Johnny C!

Ok guys! It wasn't pretty, but I drove my Dazzler into a stack of wooden pallets!
I think my FL-70 is Ok & I already have another Dazzler Arf on it's way!
Now for the fun part! The nose of the Dazzler is toasted back to the
leading edge of the wing, but everything else seems Ok. I have several servo's
& 2 Magnum .25s laying around, so why not!
I saw a Something Extra twin bash today & really like the simple hard wood
rail design. Simple & effective. Of course I have envisioned cowls & FG engine
nacelles, with header tanks & a main tank.
I guess I can use the moment of the FL-70 & get a close dimensional layout
of the .25's to get close to the correct CG & tweak it with locations of the
battery & reciever.
I've read that out thrust isn't that critical on smaller planes so I'll plan
for 4-5 degrees.
Any thoughts or comments will be appreciated. I will post pic's & updates
as this progresses, but it's going to happen to fast. The weather has been
great & I have several thing to fly!

Thanks in advance!

Johnny C!

William Robison

My Feedback: (3)

Johnny:

Many good twins have come from similar circumstances. My first bashed twin was a Hobbistar 60 that got a shortened fuselage as a result of its going out of view behind a line of trees.\\

It came out so well that it took second place in the "Great American ARF Bash" contest a few years ago in MAN or RCM, not sure which one it was. But they did give me a nice check as a prize. Picture attached.

Hope yours comes out as pleasing to you as mine is to me.

Bill.

Johnny C!

I just looked at the wing structure. It seems the spar ends
about where I need the engine mounts to go. I'm not sure
this will work, but i have noting to lose by cutting it open.
I'll keep you posted.
Thanks William!

Johnny C!

Johnny C!

Question to you guru's!
Should I make the engine mounts parallel
or flat in relation to the horizontal stab?
The wing is a very thick semi symetrical
airfoil, so it is not feasible to guestimate
from the wing. The original firewall is gone,
so I can't pick up from that.
The stab will be relatively easy to index
from. Am I on the right track here?
Thanks in advance!

Johnny C!

Johnny C!

Hey,
I'm just now getting back to this project. I have the fuse nose
constructed, but not yet attached the fuse & I have my hardwood
mounts planned & under way.
Here's my questions for tonight. Can I use a single main tank in
the fuse & use two small header tanks in the wings? This would
require two clunks & two pressure lines. Not sure if this
will work, but as I see it, if the pressure pulses are in sink or out,
they should still push fuel to the respective engine.
Or I use two smaller mains & the headers.
A question for either arrangement is that the fuel & runs will
be about 11-12". Is this too far? Or should I concentrate on
individual mains in each wing?
Thanks!

Johnny C!

William Robison

My Feedback: (3)

Johnny:

As far as the engines are concerned the header tanks make no difference to the fuel draw, fuel still has to be moved that 11-12 inches. Muffler pressure has been used successfully for this, but many more failures than successes. And using muffler pressure when one engine starts fuel will start running out of the other engine - the pressure will force the fuel through any way that's open. The ones that have worked have used separate tanks for each engine.

You can use a Perry pump on each engine, that's the way I did the plane pictured above. Or you can use the Cline or Iron Bay regulator system. With either pumps or the regulator system a common tank works fine. I'd still not use header tanks, unless they are the only way to get as much fuel as you want on board. Just more connections and seams to fail. Yes, a separate clunk for each engine is best.

HTH.

Bill.

BillS

I was not able to use a single main tank. I needed more fuel and added a single center tank. With a single main tank the high speed on the engines could not be set. One engine was 800 RPM below the previous setting and the other was a couple of hundred RPM off. The information was discovered during 30 minutes of disappointing bench testing. Pumps and pressure regulators were not considered or tested.

I was able to use two main tanks. With two main tanks the muffler pressure is isolated for each system. The fuel lines are about 21� long. The airplane is still flying in a four-tank configuration.

If you are capable of sustained 1000’ knife-edge the system might be unsatisfactory. Don’t know; don’t care since both the airplane and I are not capable. One might suspect the higher engine would starve if the knife-edge were sufficiently long. However the concept could be bench tested.

On my current project oval tanks are being used in the wing behind the spar. The tank protrudes below the wing but not above. Tank covers on the bottom of the wing are being used. If more fuel is necessary an auxiliary tank will be put in the next bay to the inside.

Bill

Johnny C!

Thanks Guys!
One of my LHS's has a wide variety of tank configs, so I
need to take the plane & try them out. I do think that
individual main tanks is best, but I'm not sure how much
fuel I can get in the wing bay. I work toward this first.
Thanks again!

Johnny C!

Johnny C!

I have another question.
I have purchased some 3/8" square
spruce that I was intending to use as the
motor mount beams. Based on original
engine weight & dimensions, I have calculated
that these beams will need to extend about
4-1/2" inches in front of the leading edge of the
wing. I think this may make for a fairly long/weak
structure. However, since I intend to place the fuel
tanks in the wings & therefore not in the nose
compartment, I can now put the battery & reciever
there which will substantially shorten these beams.
I'm guessing back to 3" or so. Will spruce be OK for
this, or should I buy some maple?
Thanks!

Johnny C!

BillS

I’m not a builder but also don’t remember seeing a wood beam mount that was not maple.

Bill

Johnny C!

Affirmative
Thanks William.

Johnny C!

This project had been relegated to the back burner for a few months,
but I have made good progress in the last few weeks.

I have the plane pretty much complete with the exception of a few things
like, nose cone & cowls are not constructed yet, I have some covering to
do, servo throw tweaking & nose gear linkage (I have converted it to a
nose dragger). As it sits now, the CG is pretty close, but I will tweak that,
as well, when the plane is more complete.

Here is my question...
With the CG pretty close, and the plane sitting on the floor, it takes quite
a bit of hand pressure to push the tail down for a take off attitude.
Do I need to move my main gear more toward the CG? I can readily move
them forward about 3/4" & I could also bend the wire gear forward as well.
I know pics will help, & I will try to get some posted by tomorrow.

This is an aspect that I had not anticipated as being a hurdle. But then again,
learning new things is what keeps this hobby exciting.

Please let me know your thoughts.

Johnny C!

P.S. How do I edit the thread title text?

William Robison

My Feedback: (3)

Johnny:

The further behind the cg you have the mains the more air speed will be needed to rotate into take off attitude. BUT if you have the nose strut long enough to have the plane sitting at a positive angle there is no need to rotate as the plane will already be in its correct attitude for getting off the ground.

The RCU software locks the thread title, you can't edit it.

Bill.

William Robison

My Feedback: (3)

Down side is that the longer nose strut makes landing harder - landing nose wheel first is usually not a good idea.

Bill.

Johnny C!

Will,
That's what I thought. I would like to get it
arranged so that the plane sits on the ground
in a nose low attitude & be able to rotate to the
mains for take off. This will allow the nose
to drop as the mains touch down & kill the lift
(lower angle of attack). I think that will be the
most desirable arrangement.
Thanks for your input.

Johnny C!

Johnny C!

Will,
What engines & props do you have in
your bashed twin above. I like the 3 bladed
props, but I really doubt I could get any
3 blades to work on my .25's.
Thanks again!

Johnny C!

William Robison

My Feedback: (3)

Johnny:

The pictured plane is a little more than ten years old now, it was finished shortly before Magnum released the XLS series engines, so it has a pair of 46XLs pulling it with Zinger 10x6 three blade props. Zinger has the best selection of three and four blade props I know of, but their smallest three blade is an 8x6 which could be cut for your smaller engines. See them [link=http://www.zingerpropeller.com/Fiber.htm]here[/link].

I'm running a cut down 8x6 (7 1/2x6) on my Eaglet with a Magnum 25 engine, it does fine with it.

If you can find them, Tornado (Grish Brothers) used to supply three bladed props in 7" diameter, but I've not seen any sign of Grish for about 5 years.

Zinger also sells nice three blade spinners, listed just below the 3b props on the page I linked. Good prices too.

Bill.

Johnny C!

Ok,
Tonight I was able to move the mains about
5/8" forward on the mount I had built. I was
also able to bend the wire to bring the wheels
forward a little more. I probably gained over
an inch.

It now takes considerably less down force to
bring the nose up. I think that with flapperons
I will at least be able to get airborne in ground
effect to rotate & go!

I'll get some pics posted tomorrow, I hope!

Good Night!

Johnny C!

KidEpoxy

Bill-
didn't I see an MAS add for 3blade in 7" & 8" ?

er, I mean
IIR there is/was MAS in 7 & 8 3blade... saw them when I got my 6x4 MAS 3blades (.074Norvel).... dont recall where, & a while ago

William Robison

My Feedback: (3)

KE:

MAS may well have smaller three bladed props than 12" diameter, but everything I have at 10" and smaller is either a MAS cut down, or Graupner and Tornado brands. Tower might be the easiest place to check.

Bill.

Johnny C!

Here's a pic. I have a short list to finish.
I'm working on engine cowls now, but they
are just for practice for the nose cone. I
guess I could fly it without the nose cone as
well, but I at least want that on, if not the
cowls. I want to bench run the engines,
but I only have a few other things to do.
Thanks for all the help!
Later!

Johnny C!

Johnny C!

Flight Report!

2 OS .25 FX's & 8x5 APC's.

UNBELIEVABLE!!! I haven't had that much fun with a
model airplane in a long time!

We did some engine tuning and some high speed
taxi runs, just to run the engines a little more (2
tanks on the bench for each). Full throttle
acceleration was outstanding. With full up elevator
deflection at full throttle the nose wheel lifts immediately.

It fly's just like my single engine Dazzler (accept that the
twin is way faster). No bad habits, a little up trim, everything
else was dead on. It's heavier than my single, so I was a little
worried about slow speed handling. No problems! I did bring
it in a little hot, but I just kept bringing up the nose & made
three of the prettiest landings I have ever made. I did not try
flapperons yet. The aileron roll rate was phenomenal.

Too much stinking fun. Twins are addictive aren't they.
I'm seriously thinking about a Herr F-82 & 2 Norvel .074's
next!

The attached pic is just before I left for the field, & I really
didn't think it would come back that way. Did I say too
much fun?

How do I edit the thread title to add "Flight Report".

Thanks for all the help!

Johnny C!