Started work on a P38 today, only had about 15 min to get started, but I managed to find a good 3 view and get it scaled into Sketchup. Looks like at about a 45" wingspan it will call for two 10" props to keep it scale. -Now from past builds I know that will be complete overkill. I will not need 10" props even for unlimited vertical...

Lucky for me I've got some 3 blade GWS props in the 9x5s in normal and reverse, so that should be perfect.

I am hoping to run two Suppo 2217-08s spec sheet from Lightflight here

On one A123 2300 mAh pack that should give about a 10 min flight given the available propellers.
Alternatively I can supply each ESC with a seperate battery, using the smaller A123s from Black and Decker... Time will tell, and I may make provisions for both.

I hope to get pics up tomorrow as well as finish up that MiG I started last week.
Just need to get up before noon!

 

Very First Step...
Acquire 3 view, determine scale (you could scale later, but it's best to try and get close...) Attached files

 

More work, this takes longer to type then to do...
Sections are drawn using the profiles,

Aligned to the view,

Then a rough body line drawn in...

Now as you can see the ideal sections for the formers are not used. Not sure why these are taken at spot where the curve is constant, it's much better to create a former where the curve changes.
This will take a bit more work to make it look 100% right, but that's ok, even as is, it would look great in foam. Attached files

 

Well, looking at it again, it isn't so bad, Section 5 I would have moved closer to the cockpit, and Section 4 just looks funny.... Section 7 is too far back, and I'm not sure I'll use Section 8... Maybe it is bad...

 

Here you can see the next step...
For those of you who have done balsa builds, this will make better sense...

Each line of each section, gets a line from its end point to an adjacent end point on the next former, much like laying a balsa spar...


The parts where then lines do not flow nicely may cause problems later on when it comes time to roll the foam, so I will clean this up to make it look very nice... Problem is I don't know of a good way to explain how to do that step... This is where mad cad skillz come in I guess. Sometimes it works best to use the arrow keys and lock in a direction and only move a point one direction at a time, other times you may want to do the same with a section of the curve... Other times it just might be easier to get rid of the problem former and start a new.

A lot of this work can be avoided in making uniform formers, so try to keep the same amount of sides on each quarter of the cylinder your making. Then if you have to adjust, hopefully you will just need to move a point around.

If your good, and lucky, the skin script can save some time here, but I like to draw so I do it manually. Attached files

 

And the cleaned up version, mainly using the moving single point technique...

Attached files

 

Cutting in canopy edge...
Line is drawn from line to line, or edge to edge using the top view transparency, then the the extra stuff is deleted...


Sometimes it can get really tricky unfolding something when you cut away from the surfaces..
The trick is to unfold what you can, stop, go back, then unfold some more in a new direction to keep it as one part, then stop... Then go in and delete the fold lines you no longer need (you have a flat surface at this point), then start unfolding again... Sounds harder then it is really. But if you don't know how, it's challenging... Attached files

 

Back at it...
Wife put me to work lol. But I'm out now see...
Kinda a neat trick here to make sure everything is even, you gotta make this stuff up as you go.


This is WAY to many formers, gonna have to purge some...


Oh great, here she comes! LOL Attached files

 

Massively cleaned up the boom, and made the wing...

Built some washout into the wing, basically this was done with a single airfoil, scaled / stretched to fit each of the three sections. I'll use 7UPs trick (intersecting plane) for making more airfoil sections / formers later on.

This was tough to model, but easy after that corsair. I think a video would be the only real way to explain how this was modeled. Lots of construction lines, lots of small changes, no real substantial steps after the airfoil was drawn... I did one section at a time, aligned it up put it down, connected the formers, then scaled the whole thing to fit the correct size (it was off). Checked the dihedral, drew a ton of construction lines and began making the rest the same way...
Attached files

 

Completely reworked the wing...
sometimes that's the way it goes, this one is much simpler, and accounts for the trailing edge foam thickness, which the corsair did not... Small improvements all along the way, eventually I wont have anything else to learn, lol yeah right!
Attached files

 

Last update for a while, getting into sectioning the wings for formers, need to add tabs, draw in some motors and servos, then unfold... Tedious stuff...


Thanks for checking this out!
Attached files

 

Very nice, you make my "Box Scale" stuff look silly!

Keep it up!

 

bah! To each his own. Box design is very strong, saves time, and is better then flat! (not Phlat lol) And if you get the EDF version to fly well, you'll be way ahead of me in that field!

Really though, thanks for all the comments guys, I really appreciate it.
I can not wait to print this one out, I hope I have enough foam left!

 

Here's the first airfoil former, I wanted to show this because for building like I do, this is the most important part of the build. I hope I didn't make all the phlatties mad about that flat comment above, there are countless ways to build aircraft, and there is nothing 'wrong' with any of them, I just have my preferences -that's all. I guess that's really the most important thing, do what you like, fly what you want to fly, and build how YOU want to build. Don't let me or anyone else tell you how to do it!

Anyway, back to the point... or the build anyway.
I used the offset command and offset the inside of the airfoil 3/16 of an inch, I typed the number in so I know the offset was true... only look at the numbers. imperfectuion.
(I should say, I did clean it up a bit, because it did look rough because of the section)

Any way that's part of the reason why a full 1/4 does not work when accounting for thickness. 3/16 is a fudge factor for my foam, the blue FFF DOW stuff from Lowes... You may need a different number, trail and error is the only thing that will work to get it right. But somewhere, somehow material thickness has to be accounted for, and this is how I do it...

 

Winglets...
Two tabs on the bottom so that I can set the unfolded wing out on a table, place the formers in, aligned by the two bottom tabs, then I can fold over the wing skin onto the top tabs (which will bite) in the rear. Take apart apply hot glue and repeat. Attached files

 

More tricks, SU 7 (and maybe 6) has an intersect with model feature, so the ribs were copied then extruded 0.25 placed in the wing and the intersection was found... All tabbed out ready to go!

(Note: the tabs on the wing ribs there are taller then the foam is thick, I'll can aways trim them flush once it's built, and taller makes them easier to make, again trial and error design

 

Last shot until I get it unfolded...
Made the cooling ducts, turbos, and a nose part that can be shaped later.

• To do:
• Nose cone template
• Canopy template
• Double up on the fins / elevator
• Attempt to fit some batteries somewhere in the model... oh boy, should have thought of this sooner...Mount servosAilerons (template only)Flaps?unfoldPhlatprint!

Attached files

 

That is freaking awsome man!!!!!!!

Eric

 

It's a good idea, but I don't have an easy way to make pocket cuts yet (poke poke). I've never made a wing quite like this before, so what your saying may be all that is necessary. That being said, when I did the corsair wing, the tabs were a life savor, and if they did not go all the way through I would have been lost -but that's a whole nother story. That stupid gull wing was DIFFICULT in every way! I know lots of people have made airfoils without tabs going through like this, so my tabs could be overkill... Pockets on the bottom would work for sure as it gets glued first. Great suggestion.

Either way, for this one, I plan on using that lightweight spackle stuff to full the holes, it works great... Probably gonna end up with glass on the bottom of the wing as well, and that will further hide it.

 

Thank you so much for this Mark! This is INCREDIBLE for me too!
Here's G-code for the wing! Going to the basement right now to try it out!
(Note: G-code assumes 1/16th dia bit) Attached files P38_wing.zip (6.3 KB)Â

 

Awesome work TV!

I can only imagine the time behind the tube.

Ken