Sethhunter

Jim great stuff! I hope you post your progress - that will be one awesome airplane!! I assume you use the foam to develop the patterns for the sheetmetal?

arspievack

Rhubeus.
You can't fool me. Antone with a back yard like that can't have a workshop much cleaner. Your project looks great. Keep us informed about progress of both the airplane and the car wrecks in your yard.
Welcome to the Pflaz thread
alan

Rhubeus

I'm glad that I happened across this forum. I kept wondering why the front cabane mount and engine cowl wasn't located quite right. After looking over the numerous pictures, I figured out the front of the fuselage was to flat on the sides of my example. One thing nice about working with a foam structure is that alterations are rather simple. So now I am in the process of adding foam and shaping it to a rounder cross section around the engine.
Jim G.

Sethhunter

Hey all - so how do these Walbro carbs work? I flipped my DA-50 to death. I've got spark. I've got fuel running freely at the inlet to the carb. The choke closes. I've spun the needles all over. The cylinder is dry. No fuel going where it needs to. What's that little tube between the carb and crank? Fuel, or air pressure? If it's fuel, it's dry! Any ideas?

Here's a final picture of the spinner with the plug. Now if I can only get the prop spinning!

BobH

My Feedback: (2)

That little tube from the carb to the crank case is probably your crankcase pressure/vent line. The pressure pulses the pump diaphragm on the carb with each engine stroke.

try turning both your lo and hi speed needles out about 3 turns.. choke your engine and turn it over until the carb is wet. Or Prime the carb with a squirt of gas and then try flipping the prop. If you have fuel draw problems (like the inlet needle valve being stuck in the carb) your engine will run on the prime and then quit... even if this is done repeatedly.

If that doesnt work then you either aren't getting fuel to the carb or the carb has an issue.

Sethhunter

Thanks Bob - I thought that line might be air for the pump. The only thing that seems odd is the needle valves are hard to turn, not impossible but as if they had loctite on them. Unfortunately the carb is deep in the airplane (can't prime it). Looks like the engine will have to come out to test. (Disappointing. One of the reasons I paid a premium for a DA was to minimize the chance of a problem like this.) Of course I don't know at all if it's the engine's fault. Should have run it before installation - would have been a better hedge against problems.

TFF

I dont have a gas engine ,but theguys at the field flip it with the choke on until it sputters once then choke off and one to two flips and it is running. If you bench run it also run it upside down because it is like your instillation. One member this last Sunday had a new never started gasser, and it took a bit of flipping the first time; then it was better.

Can't wait!

Tom

Sethhunter

Thanks Tom - I probably wouldn't have thought of testing it inverted.

FokkerAce

Seth, you've done a beatiful job on the Pfalz!.

a 1/16th inch hole or so near the carb would solve your prime problems, or run a brass tube down from the top of the dummy inside the cowl so's a prime can be done...

just trying to help.

FA[8D]

Sethhunter

Thanks FA - another good idea; do you guys find gassers often need a prime? DA confirmed the little hose pumps air to the diaphram pump. Needles are stiff because they loctite them in place. Trying a prime in the exhaust manifold or plug hole is ok; they thought once it starts maybe the diaphram will soften up and prime more easily.

BobH

My Feedback: (2)

Seth, you almost always need to prime gas engines when they are cold. After they have been run and are warm they usually start with out a prime. The choke is for priming the engine, if you have one. Most airplane gass engines have chokes.

Loctite is not something I would put on needle valve. That's just my opinion. I'm sure they have their reasons for doing it. Having worked for a Chain saw Mfg (Homelite) for ten years I never did it and never saw it done.

Sethhunter

Its been a long day but I had to let you guys know IT FLIES!!!
My flying club was incredibly helpful - on one of the most georgeous days of the year they cleared the air and allowed me to fly from the end of the flield rather than the pilots station. I hope to get some video on the net but I can share the following observations:

Safety tying tunbuckles is a pain.
Hatches that come off will when the engine is running.
CG at 35% mean chord is too far back.
Taking off with the choke on really defeats the purpose of using a DA-50.
The rudder is MUCH more effective than the ailerons.
No Dihedral on the top (combined with tail heavy) gives this plane a scary sense it will go where it wants.
2 degrees downthrust is not enough.

OK - so the take-away is this:
25 oz/sqft aint so bad. It would help not to have the choke on, although leaning out the engine to compensate worked wonders (dah)?!
Mixing down trim/right rudder into up throttle is a good idea.
Mixing rudder into aileron is a good idea.
Moving the CG to at least 33% M.A.C. is a good idea.
Building a plane that doesn't require safety wiring turnbuckles is a good idea!!!

Soft landings are SWEET!!

All in all - a successful day. My thanks to all of you for your support and interest.

arspievack

Seth,
Hooray and congratulations.
We're all thrilled. It's been a long trip for you(and us) but well worth it.
We need air photos and a full description of the flight.
I used to keep logs of my good planes which allowed me to make changes better and remember what worked and what didn't. More info please, I can't wait.

great job we're all delighted and thrilled.
Congratulations
alan

abufletcher

Yes, congratulations on a successful first flight (we not longer need to call it a maiden flight) and thanks ever-so-much for remembering the teddy! It's great to hear that it made it back to the field despite the "wild ride" -- the second flight will be much more comfortable. I'm looking forward to seeing some inflight shots.

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Erich_Prinz

WU HOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Nothing like the relief of a soft in-tact landing after the maiden flight.

Like everyone, can't wait to see the photos/video.

Congratulations Seth!

PfalzPflyer

My Feedback: (3)

Congratulations on a successful first flight. May it be the first of many!

I'm sure you'll enjoy the plane much more once you make corrections for the things that need adjusted. The CG issue in particular will really make a difference. (As will remembering the choke... )

I agree with the others that in-flight photos and video are a must. An incredible plane like that is most appealing when airborne.

Well done, Seth! Salute!

Very best regards,
Dean in Omaha

tommyp

My Feedback: (1)

Congratulations Seth!
I'm sure once you get the CG worked out you'll find it to be much more enjoyable to fly.
Looks super!
Best,
Tom P

TFF

Congradulations!

Tom

VNulk

Well done Seth,

There's nothing like a successful flight to top off a magnificent project!

Congratulations!

arspievack

Seth,
For what it's worth, when I was setting up a Bi-plane, tail dragger, I'd set the CG by blocking up the tail so the plane (fuse) was at zero incidence.
Then I'd draw a line from the rear edge of the wheel up thru the lower wing and see where that intersected the bottom of the top wing. That's the CG point.
I knew that I wanted the tail to drop when the plane was landing and the fuse was level to the ground.
That spot usually got me up and down for the first flight.
Keep going . we're all living your experience with you and we love it
best
alan

Mode One

Alan, On the SE5a I am almost ready to test fly, I looked at your formula to see if it agreed with the plans. I find that the CG indicated on the plans is maybe 3/4 to an inch aft of the point you've indicated as a CG location. I agree that there certainly is a relationship between the location of the landing gear and the CG. However, I've never heard any one say that this was another method to locate the CG. What if you used smaller or larger diameter wheels?

I respect your opinions and I know your hiistory. I have the Flying Models magazine in which your Pfalz DIIIa article was printed and I want you to know I'm not disagreeing with you; however, can you elaborate on this method better?

BobH

My Feedback: (2)

Maybe this has been mentioned already; to find the CG of a Bipe you measure the horizontal distance of the Trailing edge of the lower wing to the Leading edge of the top wing and then start at around 25% back (from the front) for the CG.

Essentially you are combining both wings into one large platform and then using that as the wing surface. The 25% CG is normally a safe starting point.

Sethhunter

My method for calculating CG location on a bipe is to use a weighted average, using the AREA of the top and bottom wings to weight the CG location calculation. I think this is the commonly accepted aerodynamic method, but I haven't looked it up for 20 years so I can't be sure my memory is correct. My CG ended up at 35% (dry) rather than a much more conservative 25%, mostly because I was so hesitant to add more weight and felt I could handle the adverse trim (I had a "copilot" standing by to crank in trim adjustments for me). Weight was not a problem, but coupled with the aft CG, she bounded off the ground in about 10 feet! Incidentally for the same reason I flew with LOTS of elevator throw, so I wouldn't "run out of down", and exponential so it wouldn't be touchy. As it turns out, pitch was way oversensitive anyway; only slight pressure on the stick was all that was required to move the nose up or down, again due in part to tailheaviness and excess travel. A couple years flying 3D planes was a big help! More than 2 deg downthrust would also have helped. The plane flew much much better at lower throttle settings. Still working on getting some video clips!

Sethhunter

Here's a link to a nice article on biplane aerodynamics including finding CG by Andy Lennon in Model Airplane News, 1998.


http://findarticles.com/p/articles/m..._n8799373/pg_1

TKFOKKER

Seth it's been fun watching your build. You certainly did a fantastic job. Congratulations on the safe test flight. Love those German planes!!! Good luck with all your future flights. Tom K.