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Ply Rolled Fuselage Part Deux - 1/2A " Mini Skorch "

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Ply Rolled Fuselage Part Deux - 1/2A " Mini Skorch "

Old 08-06-2014, 12:00 AM
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Pond Skipper
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Default Ply Rolled Fuselage Part Deux - 1/2A " Mini Skorch "

Well its time to move up to the next size power plant - 1/2A class using a Ply Rolled Fuselage - therefore I dub thee the " 1/2A - Mini Skorch "

I welcome all to follow along and enjoy the ride as I sort out the next layer of plywood rolled fuselage design / builds.
The first version flew up into the mid 60's with a 3ch stock TD .020 and is a great small field plane.

I have 4 different 1/2A engine brands to try on the nose of this craft if need be using a 1 oz fuel tank for duration.
Rpm ranges from 22k up to 36k should I want to push past 100mph.

Here are the first few stages of the build starting with a simple doodle for this 4ch plane.

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Old 08-06-2014, 12:54 AM
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Skorch may skritch off into the wild blue yonder with a G Mark .030 to get the wings wet and to see what that lil engine can do.
Fuselage as shown 17.5in wing span should be around 28in. Root cord at the wing saddle is 4in plus anticipated 1 1/2in for aileron - will be tapered wing.

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Old 08-06-2014, 07:48 AM
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The schneurle in the back with the red head looks like the quickest. Later I guess. 1/16" ply?
Old 08-06-2014, 11:20 AM
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Hi Aspeed ty for checking in,

The ply is 1/32 / .08mm there will be a inner layer added up front going back into wing saddle area may go with just 1/16th for this not sure yet.
Unlike the first generation this one will have a cut out cockpit and pilot since I will have more power on tap to combat the added drag.
Is also a great spot to hide the charging jack and arming switch from oil. The goal is a fast acro speed type model with a tapered ailerons and rudder.


Yes the rear exhaust CS is rated to 38k but don't expect to push it past 34k to keep it from stressing the components. I have a sport RC CS as an option.
I may stop at the Norvel which should have enough zip to keep me content and save the CS for a more refined purpose built plane with a tuned pipe.
Old 08-06-2014, 07:47 PM
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I had used a PVC pipe on the first build this one I used a miniature Louisville Slugger Baseball Bat approx 1/4 scale. The bat has a nice continuous taper allowing less manipulation then the first build. Using hot water I have allowed the ply to dry overnight for 24hrs.

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Old 08-06-2014, 08:05 PM
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Howdy PS.......That bat might be pretty valuable............http://www.baseball-reference.com/pl...aedeed01.shtml

The legend that surrounds this publicity stunt has a couple versions. The funniest version I've read has the owner of the ball club giving Eddie strict orders not to swing, no matter what or else a sniper on the roof of the stadium will shot his cap off.

Is fiberglass a "banned" substance for this project..?
It would be an easy way to beef up the fuselage from the inside.

Last edited by combatpigg; 08-06-2014 at 08:17 PM.
Old 08-06-2014, 09:57 PM
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Hey CP thank you for that info - that bat was my Dads so off the market one way or another I now have a new use for it lol.

The first ply fuse took a nose dive at full throttle when I had a switch harness failure nothing but a broke prop smacking into hard dirt /grass field.
The nature of the design makes for an instant strong fuse with 1/32nd ply. Now installed 5 lam 3mm firewall and one former is already is very stout had this been a balsa build I would be grabbing a roll of my thin stuff to work inside the fuse. In this case i'm going to be done very quickly with little to glue its a unique way to construct that leaves the builder with a smile in short order. Im at 26g so far should end up around sub 38g less landing gear. 4ch build hope to be under 11oz RTF.
Old 08-06-2014, 10:40 PM
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Slipping in the wing saddle secondary ply reinforcements seal the deal for strength at the firewall landing gear mount and add surface area for the bottom sheeting . It also leaves the option to use a nylon bolt to hold the wing down in the rear should forego rubber bands. I dooo like bands they save wings! But like most of us designers we find them ugly fugly indeed. Note the firewall was shaped to suit the footprint of the most common round engine mount. I don't like square mounts as they tend to have you building box fuselages.


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Old 08-07-2014, 12:15 AM
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37g difference in weights with these engines there is an engine on a test stand in the running should be around 62g. Approx 150w down to 50w range in power.
Saddle strips installed one former to add in the tail and landing gear mount. Need to install the pushrods there after so I can sheet the bottom with thin Finland Birch 1/64th ply.
The only balsa on the fuse will be the headrest per original doodle unless I form it with 1/64th to stay the all ply course lol.
Fuse as shown 29.7g has become very rigid upfront - lesson learned to block oil weeping I will add one more 32nd sheet of ply to seal the fuse skin laminations at the firewall.
I had multiple coats of fuel proofing yet on the Lil Speedy oil wicked into the lams. The extra sheet will have me at a 3/16th firewall strong enough for the Norvel!

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Old 08-07-2014, 03:48 AM
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Out of those engines I would go with the Norvel, but the helicopter throttle is heavy and awkward to hook up...

Which engine gives you 150W?
Old 08-07-2014, 05:17 AM
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Hi Mr. Cox thank you for checking in,

There is a RC Carb on the Norvel I need to remove that portion of the muffle (it did come from a heli engine I have). I may try to tap out the side tube and press fit a 9mm ID aluminum tube over that area to block off the open holes or just dremel off that entire section just in front of the side tube.The AME Norvel has a Nelson head conversion, Im guessing on the watt range hence approximate 50w to 150w. If you have dyno data with a Nelson plug please share.
Old 08-07-2014, 05:41 AM
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Nope, sorry I don't have any Nelson heads or plugs...
I posted some rpms in the other thread about Norvel engines, these typically put out around 90-95W (by using the power_prop_calculator from Peer Riever). The Norvel .074 puts out around 135W though.

There is another engine that might interest you, the MP Jet .061BB is being made again and these are at least as strong as the Norvel .061, perhaps even a little stronger on regular sport props. There was a high tuned version of these too, but it is not made anymore.

Last edited by Mr Cox; 08-07-2014 at 05:43 AM.
Old 08-07-2014, 07:04 AM
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Thank you this is helpful. I have the AME. 061 with the Nelson head and plug. With a APC 4.1 x 4.1 does 26k exceed your findings thus far?
Old 08-07-2014, 07:47 AM
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I haven't gone below the APC 4.7x4 prop, yet, but that will give around 22000rpm with the stock muffler and carb. So 26000rpm on the 4.1x4.1 sounds reasonable (about the same power). For a real screamer I think the mods by Toadsrc would be the way to go.

Most of my planes, so far, are too draggy for props below 5", but I'm working on a "sheet wing racer" that's almost ready to go, just needs an engine cowl;
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Old 08-07-2014, 08:19 AM
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Hey that looks sexy. What is the span and SQ's?
What engine are you going with?
Old 08-07-2014, 10:28 AM
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It is about 23" span with an area of about 90 square inch. I think I might have gone a bit too small but I wanted something that is faster than my Morris "Yellow Jacket". Total weight will be around 9oz (a little too much paint I guess) and I'm putting a Norvel .049RC in the front to begin with. I can always update to a .061 later if it flies well...
Old 08-07-2014, 11:27 AM
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I think that will work just fine Kris, I like the wing tips great effort in all regards, do you have a build thread going on this one?

My design goals are 80 Sq. in - will stretch to 28in span 11oz as a 4ch.
I have not drawn up the wing yet my constant thus far is the saddle at 4.2 in + 1.5in aileron at the root then tapered. I need to math this one out yet.

Last edited by Pond Skipper; 08-07-2014 at 11:30 AM.
Old 08-07-2014, 01:13 PM
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A Profi .061 will give you 34k on a 4.2x4 on 10%.. sans throttle of course

I like these rolled fuse models - nice change from the usual. I have a '60's-'70's RCM somewhere with a rolled ply fuse .60 sport/pattern model, should dig it out and scan.
Old 08-07-2014, 01:15 PM
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Originally Posted by Mr Cox
It is about 23" span with an area of about 90 square inch. I think I might have gone a bit too small but I wanted something that is faster than my Morris "Yellow Jacket". Total weight will be around 9oz (a little too much paint I guess) and I'm putting a Norvel .049RC in the front to begin with. I can always update to a .061 later if it flies well...
Too small? Nah.. the little POS I built 3-4 years ago with a single ACE wing panel and about 10-11oz flew great and glided very comfortably. I ripped out the Sure Start and one day I'll fit a throttled TD or AME in the front to perk it up.
Old 08-08-2014, 01:40 AM
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Hey Mike thank you for the feed back would be interesting to see how that plane was constructed for a .60 without question the airframe will have to hold up to some power.
The Mini Skorch may have its big brother "The Skorch" a .15 size build log done in the future as I have a never ran Mk II collecting dust.

I put the legs on today again like the Lil Speedy seems a tad lanky but once the wing is mounted in this low wing config there should be good clearance when landing in the grass field where I fly.
For now I have the CS .061 mounted with a 6 x 3 prop should give enough power to test it out in sport flying mode. 1.5in foam wheels seems reasonable.
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Old 08-08-2014, 01:47 AM
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On a side note since its so hot in Texas I think it would be best to just run the engine without a cowl. Hit a 100 deg here this week already arrroooooo...
Old 08-08-2014, 02:54 AM
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You'll need to bench run that engine before you make any further plans for it. They have the lowest quality control that I have ever seen in model engines. Even if you are lucky to get a decent one, it will still need lots of running in before it can be used for anything...
Old 08-08-2014, 05:33 AM
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Yes have read some horror stories on them. I have taken it apart thus far and looks ok turns over ok. No pin hole leaks anywhere in the case or bad threads.Rod and pin look good line up and float well. All the same will hold my breath.
This generation engine while under the wing of the original owner had made some good running engines sourced this from Japan. I have the CL version and the Speed version too.

I'm using the round 1/2A engine mount to swap out and try different engines and brands as I go along all have the control arm for the RC carbs on the left. Also keeping with the 6x3 for thrust / less rpm as not to stress it.
Old 08-08-2014, 06:01 AM
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Here is a little bench run of one that I actually flew with (about 6 years ago, time flies...); http://www.rcuvideos.com/video/CS-061-RC
Old 08-08-2014, 11:56 AM
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Thank you Kris,



http://www.rcuniverse.com/forum/1-2-...rc-engine.html



http://www.rcuniverse.com/forum/1-2-...rc-engine.html



two threads on it..
I had found a 5 page thread on this engine a while back is why I sourced one to give it a go as it appears the carb and muffler could be used on other engines. I didn't have to pay much for the one I found still in the box never ran. Everything looked good so kept it intact to test. Best data thus far for the RC .061 is 19k with a 6x3 after mods. Some saw 16k stock. Should be fun to mess with it least for now.

Last edited by Pond Skipper; 08-08-2014 at 12:00 PM.

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