ClarkFlyer

I inadvertantly ended up with a 4 Star 40 ARF. I had this same plane sometime back and absolutely loved it until I let it get too far away from me in the inverted position and then lost it due to disorientation. I'm toying with doing some modifications to this ARF and I'd appreciate some opinions. I'll power this plane with a .46AX or a .50SX, haven't decided yet. here ya go:

1. Building the plane with no wing dihedral. Looks like I can build a new flat wing joiner and then fill the gap with a wedge shaped piece of balsa, or perhaps some plywood. It looks like I'd have to create a new tab that fits into the fuselage slot.

2. Removing one bay from each wingtip. Can I simply lop it off and then put a flat piece of balsa or plywood on the tip?

3. Cutting and installing new larger ailerons....perhaps add about 1/2 inch?

4. Cutting and installing larger elevators and rudder, perhaps with counter weights?

My goal is to make it more aerobatic, perhaps with the ability to perform mild 3D manuevers.

What say ye? Any comments on the mods? Any other mods you might suggest? Thanks in advance.

lloyd a

I have done all that on a four star 60 and find that it works great, recimend lot more engine so that it will pull out of hover's we ran a gms 120 2st on ours. so I would go for about a 75-90 2 stroke on the forty size for a good ride. don't forget to use stroger servos, and I found that the ailerons worked fine at normal size just make them move 80 degrees

2slow2matter

My Feedback: (1)

Dihedral in a low wing plane doesn't fight your aerobatics near as much as it does in a high wing configuration. However, with no dihedral, it should still be more aerobatic--and a little less stable.

Ed_Moorman

My Feedback: (1)

Guys, you are wrong about dihedral. If you take the dihedral out of a low wing plane that has no sweep, it will roll to the opposite of the rudder. High wing, sweep back and dihedral cause roll in the direction of the rudder. Low wing, sweep forward and anhedral cause roll opposite to the rudder. Given a low wing location, you need sweep back or dihedral to compensate.

Any of you who have taken the dihedral out, try flying level and putting in rudder. You'll get a roll the opposite direction. In knife edge, the plane will tend to roll over on its back.

Here are some good 4* mods:
1. Remove 1 or 2 ribs from each side. If you really want some roll rate, take off 2 ribs and add end plates.
2. Add an inch to the rudder. It is under size.
3. Add 1/2-3/4 inch to the elevator.
4. Use 2 aileron servos, if the ARF doesn't have them already.

Rcpilot

My Feedback: (78)

I removed a lot of the dihedral on a 4*40 kit once. I got the same response that Ed describes when using rudder. Roll to opposite direction.

Leave at least an inch or 2 of dihedral in the wing. Or better yet--leave it stoock. It'll be fine.

Even scale aerobatic planes have dihedral in the wing. Build a kit. The wing ribs are all tapered as you get out towards the tips. And when you glue it together--the top of the wing is flat, and the bottom has all the taper from the root to the tips. Thats dihedral on the bottom of the wing.

I built my 4*40 with huge control surfaces so that I could try some hovering and knife edge loops. It worked pretty good except for that dihedral thingy that Ed described.

OS 61FX w/Macs pipe

Ernie Misner

It was fun to learn that Bruce Tharp designed the 4* series for Sig, before kitting the Venture 60 on his own.

Ernie

ClarkFlyer

Ok, based on what I'm reading, I think I'll increase the area on the tail surfaces, and leave the ailerons and the dihedral alone. I'm thinking that the 4 star ARF uses one servo for the ailerons but I'll have to check. If it uses one, I'm not sure how much work it'll be to add another. I guess its a matter of cutting into the wing covering and building a box.....hafta check. Thanks all for your opinions.

Rcpilot

My Feedback: (78)

Adding dual aileron servos is a snap. Just pick a bay and iron the covering down real good on the ribs and spars around it. Cut it open with a sharp hobby knife.

Put in a servo tray and drop your extensions through the ribs. Recover.

It's an easy mod and well worth the time and weight gain.

It will hover with a 61FX and larger tail surfaces.

Ernie Misner

Mine will hover with a 46 and 12x4 prop! Not like with a 61FX though I'll bet...... mine's lighter, ha ha

Ernie

Rcpilot

My Feedback: (78)

Yours won't hover with a 46 at 5000' elevation.

Ed_Moorman

My Feedback: (1)

It's no trouble at all to install dual aileron servos. If there are holes in the ribs, and most ARFs have them, the hard part is done.

1. Cut a hole in the center section sheeting near the outer rib for the servo body.
2. Glue a little ply strip underneath for the screws to bite into.
3. Install servo. Remove screws and harden holes with thin CA and reinstall servos.

I have used this method for tail mounted servos and in wings for aileron servos. Never had a problem.

If you do put a .61 in your 4*40, install the rudder and elevator servo last. You may need them in the tail for balance. If you do, use the same method for mounting.

Ernie Misner

>>>
1. Cut a hole in the center section sheeting near the outer rib for the servo body.
2. Glue a little ply strip underneath for the screws to bite into.
3. Install servo. Remove screws and harden holes with thin CA and reinstall servos>>>

Hi Ed, some folks might want to know; do you mean cut a hole in the center section "covering" material, or are you talking about installing both servos side beside in the center of the wing and still using the torque rods?

Thanks,

Ernie

skukreja

My Feedback: (6)

sheet the turtle deck.. looks tons better..

2slow2matter

My Feedback: (1)

I can attest to what Ed is saying with my Kit built contender. It has no dihedral, and no sweep--roll opposite the rudder, flip over on it's back in knife edge if you don't stay on the ailerons, and it will also drop the nose in any rudder turn--weird. Anyway, I have a pattern plane with no dihedral, and a swept wing--I don't have these problems with it.

He's right!

Ernie Misner

Lots of good info here on Bruce Tharp's website. http://www.btemodels.com/vt_faq.html

Note that the 4* series pitches to the belly when rudder is applied. On the Venture 60, I believe that Bruce swept the rudder hinge line back slightly to eliminate this.

Ernie

NM2K

My Feedback: (14)

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Ed is right. The phenomenon is known as adverse yaw.

However, this problem is related more to the "center of pressure" as it relates to the total surface area of the rudder. Changing the shape of the rudder so that the center of pressure (effort) is moved to a lower point, in relation to the wing centerline, can help rectify this problem. Notice that many pattern models have the widest point of the rudder very low in comparison to the wing's centerline (looking horizontally).

Don't be afraid to experiment with adjusting surface area and maximum width (actually, leading edge of the rudder, or other surface, to the trailing edge).