combatpigg

My Feedback: (3)

This is a scaled down Mike Pratt design for control line that he called, "The Force".
It has a 33 inch span and hasn't been weighed yet. It has to have the final balancing done before the weigh in.

The fuselage is mainly balsa, but the canopy and belly are blue foam. The entire fuselage was covered with silkspan and dilluted white glue. Then it was rough handled during the process of building the cowl, so the dents and scrapes got filled with lightweight spackle and more tissue was applied to the canopy and belly.
Bondo was used over the silkspan and on the fiberglass cowl, then primer filler.
Auto store touch up paint for the color coat and KlassKote clear for a fuel proofer.
monokote was used for the wing.

mtntopgeo

My Feedback: (12)

ok CP, so how long did this project take you to get (near) done??? A couple of evenings? I'd be spending all winter, & then be too burnt out to complete!!! Engine???, mods???, prop??? ................ George K.

combatpigg

My Feedback: (3)

Howdy George...I think I started looking at back issues of Stunt News about a month ago to find the article about this plane. I built the full sized version for a .40 several years ago, but it is a profile. I always liked the profile, but I wanted to build one that looked more 3 dimensional.

This was my first try at silkspan with watered down glue and nothing could be easier. The overlaps on the curved surfaces and wherever there is a seam are pretty sandable, but do need to be feathered with Bondo if you want them to disappear...totally

The stock Norvel carb would have spoiled the tightly cowled look, so I made a compact venturi and put a Cox TD NVA on the firewall.

I'll run it with a 7x3 APC and fly it on 50 feet of Spiderline braided string. Hopefully the combination will keep the lines tight everywhere the plane is told to go....!

WINANS

Mike would love to see that. He developed the force while we worked together. Good guy, Mr. Pratt. I actually have a profile proto version of that shape in half-A size that preceded the development of the last Cox CL model, the Viper. That was Mikes work.

Scott

combatpigg

My Feedback: (3)

Hi Scott...small World..!

The copy of Stunt News I found the FORCE in was in 1999. I think it was about 2002 when I built it and a friend had me build one for him too.

I still have mine hanging in the rafters ready to go with a LA.40 and probably a 11x4 prop on it.

Real handsome and simple design.

WoodCutter

My Feedback: (8)

Awesome job C.P.

WoodCutter

skaliwag

My Feedback: (1)

CP.. You are an Artiste. Have you ever done a Bronze? Is that Orca up on Friday Island yours from another hobby?

combatpigg

My Feedback: (3)

Thanks guys. ...[8D]
I did some electrical work for a sculptor who was building a custom house on the west bank of Lake Washington. It had an indoor pool with marble floors, imported columbs, an elevator for bringing large sculptures and slabs of stone from street level down to this guy's workshop. What a life this guy made for himself...!
All the rooms and corridors had curved walls, the doorways were all arched.
Lots of money went into that place.
Hard to believe there is so much money out there for sculpture work.

Japanman

That looks great!
You have a real eye for the finishing proportions of these things- the canopy looks just right.
How much weight did the silkspan add?

J.M

combatpigg

My Feedback: (3)

JM, I didn't weigh it before and after. I didn't know which weight of tissue it was, either. I'll bet it was the heaviest..I think SIG calls it "D" weight. I've had it laying around for years. I think this fuselage used up about 1/3 of a sheet. A lighter weight could probably be recommended for going over solid surfaces, but IDK for sure. The areas that are blue foam needed 2 layers of this tissue to get adequately tough for normal handling. I kept my supply of diluted glue in a sour cream container with a lid, since I spread the tissue work out over a several day period, one area at a time with maybe 15 minutes of work. The same brush was kept in a jar of water.
The tissue sometimes needs to be trained to lay flat with your fingers as it dries and it dries pretty fast.

ProBroJoe

Wow, CP, that turned out really sweet - of course we should expect no less from you! Got the helmet camera ready?

combatpigg

My Feedback: (3)

Yep, the old battery's charged up in the helmut cam. It should be pretty interesting to see what C/L footage looks like and how much zoom works the best. This plane ought to fly pretty slow with a 7x3 on 50 foot lines....so it would be a good way to get the video techniques worked out before trying to shoot a C/L Combat plane.

Another thing to experiment with here is to see how well it'll pull the lines on zero nitro, but first it's going to take time to get it trimmed out as good as possible with high power runs, then I'll lock in the final leadout position and cover the gaping hole in the wingtip.

Attempting this small of a C/L stunt type plane [not counting Goldberg Profiles] is a first for me, I've got no clue if it's too heavy or what else could possibly not work right.

combatpigg

My Feedback: (3)

The model needed 1/2 oz of weight in the tail to bring the CG to 25%.
The model also needed a control horn that would work with the .100" diameter aluminum pushrod.....so I made a control horn out of steel and brass to kill 2 birds with 1 stone.

The outboard wingtip got a 1/2 oz of weight [to get the model to tip the balance outboard]..so there's a whole oz of dead weight going along for the ride. A future design refinement would call for a longer tail / more fin.

As it sits, this plane weighs 15 ozs...so it is probably pushing the limit for a good flyer...?

Max_Power

Looks Great! I'm assuming a CL model (never flown one...but been tempted by the cheap Brodak profies) allows you to get away with a much smaller vertical fin? Todd

Rendegade

15oz sounds heavy for the size of model I'm thinking of. what span is it?

vertical grimmace

My Feedback: (1)

Hey CP, be careful with that EZ connecter on the elevator. I had one of those fail on a 1/2 A combat model I put on the bellcrank. Just like losing a line. it will go straight in.

Maxpower, Cl models do not need any vertical area at all really. It is more about looks. The main item that keeps the model tight on the end of the lines is lead out rake. This is the position of the lines exiting the wing tip. Imagine this and how it effects the angle the model flies relative to the circle of flight viewed from above. You want the plane to want to fly straight ahead. Other items to maintain line tension are incorporated as well, like engine thrust and rudder offset. Lead out rake and wing tip weight or the most critical items though, when setting up a CL plane.
For RC flight, tail volume is important though, and vertical tail volume is an important factor in design. Otherwise tracking will suffer if the area is too small.

combatpigg

My Feedback: (3)

It's got about 240 sq inches of wing area. If it was RC, 15 ozs with a .074 is "party time"...but it remains to be seen if it has enough oomph to work with control line.

Cross Check

Hi CP,

Very Nice ![8D]
I like the way you have 'fleshed out' a cool profile design ![8D]
The Science of model airplanes is all numbers...(I just make sure the CG is OK, then weigh it after the test flight !)
The 'Art' part is the most challenging for me. From my 'plans', the final 3-D result is not what I imagined while drawing...
Eventually, I'll get it right... I'm having fun learning as I go...

I have used 'butcher paper' and white glue to cover foam. It is good, until you get to compound curves. It gets frustrating real quick !

Never even considered silkspan as an option ! Doah !

Thanks for sharing with us CP ![8D]

Oh, I almost forgot... I can spot a "Flight Streak" wing from a Mile away...

HeHeHe

Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

combatpigg

My Feedback: (3)

VG, I made that EZ connector out of some bronze bushing stock. It has a #4 screw mounted rigidly to the control horn with about 4 or 5 threads that it pivots on. The set screw on the opposite end pinches the aluminum pushrod. So yah, there are more failure points than the standard clevis, that's for sure.

Yes, for much of the flight through the hemisphere, the side area of the plane is providing lift...
You figure with the overhead maneuvers you've got pure, raw line tension from the prop's thrust and the fuselage is just helping with lift if you keep the speed up.

A good C/L combat plane has such a high power to weight that they should be stall proof, but this .074 model will need to be flown with some caution I'll bet.

combatpigg

My Feedback: (3)

Howdy Crosscheck...!

Now that you bring it up...it DOES look like a Flight Streak wing.

If this plane can't cut the mustard flown on string...it'll be a quick conversion to RC....

Cross Check

Hi CP,

I am having a Laugh with my friends/foes flying Maac Scale R/C Combat.

As a 'byproduct/recycling' venture, I am going for 80mph Canadian CL Combat ![8D]
(I have plenty of old .25s that cannot match an OSFX or MagXLS...)
And eventually want one of these ![8D][8D]
http://aerohobby.ca/store/index.php?...products_id=77

It is hard explaining (technically ex-plane-ing!) any form of Combat. I just like tying streamers on model airplanes !

It is the thrill/battle that is fun for me. I'll keep my score, but do not care about 1st or Last place...

I have a Question for you CP:

How can an R/C pilot learn CL flying?

I learned FF, then CL, then R/C. (with lots of crashes !)

I know some great R/C Pilots that are actually 'spooked' at trying CL !!!

Take care
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

Cross Check

Hi CP,

I'm having fun with my old silkspan ! (And various other tissues, including Kleenex and Toilet Paper !)

Think of it as a superlight 'Paper Mache"...[8D]

Works with thinned white glue and also WPV(Waterbased Polyurathane Varnish)

A hairdrier (It was the 1980s...don't ask, and I am lucky there are no photos !) speeds things up...

Ripping the tissue/paper is better than scissors...

Newspaper !

I can build a model airplane from a Newspaper ! ! !

(I forget how many I had to deliver, to get my first Cox.049...)

Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team

combatpigg

My Feedback: (3)

Crosscheck, I learned how to fly C/L with a plastic RTF .049 plane that could only fly on 15 feet of string. It was mainly just a "Rock on a String".
It got real boring, real fast.
I was back at the hobby store the next day and got a Carl Goldberg Lil Wizard .049 balsa trainer kit and that was my first "Real" model airplane. I flew it on those dacron strings that Goldberg used to sell...I think I flew it on 26 foot long lines. It was set up for mostly just level laps. I knew nothing about "CGs", so it was probably way too nose heavy to do a inside loop....but I remember doing some big, "Wingovers" with it.

For the best control feel, you want the spacing of the strings at the handle to be about the same as the spacing at the bellcrank. I flew for years without paying much attention to this.

My first aerobatic C/Ler was the Goldberg .049 Swordsman..still just all solid sheet balsa, but with lots of wing area.

The best trainer nowadays might be a coroplast flying wing for .049 power. I think the "Balsa Beavers" website has free plans for it. It could be built very quickly with what materials you have laying around. A plastic joiner biscuit can work for a bellcrank. I would recommend Spiderline braided string for flying lines and thread a continuous loop of string through holes that you drill through a chunk of old broom handle for your flying handle. I space the holes in the handle so that the strings will exit on either side of my middle 2 fingers.
Set the neutral elevator by holding the handle in a comfortable position and slide the string through the holes in the handle until the elevator is set for "zero", then tape the string tightly to the handle with electrical tape so it can't move. This arrangement is just fine for low power 1/2A..but you wouldn't want to rely on tape to maintain your zero adjustment with a harder pulling plane.
Pick low pitch props for slow lap speeds. A 6x2 prop is great for training. Be as smooth as you possibly can in the beginning, keep all your control movements gentle as you feel the plane out.
Climb and dive the model, always be aware that if you climb against the wind and the model isn't pulling hard enough you might always need to take a quick step back to maintain line tension. Think of yourself as an outfielder always ready to back pedal to keep the lines tight. .049s don't exert a ton of pull, especially traveling up wind.
Do all your launches down wind, to keep the lines tight.

I don't know who belongs to the plane in this picture, but it looks like a great design for a combat trainer once you have learned the basics on a coroplast or solid balsa sheet trainer.
Most of the time you would see a TD used on a plane like this, but this is a good looking design if you have a hot reed valve engine like a Black Widow or Killer Bee.

Jim Thomerson

If it were my airplane, I would start out with the CG around 15%, but then I don't have reflexes up to even watching modern 1/2A combat. 15 oz is a little porkey. 12 oz would be better. You may have enough power to make it fly faster on longer lines and still look pretty good in the turns. Good and interesting project.

combatpigg

My Feedback: (3)

Jim, is 15% a pretty normal setting for CL Stunters...?