Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
April 08, 2020, 05:37:20 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs  (Read 466 times)
0 Members and 1 Guest are viewing this topic.
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« on: February 21, 2020, 04:21:19 PM »

Hi, I have been building this model for over a month now, my time restrictions (an ankle biter always somewhere near) do not allow me to crack on with it as fast and as often as I might wish. But hey, never mind, c'est la vie. Now, I will share with you only some images from the past month to show what I have done until recently and my next post will be sent when I have made a new progress with the tiny white Airabonita model.

These first two images show the drawings used to start working on the type.
Attached files Thumbnail(s):
Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #1 on: February 21, 2020, 04:24:51 PM »

A real great inspiration to work the foam for me was the pdf available from Mike Stuart's web site: http://www.ffscale.co.uk/foam.htm

This pair of images show the fuselage halves cut out from the foam with the side and plan elevations from the Airabonita drawings attached to them, the shape would later be carefully carved.

Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #2 on: February 21, 2020, 04:28:12 PM »

And now, the wing has also been cut out and the airfoil section sanded. The next image show the fuselage halves after being roughly hollowed out and the balsa wood nose block glued in place.

Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
piecost
Gold Member
*****

Kudos: 8
Offline Offline

United Kingdom United Kingdom

Posts: 453



Ignore
« Reply #3 on: February 21, 2020, 04:36:35 PM »

Very nice. Can you tell us the weights of each finished part?
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #4 on: February 21, 2020, 04:42:21 PM »

A template has been made enabling the wing, tailplane and canopy cutouts been done with some degree of accuracy - to maintain the wanted angle of incidence for example as well as to achieve a perfect symmetry of the cuts on either side of the fuselage.

The next pair of images show the main components carved out of the foam and laid out for you to see. Note the balsa stringer inside the fuselage, added to cope with the stress to the airframe from the wound rubber.

Then, the parts were assembled and weighed, mere 2.8 gms. Is it too much? Will it fly? Let's see…

And the final buch of images for this evening show the latest progress done today and the day before, the balsa sheet prop blades, spinner with paper tubes making the hub, underwing radiator housings and wing root fairings - all carved from from the insulation foam called XPS Styrex here.

Do not tell me off for the monkey in the cockpit, I admit I am never going to be a sculptor. It was supposed to be a brave Bell test pilot and it came out as some scary creature. My deepest apologies.



Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #5 on: February 21, 2020, 04:51:49 PM »

Very nice. Can you tell us the weights of each finished part?

The fuselage + wings + empennage subassembly came out weighing about 2.8 gms as given above, the fuselage halves themselves were at about 2x 0.6gms - hollowed out, covered with a thin tissue and with (perhaps unnecessarily massive-ish) balsa nose section added.




Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
OZPAF
Palladium Member
********

Kudos: 183
Offline Offline

Australia Australia

Posts: 5,456



Ignore
« Reply #6 on: February 22, 2020, 01:05:23 AM »

Very careful work Petr. You make carving a symmetrical shape look easy.

John
Logged
TheLurker
Gold Member
*****

Kudos: 26
Offline Offline

United Kingdom United Kingdom

Posts: 967




Ignore
« Reply #7 on: February 22, 2020, 04:02:50 AM »

What a lovely bit of work.

You have my complete understanding and sympathy regarding the "monkey" but you deserve credit for trying. I've given up making pilots because the results are always too awful for words.

I'm intrigued by your balance.  What diameter & length of wire are you using and how did you calibrate it?  Have you a set of weights?  Is that a 3.5mm foam board "body"?  More details please.

Cheers,
Lurk
Logged
Crabby
Titanium Member
*******

Kudos: 135
Offline Offline

United States United States

Posts: 2,229


I never met a modeler I didn't like



Ignore
« Reply #8 on: February 22, 2020, 11:09:30 AM »

Petr will you be using a hot-wire to remove the wing-saddle area? BTW no worries on your pilot, most humans aren't much on the eye anyway, besides Charles Darwin would completely approve! Roll Eyes Roll Eyes Grin Grin
Logged

The Threadkiller!
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #9 on: February 22, 2020, 12:45:56 PM »

Thanks y'all, guys!

re the wire balance, nothing very difficult, really. The basic idea behind it is that a common 80g/m2 A4 size office paper weight exactly 5gms. Why?

Well:

1) one square meter of this paper weighs 80gms, hence its name.
2) one square meter is the same as A0 size
3) A4 size is exactly one sixteenth of the A0 format
4) thus, one sheet of 80g/m2 office paper weighs exactly 5gms.

And there we are, we have the first one of the set of weights. Then, we can cut up this A4 size paper into 5 identical stripes (I prefer lengthwise) and voila, we have a set of five 1gm weights.

Then, very simply hang these one gram paper stripes one by one onto the hook at the end of the wire, marking the position of the wire as you go, starting with the Zero position, then 1gm mark and so on until you reach the 5gm. Or, of course, cut these strips even into halves and you'll also get 0.5g, 1.5g, 2.5g marks as well, you get the idea by now I know.

The body of my balance is made of a 5mm foam board, but you can use almost anything, a cardboard, a block of balsa wood etc.

Just beware, the board should be heavier than the model (or its parts) which you are going to measure.

The wire diameter is not that important too, mine is 0,5mm.

And please also note that there is a pin inserted into the board on which the wire rests at about 1/8th of its length. The closer this pin is to the attachment point where the wire is held in the board, the "finer" the measurement you get. And I also have a second pin, a lot further from the attachment point, this enables me to change the range from 0-5 gms to 0-15gms using still the same balance. You can see there are two scales on the forward edge of the foam board.

If you want, I can make some simple scheme showing all the dimensions of this balance.

to Crabby: no, I haven't made my hot wire yet, I use very sharp and thin scalpel blade or even a razor blade throughout.
Logged
TheLurker
Gold Member
*****

Kudos: 26
Offline Offline

United Kingdom United Kingdom

Posts: 967




Ignore
« Reply #10 on: February 22, 2020, 01:06:05 PM »

Quote from: Petr P
The basic idea behind it is that a common 80g/m2 A4 size office paper weight exactly 5gms.
So you have got a set of calibration weights.  Smiley 
I like that very much indeed.

Quote from: Petr P
I can make some simple scheme showing all the dimensions of this balance.
Only if you've got nothing better to do as your written explanation is perfectly clear.  Thanks.
Logged
kaintuck
Bronze Member
***

Kudos: 1
Offline Offline

United States United States

Posts: 49



Ignore
« Reply #11 on: February 24, 2020, 07:16:57 AM »

Beautiful workmanship!
Marc
Logged
LASTWOODSMAN
Platinum Member
******

Kudos: 27
Offline Offline

Canada Canada

Posts: 1,179


REAL PLANES HAD ROUND ENGINES AND TWO WINGS



Ignore
« Reply #12 on: February 24, 2020, 07:30:21 AM »

Hi Petr P.   I like those kind of things, and I for one, would like to see your simple scheme, to go along with your written explanation.   Thanks for posting.   Smiley

LASTWOODSMAN
Richard
Logged

OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
strat-o
Gold Member
*****

Kudos: 8
Offline Offline

United States United States

Posts: 414



Ignore
« Reply #13 on: February 24, 2020, 09:28:12 AM »

I carved a peanut a couple of years ago but I was not satisfied with how easily the foam surface was marred.  Just handling it or setting it down, I would then turn it over and find dents and scratches. I did not have in mind the idea of covering it with tissue which I think might help a lot.  Do you have an approach to doing this?  Like perhaps using thinned white glue for adhering?

I did work out a satisfying technique for removing foam from the interior of the fuselage.  I would start with the exterior shaped and sanded.  Then I would just pinch and gouge away at the interior using my fingers.  By working straight down the line consistently you would get a nice pattern of removed foam. From there you can then pull out interior details at random and work your way to creating a thin shell. This worked to remove about 80% of the interior foam.  The rest could be done by sanding using sandpaper attached to rounded forms.  What I liked about this approach is it cut down on a lot of foam dust that would otherwise be created.

Marlin
Logged
OZPAF
Palladium Member
********

Kudos: 183
Offline Offline

Australia Australia

Posts: 5,456



Ignore
« Reply #14 on: February 24, 2020, 09:27:21 PM »

ingenious calibration system for your scale Peter. I would have missed the importance of the weight of the paper for a modeller.

Looking back at your photos I was wondering whether it would be a little easy and more accurate to use the template for wing/tail/canopy cut outs on the blank before you carved them? The blanks would need to have a accurate datum face and the pieces spot glued back on for the carving - so maybe not.

It's a technique that has always fascinated me but I am a lousy 3d carver. Smiley

John
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #15 on: February 25, 2020, 06:27:06 AM »

Cheers mates for your kind comments.

ad Strat-O:
This behaviour is thought to be common for the very fine grades of the blue foam. I have never experienced it while building the Airabonita, my material is not a blue insulation foam as is available in local DIY stores, my white foam board is in stock where they sell stuff for students of architecture at the local uni to build their models from.

I suspect, however, that the blue foam gives much finer surface and also weighs a lot less, which as it seems comes with being really very prone to getting dented on the surface. I will have to give this blue foam a try soon.

Really interesting sounding idea, this nipping out the foam core!

Now, as for the balance scheme Richard asked for, there are in fact a couple of balance designs in the US magazine called Indoor News and Views from the 1990s. I have attached two of them here, in hope it won't be violation of any rights.

My scheme is below as well. And do feel free to ask any questions if the sketch is not clear enough.



Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #16 on: February 25, 2020, 06:33:04 AM »

I forgot to mention the paper covering of the foam - firstly, not my invention really, I cannot accept any credit for that.

The tissue paper is used for making the surface nicer and smoother, it is applied using a Henkel Metylan sort of wallpaper glue which comes in white powder to be diluted with water. The expert modellers here who invented this technique use to mix this stuff with a few drops of standard white glue. And heavily diluted lightweight balsa filler (Deluxe is the brand name I think) mixed with a few drops of clear acrylic dope can make the surface even smoother at the end.
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #17 on: February 25, 2020, 06:54:34 AM »

Two more detail views of the pin position and fine / coarse scales.

Attached files Thumbnail(s):
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Re: Foam Airabonita (Bell XFL-1) - my first build in twenty yrs
Logged
lincoln
Titanium Member
*******

Kudos: 34
Offline Offline

United States United States

Posts: 2,161



Ignore
« Reply #18 on: February 25, 2020, 10:26:27 AM »

Speaking of blue foam, it's not all the same. Dow Highload 60 and Plazamate are examples,of blue foam that can take higher compressive loads. Very fine texture, worth wet sanding with 600 grit. Other manufacturers have similar foam, though you may have to look around to find it.
Logged
Petr P
Bronze Member
***

Kudos: 1
Offline Offline

Czech Republic Czech Republic

Posts: 10


Topic starter


Ignore
« Reply #19 on: February 25, 2020, 10:49:49 AM »

Lincoln, you are right of course. You know what is the trouble with testing several brands of foam? These foam boards come in large size, about 1.2m x 0.6m if memory serves well, and what is one supposed to do with the heaps of unsuitable boards after picking up the only one with the best properties?  Grin

I simply cannot come home bringing even one uncut board, the flat would become inhabitable the very moment and She who must be obeyed would rage with anger….

I usually bring just small foam samples which easily fit into my jacket pocket  Roll Eyes

(kidding a bit, of course)
Logged
strat-o
Gold Member
*****

Kudos: 8
Offline Offline

United States United States

Posts: 414



Ignore
« Reply #20 on: February 25, 2020, 11:00:36 AM »

It looks like Amazon lists Henkel Metylan but it is not stocked for the U.S. market (currently?).  Looking at the MSDS, it says that it is a powder containing starch derivative and poly vinyl acetate.  Any comparable product for the U.S. market, anyone?
Logged
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!