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Dec 29, 2018, 06:56 PM
Retired CAD guy
birdofplay's Avatar
There's a school supply store here in Indy that has that type of material as well.

For 48"x 24" x 5mm foam MPF is the place to go http://www.modelplanefoam.com/

I'm here because I am old school and over $400 for the FMS 3M Fox is hard to justify.

My CNC bed is 4'x8' so I can entertain larger projects.

Not much available for slopin' in Indiana ;^{
Hence lurking in electric gliders forum
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Dec 29, 2018, 07:32 PM
And Repairs
TyFlies's Avatar
birdofplay, it sounds like experimenting with an e-VTPR project has your name written all over it.
Dec 30, 2018, 02:12 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP
Quote:
Originally Posted by birdofplay
There's a school supply store here in Indy that has that type of material as well. For 48"x 24" x 5mm foam MPF is the place to go [url]http://www.modelplanefoam.com/[/url
If your going to build a foam board wing of any significance, you canít use this material. There is no paper skin that I see which is essential for stiffness and to develop a nice leading edge. And a true like airfoil. You would have to glue 2 clamshell pieces together. Then you loose the clean airfoil shape to something like a plank.

Eric
Dec 30, 2018, 02:12 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP
Quote:
Originally Posted by TyFlies
birdofplay, it sounds like experimenting with an e-VTPR project has your name written all over it.
Yes yes...
Dec 30, 2018, 11:34 AM
Retired CAD guy
birdofplay's Avatar
From the long list that I observed on the linked page I don't see the need for much further experimentation or development.
All very desirable model designs.
But, as I said, with no nearby slopes , I need a powered model.

IF I was there I'd be on the slopes with you as often as possible.

Also, I am still struggling with the distinction of VTPR and aerobatics in general.

If it's just a very low altitude thing, then cheap, easily repairable and replaceable models are indicated.

Or is it just a subset of 3D flying ?

Or is it just another Que es mas macho thang.

As if gravity is not a large enough challenge, we need more ways to break models.

So going cheap seems to me to be the Ideal way go.

Foam, like Depron and MPF, can bent to form a rounded LE.
BUT ! Be sure to Apply packing tape to the outside of the foam
and impress a crease line on the inside
then bend over a sharp table edge.

The scratch built foamy forum has a lot of Working With Foam pointers and tips.

As far as airfoil worship go's ...,

Models at this size and wing loading are not going to accrue much benefit from
using a "true airfoil" .
I know worshiping at the alter of Airfoils is a big part of some modelers beliefs,
but, I lost my religion years ago when foamys
with incredible power to weight ratios came on the scene.

Here are a coupe of FLAT sheet , Square LE & TE planes that fly LOW
Crossbow 2x 72" span (0 min 0 sec)

Horten flying wing (0 min 0 sec)
Last edited by birdofplay; Dec 30, 2018 at 12:01 PM.
Dec 31, 2018, 12:41 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Foam Board Layout


Modelers begin a new project in differing ways and points of the build. I have always done mine with the wing as the starting point. Reason is, the wing is the thing (TWITT) and what any plane or glider should be designed around. For it is the wing that determines the type of performance that a particular aircraft will produce i.e. Jet, Prop plane, Flying wing, 3D powered plane, Glider for slope or the park and on and on. So, with that said, this wing is specifically designed in size, shape, thickness and airfoil for a motorized VTPR glider in the park, the Velectro 2.8.

I can get long winded with written descriptions so I will try to keep the posts short, and I will be posting many videos to explain processes and results. Still images will also be posted that are relevant to the subjects. Questions related to the topics are always welcome. This post is the beginnings of my foam board wing design and layouts. The video is not the actual wing but the prototype. Just so you know, the real wing is pretty close to this one except for the spar assembly and a couple key dimensions. And as the build unfolds, you will see the actual wing and its components being assembled.

Eric

53" Board wing 1 (4 min 47 sec)
Last edited by oldscooler; Dec 31, 2018 at 05:44 PM.
Dec 31, 2018, 01:13 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Peel it...


Video and photos of the paper peeling process.

Foam Board Paper Peel (2 min 20 sec)
Dec 31, 2018, 03:02 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP
Quote:
Originally Posted by birdofplay
I am still struggling with the distinction of VTPR and aerobatics in general.
Thanks for your comments, but let me remind - this is a build thread. Your questions about the style and type and more general conversation can be posted over on these two threads for everyone's education about VTPR aerobatics and General aerobatics and they're distinct differences and approach. This way we don't get too off topic during the details of the build. In fact I believe your questions have already been addressed over there in great detail and more. Check them out. Here are the thread links:

PARK-VTPR Aerobatics Intro
https://www.rcgroups.com/forums/show...robatics-Intro

The VTPR Channel
https://www.rcgroups.com/forums/show...e-VTPR-Channel

Thanks, Eric
Last edited by oldscooler; Dec 31, 2018 at 11:27 AM.
Dec 31, 2018, 02:21 PM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Foamboard Foils


Before we get into the nuts and bolts of the wing, here is some more insight into what I learned folding foam board into an airfoil. A word of caution. If you decide to do a symmetrical shape there is much attention needed to ensure a true sym shape top and bottom, that both sides are equal in that it is flying correctly in relation to the fuselage! If you choose a semi-sym or flat bottom shape it’s not so critical and easier to control the fold.


Foamboard Airfoils (5 min 43 sec)


Here is an impact test we did. The force generated was with all ones might onto the round pipe. It’s quite amazing how the front part of the foil remained intact with no splits or tears whatsoever. The skin did not delam at the spar glue line, but you could hand form the foil back to a semi-state of integrity and keep flying. Remarkable actually...

Eric

Foamboard Foil Impact Test (0 min 34 sec)
Last edited by oldscooler; Dec 31, 2018 at 04:57 PM.
Jan 02, 2019, 03:52 PM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Spar system


Looking at CF tubes, solid rods and have determined they just arenít stiff enough for this thin wing panel. So I am developing my own design that I can make out of hardwood and CF caps.

VeLectro 2.7m spar (1 min 52 sec)
Jan 03, 2019, 01:12 AM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Heart of the build! No Spars, No wings!


Next is the spar caps and gluing.

I was careful to find the straightest wood selections I could find. Then I used medium CA and accelerator to join the spar joints. There will be some slight bowing no matter what you do because of changing humidity conditions. Longer than normal parts tend to show stuff like this. So you have to set and shim them for awhile then go for applying the CF matte when they are really straight and clamped against a straight edge (see C-clamp below). CF strips are installed top and bottom. Once its time, I laid a nice bead of medium CA down onto the wood the first length, then carefully put the CF strip in place and pressed with a long straight edge, then shot accelerator on it. Repeated same with rest of length with a 2" overlap at the wood joint.

VeLectro Spar Caps (0 min 43 sec)
Last edited by oldscooler; Jan 03, 2019 at 03:14 PM.
Jan 06, 2019, 03:27 PM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Spar Layout


Doing a full size sketch was needed in order to come up with the root and tip positions of the wing spar. Mainly because when folding the foam board its critical to be able to "see" the chord and contour of the skins and how stressed they will become in the folding and gluing process. Foam board moves all over the place, so its nearly impossible to predict how the folded airfoil will come out. Taking the time to do this is a good use of time believe me... Plus I now have a template for easy reproduction or adjustment of this step in the build folder.

Spar Layout (1 min 11 sec)
Last edited by oldscooler; Jan 06, 2019 at 03:44 PM.
Jan 13, 2019, 06:44 PM
vtpraerobatics.blogspot.c om
oldscooler's Avatar
Thread OP

Wing Layout Review


This is an overview of the wing innerds before folding.

Wing pre-fold review (4 min 6 sec)
Last edited by oldscooler; Jan 13, 2019 at 06:50 PM.
Jan 13, 2019, 09:15 PM
And Repairs
TyFlies's Avatar
Nice clean work!


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