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Old Dec 10, 2012, 07:37 PM
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United States, FL, Port St Lucie
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Originally Posted by coreman View Post
If there is a kite shop locally, they use CF tubes for keels and spars
Not that we have a kite store but I got a kite I purchased from a kite shop years ago that I never fly anymore. After you mentioned that, I went to the garage grabbed the kite and its got 3 CF rods, 1/8" diameter that's 45" long each. Would it work if I put one of those on each side, or one on top of the other for the entire length of the fuse? They have some flex if I'm flexing them from each end, but gripping the rod 20" or so apart it hardly flexes at all.
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Old Dec 10, 2012, 07:42 PM
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Originally Posted by Brian VT View Post
+2.
At our archery club there's a trash barrel full of arrows that are slightly damaged or were found in the woods. They'll be happy to give you as many as you want. You could also post on CL. Most archers have a few lying around.
Don't buy one unless you have to. They're @ $10. If you have to, go to Walmart or K-mart. They're crappy arrows (not as perfectly straight as good ones) but will be fine for this purpose.

I'm googling archery clubs now. Walmart was one place I went today, they had nothing, there is a Kmart close to my job I will try tomorrow.
I was surprised to find out no one at my job hunts either.

One of the sporting goods stores had 3 packs but they were fiberglass, not carbon and I pulled one out of the package and it seems to weigh a lot, so I passed on those too.
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Old Dec 10, 2012, 08:17 PM
Tossing planes into the snow
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Originally Posted by campbellj View Post
Would it work if I put one of those on each side, or one on top of the other for the entire length of the fuse? They have some flex if I'm flexing them from each end, but gripping the rod 20" or so apart it hardly flexes at all.
There is no question that a hollow tube provides a better stiffness/weight ratio than a solid rod. It's is only a matter of time before you track down a suitable arrow shaft. My advice would be to do the other mods, one at a time, and do lots of flying in between. There is no rush, as it is already a great flying airplane. The more time you spend flying with the stock setup, the more you will appreciate the performance increase that the mods provide.
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Old Dec 10, 2012, 08:37 PM
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Originally Posted by Jovanx View Post
There is no question that a hollow tube provides a better stiffness/weight ratio than a solid rod. It's is only a matter of time before you track down a suitable arrow shaft. My advice would be to do the other mods, one at a time, and do lots of flying in between. There is no rush, as it is already a great flying airplane. The more time you spend flying with the stock setup, the more you will appreciate the performance increase that the mods provide.
Good advice and very true. Thanks for talking some sense into me, lol I can tend to be a little over anxious at times to get stuff done.
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Old Dec 10, 2012, 09:24 PM
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Originally Posted by campbellj View Post
Good advice and very true. Thanks for talking some sense into me, lol I can tend to be a little over anxious at times to get stuff done.
I agree with Jovanx on this for sure. Fly her stock at least until you get comfy with the plane. Then make improvements where you want them. If you don't, then how will you know if the mod is an improvement?

My pick for first mod is a stiffer wing spar (CF Arrow shaft). It makes a world of difference. H/T to Jovanx on that one.
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Old Dec 10, 2012, 10:03 PM
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I agree with Jovanx on this for sure. Fly her stock at least until you get comfy with the plane. Then make improvements where you want them. If you don't, then how will you know if the mod is an improvement?

My pick for first mod is a stiffer wing spar (CF Arrow shaft). It makes a world of difference. H/T to Jovanx on that one.
I bought a replacement wing joiner and I got a square piece of carbon tube for the tail, but after launching my RP with a camera facing rearward, I don't see a lot of boom flexing and by moving the CG rearward I am getting arrow straight climb outs with no nose up tendencies and so the tail support (and wing tube actually) is still sitting on my bench. My only mod so far has been to upgrade the ESC, prop and spinner and tape 2 quarters under the stab to move the CG
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Old Dec 10, 2012, 10:27 PM
Tossing planes into the snow
Canada, BC, Smithers
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I believe that one of the reasons this plane is so popular is because it means different things to different people. Many people see a way they can make it better for their particular needs. Some like to make the wings or the tail stiffer, some like to put a different prop and spinner on, and some like to add smoother control rods, cameras, or paint for better visibility. Many are happy with it right out of the box. We all end up getting what we want in the end.
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Old Dec 11, 2012, 02:39 AM
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I think i posted this awhile ago, But a viewer noted a few gun shots...When i was watching/replying the raw file i heard the sound but didn't know what it was...turns out its gun shots..i uploaded the video, then a few days after one of my Subscribers pointed it out. I've heard gun shoots before on the farm across the way, wasn't sure if they were shooting cows or just messing about target shooting..i guess the nice lights made for a great one. im glad there aim sucks lol...
RadianPro Tail View (11 min 53 sec)
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Old Dec 11, 2012, 10:04 AM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Speaking of guns...somewhere in the back of this thread is a bizarre story of a farmer who shot down 3 rc planes and then threw them in a pile and burned them. I stumbled across it when I was doing a search, and it went back to a time before I got my RP. It was the craziest story and it went on for pages...they went to his house and tried to talk him into reimbursing them for the planes, and then one of the pilots challenged him to a contest where it would be gun against plane and the winner takes all. At the last moment the farmer pulled out of the contest because he didn't want to risk losing his favorite gun.

In the end the guy did give them some money and then said he wanted to learn to fly so they taught him and a new pilot was born and everybody lived happily ever after. I don't know if I believe any of it, but it was an entertaining read. A few minutes ago I tried to find it here and on the Radian thread, but I couldn't come up with the right keywords.
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