RingWinger

Hello fellow Spad fans:

I would like to show you the latest of my designs. I call it the “Fedx 3D FunFly�. It is made out of ½ blue foam laminated with Fedx Tyvek envelops. The wing is a single sheet of 2-mil Coro that I molded over a 1 ½ steel pipe.

As you can see in the photos it also incorporates boost tabs on the ailerons. The boost tabs allowed me to us low cost standard servos on these very large ailerons. All flight control surfaces are controlled with pull/pull cables. I have dual servos for the split elevator controls, which allow for the use of Ailevator control. I can switch between normal and Ailevator control in flight.

To my great delight it is extremely easy to hover. Roll rate is breathtaking and I use exponential on all of the flight controls, especially the ailerons. It has a lot of drag, so it is not extremely fast, but it is easy to do all of the standard 3D maneuvers. Landing speed is remarkably slow. Gliding distance is very short and you must pay attention to the possibility of an off field landing if you flame out too far from home.

This is defiantly not a beginner’s airplane. It is neutral on all controls. It is interesting to put it into an uncoordinated maneuver and release the controls and watch it just hang onto its flight condition. This works very nicely for advanced flight maneuvers but is makes for a demanding amount of pilot concentrations. Flown on low rates the craft is pleasant to drive around the sky. Flip on high rates + lots of power and it will mix-up a lot of great fast fun.

I should mention that I designed the empennage symmetrical to improve the hovering capabilities. The stab/rudder are the same shape and area. When the twisting spinning slipstream from the prop strikes the vertical tail and horizontal tail area it with apply equal forces helping to eliminate the need for rudder input during very high angles of attach (hover flight). This seems to have work very well. The craft is extremely easy to hover.

As you can tell from the photos I originally had just a single landing gear wheel. This did not work well and I cart wheeled it on the first landing. I added a plywood doublers and the crazy legs style landing gear. Ground handling is excellent now.

Here are the dimensions:

Span 48�
Mean Cord 15.5�
Length 48 “
Weight 5lbs 2ozs.
Engine TT .46
Tower Muffler
Radio Futaba 9c
6 servos
700 MAH battery
Pull/Pull cables for all fight controls. Pushrod control for throttle.
The Coro for the wing had a flat shape of 26 x 48� before I molded it into an airfoil shape
Dubro landing gear with 3.25 foam wheels
All controls surfaces have Tyvek hinges made out of Fedx envelopes
All control surfaces and fuselage/empennage/spar areas are ½ blue foam with Tyvek (Fedx envelopes laminated with Elmer’s Ultimate Polyurethane (foam glue).
Spar also has 12K Carbon TOW wrapped around the outer edge and foam glued into place. Cotton string would also work just fine if you don’t have Carbon TOW.

Here is a link I wrote explaining how to setup and use Pull/Pull cables and Boost Tabs:

http://spadworld.net/viewtopic.php?t=7694

I will post more photos and construction detail.

RingWinger

More photos

Poppy Parrot

RingWinger

Here is how I made the Fedx 3D FunFly:


First find the envelops, you can call Fedx or just stop by one of the drop boxes and borrow a few. I used about 20 to make the entire plane. Next you need the glue, and a screed to move the glue around. Also you need a spray bottle of tap water set to give a very fine mist of water.

Cut out your foam about ½ larger that needed. Put a very thin layer of Polyglue evenly over the entire surface of the foam using the screed. Mist lightly with water and put on your first layer of Tyvek (Fedx envelops or use the House Wrap from your local construction project). House wrap is the best and is cheap. Envelops work fine.

Now lay down a second layer of glue and screed it out very thin and mist with water. Don’t forget the water! Water is what kicks off the glue. I used two layers on all control surfaces and they are extremely light and ridged. I used about 6 layers on the fuselage sides. Now put waxed paper on a clean level table. Set you lay-up on the table and cover with waxed paper and put some weight on top and allow to cure overnight. Excess glue may run out and get on your nice workbench if you don’t put the waxed paper down.

If you coat it with a layer of water bases polyurethane clear it will machine very cleanly. If you don’t coat the top layer of Tyvek the spun fibers within the Tyvek will pull up and it does not look as nice. Just one light coat of clear coat will hold down the fiber so that you can cut it on a table saw. You don’t have to coat it if you use a band saw or don’t plan on trying to sand the upper surface. It behaves a lot like Kevlar, but it is easy to cut. You can paint it with latex paint as I did on the edges and or cover it with vinyl colored plastic.

You can also incorporate a hinge into the design. After you are done with the lay-up and cutout the shape you want, you can cut a v grove on one side and you now have a hinged control surface. I will take some detailed photos tonight and post them for your convenience

More to follow over the next few days return for more constructions details

Poppy Parrot

RingWinger

I made the fuselage by making the design layout on a piece of cardboard and using Douglas fir for the motor mounts.

Poppy Parrot

More photos to come soon.

RingWinger

The Spar:

The spar is ½ inch foam with two layers of Tyvek and it is 3 inches tall. I routed a groove around the outer edge with the table saw. I wrapped it with about 6 wraps of 12K Carbon Tow. (You could substitute cotton string.) I hit it with a good layer of foam glue. I put scotch tape on the end points only to keep it from foaming all over the place. I sprayed with a light mist of water and slid it into place within the wing. I stacked 2x4 boards on top to weight it down. See next series of photos for wing details.


Poppy Parrot

More to come soon.

RingWinger

The Wing:

A piece of 2 mil Coro was cut to 26 x 48. I attached a fur strips to each side to add weight. I marked the exact center of the Coro.

Next I heated up a piece of 1 ½ inch steel pipe. I was just heated to the point where I could not hold my hand on it for more than about 5 seconds.

I placed the plastic on the pipe and put two small pieces of tape to hold it in place and heated the plastic with a hair dryer. As the plastic heats up the sides drop down and you can then clamp them together. I applied heat after clamping the two sides together to make sure the plastic took the shape. It takes about 3 or 4 minutes to form the entire wing panel. I remove the plastic after about 30 minutes. It is important to let it reach room temperature slowly. After it has cooled I reclamp it into an airfoil shape and set it as side until I’m ready to install the ailerons.


Poppy Parrot

RingWinger

The Ailerons and Boost Tabs:

I mark the lines for the glue and position the parts on top of a soft construction board. I push pins into the parts to hold everything in alignment and cut off the heads of the pins. Next I put the glue on top of the aileron and position the upper sheet of plastic and push pins into it to hold it all in alignment. I cut off the heads of all of the pins. Later after it has cured you can pull out the pins and toss them away. The pins hold everything in proper alignment during the build. I cover all areas with wax paper and stack 2 x 4’s on top. Let it cure over night.

Poppy Parrot

RingWinger

You can see the Tyvek hinges and the application of latex paint to the outer edges of the control surface. Also the application of vinyl plastic for the colors

Poppy Parrot

More still on the way:

RingWinger

Pull/Pull cables and the location of the Radio Reciever.

Still more on the way:

Poppy

RingWinger

The Reciever is held down with hook and loop that was foam glued onto the under side of the top wing surface.


Poppy

I have more photo left to post:

RingWinger

Details of a control surface:

You can see the Popcycle stick that is the control horn and the 1/8 diameter dowel rod that guides the control cable. The control cable is made out of 20 lb nylon coated fishing leader.

I'll post some more photos in the next few days

>[email protected]

Poppy Parrot

Deadeye

Gorgeous! I can't wait to try my hand at one. Thanks, RingWinger!

RichD

RingWinger, that is one beautiful plane !

I wish I had 1/100th of the talent you have.

Deadeye

RingWinger, would you be so kind as to show a pic of the ailerons in movement? I am a little confused on the 'booster tabs', and how they work.

RingWinger

Here are a couple of shots of the ailerons in action. Notice that the upper boost tab cable is loose. This in normal, it will become tight at the neutral point. This is call the Ackerman geometry. This is a very important concept for Pull/Pull cable installations. If you look at my first posting you will see a link that I wrote on the Spad World forum. I will list it here again so that you can get a clear idea how to setup the boost tabs. Read everything on this link and be sure to follow all of the links I posted. I'm sure it will clear up your confusion.

http://spadworld.net/viewtopic.php?t=7694


It will give a good idea what is going on with the boost tabs . You will see a good link on how to size the boost tabs also and how to set up the Ackerman geometry.

My boost tabs have a surface area of 10% of the surface area of the aileron. The control horns are the same length on both the boost tab and the aft area of the wing.

Boost tabs move the opposite direction of the aileron. If you look closely at the photos you will see that the boost tabs not only move opposite of the ailerons but they remain horizontal with respect to the centerline of the wing. This is achieved by having the control horns the same length at both the boost tab and the aft of the wing

The boost tab in effect really moves the control surface. The servo must exert only enough force to move the boost tabs. This is somewhat misleading, the boost tab just follows along with the movement of the aileron. The servo is moving the aileron. But as the aileron is deflected either up or down the boost tab exerts a force opposite of the aileron thus the boost tap creates the majority of the force required to move the control surface.

That is why you don’t want to exceed a ratio of 10 % of the area of the boost tab to the area of the aileron. It would be overly powerful and the neutral point of the control will tend to hunt around the center point. I have not experienced this, but it is clearly pointed out in the articles listed on my first posting.

It is free power steering. Well almost free, there is some drag associated with the use of the boost tab.

You can also do a search on RC Universe for "boost tabs" and you will see several examples of various aircraft with boost tabs. Also do a Google search on the Web for boost tabs and also try Flettner tabs. They are also called Flettner tabs after the man who created the first devices

Here is a link to get you started


http://www.helis.com/pioneers/f_flet.php


Regards,

Poppy Parrot

Mitty

Wow.Thanks so muchfor taking time,my man!
I love that idea of melting coro over a hot pipe.Thats too neat!

Cajun

WOW, hi-tech designs and aero engineering are finally catching on for Spads.

Great job Poppy. Keep up the great work.

Cajun[8D]

erbroens

Fantastic design, congrats! liked so much the idea of the trim tabs that I am thinking about using it in my unfinished f3a -3d plane!

Regards, Enrique

ChrisSpad

Ok, i'm not an aerodynamicist, but i do know a little math. Looking at the boost tab, it appears to be half the aileron chord, and therefore no more than 20% of the aileron's span. Since there's exactly the same airflow over the rest of the aileron, (and airflow is rough the same above and below the wing, i can't see how the boost tab can produce anymore than 20% of the force required to move the control surface. And, since its actually in very dirty air, as opposed to the rest of the aileron, i can't see that its producing the majority of the force, 10% probably 20% absolute max. If that were the case, everyone would run micro servos on giant scale planes.

While i agree that it would reduce the amount of torque required, i don't think that it'd be by more than 20% at the outside. On a surface with counterbalances, you pretty well double the area of the counterbalance, and subtract it from the total are of the the area of the counterbalance, and that gives you a good estimate of the size of the surface relative to the amount of torque required to actuate it.

FrankC29

A lot of Showcase material being put out lately, I'm having a hard time keeping up!

Deadeye

Don't forget my Cor-Star Ultimate Bipe, Frank! Website r0x0rs, by the way. [8D]

RingWinger

Hello ChrisSpad,

You requested further documentation regarding the merits of the use of Boost Tabs.

Boost tabs have been used for over 85 years. They were conceived by Anton Flettner during World War I and are also call Flettner Tabs. They have been successfully employed on dozen if not many score more of aircraft designs. Boost tabs were frequently used on the large bombers and other heavy aircraft of the 1920’s up to and including their use on aircraft such as the Douglas DC-8 and DC-9. Aircraft of the 1920s to late 1930’s did not have any form of auxiliary boost power, such as hydraulic assisted controls to aid the pilots in controlling very large, heavy control surfaces. As aircraft design improved so did the airspeed of these aircraft only making the workload on the pilots increase. Thus the use of the boost tab became a necessity.

There are a number of different variants of Boost Tabs. Below is a quote by Carl Risteen from his web page: http://www.geocities.com/roger_forgues/Boost-tabs.html There are several excellent photos and a good article about boost tabs located on this sight. Carl has done a nice job of documenting and explaining Boost Tabs.


Servo-Operated Boost Tabs
A super-effective variation of the boost tab is used on a number of large full-scale aircraft. The control system is connected directly to the boost tab, and it doesn't directly move the control surface, which is counterweighted and left free to weathervane in the slipstream. Movement of the direct-operated boost tab causes the control surface to change its angle relative to the slipstream and provides the necessary control force. The result is an extremely large multiplication factor between the force exerted by the pilot and the effective force on the control surface. This enables a big, fast aircraft to be flown easily without hydraulic assist.
The Douglas DC-8, for example, uses manually operated boost tabs on the elevators, connected directly to the control column by cables. This avoids the complexity and weight of hydraulic assist and gives light control with an excellent feel. Many DC-9 pilots joke that the "DC" stands for "direct cable". Both the ailerons and the elevators are operated by simple, simple, reliable, cable-connected boost tabs and have no hydraulic assist in normal operation. Even the rudder on this beautifully handling big bird can be tab-operated manually, should the hydraulics fail. The ailerons and rudder on the larger DC-8 can also be manually controlled by similar boost tabs, if necessary.

ChrisSpad you also commented that if boost tabs work so great then it would be possible to use micro servos on giant scale model aircraft. Yes, this is a true statement. Micro servos do in fact have adequate power to drive properly design boost tabs. Many other modelers have done it.

Here is another quote by Carl Risteen:

If you've been struggling with overloaded servos on a giant-scale model, slaved boost tabs (as described above) are well worth a try. They'll reduce the load on the servos by about 85%. Direct, servo-operated boost tabs, although they're a bit more complicated, open up new vistas of really gargantuan, high-power model with tiny servos providing all the control response the pilot could desire. Many early WW II heavy-bomber pilots who were forced to wrestle with unassisted controls would have found direct-operated boost tabs a godsend as they nursed their bent and broken machines home.
Millions of hours meeting the precise control demands of airline service is evidence that the McDonnell-Douglas flight-control system designers deserve an "A" for their efforts. We modelers might find this relatively simple system worth a try on our own "heavies".

I hope this has been useful information and will encourage you to give Boost Tabs a try. Let use know how your experience turns out.

Best of luck,

Poppy Parrot

RingWinger

ChrisSpad,

Look carefully at the attached photo. You will see that boost tabs can increase the control force by over 200 times the input force. That is why you do not want to exceed a boost tab area of 10% of the total aileron area (or any other control surface). You can over drive the control surface. I have used this 10% rule with excellent results. I have notice a large reduction of battery drain with the use Boost Tabs. This has allowed me to use a smaller on board fight battery saving more weight.

Thus the overall benefits of Boost Tabs are:

Cheap standard servos can be used on giant scale aircraft.

Micro servos can also be used but cost a bit more to purchase.

Small, lighter weight flight batteries maybe used, do to the reduction of current draw.

Boost tabs are easy to setup and use. They require no additional maintenance and only a very small penalty of drag for their operation.

Regards,

Poppy Parrot

ChrisSpad

please show me an example of any 25% scale or larger plane flying with a standard, or micro servo, on anything except for throttle. I've yet to see (or hear of) it being done successfully.

RingWinger

ChrisSpad,

May I suggest that you contact Carl Risteen. Here is his email address [email protected]

I'm sure he would be glad to furnish you with photo documentation. Carl has a great deal of experience working with boost tabs and is the author I mentioned in the proceeding post. Also do a Google search for "Carl Risteen". You will find some interesting links about boost tabs.

I currently do not have any photos documenting boost tabs on giant scale aircraft. I'm currently building such a craft and will glad to post these photos for you in the near future.

On a personnel note: I want to let you know that I have enjoyed your creative designs that you have posted on the Internet. I have looked at many of your photos documenting SPAD construction. I have incorporated some of your ideas into my aircraft designs.

Thanks again and keep up your great work.

Regard,

Poppy Parrot