Monster sized Fock-Wulf FW-42

rockyboy

Skill Collector
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For my first big foam build, or rather, the first time I'm crossing the 48" wingspan mark, I'm going to attempt a super-sized version of the Focke-Wulf Fw-42 Luftwaffe Bomber. This will be a team effort and an extension of the Team Rockyboy Mini FW-42 being entered into the 2018 Flite Test Forum WWII Design/Build Challenge

fw42-1.gif

https://en.wikipedia.org/wiki/Focke-Wulf_Fw_42

http://www.luft46.com/fw/fw42.html

So why the separate thread? This build is going to be very different in technique and approach compared to the Mini FW-42. To help keep confusion down, let's keep the lanes separated. :) At one point I was thinking to keep this largely under wraps for a big unveiling at FFE18 but the more I get into the planning phases, the more I realize I'm going to need community help from others who have tackled big projects if this is going to be as succesfull as I want it to be.

A couple expectations I'd like to express, mostly to keep myself on track, but happy to receive input from others too.

  • There are still going to be some special sauce surprises that will be built into this project (you know what I'm talking 'bout Psybog), but I want to keep the bones of the construction and planning in here to help both myself and others who are considering taking on a big foam build.
  • Plans will be released - as much as I end up developing plans for this anyway - but think a good bit of this might be 'furnished and installed by contractor' as we used to say in the architectural business.
  • Target completion date is a maiden flight pre-FFE18
  • I'm going to try and keep the 'totally new to me' techniques down to two or three, which might mean leaning on tried and true but less elegant solutions to some problems. Don't think I'm going to hit Joshua's target of one new thing per project here. :confused:

So I'm going to wrap up this post here, create a reserved one below this for the final pictures / video / plans, and then start out some considerations and strategies I've been thinking about and would appreciate some community input around.

Thanks for joining Team Rockyboy on this project! :applause:
 

PsyBorg

Wake up! Time to fly!
From what I have seen in the past with "Monster FT style builds are this...

A lot of them failed out of the gate for under engineered main wings. they either fold up in flight from not enough support structure or the flap like a bird and are hard to control. I think if we can get the wing solid enough the rest will fall together easily for the skills you already have.

The next thing is control surfaces. Most suffer from to much movement and do not fit the style of the air frame they are on. seems like everyone wants to make each plane a 3d plane whether its a fighter or bomber or experimental. As long as we keep in mind we are doing a heavy bomber and stay on the reserved side of things we should have a decent result. I know the mini Josh has produced seems to be pretty agile and sturdy so we know its upper range and capabilities already.

I think we should focus on looks and function and keep performance within its original designed purpose. Big , slow, and capable to carry serious weight.. (which btw should be part of the judging for the larger sized bombers in the competition.)

I am nearly done with one of the sections we have discussed. Just need to smooth things out around the edges. Also need some final dimensions to work with for other aspects but will talk to you in Asana or pm's about all that.
 

rockyboy

Skill Collector
Mentor
Oops! Sorry about the out of order posting Psyborg - I see we are already very much on the same page, I was just typing into this window for a couple hours between work distractions and forgot to check for new posts before I hit save! :black_eyed: I'll continue the discussion of the specific things you brought up in a sec...

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Ok, on to the planning. :)

Flight objectives: I plan to fly her 'scale like' for a big bomber - i.e. going around in big circles and not carving up the sky with crazy 3D moves, or even aggressive rolls and climbs. She should be able to handle the G forces of pulling up from a good dive run, and that's addressed as a factor of frame design rather than power wattage or control surface sizes.

Scale: A Monster Build needs to be big enough to justify the title. I've really been inspired by seeing creations up close like the 102" PBY by @Localfiend, the beautiful Goth Bomber by @wilsonman, and the awesome big Russian bomber with the super cool custom aluminum dual axle / dual wheel landing gear at FFE17 (so sorry I've forgotten the name of the amazing builder at the moment). So I'm roughly planning for a 102" wingspan here too. This is a derived number from dual 48" wing panels and the resulting 6" wide fuselage.

Aerodynamics: As a canard I'm looking for friendly stall characteristics, and as a big bomber she needs to have a pretty serious amount of lift. From digging around a bunch of airfoil info, and re-reading the materials Joshua put together for his FTFC18 project, I'm leaning towards either the more scale appropriate Davis airfoil, or the stable and high lift Clark-Y (which I happen to know I can easily create at any size needed for the main wing and canard - Lowrider test cut succesfull last night! :) )

Wing Construction Style: This is an area where it's going to be new techniques for me. Haven't done one this big. Pretty much all my foam wing building experience has been spars with foam sheeting - haven't done any significant hotwire work yet. So I'm leaning towards foam ribs with foam sheeting, spars of some sort - wood/fiberglass/aluminum, and perhaps balsa / ply reinforcements on selected edges and mounting spots.

Fuselage Construction Style: My experience here has been DTFB and balsa, but this is another area I'm thinking to stretch my skills. I like the more scale like shapes of hollowed out block foam construction, and with the right type of longitudinal reinforcements I think we can make this work.

Controls & Linkages: I definitely want the fine tuning of adjustable canards on this one, and would love to have a more scale looking beastie by keeping all the linkages hidden. There are lots of good ideas and examples out there for doing this on both canards and ailerons, but it's another 'new to me' area. Plenty of new things to do from a receiver/wiring harness perspective, but I'm not worried in the slightest about this area of the project. That area of design & build always been a strong one for me.

Landing Gear: Here's another area where I'm conflicted. There are only pictures and descriptions of wind test models for this design, and none of those had fixed landing gear. So obviously the gear are intended to retract. But there are a whole lot of retract messes out there, especially at large scale. The consensus seems to be 'Robart or bust' - but that just transfers the pain of poor performance directly to the wallet. I don't think I can afford a set of Robarts for this. And I'm not sure I want to tackle custom designed/built retracts on top of all the other new things I'm already doing with this project. That leads me to options of fixed gear or belly lander with a launch cart - I just don't think this is a hand launch kind of plane. Then again, the 100" PBY looked amazing on it's hand launch, so it can be done... input especially welcome on this one.

Power System: Oh yeah, she needs a way to put watts into the air! Twin engine design obviously, and once I get some idea of how much she's going to weigh I'll be able to get the number of those watts figured out. Not too worried about this part of the build... yet. :p

So thoughts anyone? I appreciate all constructive input or emotional support here! :p

Thanks!
 
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rockyboy

Skill Collector
Mentor
From what I have seen in the past with "Monster FT style builds are this...
A lot of them failed out of the gate for under engineered main wings. they either fold up in flight from not enough support structure or the flap like a bird and are hard to control.

Yeah, this is probably my biggest worry too.

The next thing is control surfaces. Most suffer from to much movement and do not fit the style of the air frame they are on. seems like everyone wants to make each plane a 3d plane whether its a fighter or bomber or experimental. As long as we keep in mind we are doing a heavy bomber and stay on the reserved side of things we should have a decent result. I know the mini Josh has produced seems to be pretty agile and sturdy so we know its upper range and capabilities already.

Good point - I know I often lean towards 'make 'em bigger just in case' with control surfaces and need to "control" that tendency here :p

I think we should focus on looks and function and keep performance within its original designed purpose. Big , slow, and capable to carry serious weight..

Agreed

(which btw should be part of the judging for the larger sized bombers in the competition.)

Good point, but I think we should have put that more directly into the scoring before now - I feel bad about changing things on people after they have already started the journey with one set of goal posts.

I am nearly done with one of the sections we have discussed. Just need to smooth things out around the edges. Also need some final dimensions to work with for other aspects but will talk to you in Asana or pm's about all that.

Awesome!! :applause:

Now that I've gotten that CNC obsession scratched to the point I can hold at least one other thought in my head, I'll get those updated dims and plans to you pronto!
 

PsyBorg

Wake up! Time to fly!
6 inch fuse sounds awfully skinny for a 101 inch wingspan.. at least what I am picturing in my head verse scaling in the pictures.
 

rockyboy

Skill Collector
Mentor
6 inch fuse sounds awfully skinny for a 101 inch wingspan.. at least what I am picturing in my head verse scaling in the pictures.

Good point. Might be working from a faulty memory memory block there. Gotta go back to the CAD on this tonight for sure!
 

Hai-Lee

Old and Bold RC PILOT
I applaud your ambition and wish you great success.

For scale like performance I would recommend keeping the build very light. The use of FB as more of a covering than structural support would aid in this. As for the wing profile a standard clarke Y might be a little too sever though a modified clarke Y of suitable thickness ration would look and perform quite well if the plane is not too heavy.

A ribbed wing structure is obvious for weight Vs strength but in a pinch the outer wing panels/tips can remain standard FT FB techniques for strength and simplicity. A ribbed/former fuselage construction is also recommended so that you do not need to double up on the FB just to gain strength and torsional resistance. If you wish I can assist with some structure possibilities to obtain the strength without severe weight penalties off forum!

Do not forget transport issues and so a set of multi-panel wings, removable canard/forward fuselage, and the like will need to be considered as well as retracts.

On this aircraft I am not familiar with the undercarriage type or locations but It appears that it might have been a tricycle, (nacelle mounted main wheels), with a 90 degree rotating nose wheel on retraction. Please advise. As for the undercarriage simplest is to find a commercial design with the same of similar landing gear and order the replacement parts.

Have fun!
 

PsyBorg

Wake up! Time to fly!
Lights just popped on in my head again Rockboy... Maybe we do not need expensive retracts... Somewhere in my pile of RC car parts I have spare oil filled adjustable shocks. I am sure with a little adaptation we can simply use them in some tri pod configuration where the entire thing could just rotate 180 degrees in and out of the fuselage and surely be strong enough as well as soft enough for a big bird to sit on.
 

rockyboy

Skill Collector
Mentor
Lights just popped on in my head again Rockboy... Maybe we do not need expensive retracts... Somewhere in my pile of RC car parts I have spare oil filled adjustable shocks. I am sure with a little adaptation we can simply use them in some tri pod configuration where the entire thing could just rotate 180 degrees in and out of the fuselage and surely be strong enough as well as soft enough for a big bird to sit on.

Hmm... now that's an interesting idea... :cool:
 

rockyboy

Skill Collector
Mentor
I applaud your ambition and wish you great success.

For scale like performance I would recommend keeping the build very light. The use of FB as more of a covering than structural support would aid in this. As for the wing profile a standard clarke Y might be a little too sever though a modified clarke Y of suitable thickness ration would look and perform quite well if the plane is not too heavy.

A ribbed wing structure is obvious for weight Vs strength but in a pinch the outer wing panels/tips can remain standard FT FB techniques for strength and simplicity. A ribbed/former fuselage construction is also recommended so that you do not need to double up on the FB just to gain strength and torsional resistance. If you wish I can assist with some structure possibilities to obtain the strength without severe weight penalties off forum!

Do not forget transport issues and so a set of multi-panel wings, removable canard/forward fuselage, and the like will need to be considered as well as retracts.

On this aircraft I am not familiar with the undercarriage type or locations but It appears that it might have been a tricycle, (nacelle mounted main wheels), with a 90 degree rotating nose wheel on retraction. Please advise. As for the undercarriage simplest is to find a commercial design with the same of similar landing gear and order the replacement parts.

Have fun!

Thanks! I'm not too familiar with the differences in Clark Y - I found the Easel online CAM tool will auto-generate ribs for a Clark-Y 11.7% - any resources you'd recommend to help better understand how this might perform in comparison to others in that line? I'm getting a bit lost in the University of Illinois explanations and flow dynamics info on these... :confused:
 

agentkbl

Illegal Squid Fighting?
I know someone was doing a 3d printed geneva drive-esqe retract hinges. might talk to him about that. I'll go forum hunting and post back any results I find.
 

Fluburtur

Cardboard Boy
Haha don't worry I haven't forgotten about that, I have been talking a bit with Robobob about that in order to sort out the mechanism.
It will come but I don't know when.
 

Hai-Lee

Old and Bold RC PILOT
The modified Clarke Y I was thinking of was basically to have a symmetrical, (or semi-symmetrical), first 25% and the classic flat bottomed trailing edge. It came to mind because of the aesthetics. Also the classic clarke Y has a very high drag when you try to push the speed envelope.

If the design is kept light the wing profile is not overly important. At model Reynolds numbers the lift differences are not overly dramatic. Also don't forget to add a touch of dihedral!

Have fun!
 

rockyboy

Skill Collector
Mentor
The modified Clarke Y I was thinking of was basically to have a symmetrical, (or semi-symmetrical), first 25% and the classic flat bottomed trailing edge. It came to mind because of the aesthetics. Also the classic clarke Y has a very high drag when you try to push the speed envelope.

If the design is kept light the wing profile is not overly important. At model Reynolds numbers the lift differences are not overly dramatic. Also don't forget to add a touch of dihedral!

Have fun!

With my flight characteristics specifically trying to be slow & high lift, the high drag at higher speeds isn't much of a drawback for the lift characteristics... and yeah - I've learned the "twitchy as a squirrel on espresso" effect of not adding a little dihedral the hard way :black_eyed:
 

rockyboy

Skill Collector
Mentor
OK, I'm all wrapped up with the mini FW-42 plans, skins, and build instructions so it's time to focus on moving this project forward again :applause:

Through a crazy good hobbyking sale and a flat out steal at my clubs auction, I've ended up with two sets of retracts that *might* be good for this project, depending on the final weight. I need to look up some specs on the planes these retracts were intended for and see what's what.

I ran across a really cool looking CAD program that is purpose built for foam RC plane design - http://www.devcad.com/eng/devfusfoam.asp But at the price, and since the fuselage is so boxy on this design, I think I'm going to save purchasing that for another project.

On the wing design my current plan is DTFB ribs cut on my Lowrider CNC, with a couple fiberglass arrow shafts for spars, sheeted with skinned DTFB, and then fiberglassed. Each wing side will be a single piece panel that bolts up to the fuselage with a little dihedral for luck.

The fuselage will be pink/blue insulation foam from the hardware store, cut with a hand-held hot wire using CNC cut templates for top and profile shape, sanding to final shape, with fiberglass arrow shaft spars and fiberglass covering.

I've got the rough CAD outline scaled up and cleaned up, except for deciding how the rear part of the fuselage taper is going to be worked out. At first glance the rear of the fuselage looks straight, but lining a straight edge up on the image shows that there is a taper that happens somewhere in the wing join area so the front and rear turrets are the same size with the same amount of fuselage around them.

What is driving me a little batty is the dimensioning tools in Draftsight (which I've been trying to use cause it's free) don't work the way I expect from my years of AutoCAD experience. But I'll get proper info on the cargo bay & turret sizes figured out for the team tonight. :)
 

PsyBorg

Wake up! Time to fly!
I was looking at Josh's new 3d print of the retractable tail assembly and going.. Hrrrmmmm... Slight beefing up, sideways mounting and a set of Nitro Truck oil filled shocks could make for some smooth landings on large scale foamies.
 

rockyboy

Skill Collector
Mentor
It does look encouraging... I have no idea how much this FW-42 is going to weigh yet... *sigh*

So the retracts I have are replacement sets for a 3.5 pound Avios Yak 52 trike with forward retracting main gear. I sort of suspect a 100" wingspan plane - especially my first one at this scale - will end up a bit heavier than that. But maybe we can do it as a dual gear setup - after all, none of the documents I've been able to find show any kind of landing gear :)

I put a file with the dimensions up in the Asana site - lemme know if you have any issues getting into it.

And for a little color here, this is a screen shot of slicing up the fuselage top so it can be cut out of DTFB and wrapped in aluminum tape for a hot wire template.

Fuse_Top_Cut.PNG