mikeflys

Hi everyone!
I have been flying a Tower Hobbies 60 trainer for quite some time. At my income level I am not able to upgrade as much as I would like. I recently had a somewhat unhealthy landing and my plane is up on blocks getting repaired. Well as I was working on my wing, I had a possibly crazy idea. What would happen if I decreased the dihedral on my wing? Would my plane be more responsive? Would I be able to coax more performance out of it? Would it crash into a hopeless pile of rubble? Any ideas from the more experienced and level heads out there?

southern_touch99

I always suggest taking some of the dihedral out. For one, it looks better, it becomes a little less apt to float, you will get more roll rate out of it and well yeah...take it out. I wouldnt do all of it but just most of it. Just make sure to get everything straight before putting it together with the glue. If you are really ready for a kick you could always bulid bigger control surfaces. I have flown for years on a budget (for all of my Middle School, High School, and College life). Thankfully now I am out and the money is starting to come in. Dont be afraid to experiment with things like this, just do it one step at a time and see how you like it. Worked for me [img]i/expressions/face-icon-small-happy.gif[/img]. Since we are on the budget subject I could give you the name of a few kits that are cheap and FAR underrated as far as performance goes. One being the Uproar (it comes in both .40 and .60) This is a GREAT flying sport airplane. It could be a great second airplane if the rates are turned down. I have owned 5 of the .40 size uproars and am currently modifiying theone I have now for 3D. (I have thrown the servos to the aft and made a CAP 232 3D tail for it). Balance is the key here. Another thing to look into is the SPAD airplanes that can be made for under 20 bucks usually, visit this site www.spadtothebone.com (great site, lots of info). If you have any experience building you should be able to fix the dihedral in the wing. If you do choose to enlarge the control surfaces (i.e. build new ones) then be sure to check the CG and shift your battery pack accordingly. Let us know how this turns out and good luck.

mikeflys

I have looked at the SPAD's and I do find them interesting. I just havn't decided what I want to do for a second plane yet. I need to keep the one I have in the air until this winter. I hope to have the f4ree cash to build a new one over the cold months. I am looking at the 4* right now. Thanks for the info I think I will try to flaten out my wing a little.

LouW

If you reduce the dihedral, the airplane will have a little less lateral stability. It will require a little more attention and will not right itself as easily after an upset. Most model aircraft pilots like the feel of this after they have gained some confidence in their flying ability. Decreasing the dihedral will not effect the performance at all, nor will it increase rate of roll. It will not actually be more responsive, but since you have to be more active on the sticks it may seem so. At any rate, it will help prepare you for a more responsive airplane you may build later.

To determine if larger control surfaces will benefit, think how often you have the sticks fully deflected during your typical flight. If it's frequent, larger surfaces may be called for. If it's not often, you aren't using all you have now so adding more control wouldn't help you much.

ballgunner

My Feedback: (1)

Happy to see that you are going to rebuild the wing on your TH .60. This means that you are at least partially into the building stage, the ultimate modeling experience. Southerntouch has a very good suggestion about the TH Uproars, both 40 & 60 size. A .40 size kit costs 40 bucks, the .60 size 60 bucks. Both can be 3D aircraft or gentle as a lamb. One of our pilots learned to fly on a 40 Uproar fitted with an OS 46FX. He now has many other aircraft but always keeps an Uproar around for fun flying. When you advance to the aerobatic stage you can increase the control surfaces by a few sq.inches, dial up the throws and it will do all you ask of it and maybe a few things you didn't know you could do. They are build it yourself kits but that shouldn't be a problem for you if you can rebuild the TH .60 trainer wing. Hang in there. Most of us started in the limited income stage too. In my case it was mowing lawns and selling newspapers in the 30's. It gave me the incentive to keep up modeling for 70 years.

southern_touch99

As said before go ahead and take it out. I dont know how Lou says that it wont effect the performance at all? He has been doing this for a while but all of the planes in which I have taken the diheadral out of performed much better. I say if it takes the self righting effect out of the airplane then it is reducing washout and thus will respond better to your input. It seems to me that if the airplane is fighting you to come back to center b/c of the design of the wing then redesigning the wing would allow the control surfaces to have more effect as far as the roll rate goes. Plus a flatter wing is better for inverted flight (this has to do with the airfoil as well). You might also want to try to shorten the wing??? I dont know how comfy you feel with going this far but it will make the airplane fly all together different. If you notice hightly aerobatic high wings (citabria, decathalon) you will notice that the diheadral is little to none (depending on how many modifications have been made ). If the amount of diheadral doesnt effect performance then why wouldnt the manufactuers leave it in order to provide more stability on landing?? Maybe I am totally off base here but from my experience of redesigning stuff it always seemed to help performance.

LouW

Southern touch 99 is correct in observing that airplanes designed for aerobatics usually have little or no dihedral. There are two reasons for this, maneuvers involving inverted flight, and knife edge flight. With no dihedral, the airplane flies the same inverted as right side up. In knife edge flight, dihedral effect tries to roll the airplane away from the side slip and requires constant correction to resist the roll. In no case does dihedral affect rate of roll. Maximum rate of roll is determined by something called “roll damping” which is a function of wing area and span. To increase rate of roll, you can reduce wing span/area (clipped wing) or increase control forces (larger surfaces or greater deflection) but taking out dihedral won’t effect it. The airplane may feel like it’s more responsive due to the fact that you are busier on the sticks to fly the less stable airplane.

Another modification toward aerobatic characteristics is to move the cg a little aft. This will lessen the longitudinal stability, and make the craft more responsive in pitch. Seriously aerobatic planes are balanced just forward of the neutral point which makes them quite responsive but require a careful thumb not to over control.

As far as performance goes there are only two ways to achieve it, reduce weight or add power.

To make your trainer fly like a more advanced bird do the following:

1. Reduce the dihedral. This will make inverted flight and knife edge a little easier.
2. Clip one bay off each wing. This will increase the roll rate. It will also increase the stall speed, so be prepared to land a little faster. It also reduces available lift so what you gain in roll rate you will lose in loops and such.
3. Move the cg aft a little at a time until the pitch response is like you want. Go slow here. Too far and it might not be controllable.
4. If possible increase deflection of all control surfaces (up to about 45 degrees)
5. Get rid of all unnecessary weight. If you have used lead for balance, try shifting the batteries and servos around instead.

If you do all this you will be surprised at what a different airplane you have.

mikeflys

Thanks for all of the great ideas! Right now I do not want to modify this aircraft too much. I am using it to teach both of my daughters how to fly (ages 12 and so to be 14). Once they have soloed and are feeling comfortable then we can start getting a little crazy with the xacto knives! I will take a little out of the dihedral just to start, not much just some to see what will happen. Thanks

Juice-Dog

I have the same plane and have just had to replace three of the ribs in one side of the wing after a stall on dead stick landing. While I was at it I added a half of inch to the alerions and elevator and 3/4" to the rudder. I pland on using the dual rates to allow the plane to somewhat had the same defections as before for landings, but flip the switch for more deflection while flying.