.074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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....!

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

Awesome job C.P.

WoodCutter

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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...?

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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...:eek:
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.:eek: It gets frustrating real quick !:)

Never even considered silkspan as an option ! Doah !

Thanks for sharing with us CP ![8D]:D

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

HeHeHe:)

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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....:D

RE: .074 MARAUDER !!!
 

Hi CP,

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

As a 'byproduct/recycling' venture, I am going for 80mph Canadian CL Combat ![8D]:D
(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 !:D

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

RE: .074 MARAUDER !!!
 

Hi CP,

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

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

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

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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.

RE: .074 MARAUDER !!!
 

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

RE: .074 MARAUDER !!!
 

Quote

"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 !!!"



Hi Crosscheck,

I learned similarly, first CL, then FF, then RC. I think FF is the real training ground. You have to both think ahead and think and watch after the plane leaves your hand to truly understand what is going on with the plane, and what to alter to affect it positively. It's a true aerodynamics training ground, if you choose to approach it that way. CL is great for the visceral feel it provides.

Funny that some would be afraid of or aprehensive of CL isn't is? Maybe it's a bit different from the days of half-A control liners in the local park or school yard and a cheap and fun way to be flying. However, it can still be done very inexpensively (homemade cardboard ariplanes with pine motor mounts is what worked for me in the 70's). It's just fun to be thinking and talking about it. This thread is a fun one. Thanks Puerco del Combate.

Scott

RE: .074 MARAUDER !!!
 

I don't understand the apprehension with control line planes, either.......

RE: .074 MARAUDER !!!
 

What do you do if your receiver browns out?

I guess you change your pants.

RE: .074 MARAUDER !!!
 

I never understood CL, and went from FF directly to RC, even before we had lightweight radio stuff.
The idea of a plane flying around a centre point is too much like an airborne tethered car to me. I just itch to cut the cord and set them free... ;)

RE: .074 MARAUDER !!!
 

I wanted to experience flight, but couldn't afford RC. C/L at least was a way to get to play with engines and get familiar with how planes fly. Since the advent of RC, C/L has evolved into a competitor's hobby and RC inherited the casual flyers.
There is some "sport flying" going on, but most C/L flyers are working towards some kind of a goal nowadays.
With task oriented categories, you can enjoy the pursuit of the perfect engine set up, prop, airframe and then practice to execute the correct manuevers, or actions to fly a perfect pattern routine, or fly a knock down, drag out, combat match, or maybe put everything together "just so" for a record speed run.
An interesting website to look at is "Flying Lines" to get a snap-shot of what's happening in NW control line.

RE: .074 MARAUDER !!!
 

Just a "blog entry" more than anything tonight.
The plane flew perfect right off the work table today.
The CG was moved forward slightly per Jim Thomerson's advice. What I did was grind down the steel control horn until it is 1/4 of what it originally was. The plane grooves nicely on the level.
The leadout position was spot on. Just behind the CG. I glued the adjustable block in place and covered up the wingtip.
The wingtip weight was just enough to tip the balance outboard and that was enough.
These 20 pound test Spiderlines are nearly weightless and practically invisible, too.
The plane pulls these 50 foot lines nice and tight through the entire routine.
After the engine quits, the glide is good enough for me to get about 1/2 of a lap to choose a landing spot. Wouldn't want to see this plane any heavier.
The 2 inch line spacing at the handle worked well with the 2 inch spacing at the bellcrank. If the handle is cranked hard, the plane will respond pretty tightly. I never did get it to stall.
I tried to get some video, but even with a zoom backed all the way off there were only short glimpses that were worth looking at. The allignment of the camera was set too low and I ran out of day light to play with that any more.

RE: .074 MARAUDER !!!
 

Right on brutha!!!

I bet one of the tiny "keychain" or "gumstick" video cameras attached above (or below) the leadouts on the wingtip (pointing back to the center of the circle) would provide an interesting perspective of the pilot. ;)

RE: .074 MARAUDER !!!
 

Joe, the wing-cam would give an interesting look..!

I might make up a set of 60 foot lines and head down to the control line area at our local airport to see how that goes. Flying this thing at 50 feet makes it seem like it's right there in your face.
Flying at 60 feet is riskier, I'm not sure how many 1/2A planes have tried it.
The was a guy back in the 1990s who flew a gigantic stunt ship with a TD.049 that was angled way out to the right...maybe 15 to 20 degrees..? The plane was extremely light for it's size and IIRC, he flew it on 60 foot lines and competed with it against .35-.40 sized planes in precision stunt.
What can happen with a plane that has marginal pull is it can cut across the circle with the lines going slack, then make a course correction that snaps the lines after it takes up the slack. So on a windy day, something like this is more prone to happen.

RE: .074 MARAUDER !!!
 

Lovely job on that model CP. And yes 15% is a good starting point for the CG. You may find that you can move it back a little but likely it won't be much. Go back too far and it'll get too prone to wanting to overshoot and will become very touchy to fly well with a groovy style.

As for weight I know that 15 oz was a good target for the diesel combat models that I used to fly. And I was able to build a 16 oz .15 stunt model version of the Jr Magician back in my teens which flew well. And the wings on those were up around the same amount of area as your 240 sq inch size. So if you're flying on 52'ish foot lines don't expect to be able to fly slowly with a two to four cycle stunt style engine run. With the .074 you're likely going to need to peak or near to peak out the Norvel and then use the prop diameter and pitch to get it to fly at around 50'ish mph to ensure adequite line tension. An online control line speed calculator tells me that this means you want around a 4.2 second lap or lower to ensure you get to 50 mph.

I just noted in your last post that you want to try it on 60 foot lines. I really would not suggest it for a smaller model with this size engine. The weight of the lines combined with the light line tension you'll have will produce some funny control effects where the inertia of the lines wants to keep going instead of stopping when you move the handle. This model needs the shorter 52 foot length combined with .012 wire. Hell, if you know you can be careful with the lines I'd even say .010 would be better.

RE: .074 MARAUDER !!!
 

If CP is using 20lb Spiderwire, line diameter is about .009" . The EZ Braid Spiderwire is pretty incredible stuff with almost zero stretch and lighter than equivalent diameter steel.

RE: .074 MARAUDER !!!
 

Thanks Bruce.
As it turns out, the Norvel running on muffler pressure seems to flood itself out if I don't keep it right at the edge of a full scream. It's also mount upside down, which might contribute to that.
The venturi allows 17,000 rpm with a 7x3 prop, pretty much identical to the stock carb

Your're right about this size and weight of plane having a comparable feel to the British Diesel planes that we flew with 8x6 props. Those we set at 64 mph or under....mine would never threaten that mark.

Andrew is right about the Spiderline...this stuff is practically weightless. I guess the drag is comparable to the same gauge of steel. If I try 60 footers, I'll approach with caution. If it works, the reward is pretty high. This time of year we have alot of dead still days without even a breeze, so no time like now to experiment.

RE: .074 MARAUDER !!!
 

The drag issue with the Spectra line would be my only concern. But with a nominal size for the 20 lb test stuff at .009 it sounds like it fits the bill in every manner. Certainly weight or mass wise they fill the niche most excellently. And a spool of the stuff is cheap enough that you can have a set for 52 and one for 60 foot line lengths and just chose based on the wind conditions of the day.

I look forward to hearing about the flight results.

RE: .074 MARAUDER !!!
 

Bruce...funny you should ask....[&o]...looks like this will be a "reverse" build thread...[I needed a new project, anyway].

I made up a set of lines that put the center of the model 60 feet away from the handle grip [actually about 58 foot lines from end to end]

Went down to the park and gave it the old college try. The plane immediately came right at me after it cleared the launch ramp. I'm not sure if a line was snagged in the grass, or not...but the plane snapped both lines as soon as it regained line tension and this is where probably 99% of the damage occurred. The plane went straight in at basically 0 mph 10 feet off the deck.
So, it could have been much worse.
If the lines weren't snagged in the grass, then the extra weight and drag of the lines were just too much for the amount of thrust. If there was some wind, that could have been used to some advantage to keep the lines tight at launch, but this plane would have been challenged to negotiate the upwind part of the circle.

RE: .074 MARAUDER !!!
 

My thought on stunt airplanes is that the engine is set to run its happiest. The prop is selected to fly the airplane at the speed at which it is happiest. The line length is a compromise between having enough line tension and a comfortable lap time. Top stunt fliers say that can tell a difference with a change of six inches in line length.

Line length in feet x number of laps x 4.285/ seconds = speed in MPH.

So, one can determine how fast the airplane is flying; and, using simple algebra, how long the lines need to be for a particular lap time at that speed.

RE: .074 MARAUDER !!!
 

I wonder what kind of power it would take to fly on 100 foot lines...?
The biggest set up I ever flew was a Dick Sarpolus design with a Royal .50 on 70 foot lines.
At 70 feet, I liked the illusion of depth...that there was a plane that seemed like it was WAY out there faithfully chugging it's way through my commands at a fairly slow pace.