heggen

I am preparing to build a 33% Lanier Laser 200 from plans. The plans show a flat stick built stab and rudder and from what I have read, it is a great flying airplane. The question comes to mind - what is better for this giant scale aerobatic airplane and why - the flat stick built stab or the a stab with a symetrical airfoil? Thanks for your thoughts.

wellss

A flat stab is symmetrical. Not likely to make much difference, although the airfoil shape will give it more structural strength and therefore probably better for severe aerobatics that guys like to do these days.

gene6029

That model flies just fine with the flat stabilizer ( i had one ) if thats your concern. I'm not sure it would make a significant difference in flight characteristics either way. That model was designed before the 3D craze & todays trend of airfoiled stabs & elevators. I used it to fly IMAC years ago & wish i had another one again....Gene

rmh

It's all about rigidity-
full scale or tiny model
The full scale guys used simple tube and covering setups because they were the lightest setup - they typically required rigging to maintain shape
as for efficiency- You can make the case for either approach
I have been building tiny models which are extremely aerobatic. these use flimsy thin EPP or Depron
sheet for tail group and the careful addition of tiny carbon fiber rods is very necessary
The big aerobatic stuff with 200-300 sq inches of stabilizer area were always easier to do in curved symmetrical sections - rigging the big ones is harder to get right.
That Lazer is a great flier as good as any of the latest stuff .

speedracerntrixie

My Feedback: (29)

Agreed, Ihad one recently and built it pretty much stock except getting it as light as possible. It came out at 15.25 lbs and I powered it with a DA 50. Flew great! I actually liked it better then my AW 42% Extra 260. Lost it due to a regulator failure. Have another two under construction now. I can post pics after work today if interested. I also have molds for the cowl, wheel pants, hatch/canopy and tail fairing.

acdii

I doubt it would make much difference. Check the tail of a P-51, all flat top and bottom.  I would say they did pretty good when you consider the stress put on the tail on a heavy  fighter plane. If you look at the tail sections of most modern planes built today, they are also flat, I think the curved tail cross sections went away a long time ago since the tail is more for control than lift.

heggen

Thanks for comments. Flat is easier so flat it will be.
I am encouraged to hear that the Lazer is an excellent airplane. Lost my Yak 54 to wing failure and wanted something to replace it that not everyone else had from the cookie cutter. I am looking forward to the build.
Pictures of your Laser 200's and other thoughts and ideas are most welcome.

onewasp

_____________________________

Not true ! See pictures cited below


http://www.mustangsmustangs.us/p-51/...2forsale-1.jpg

http://www.mustangsmustangs.us/p-51/...2forsale-3.jpg

speedracerntrixie

My Feedback: (29)

Ok I have a little more time for details. The airplane really is close to being 100%. Even at 15.25 lbs the airplane had just a little more drag then the 50 could handle. My new versions have provisions for a cannister exahust. The wings are a little too high aspect ratio. Here are the changes I am making and some I did on the first one.



Fully sheet the wings with 1/16

Trim 2" off each wing at the root

Eliminate all dihidral

Use 1/8 balsa for the fuse sides

Use 2 plys of 1/8" plywood with glass between the plys for the firewall and landing gear plate.

Get rid of all the ABS plastic and use light weight glass parts.

Use 1/4" spruce stringers for the turtle deck

Use a 1.5" CF wing tube

Use CF landing gear ( Ebay item )

Use pull pull with coated kevlar for rudder and elevator. This means a total of 5 servos.

For tail wires, use .070 CF rod and dubro locking clevis.

Use as light of hardware you can to safely get the job done. Tailwheel, hinges, control horns, clevises, pushrods, wiring, batteries, switches all contribute to weight.


My goal with the new ones is 16 LBS with the 6" less span and powered with a DLE 55 cannister set up. Here is a couple links to some flying vids. More pics soon

http://www.youtube.com/watch?v=bpm4cwaFrAg

http://www.youtube.com/watch?v=IK_oNSUGtro&NR=1

heggen

Thanks for the good info. I am currently gathering ideas, parts and supplies for the build so anything else that comes to mind from anyone will be appreciated. Pictures would be fun.
Did you use a foam or built up wing?
Also, do you custom make fiberglass parts from your molds for others? Is there a reason you wouldn't use parts from Fiberglss Specialties, i.e. weight, cost, etc?

speedracerntrixie

My Feedback: (29)

The Stans parts will work well. I did a set of molds because I wanted to use a Laser fuse as a basis for a 2 meter electric pattern airplane. That ment shedding some serious weight because the weight limit rule for pattern is 11 lbs. As a result, my parts are lighter and are pre primed. I also have the hatch/canopy as one peice with a much more pleasing shape. The pics are of the build of the pattern version but are the same mods I did for the gasser. The holes in the fuse sides are not needed as the gasser came out nose heavy as it was.

speedracerntrixie

My Feedback: (29)

A few pics I just took of the gasser build

heggen

Very nice job on the build of the the Laser. You are an insspiration for me to do as well. Keep the pictures coming.

acdii

Yeah, figured that out the next day when I started putting the tail together on my TF P-51, just forgot to update my post. It does have a slight curve to it after all, it just isnt as noticeable in the smaller plastic kits.

cutaway

Thickerish flatish slabish things can work OK and exhibit less tendency to stall than thinish .40/.60 size trainer slab tails ex. many of the FAI combat planes coming out of Russia and Eastern Europe are thick slabish wings. Not as esthetic as say a NACA 0010, but in practice they work OK and are much easier to build straight.

The idea has been in use as far back as the (very ancient) FAI Dominator design and really came into vogue with Wilkins Blasta back in the 70's

BMatthews

I've flown a number of those "continental" flat wing combat models over the years. Both the classic diesel powered combat models as well as some later generation glow powered ones from about a decade and a half back. And I'm going to run counter to your post to say that they do NOT fly as well as similar size and wing loading models that use "proper" airfoils. They can't be made to turn as tightly and they tend to bleed off more airspeed in the turns compared to a similar model with a "proper" airfoil. Their one claim to fame is their ease of building and ability to build lightly.

The new class of "slab wing" models with the foam leading edges are shaped to be more like a proper airfoil and reduce the "slabbiness" of the airfoil over the majority of the wing. They've done that by making the foam leading edge a lot wider and thicker than the old "1 inch square" balsa leading edges found on the old time British style designs. Other than that they rely on their high speed and very light wing loadings to turn as tightly as they do.

But getting back to stabilizers it's really a wash. Some excellent models have been flown over the years with both flat and airfoiled stabilizers. The key is to keep in mind that even a "flat" airfoil suddenly becomes a thin and highly arc shaped airfoil when the elevator is deflected. So comparing stabilizers with elevators to a wing isn't really all that valid. It really comes down to the nuances found in precision aerobatics to determine if one has a slight advantage over the other.

cutaway

Of course. That's why I said they're only "OK". Better than a 1/4" slab of balsa, not as good as the real thing.

BMatthews

Fair enough. They certainly were all of that.

djmp69

The thing about control is smoothness, and that's what stabilizers are all about.  What are you going to view as "in control", jerky movements or smooth transitions?  How this relates is simple.  A flat surface moving through the air is going to be way more touchy in terms of angle vs airflow.    Take a piece of cardboard, flat, hold it at the back, and start moving forward.  You'll notice that even with the slightest change in angle, the cardboard pitches up or down sharply.  Now, take that same piece of cardboard, form an airfoil, and do the same thing.  Depending on how you did, the pitching will be smoother.  It might still be sharp, but not AS sharp.  Because an airfoil will direct air a lot more smoothly than a flat surface.   Take this to a stabilizer, well, even though the elevator or rudder may be neutral, any prop wash or wing turbulence will go over airfoil feathers more smoothly than flat stabs.  The result is a more smooth, less twitchy flying craft with airfoil feathers.  Of course, it's not an end-all solution, but a noticeable difference.  Point being, the more smooth the air is directed over the controlling surfaces, the more minute control you will have over your aircraft.  The little things will still affect flight characteristics, but not as much.  Ever notice how that fine line is much more pronounced in a flat stab aircraft vs an airfoiled stab aircraft when trimming on a maiden?

Just my 2 cents...

speedracerntrixie

My Feedback: (29)

Well after some careful thought, I decided to go with an airfoiled tail on the new Lasers. I'm not completely convinced it will be a performance improvement but it won't hurt and it will add to the astetics. I decided to to a build thread in the classic pattern forum for anyone who is interested.