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Hot Topic (More than 10 Replies) EBM Jr. Commercial build and fly (Read 1530 times)
Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #15 - Jan 16th, 2024 at 3:10pm
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Ah alfakilo,
you may have busted me for being cheep...
I didn't want to put new wood into this.
I thought the gussets would add weight and
the tail needs to be a little heavier and
I hate installing gussets and
my tissue application needs a more stout frame
more wood is gooder...
or...
I could learn to cover with less tension.

thus gussets.

now, when I am writing this, I realized I may have the kit wood still.
If I had found some wood the correct size, I may well have tried
the dado technique you show.
The crossover cuts give me pause, I never thought to try that...
it seems a great way to add a little triangulation to the stabilizer
the hinge line can be a little fatter and a very slight angle
to the leading and trailing edges.

all that said...
your post had me checking some results.
I wanted to see if dados helped stiffen the tail feathers
I cut them into the birddog empennage,
so far, that trial says use the joint whenever you can.
it adds work to the build, yeah and
less work than gussets and lighter results

... I wonder if I can do that center joint...

victor
  

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alfakilo
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Re: EBM Jr. Commercial build and fly
Reply #14 - Jan 16th, 2024 at 1:20pm
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Traditional flat horizontal and vertical stabs typically use butt joints. Never liked the method so with the Pfalz, I tried something different. Instead of butt joints, I used a "dado joint"...using notches. In this way, I could have the spars and ribs stay as one piece by notching them so that they could interlock. I used thinned white glue on the hope that the glue would soak into the notched joint for better strength. I also notched the leading and trailing edges. Turned out ok and seemed to resist bending.

I used a former notching tool to make the notches.
  

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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #13 - Jan 16th, 2024 at 12:36pm
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Hi terryman,
I went gussets... see the bones photo
and yes I forgot a pair,
they were added after photo and before cover.

I have it covered with some yellow tissue I found.
in my collection of tissues.   not sure where I got it.

the assembly was wet covered and then doped
it flat so far, and I will stack the encyclopedia on it just to be sure.
The main wing is being set straight.
it look serviceble last night.
and it seems to revert to old shape
it takes longer after each flattening
so I think I am doing good.

the next post here should include trimming.
we shall see what the weather does.

I guess I can fly if the snowflakes are going straight down.

victor
  

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terryman
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Re: EBM Jr. Commercial build and fly
Reply #12 - Jan 9th, 2024 at 10:20am
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" ... does anyone know why rudders rarely curve?"

My guess is rudders are often more triangular in shape so resist twisting better than the more rectangular shape of stabilizers.  Rudders are also often smaller than stab's.

Things to help prevent warpage:

Pre-shrinking the tissue,
laminated frames,
datto joints,
gusseted joints,
add camber.

Terry



  
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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #11 - Jan 8th, 2024 at 8:29pm
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... the fog of time lifted her skirts
and I got to see well turned ankles...

my EBM Jr. Commercial  rose into my awareness
as now would be a good time to fix the potato chip stabilizer.
time and different sorts of tissue is my best guess for why.

it is a hard to see oversite for how a 'fix' like this one
can  take a  "I'll fix that later" second place and years kick past.

unglued the tail parts. 
does anyone know why rudders rarely curve?
the rudder is glued to stab.
stab got vaporized in acetone in a zip bag...

the parts fell loose and I marked 'em with a pencil for place.
I took a photo...

that was all I expected to need to do.

wing has curved a bit .... the main wing leading edge is broken. 
I am pretty sure that break happened while inside...
so more to fix. 

more patches will make it look more 'mine.'
I doubt I have any of that yellow left...

victor

edited to add a missing word...



« Last Edit: Jan 9th, 2024 at 12:05pm by Rekitus Maximus »  

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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #10 - May 19th, 2021 at 7:30pm
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hi all,

I set the main wing on my building board covered in
carefully arranged  clamps with weights to hold it flat...
I used very thinned dope to re-shrink the tissue.
the wing was mostly arched  it seems to be reasonably
flat and true as of my writing this.
I think more than two days after the flattening.

After repairing and adding gussets to the landing gear mount,
seein' as how the glue and repair/build stuff was out... awaay I went...
'n added a plate to hold a weight at the bottom and rear of the fuselage.

:--D   as the new tissue n glue n dopes all dried...

I strolled out to the flying field.

I got in three flights.  The wind picked up and so I went back home

a couple glides for balance and flight characteristics.
Then wound it up to 150...(motor is a 1/8 loop about 12 inches long)
it drifted on a lazy left slowly losing height.
it stopped on a camper... neither was hurt.
that was a fairly long flight and looked good
second... wound to 170  got a nose up to stall
and a gust of wind lifted left wing... it was a pretty wing-over.
I was picturing a cartwheel landing.
it leveled out quickly and did a steep glide to ground.

back to 150 and toss...
it went three feet and hung there... twitching while rising a little.
it dropped the nose and glided of to the left a bit I had to walk 10 feet
to get it...

I am pretty sure I can add turns onto the motor.
If I have it, is a  similar length of 3/16 a lot more power?
I think I have 3/32 and I was thinking two loops...

The gizmo geezer prop assembly has been performing
as it claims.  That is rather pleasant.

victor








  

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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #9 - May 16th, 2021 at 1:34pm
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the tissue and covering is a skill no doubt.

I am certain I am applying it too tight. 
I'll look for ways  to get what I want without over doing it.

onto the flights
I think it is going to rain soon anyway..

flights it didn't do anything other than dive.
I lifted the leading edge about 3/32 the thickness of a scrap that came to hand

that got flatter and less active diving
added tailweight.  and a reasonable glide, the plane does a fairly straight flight

it ummm, flies faster than I'd like and the slope is ...
weeeell... not bad and I think at that speed the nose should come up a bit.

On one landing the gear broke the mounting inside the fuselage.
so I took the wheel assembly off and removed the tail weight.

balance and flights were similar.
so I gave it a fairly hard toss to see if it would zoom up.
oooof... it went straight and level and lost a bit of speed then glided down.

I can't decide what to do with that result.
I think I'll try tail weight to see if I can get scalloping.

after looking the plane over, it looks pretty close to the plans.
I guess I could flip the elevator over.
Gunna repair and reinforce the landing gear mount.

that is why they made rainy days.

victor
  

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Sky9pilot
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Re: EBM Jr. Commercial build and fly
Reply #8 - May 16th, 2021 at 12:54pm
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Looks like you have a pretty good handle on tissue application.  It is a skill that is learned and improved upon as you experiment and find what works best for you.  Everyone has their own techniques!!! Smiley
  

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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #7 - May 16th, 2021 at 12:16pm
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is all its preflight glory.

what ever else is true
I am convinced that what I see here for tissue covering jobs
is currently past my abilities.

I gave a bunch of ideas a try on this covering job

:--D
mostly I expect to hear gulps while y'all try to find nice things to say.

with any luck I'll write a flight report soon.

  

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Rekitus Maximus
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Re: EBM Jr. Commercial build and fly
Reply #6 - May 15th, 2021 at 5:59pm
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thanks Toulouse,
you are kind.

I picked it out as what I thought would be a simple build.
straight forward, clean... nothing complicated...
I think perhaps the more reasoned outlook would be
to say that RC airplanes are easier to build?
stick n tissue lacks servos and pushrods and that does not
make the overall build easier.  ... different mostly.

I expect I will build the next one with a different nose block
so of course I ordered a different high wing thing.
a plain plane.

after all one should always make plane plans.


ah the tissue problem... I seem to have success with
damp shrinking the tissue.  then after it dries
damping the tissue again and  setting the stuff with my normal
covering techniques...

victor







  

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Re: EBM Jr. Commercial build and fly
Reply #5 - May 15th, 2021 at 2:49pm
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Smiley

Bones picture looks great.
Neat design.
I am sure you will sort out the wing tissue issue.
All the best
Enjoy your posts
Smiley Smiley Smiley
  
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Re: EBM Jr. Commercial build and fly
Reply #4 - May 15th, 2021 at 2:49pm
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Smiley

Bones picture looks great.
Neat design.
I am sure you will sort out the wing tissue issue.
All the best
Enjoy your posts
Smiley Smiley Smiley
  
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Re: EBM Jr. Commercial build and fly
Reply #3 - May 14th, 2021 at 7:55pm
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almost forgot in the excitement.

I took a photo before I started covering.

  

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Re: EBM Jr. Commercial build and fly
Reply #2 - May 14th, 2021 at 7:49pm
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Hi sky9pilot,
the sticks were marked
I rather brainlessly chopped the marked end off
here and there by being thoughtless...

and onto today's adventure...

lets go with I am a little unhappy.
see picture....

I want to state this is new for me. 
I've poked a hole with a finger or a brush and gotten a ...version of that.
Just not along the whole wing.

I damped the tissue and thin doped through it.

I took it off the wing and will consider solutions...

Edited to add: I hate to dry cover wings because
I think that part should be taut.

victor
  

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Re: EBM Jr. Commercial build and fly
Reply #1 - May 13th, 2021 at 12:04am
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If you have some colored felt markers you can mark you balsa stringers on the ends or with a short line near the end of the stick using a separate color to designate hardness. Color is up to you. 

Check out the tutorial section to determine how to tell where to use the various cuts of balsa. In the Balsa Grain check out the balsa density pdf also: Balsa Grain Click Here
  

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And ye shall know the truth, and the truth shall set you free. Jn 8:32
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