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RE: CoroCub - a little bigger one. - 10/7/2007 6:00 AM   
RysiuM



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Status: offline 		Here is the new update. I just finished the landing gear. Of course I made my own one - I'm cheap.

First I bought 6061 aluminium plate 4.8mm thick - the weight was 2 lb so I paid 6 dollars. I cut the shape out of it and bent it using one yard long piece of two-by-four and heavy duty vise. This landing gear is twice stronger than in my 15lb H9 Edge yet it weights only 16 oz. Add to it 6 inch Du-Bro wheels and axels, and the whole LG weights about the same as my engine But it is plenty strong for that plane - free fall from 3ft proved it.

With added pieces of coroplast screwed to the sides of the LG now the plane really looks like Piper J3 Cub. All pictures below.

1. One piece landing gear cut and bent to shape.
2 LG mounted on the plane
3. 3/16 axels screwed in
4. Landing gear is screwed with five metal 1/4 screws to blnd nuts in the fuselage (three on the back, two in front). Two front screws are going through gutter pipe engine mount.
5. Piper J3 Cub.


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RE: CoroCub - a little bigger one. - 10/8/2007 2:41 AM   
GravityTester



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Status: offline 		Looks great. when is it going to fly?

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RE: CoroCub - a little bigger one. - 10/15/2007 6:41 AM   
RysiuM



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quote:

ORIGINAL: GravityTester
Looks great. when is it going to fly?


Thanks. It will be soon. few weeks or so (I'm not retired and have to work for my living )

So far I'm solving small isses one by one. I figured out how to mount a top cover on the nose, so I can have easy access if I need. Also I mounted the windscreen (no glue, just screws). Then I had to take care of my engine and make a new spacer under the carb. The original was quite bulky and made the throttle arm in very weired position. New spacer rotated carb 90 degrees what allowed me to simplify the throttle linkage.
Now I'm working on the hlow plug power circuit. There will be two 3600 NiMh batteries, a swich and a power-on indicator. I will post pictures soon. So far here is the front deck and the windscreen.


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RE: CoroCub - a little bigger one. - 10/16/2007 10:39 AM   
mikenlapaz



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Status: offline 		Nice work. I like your main landing gear. Those control horns should stay put.

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RE: CoroCub - a little bigger one. - 10/20/2007 10:03 AM   
RysiuM



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Status: offline 		Here is the update. I fixed broken muffler - I hope this time it will hold. I also made new carb spacer and that allowed me to simplyfy the throttle linkage. I finished ignition circuit (it is glow plug that is powered all the time) and plumbing (for gas-glow). As a nice touch I added engine cowling made of .... coroplast.

So here are some pictures below:
- carb spacer
- engine mounted
- muffler fixed
- overal view from three sides

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RE: CoroCub - a little bigger one. - 10/21/2007 2:31 AM   
RysiuM



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quote:

ORIGINAL: RysiuM
The wing is mounted with four 1/4 -20 screws. I wonder, what is the strenght of 1/4 nylon screw - can I use them or should I use metal? I estimate that RTF plane will be between 12 and 15 lb


Can someone answer me that question? How strong are 1/4 nylon screws? Will they hold or break?

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RE: CoroCub - a little bigger one. - 10/21/2007 9:46 PM   
neflyte3


 

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Status: offline 		Shouldn't be a problem I used 4 on my bud nosen trainer wing and I would estimate its approx the same weight. My experience with metal screws is that they can and will back out with vibration. I have never seen a nylon do that yet.

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RE: CoroCub - a little bigger one. - 10/21/2007 10:50 PM   
RysiuM



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Status: offline 		Thanks. I will keep them, then. I found some nylon screws 5/16 - Maybe I can use them at the LE, where the pulling force from G is twice bigger than at the TE. I found, that I overdid a little the nose size, as even with this light engine the plane is nose heavy. So I decided to use big NiMh battery pack for the radio (5 cells Elite 3600 - that is 6V 3600mAh) mounted on the back of the fuselage. The only drawback is that it is about 8 oz more than I planned so the final weight will be about 15-1/2 lb.

I almost forgot - I also fixed the horizontal stab. Playing with RF G2 I found, that the best trainer-like flying was with the horizontal stab span 32 inches, so here it is. I put many CF tube to make it stiff and it should do the work. I will know after the first flight

BTW Piper is almost ready for the maiden flight - it needs some cosmetics (side windows, paintings), charged batteries (forming now) and final checkup. It is to windy tody anyway, so I will have to wait.

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RE: CoroCub - a little bigger one. - 10/22/2007 4:40 AM   
MrGreenSpeed



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quote:

BTW Piper is almost ready for the maiden flight -

Awesome!
Good luck on the maiden.
Awaiting the flight report.
Jeff

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RE: CoroCub - a little bigger one. - 10/22/2007 4:53 AM   
MrGreenSpeed



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Nylon 6/6 Mechanical Properties (73o F / 23o C)
Tensile Strength 12,000 psi.

Elongation 60%

Shear Strength 9,600 psi.

Melting Point 500 F


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RE: CoroCub - a little bigger one. - 10/22/2007 5:57 AM   
RysiuM



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quote:

ORIGINAL: MrGreenSpeed
Nylon 6/6 Mechanical Properties (73o F / 23o C)
Tensile Strength 12,000 psi.
Elongation 60%
Shear Strength 9,600 psi.


Cool. Tha means two front screws will hold 720 lb. With 2/3 of load at LE it is - over 70 G.

I don't count the shear force as the thread is over 1/2 in long so it is not the weakest point. I will keep 1/4 screws then. Thanks for the info.

Now there is another fun part. How to place flat windows in a coroplast plane. I figured it out. Simple, easy and holds forever.

1. Cut the windows in te fuselage - no limits regarding window's shape - can be square, triangle, oval round - whatever you need. Just make sure, that when you run a cut along flutes don't cut flush with flute's internal wall - rather leave some plastic so it forms about 1/16 inch deep grove.

2. Using exacto knite cut all perpindicular flutes' walls flush with the outside coroplast's wall. This grove needs to be about 1/8 inch deep. Note it is important that you cut flutes flush with the inside wall of coroplast's external layer.

3. Cut the window's shape of some transparent material (thick foil like used for merchandase contatainers) a littel bigger than window's opening so it will fit in cuts you made in step 2.

4. Place windows in the groves - it will fit like in a frame and will be almost flush with the fuselage (just the thicknes of the coroplast's one wall). Work it a little so it fits without distortion.

5. From the inside of the fuselage "seal" the window with the transparent hot glue. The glue sticks wery well to the transparent foil and coroplast.

Such windows will stay forever.

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RE: CoroCub - a little bigger one. - 10/22/2007 7:41 AM   
MrGreenSpeed



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quote:

(thick foil like used for merchandise container's)+ hot glue


Great tip, thanks.
Jeff

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RE: CoroCub - a little bigger one. - 10/22/2007 11:38 PM   
RysiuM



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Status: offline 		Here are some latest pictures. There are not much change from the outside so here are some details from the inside.

1. Extended horizontal stab. It is now 32 inches wide and there are eight rows of CF tubes in there (5 in the stab and 3 in each elevator half). The seam is under the blue ZAGI tape.

2. Interior. Plenty of space inside - 500ml fuel tank (scrap from some ARF). I planned 24z, but that had bad rubber seal. Futaba 8-channel PCM RX wrapped in two layers of thick foam. Ignition circuit switch is on the right, Radio switch on the left.

3. Tail servos' wires. You can see how the wing mount is designed here. You can hardly see that, but windows are already glued in.

4. Windscreen is not glued in. There are 15 screws that hold it to the fuselage. Having the front hatch also screwed in (2 long screws at the front) I can have access to the back side of the firewall.

5. Electrical power for the radio is provided from 5 cells of ELITE 3600 (NiMh 3600mAh) and power for the glow plug is from 2 cells of the same batteries connected parallel making 7200mAh


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RE: CoroCub - a little bigger one. - 10/23/2007 2:48 AM   
Smooth Spanky



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Status: offline 		Lookin' great, LysiuM, thanks for the pics! How much longer before you're ready for the maiden flight?

Good luck with the rest of it.

Smooth

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RE: CoroCub - a little bigger one. - 10/23/2007 3:38 AM   
Villa



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Status: offline 		Hi RysiuM
I am very interested in your build because I also build a CoroCub. Mine has a wingspan of only 71 inches and uses an OS 46 AX engine. I notice that your cabin sides under the wing have very little structure to hold up the wing during a rough landing. I could be that mine has too much structure, since mine came out heavy at 7#. I hope you describe how the cabin sides under the wing stand up to hard landings once you start flying it.

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RE: CoroCub - a little bigger one. - 10/23/2007 7:47 AM   
RysiuM



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quote:

ORIGINAL: Villa
I notice that your cabin sides under the wing have very little structure to hold up the wing during a rough landing.


Look at the pictures . The wing is not resting on the cabin. Wing is supported and mounted to two spruce squares (1 inch wide, 1/2 inch thick - these with holes in them). These two squares are glued (via triangle spruce stock) to the plywood enforcement going down to the fuselage. The front support goes all the way down to the landing gear block and it is also glues to the sides of downspout. At the front of the plane (where the cabin is) the coroplast does not carry any load - just keeps it's shape.
At the back of the plane the load from the wing is spread to both coroplast walls behind the cabin - these plywood enforcement is spreading the load to the almost entire height of the fuselage wall.

For testing I just dropped the plane from 2 ft straight down to the concrete garage floor. Than it happened, what I was worried about: the tail wheel bracket (from some ARF) collapsed. I made a new one of 4mm 6061 flat bar (1/2 inch wide). Next drop test proved the entire design is sound and crash-proof

The plane is almost ready. I figured out CG and to balance the plane I have to put batteries behind the cabin (it is nose heavy). I just glued batery trays for both batteries) and tomorrow night (I work all day) I will finish the plane, so maybe I will take it out the day after tomorrow. I hope the engine will not play fool with me.

Anyone from MASM goes out there?


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RE: CoroCub - a little bigger one. - 10/24/2007 2:19 AM   
spad4mebaby



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Status: offline 		RysiuM I drop tested my spa3dt landing gear and wound up using 1/4 steel rod rod with wooden spools for hubs. Later I realized I needed lighter not necessary stronger.
3/23 insulation hangers with superglued thread now work for me .

Only with a spad could you Drop test a finished plane.


For testing I just dropped the plane from 2 ft straight down to the concrete garage floor. Than it happened, what I was worried about: the tail wheel bracket (from some ARF) collapsed. I made a new one of 4mm 6061 flat bar (1/2 inch wide). Next drop test proved the entire design is sound and crash-proof.

I hope you fly this for a long time.

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RE: CoroCub - a little bigger one. - 10/24/2007 2:41 AM   
RysiuM



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ORIGINAL: spad4mebaby
Only with a spad could you Drop test a finished plane.


Nope. Believe me or not, but I did the same test to my 23% Wilga. I was testing if knees in the LG will work properly. It did


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RE: CoroCub - a little bigger one. - 10/24/2007 4:24 AM   
Ralphbf



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Status: offline 		Just finnished reading your post.
This is some good stuff.

I have a 1/4 scale clipped wing cub powered by a 25cc Toro.
By streaching the nose 2 inches I was able to loose
1 1/2 pounds of balast off the fire wall.

I haven't been able to fly it since the mod. but
It was a real slow flying floater before.
I can only imagine how well it will fly now.

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RE: CoroCub - a little bigger one. - 10/25/2007 1:19 AM   
RysiuM



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Status: offline 		I flew this Piper this morning. There were very minor issues - the biggest was with the engine. But the plane flew just great. Big, gentle and stable trainer - easy to fly and land. The only flying issue is that I need to fix ground looping problem on take-off and landing roll. This plane teaches you to use rudder - if you don't the turn looks very ugly and strange. Like the real thing.

Now here are details:

1. Preflight and radio test:
I notice "static flatter" on ailerons. When I move the stick rapidly it takes about one second to stop thef oscillation at the endpoint. I think this is because this Futaba PCM receiver doesn't like 6 fully charged cells. I will need voltage regulator. Radio range was awesome though. Over 200 ft with collapsed antenna and no hesitation. This is great receiver.

2. Engine run-up.
After I started the engine I couldn't tune it up. Idle was great but high end was way to lean. I will try just gasoline with glow plug - no glow fuel in the mix. I set it up so it run stable but not the best power.

3. Taxi and take off
This plane does not hesitate to make a ground loop. My springs on the tail wheel are way to soft. And I need some toe inn. Anything more than walking speed and I had to be on the top on ruder. The plane lifted in very scale manner even I couldn’t get more than about 2/3 of max power from the engine.

4. Flying
The plane required just two clicks on the aileron trim and about 10 clicks on up elevator - the horizontal stab incidence from that design made the plane diving a little. For turning ruder is mandatory. Actually turns are better with ruder only and using ailerons for controlling the bank angle. Very scale flying. Flying is very similar to simulated plane on RF G2. It requires about 4500 rpm (only) to fly.

5. Landing and roll.
When I chopped the power to idle on final the plane started to glide. It is very good glider. Just a bit of flare at touch down and the plane started to roll on two wheels. As soon as the tail wheel dropped, the plane mage 3-tuns ground loop. It was like a flat spin on the ground.

So the plane is a great flyer, easy, gentle and slow. Jus a few minor things to fix:
1. Tune up the engine.
2. Try 6V regulator for receiver or 4cells NiMh
3. Replace springs on the tail wheel with something stronger.
4. Add toe inn to the landing gear
5. Program the radio to mix ruder with ailerons

< Message edited by RysiuM -- 10/25/2007 1:22 AM >

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RE: CoroCub - a little bigger one. - 10/25/2007 3:27 AM   
GravityTester



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Status: offline 		glad it went well. keep us posted on the progress

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RE: CoroCub - a little bigger one. - 10/25/2007 3:38 AM   
Ralphbf



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Status: offline 		I had a plane that was terrible about ground loops.

I found that raising the tail along with toe in helped a lot.

It was something about wing incidence. Raising the tail made the most difference.

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RE: CoroCub - a little bigger one. - 10/25/2007 4:00 AM   
RysiuM



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quote:

ORIGINAL: Ralphbf
I found that raising the tail along with toe in helped a lot.


I have my own custom tail wheel bracket, so I can bend it any way I like BTW you should see that ground loop. The tail wheel was perpendicular to the fuselage and one main wheel was turning forward while the other one in reverse direction It was not a ground loop, it was a pirouette Everything was cool till I saw the plane coming towards me, and the rudder did not do a thing – that reminded me a quote from “Monty Python and Holly Grail”: RUN AWAY !!!! :


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RE: CoroCub - a little bigger one. - 10/25/2007 4:43 AM   
MrGreenSpeed



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Status: offline 		Congratulations on a successful maiden flight.
Great flight report.
Hope to see some in the air pics or a video soon.
Jeff

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RE: CoroCub - a little bigger one. - 10/25/2007 6:22 AM   
DLSmith2



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quote:

The tail wheel was perpendicular to the fuselage and one main wheel was turning forward while the other one in reverse direction It was not a ground loop, it was a pirouette Everything was cool till I saw the plane coming towards me, and the rudder did not do a thing – that reminded me a quote from “Monty Python and Holly Grail”: RUN AWAY !!!! :


Congratulations on the maiden!!! Sounds like an exciting landing!

Looking forward to more pics, too!

SPAD skies,

DL


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