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Old Sep 25, 2006, 09:04 PM
volare est vivere
ray foley's Avatar
United States, OH, Toledo
Joined Jan 2005
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Build Log
Sig 4*60 kit build and conversion

Well hello from sunny Toledo!

I came upon a 4*60 kit, something rare these days, at a hobby store in michigan. I don't really care for arfs so, a kit version of a 60 size sport plane
is just the thing for me.

I have the following gear available for the installation / conversion:

an Axi 413016,
two 3s pq 4400 lipos,
a CC phx 80 ESC,
an APC 16 x10 eprop,
a 5 volt ubec,
a futaba 9cs and pcm rcvr,
some hitec 475 servos.

This is not the arf version so I will be doing some kit bashing in the ares of:

landing gear, lengthening and strengthening,
fire wall modifications, air inlets and repositioning
hot air outlet, too easy for words
battery hatch / fuselage top, extensive refit
wing structure, better spar and dihedral bracing, fewer ribs, etc.
general lightening of most parts, fuselage, tail feathers, wing

So come along for the ride, it should be fun. All thoughts from the members are welcome and may be incorporated as seems appropriate.

ciao -rjf
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Old Sep 26, 2006, 07:16 AM
Awsome 2.5D Pilot.
bigbobed's Avatar
Foxfire Village, NC
Joined Nov 2003
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That's an AXI 4120-18. Swings an APCe 14x7 on 6s. At 7.5 lbs, has good performance.
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Old Sep 26, 2006, 09:46 PM
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flatlander, illinois usa
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Very interesting conversion. I will like to hear about the difference between the 4120 and the 4130.
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Old Sep 27, 2006, 08:15 AM
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ray foley's Avatar
United States, OH, Toledo
Joined Jan 2005
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Well, everybody has their own way of building a kit, I'm no different. I try to ease my way into the building and so I start with the easy stuff first, that is the rudder and elevator end of things.

Vertical Stabilizer and Rudder:

I looked over the plans and searched for the laser cut parts for the Vstab and rudder. There were several 1/4" frame parts and some 1/4 x 1/2 stick necessary. So, out came the zona saw and the medium CA, and in about ten minutes the vertical stab was framed up. The plans then show sheeting both sides of the Vstab frame with 1/16" balsa. Well as I said before I like the idea of lightening things, so the 1/16 sheet has been eliminated. The frame parts were medium balsa and are quite strong by themselves

Well, that's fine but the rudder is cored out 3/8" sheet, so, out comes the master air screw razor plane and in about 5 minutes of making curly balsa bits, The rudder was trimmed to fit the thickness of the Vstab. Cool, the Vstab and rudder are significantly lighter but quite strong, neat!.

Horizontal Stabilizer and Elevators:

The construction of the Hstab was pretty much the same as the Vstab, So...
out came the zona saw and the medium CA, and in about twenty minutes the horizontal stab was framed up. The plans then show sheeting both sides of the Hstab frame with 1/16" balsa. Well as I said before I like the idea of lightening things, so the 1/16 sheet has been eliminated. The frame parts were medium balsa and are quite strong by themselves

Well, that's fine but the elevators are cored out 3/8" sheet, so, out comes the master air screw razor plane again and in about 10 minutes of making curly balsa bits, The elevators were trimmed to fit the thickness of the Hstab. Cool, the Hstab and Elevators are significantly lighter but quite strong, neat!.

Sorry about the Word Processor jive but the tail feathers were so much alike that I couldn't resist.

I still haven't figured out how to get photos from my camera to the internet but my wife the computer geek says it is easy, we shall see and soon.

ciao -rjf

coming soon to a computer screen near you!

The revised wing spar and structure
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Old Sep 27, 2006, 07:37 PM
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ray foley's Avatar
United States, OH, Toledo
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well hi there:

Some of the changes I will put into this build will reflect modern building techniques and structural improvements. The obvious lightness of modern 3D aircraft have opened a lot of eyes about airplane structures. So the upgrades I will use will reflect some of thes improvements but still use most of the kit parts.

Vstab and Rudder photo:

The photo of the Vstab and rudder shows the framed up parts without the sheeting to save weight. I still have to bevel the LE of the rudder and slot the surfaces for the ca hinges. I may also take the razor plane to the rudder and taper it some for better aerodynamics and lower weight. I plan to use dubro threaded bolt type control horn with 4-40 hardware.

ciao -rjf
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Old Sep 27, 2006, 08:00 PM
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ray foley's Avatar
United States, OH, Toledo
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Hi guys:

Hstab and Elevators:

The photo is the Hstab framed up without the sheeting again to save weight. The elevators were thinned to match the Hstab thickness/ thinness. I will also bevel the elevator LE, add slots for the CA hinges and taper the elevators for aerodynamics too.

A single servo will drive both elevators so a linkage splitter with two 4-40 rods to operate each elevator half will get the job done or maybe just a CF tube epoxied between both halves and a single 4-40 rod would be better. What do you think?

ciao -rjf
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Old Sep 27, 2006, 08:39 PM
Deletedfor proving Nauga wrong
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Quote:
Originally Posted by airorv
Very interesting conversion. I will like to hear about the difference between the 4120 and the 4130.
4120 is appx 2/3 the length of the 4130. The 4120 has a considerably higher KV and lower maximum wattage.

The 4120 is typically a .40 to .60 replacement... where the 4130 is typicly a 60 to 90 replacement. But the 4120 can put out ... useful power than a .91 4-stroke. (14X8 @ 11,000 rpm on 6 cell Lipo.... 4120/18)
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Old Sep 27, 2006, 08:46 PM
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ray foley's Avatar
United States, OH, Toledo
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Yet another session of 4*60 build:

Wing Spar and Structure:

Okay let's talk, ponder, ruminate or jackjaw about wing spar structures. The 4*family of aeroplanes were new about 20 years ago and reflected the design philosophy of the times. The structure is quite robust in some ways but questionable in some ways from a structures point of view. The dihedral joint as designed scares me and the liberal use of diagonal bracing is pretty but well... I don't know.

The main spar as designed is made up of two full lenght 1/4 by 1/2 balsa sticks with a same size balsa doubler from the root to the w4 rib. There is a 3/32" balsa web glued between the spar stick assemblies. a 1/8" plywood dihedral joint is then glued to the balsa web and spar sticks. The ribs are slipped over the slotted balsa web, the spar sticks are then installed and glued to the balsa web and ribs.

The balsa web however has the grain direction in the same direction as the spar sticks. Most modern wing structures use end grain balsa as spar webs or attach the shear webs to the side of the spar sticks for greater gluing area.

Another area of concern was balsa spar sticks instead of pine or spruce spar sticks.

Wing spar and structure, How I am going to do it:

I have decided to add strength (and weight, okay) by using 1/4 by 1/2 spruce as the spar sticks with balsa doublers. The plywood dihedral brace will be replaced by 1/2" medium balsa of the same shape and dihedral angle. The dihedral joint will then be reinforced with two shear plates of 3/32" aircraft ply, epoxied to the outer edges of the dihedral brace and spar sticks. Much better, indeed.

The wing will get 3/32" end grain shear webs instead of the longitudinal balsa web.

Fleshing out the wing structure:

While we digress, lets talk about the scarcity of wing ribs in modern 3D wings. It seems that the spacing between ribs has increased a lot in recent years. So I will use ribs with about 5" spacing outboard of the wing sheeting and retain the root ribs and sheeting per the original wing design. The diagonal bracing will be used up to the first W5 rib and deleted from there to the wing tip.

The liteply wing tip cap will probably turn into medium grade balsa. Or maybe, keep the liteply tip caps but fit them out for addition of SFG plates ala the new funtana, Cool no?

Overkill, maybe but I don't think so. Just putting strength where it is needed, IMHO, while minimizing ribs, diagonals, other questionable stuff whenever you can.

What do you think about the proposed wing mods?

ciao -rjf
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Old Sep 27, 2006, 08:55 PM
Deletedfor proving Nauga wrong
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The stock way is a joiner between the elevator halves. Building the thing with the stock structure thats fine. With the reduced thickness... I'm not sure. (been too long since I built mine)

If you are REALLY out to save weight... then dual pull-pull would work well. Pushrods add more weight than the extra control horn parts.


*************

I personally recommend retracts in the wings. Adds some weight, but the 4*60 is MIGHTY LIGHT to begin with... and the wider wheelbase makes ground tracking so much better...

and while you are "playing with" the wing structure... reduce the dihedral by half. Gets rid of a lot of the roll coupling to the rudder, making knife-edge easier to hold. There will still be ebough roll coupling to be able to save the plane if you have the ailerons come unplugged in flight. (as long as the ailerons are near neutral...)
******

The wing structure of the stock kit is VERY strong... my wing survived an impact that wrapped the rudder around the engine. I still have the wing... I didn't repair the minor damage (at the LE mounting dowels) yet.

******

I would go with the 4120 instead of 4130 for one reason only... ground clearance. The 4130 will demand you use a longer prop due to the lower KV. But the 4130 can output considerably more power... Depends on how you want to fly it. But the 4120 has plenty for most sport flying needs.
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Old Sep 27, 2006, 08:57 PM
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ray foley's Avatar
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Both of the AXI motors are beasts. I think the 413016 will be better if I get a cc phx hv 85 and upgrade to an 8s lipo pack. Then "oh, my God!" and yeeee haaaah!

ciao -rjf
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Old Sep 27, 2006, 09:03 PM
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yes.. the 4130 willl take the thing and let you do vertical hand launch. Should accellerate on a straight up line for over 300 yards (then be at almost pitch speed...)
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Old Sep 27, 2006, 09:34 PM
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I'll jump back in with some observations. I don't think weight will be a factor with the power setup you're planning on using. Since you're a builder, making changes can be a lot of fun, so why not and see what you get. Bottom line is, as you pointed out, an old design that flys like one. If I were to do it over, I would increase the ailerons significantly and, as someone else pointed out, reduce the dihedral. I managed to smack a post on landing and the wing survived with minimal damage, so the structure is strong.
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Old Sep 28, 2006, 06:32 AM
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Long Valley, NJ, USA
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Ray,

I wish you the best on your 4*60. I fly a 4*40 and I have been saved several times by that efficient, forgiving wing.

I recommend that you do not remove any of the ribs. The only reason that modern ARFs have less of them is because it's cheaper. Keeping all of the ribs will enable the wing's covering to better maintain the integrity of the airfoil - and it will fly better.

Thanks,

Paul
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Old Sep 28, 2006, 07:59 AM
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Quote:
Originally Posted by ray foley
Both of the AXI motors are beasts. I think the 413016 will be better if I get a cc phx hv 85 and upgrade to an 8s lipo pack. Then "oh, my God!" and yeeee haaaah!

ciao -rjf
Hi Ray,
Nice project ! She should be a great flyer
On the motor issue ....
The 4130/16 s really a 6S motor. 8S will probably fry it. The 4130/20 is what you want if you are going to use 8S.
Ed
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Old Sep 28, 2006, 10:54 AM
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I thought the 4130's were rated to 10 S....

4120s are rated to 6S

You can easilly over-prop and fry either on less than the voltage they are rated for... be sure to use a wattmeter.
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