Flew my Brodak Twin and Big Otto today

Cool looking planes, Ken. What's the capacity of the wedge tanks on the twin, and what kind of run time do you get with them?

Hi Ken,
How exciting for you! I was watching this on the front end, wondering how the shorter engines would do. Any chance we can get video?

What/where did you get the copper line? I used automotive engine oil pressure fuel line for the Mosquito tanks...but did pick up some smaller brass pipe.

I'd love to see a straight-on right side shot to see tank height vs spray bar hole/ crankcase centerline.

Is there any engine downthrust? Any difference of incidence between the tail, wing and thrust line? I ask because I probably need to take these clues and apply them to a DPC (Sterling Reproduction) P-38.

The P-38 plans show Babe Bees, but AirSoft Brenda and another builder on the FB Sterling Models page indicate this kit also builds nose-heavy. My intent is to use horseshoe backplates and external tanks. Of course, I expect tank location problems. Custom in-wing tanks may be the answer.

Thanks in advance,

Jim in MS

The tubing is K&S 1/8" copper. The stock tubing with the Perfect tanks is generally 3/32" or even smaller and also brass. Fuel tubing doesn't fit properly and the brass tubing they used is not seamless and it splits internally. Not to mention that Perfect NEVER EVER solders the fuel pickup internally to the inside of the tank at the proper height. This is imperative for continuous good runs. The pickup can't be in the tank vibrating as it will cause poor runs and it will also work harden the tubing causing it too split even faster.

      I managed 2 1/2 flights on the twin due to the one coming in inverted and cleaning the props off. Yesterday was a cool day and required lots of prime which just kept making the engines run backwards which was driving me crazy. I don't generally find that a problem but even the TD's we were running was doing the same due to over priming. This impacted flight timing because I didn't top off the tanks evenly when both engines were running. One would always fire off and then while it was running the opposing would sputter and run backwards. I was more concerned with how it was flying in terms of turning and wings level. The other factor was that the SPI #1 cylinder was turning up quite well while the other slit style cylinder was more economical. I can resolve that and plan on doing so this week. My main goal is too insure that I can fly the pattern without refueling.

        The tank height is essentially centerline of crank however when the plane went inverted, I did get a bit of burp and the engine richened slightly. I left room to raise the tank to solve this and when I settle on a height, I will glue wood under the tank.

          As far as offset is concerned, this plane has none. I use no engine offset, no rudder offset and everything is essentially 0 degrees with the exception of a slight bit of yaw from the leadouts which is minimum. I flew this on both 35' lines and 42' lines. Line tension was fine but one maneuver that I didn't do was the square eight which I feel is one that really taxi's the plane. If done too tight, this maneuver bleeds off a lot of speed in the corners and this can create line tension loss. If this occurs, I may just offset the outboard engine out with a #2 washer.

Ken Cook wrote:            My Brodak Twin Mustang took off with a huge head of steam. It quickly was delayed when I screwed on the engines discovering that the plane required a huge chunk of tail weight. Having built one of these in the past, I already was aware that the plane builds nose heavy. I didn't taper the fuselages out in the rear to retain a little weight and I chopped some nose off as well. Unfortunately, this wasn't nearly a enough and I was well into the paint stage when I figured out how much was needed. At this point, I switched engines and went to horse shoe backplates and tanks.
       

Love that twin Ken.

What were your original engines? Seems like Black Widows would be a good fit but probably not enough fuel carry to do the full pattern. Perhaps the reason why you went to horse shoes and tanks? Tanks and horse shoes moving the CG back a bit and requiring less tail weight.

Bob

K&S tubing...that's right. You mentioned it in my tank saga on the Mossie thread. Thanks for reminding me, teacher!

Running backwards in cooler weather...wouldn't help to drop an extra head gasket under the plug? You may lose a bit of power, but it may steady out the cantankerous engines.

Power offset. Can you swap the cylinders side-to-side? You'll lose the p/c pair, but as a quick test it may be easier than swapping the strong one inboard.

Of course, I'm thinking out loud. I'm pretty certain these are considerations you've already made.

Lastly, can we expect a well sorted aircraft in this scale to do "the pattern?" I hope my P-40 will do the old time stunt pattern. If it carries me that far, I'll work the next pattern up. I expect combat wings should do anything, but am holding judgement with profile semi-scale until I have a quick building airframe to learn with ( probably the P-40).

TIA

The 1/2A pattern as far as I know is just the same as it’s bigger brothers as in regular AMA/PAMPA. I imagine scored the same as well. I’ve never seen 1/2A flown in competition ever, so take that with a grain of salt.

Glad you got out and had some fun and sounds like things when well , i think changing the pis/cyl on the weaker engine will make a big difference , i have not had any good experance with the slit cylinders / probably just me .

Regarding a pattern for these little guys, I found two sources:
http://www.bjm-home.com/BJMEnterprises/page38.html

http://brodak.com/stunning

I'd be tickled pink if I could pull off the beginner pattern as described at Brodak.
Should I pull that off, then I'd do the OTS pattern.
My current P-40 will be used (trashed) trying these two patterns.

I suspect they won't look too good unless the plane can be hung out on longer lines. Time to make my 42'-48' (in tow foot increments) sets. No way would I try anything beyond a wing-over or loop on 27'-36' lines...too close to see what I'm screwing up!

My intent is to do the PAMPA pattern. While this sounds like something easy, it really isn't. Having the plane not fly too fast and do smooth transitions with 1/2A takes a bit of finesse. I currently have 3 1/2 A's that will do this. One is Norvel powered and was the easiest as it just offers constant drive trough the maneuvers, the rest are Cox powered and each one has taken a lot of tank playing with to make them do this. Brodak is going to do 1/2A stunt this upcoming year. I would love to participate. Working out the run time is critical as it's very easy to run short, but at the same token you can't over run either.

Ron, Larry Renger came to one of our club meetings some time ago. I had a blast talking with him. However, many don't take 1/2A serious and no one wants to give it a try because of all the work needed. Larry puts in a lot of work with the 1/2A crowd. Larry will be the first to tell you though he's a designer and not as good as a pilot. Just because the plane is 1/2A, you can use it in ANY contest. I've always wanted to participate in flying a 1/2A at a contest level. The problem with that is or could be the judges. They don't see 1/2A, they don't recognize  it's limitations and to them it looks different then the big boys. Seeing that Brodak wants to do this many of our guys and some of the Jersey guys want to participate in it equally. The rules though keep ever changing because this guy wants this and another wants that mind you neither of them will participate. I think I have some skin in this game and I have already suggested some opinions on this. Larry and the guys out west actually fly integral tanked bees, this requires pitstops.

Ken,

You mentioned having three available planes. What are they? Is this where we want lots of wing area to slow down a plane? How big before it loses too much speed to stay up? And can a small plane actually do an overhead 8 without falling off the lines?

Lastly, is it possible to see a triangle or square moving that fast and small?

I noted a guy posted software that will trace a video for after-flight review. This was posted over on StuntHanger...the video is awesome to watch. I'm going to try the software in my flight videos.

Hey there Ken. Good looking models you have there. Anyways, can I ask a question of your Big Otto. What material are the tail booms made from, as the plans do not indicate that. As well, can I ask what the actual wing chord on yours is as I just printed out the plans, and this thing looks huge. I have decided to start building one of these as I saw yours yesterday, and today I got myself a Silver Bee in the mail. Thank you.

The majority of Scientific kits build nose heavy. When a Cox engine is added, this only compounds that. I rebuilt the nose and pulled it back considerably. I also didn't make it as thick. I wanted to pull it in closer to the leading edge but I have a tank compartment I left behind the firewall for a later engine I plan to use. The run times are really just too short for me on integral tanked bees.

I will get a measurement later today on the root of the wing. The balsa tail booms are weak, they can split and I recommend plywood as this will prevent breaking and offer tail weight without adding weight. In addition, I made the elevator from bass wood. I still have 1/4 oz. of tail weight in the plane with these mods but it was flying quite well and looking real good. Big Otto has a very thick wing which is quite draggy for the Cox reedie. I wouldn't say it was under powered, it just could use a bit more ummph.

In addition, if you don't need the gear, I highly recommend losing it as it really is just a tripper on landing.

Big Otto from leading edge to trailing edge measures 8" The high point of the airfoil is 1 5/16".

Thank you very much Ken. That is exactly what I was looking for. Just for clarification for my build.

Jim , I just saw your question and I will answer the best I can do. The models I'm flying are the Brodak ARF Baby Clown, this plane flies terrific and in no means is it designed like the original PDQ baby clown. There's some many variations of this plane, Brodak claims authenticity, but it does share similar outlines. It has a fairly large wing for a 1/2A. This is a big plus. The other plane is a Dumas Baby Tomahawk. This is my favorite 1/2A plane of all times as I recognized it's capabilities 30 years ago or more. Same thing again, nice wingspan. The other is the Brodak Baby Lightning Streak, essentially a Flite Streak with squared off tail feathers. If you haven't ever flown a Flite Streak or a Baby, it's a must because they just fly incredibly well. The Tomahawk shares close similarities to the Streak wing.

All of the above have had their fuselages modified to either shift CG or to achieve enough area for a tank. The next problem is taming down the 1/2A's so that they're no so flighty. Well , this means limiting control throw and handle spacing but making the plane a little tail heavy for quick turning if needed. I have had good success with Brodak's offerings in terms of flying ability. Extremely free control surfaces are a must. I like to give up speed for rpm's and I usually go with Cox 5x3 blacks or Tornado 5 1/4x3's for props as they offer good drive maneuvering without making the plane too fast. If the plane is flying too fast, the maneuvers are going to be jerky which is exactly what you don't want.

Will any 1/2A do overhead maneuvers? This depends on several factors, weight being the most critical, the next is horsepower. Cox reedies are not all that powerful when compared to Norvel's. This is not to stir an arguement, I can fly almost any Norvel .049 with line lengths 7- 12 feet longer than Cox equipment. This doesn't mean Cox equipment is not a good choice. I like using Cox powered stuff with the exception of reedies trying to run backwards. If one tries flying overhead maneuvers with Cox Bees, one better be prepared because they work well when they're on, they're just never consistent and at some point they're starving for fuel causing a loss of power. This is where I try and do whatever I can to assist in making the tank feed better.

Having the correct prop is essential, too many times I see the wrong props being used. The Cox reedies have a little wiggle room for prop use for control line. Beginners usually start with 6x3's. This works for most offering decent speeds and occasional loops, however when you start flying consecutive maneuvers it's no good. Obviously it all depends on the plane, but for how I'm flying them, I'm not using 6's. The old Top Flite nylons were different and worked quite well due to thin blades. I also use line length to control speeds, I keep 35's, 38's and 42's on hand. I use Spectra or .012 steel lines.

Most important is the use of your entire arm. You need to lead the plane. One can't just flip their wrist and plane is going to follow suit. By using your entire arm in conjunction with slight wrist movements, you can gracefully make the shapes clean and NOT lose speed doing so. This is where the herky jerky problem occurs when one bleeds off too much speed and the plane stalls and the next reaction is full up to avoid terra firma. Having confidence and a backup plan is something you need to always think about. If you go into a overhead and find the plane is not going to make it, tuck it under and pull out inverted. Don't panic and have the lines raining down around you as the plane freeflights over the top and into the ground. If you can fly inverted, YOU can fly the entire pattern.

Ken what do you think about this plan .. https://outerzone.co.uk/plan_details.asp?ID=4540 Thanks

A few things I would change, I wouldn't core the holes for the wingtips as it's not needed, it saves no measurable weight and weakens it. I would also lengthen the nose and use 1/4" x 1/4" beams for engine mounts and add 1/64" ply to each side for doublers extending them back onto the high point of the wing. Even with the additional wood, I wouldn't lengthen the tail. If required, smash small split shot or wheel weights paper thin and use a hinge slotting tool and cut a slot on the tail of the fuse and glue them in. While the over and under rib/spar setup builds easy, it can cause problems if not cut accurately. If there's not enough room or leeway in the rib or spar due to tight fitting joints, it will dial a twist right into the wing.

       The real Top Flite Baby Streak is built on the same design, the Brodak version isn't. The Brodak version though is a bit problematic to build, there's more ribs and also half ribs. Brodak also uses a two piece leading edge and trailing edge which unless one is familiar with this type of construction, you can really foul it up. My personal opinion would be to build the Brodak Baby Lightning streak, it uses solid leading and trailing edge, no spar and has less ribs with the same outline and is equally as strong.

Thanks Ken i respect your option knowing you fly a lot the streak will be the way for me to go , not needing the extra problem in getting the wing straight .