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Old Feb 09, 2012, 09:13 PM
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DerekB's Avatar
Cape Coral, FL
Joined Nov 2001
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Originally Posted by markyb13 View Post
hello derekb yes it finally arrived just waiting on the esc's and battery also vinyl couple other odds and ends its huge lol cant wait to get started
I could not resist putting the model together with blue masking tape for a quick photo. (blue masking tape is just low sticky masking tape used for painting - it won't leave glue behind).
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Old Feb 09, 2012, 09:31 PM
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United States, WA, Seattle
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Originally Posted by Fotor View Post
That was my thought too.
The curbs make for quite the incentive to maintain directional control for the full rollout...

It's no time to get sloppy on the rudder...
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Old Feb 09, 2012, 09:57 PM
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Originally Posted by Doug W View Post
The curbs make for quite the incentive to maintain directional control for the full rollout...

It's no time to get sloppy on the rudder...
Thanks for the great videos. Nice landings!! I can feel the pressure.
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Old Feb 09, 2012, 10:43 PM
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Cape Coral, FL
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Carbon reinforcing

Doug W,

Regarding your wing reinforcing, are you adding more than what is already in there? Or is this something new that Mr. Ming added since your build? There is a carbon tube embedded almost full length of the wing and goes right through the plywood pylon. This is in addition to the main carbon solid rod that joins the 2 wing halves. There is also a carbon tube in the horizontal stab.

In my "X-Ray" photos, you can see the foam cells which might give you the impression the surface is rough. Not so, that's just the internal cells. The finish is very smooth for a molded foam airplane.

Derek
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Old Feb 09, 2012, 10:53 PM
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Cape Coral, FL
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Plywood pylons

For mounting the engine nacelles, I think we are supposed to cut out the foam where my knife is pointing in the first photo. The main carbon rod (used for the wing joiner) passes right through there and looks like it aligns exactly with the hole in the plywood pylons. That foam has to be cut out so the plywood can slide into the slot, then the rod is inserted.
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Old Feb 09, 2012, 11:02 PM
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Cape Coral, FL
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Hinges

OK, my last question for the night

I can't tell if the hinges are simply molded foam, or if some type of hinge material is embedded. They feel pretty stout. But I think it's just foam. If so, I'm cutting it and installing hinges.
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Old Feb 10, 2012, 12:33 AM
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United States, WA, Seattle
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Originally Posted by DerekB View Post
Doug W,

Regarding your wing reinforcing, are you adding more than what is already in there? Or is this something new that Mr. Ming added since your build? There is a carbon tube embedded almost full length of the wing and goes right through the plywood pylon. This is in addition to the main carbon solid rod that joins the 2 wing halves. There is also a carbon tube in the horizontal stab.

In my "X-Ray" photos, you can see the foam cells which might give you the impression the surface is rough. Not so, that's just the internal cells. The finish is very smooth for a molded foam airplane.

Derek
Derek,

See the attached mock-up photo where I ran an additional CF reinforcement- it is a long rectangular in cross section piece inserted vertically from the underside- just cut into the wing with a japanese saw and sand the cut slightly so the CF fits snugly. You will need to dremel an odd shaped (but small) hole in your engine beaer as the CF needs to cross through to the other portion of the wing slightly- otherwise it forces all the flexing moment onto the pylon instead of the inner wing section.

Keep in mind I primarily added the additional CF because I lost a lot of structural integreity cutting out about 20% of the wing (the flaps) and felt it prudent given I'd have a higher AUW as a result of my mods. If you keep your weight lower and don't add flaps, I don't see a major need for it.

I'm just an overly-cautious structures person and hate seeing a wing fold in flight...
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Old Feb 10, 2012, 12:35 AM
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United States, WA, Seattle
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Originally Posted by DerekB View Post
For mounting the engine nacelles, I think we are supposed to cut out the foam where my knife is pointing in the first photo. The main carbon rod (used for the wing joiner) passes right through there and looks like it aligns exactly with the hole in the plywood pylons. That foam has to be cut out so the plywood can slide into the slot, then the rod is inserted.
Yes- cut that small piece out. (And keep in mind among the 4 engine bearers plywood pieces there are 2 different thicknesses. Put a skinny one with a thick one and epoxy them together.)
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Old Feb 10, 2012, 12:38 AM
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Originally Posted by DerekB View Post
OK, my last question for the night

I can't tell if the hinges are simply molded foam, or if some type of hinge material is embedded. They feel pretty stout. But I think it's just foam. If so, I'm cutting it and installing hinges.
Molded foam, and I wouldn't install hinges- the whole plane is like that (ailerons and rudder) and it works fine.
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Old Feb 10, 2012, 01:11 AM
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Danmark, Midtjylland, Horsens
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Originally Posted by jakob k View Post
Well today my HET6904 fans arrived today and here is my question:
After having made room for my Hyperion motor and I mounted in the center as much as possible, then I fired the fan up with very little throttle and the fan started to scrape the inside of the housing. I stopped it immediately and took a piece of sandpaper and started to polish the inside and fired it up again and this time it sounded a lot better.

Can this really be true? Do all of you guys have scrapes on your housings?


-Jakob
Still no thoughts on this matter?

Doug you also use HET does your houing have scrape marks on the inside?
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Old Feb 10, 2012, 08:10 AM
6 months to finish a rtf
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upstate ny
Joined Jun 2003
1,843 Posts
jakob k

the scraping happens alot , its no big deal , what I do is to balance the
rotor on a magnet balancer :
http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML

then to help center the motor I wrap it with plan paper(which is removed
once motor is secured . the paper just makes the motor snug and
helps center it . then when you attach rotor slowly rotate the blades and
check the clearance .

I then run the fan increasing power slowly , if its properly balanced
it will run smoothly all the way through the range .

but if you did get a little rubbing - sand paper will fix it
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Old Feb 10, 2012, 09:47 AM
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Danmark, Midtjylland, Horsens
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Well HETs do not need to be balanced they already are from factory.
Right now I am considering purchasing 2 new HETs with HET motors so the issue won´t be there. _But then I would have used about....hmmm..... Way too much money on fans and motors.

-Jakob
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Old Feb 10, 2012, 11:15 AM
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Cape Coral, FL
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Originally Posted by Doug W View Post
I'm just an overly-cautious structures person and hate seeing a wing fold in flight...
I'm a structural engineer myself, so I hear ya .

I intend to do the flaps and I'll probably skip the working spoilers (like you said, 4 extra servos and a lot of work).

Can you remember where you got your rectangular carbon tube and what dimensions?

I noticed the 2mm plus 3mm plywood laminate for the engines. I'm going to look into adding some carbon tubes parallel with the plywood. My reason is where the plywood exits the leading edge of the wing, the plywood has the thinnest cross section, and will have the maximum bending moment. One good bump to the engine nacelle looks like it could snap that plywood.

The next worst thing to a folded wing would be a folded nacelle . That would be quite fun with both engines still working, but one pointed off 30 degrees .

I see only 3 primary things that need "fixed"
1) Additional wing reinforcing.
2) Additional engine pylon reinforcing.
3) Stiffer landing gear wire and tighten up the slop.
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Old Feb 10, 2012, 11:58 AM
6 months to finish a rtf
pulsery2k1's Avatar
upstate ny
Joined Jun 2003
1,843 Posts
DerekB

reinforcing is a good thing , but a lighter model will fly better
and have a lower stall speed - landing speed and last a lighter
model will have a much lighter wing cube load .

I cover my wing's with tissue and Water based polycrylic and
this made them stronger - I get alot less flex than with just painted
wings. weight gain slight .
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Old Feb 10, 2012, 01:27 PM
Don't Move I've Dropped My Nut
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United States, AL, Huntsville
Joined Feb 2009
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Quote:
Originally Posted by DerekB View Post
I noticed the 2mm plus 3mm plywood laminate for the engines. I'm going to look into adding some carbon tubes parallel with the plywood. My reason is where the plywood exits the leading edge of the wing, the plywood has the thinnest cross section, and will have the maximum bending moment. One good bump to the engine nacelle looks like it could snap that plywood.

I see only 3 primary things that need "fixed"
1) Additional wing reinforcing.
2) Additional engine pylon reinforcing.
3) Stiffer landing gear wire and tighten up the slop.
Derek;

I can appreciate the fact that you are a structural engineer, but IMHO, you are "over engineering" just a bit here. Based on my experience with my 737, items #1 and #2 are not necessary.

In regards to #1, EPO will flex MUCH more than the other types of foam before breaking. As I will eventually mod mine for flaps, I did install a 5/16 dia CF tube just ahead of where I intend to cut out the wing for flaps. I extended it to about the mid area of the aileron hinge line. Got about 9 flights on it. The wing flex looks pretty much "scale", as the full size wing flex.

As for #2, a good glue line of the ply/EPO "sandwich" will yield a very strong pylon assembly.

I totally agree with #3. I installed some stainless steel 3mm rods. But I still managed to bend them slightly. (I need to make better landings!)

Anyway, good luck with your build and whatever mods you choose to do. You'll love this model!
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