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Old Nov 18, 2012, 04:57 PM
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20 /25 size class

Hi

Do you thank we will have a 20 / 25 size pattern classs?
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Old Nov 18, 2012, 06:05 PM
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I honestly don't know. I am sure if there were enough interest, and in this day and age of smaller flying fields and electric power, a .25 class might have a future.

SpadCat
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Old Nov 19, 2012, 12:23 AM
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SC,

Well done and glad to hear you're enjoying the wee Birdy.

Did you leave the underside open for access to the motor and battery through the retract bay? I'd be interested in seeing your gear layout and install.

David
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Old Nov 19, 2012, 06:42 PM
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I installed the gear as a tail dragger, even though I have a nose e-retact. Just makes for less complications. Taxiing is real easy and take off takes very little rudder input. In a crosswind, it might be more of a handful, but that would be part of the fun. Plus she sits real pretty with the nose up in the air.

SpadCat
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Old Nov 19, 2012, 07:10 PM
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SC,

By gear I actually meant the motor, ESC and radio. Access to these components is always interesting to adapt with the classics.

Could you snap a couple of pics showing the "guts"? It might give me some good ideas.

Thanks, David
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Old Nov 19, 2012, 08:28 PM
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OK, here you go.
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Old Nov 19, 2012, 11:44 PM
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SC,

thanks for the pics - now I understand. Do you have capability to install and remove the motor from the front nose ring?

It's a smart way to do it if you do. The X-mount can't come out (usually) but so long as the can slips through, then you can bolt it down to the mount from the battery compartment or even from the wing saddle area with a long driver.

I'm considering a hatch on the top with a split canopy more akin to how the Super Pacer is done. This is mostly though because I'm thinking trike gear with a nose retract. I am also planning a glass cowl which is magnet mounted much like is done with several ARF's these days.

I drew up templates for the cowl so that 4 small blocks of foam in the corners allow the "plug" to be produced and then painted and glassed. If done properly, the plug should be re-usable to make additional cowls. I put a "pull tab" on the plug so it is hopefully easier to pull from the glass work once it sets up. Good old wax and PVA will naturally be required.

There are still a few more things I want to iron out on the e-conversion though. Attached it's where it's at for now.

I think I might also drop down to series 4000 Spektrum servos (4) rather than the larger and more powerful 5000 series now shown.

David
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Old Nov 20, 2012, 09:00 PM
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To take motor out, I have to cut the cowling off and then reattach and refinish. Actually not that big of a job as long as it is only once in while. The enlarged nose ring may be something to consider in the future. An electric motor should have zero maintenance except in a crash. If you come up with a fiberglass cowl for sale in the future, I might buy one.

I am not at all missing the nose gear as the conventional gear works beautifully on this plane. It even looks good, even though I have been one that likes a tri-geared pattern ship. Taxis real well, take off tracking is excellent and landing is not a problem at all.

The top split canopy will work well as it does on the Super Pacer.

Not sure of Spectrum servos, as I have never owned one. I have been using Hitec HS-81s with no problem. Heck, we used HS-81s, even with one aileron servo in combat planes with tuned piped OS .25s and never lost one due to a servo failure except during a crash, and even most of those servos survived if they were metal geared.

SpadCat
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Old Dec 15, 2012, 03:48 PM
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Hey David,

Been doing a lot of flying with both the Tweety Bird and Super Pacer and as much as I always liked how the SP flies, the TB is just a better flying plane in every aspect. I thought with my limited pattern skills I would not be able to tell the difference, but I sure can.

For your Tweety Bird plans, you wrote that you were not sure if you would draw up a built up hor stab or a flat one....well, I can tell you the built up makes the DB fly so much better. It is really noticeable on take offs and landings. The DB always lifts off before I think she is ready in a towed sail plane sort of way. It lifts off really flat, kinda levitates at a very low airspeed. Sure, I can hold her on the ground and rocket up also. Landings are quite a bit slower then the SP. While it takes more time to build the built up stab, it seems to be really worth it.

Lon
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Old Dec 15, 2012, 06:04 PM
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Lon,

Glad to hear that you've been enjoying the pair of them.

Good info on the TB stab too. I've actually settled on my final planform for the bird which is going to be a tad experimental since I've made some minor changes which may impact flight in a hopefully positive way. I'm actually drawing on experiments I did 25 years ago with models I used to scratch build with a bud. They were invariably 15-25 size models on 2-4 channels. I often found the models I scratched based on RCM plans to be squirrelly until I modified the tail end. After the mods, they always flew better until I started changing the planform from the start. Maybe it was just how I liked the plane to fly and respond. They would fly on wing and stab, tracking, rather than responding to pitch and roll on the wing alone.

With that said, I was still on the bridge about the stab and thought that I might just build an airfoiled stab for my bird. Granted the scaled DB plans have a pretty thin airfoil but the overall stab is a fair but thicker than the 3/16" sheet stab of the original.

Did you use scaled DB20 plans for the stab ribs? I'm going to design it do that it's fast and easy to build - two halves, 5-6 notched ribs, no spars, 1/16" sheeting. Optional anhedral center rib guide for fun.

Remind me, is the wing top flat or is there more dihedral to it than that? I'm on my phone at the moment...

David
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Old Dec 15, 2012, 11:35 PM
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You could always draw up both flat and built up stabs so each builder could choose their preference.

I used the DB20 plans for the stab with little modification. I posted somewhere that the built up stab was quite a bit lighter, but don't remember the numbers. The ribs did get a little small, but the finished stab is still quite a bit thicker then the flat stab. I used a mixture of yellow glue and balsa dust to beef of the butt jointed sheeting to the leading edge which helped strengthen that area.

There is a small amount of dihedral added to the wing. I think I used a pencil at the center joint with the wing panels upside down. The spec is on one or both the TB or DB20 plans and will check it out. I had not glued the center ribs in until the dihedral was set, so they could be glued together without a gap.

It will be interesting to see your new and improved version of the tail section. Most of my planes in the future, except flat slow flying 3D foamies, will have a built up airfoiled stab.

I just completed a 4th Formosa ARF (2nd for myself), and it has an airfoiled stab. This one features the new EPO foam and it is a delight to work with. Much better then the old EPS versions.

SpadCat

PS an anhedral stab would be cool!
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Old Dec 16, 2012, 10:16 AM
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David,

The Tweety Bird plans show 1/4" at center of wing. The DB .20 shows nothing. I built the DB 20 wing because it was a little shorter and a little wider.

Lon

edit: but with the 1/4" at center of wing
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