Thermal plank 2.4m, foam - Page 3 - RC Groups
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Sep 04, 2016, 09:07 PM
Plank addicted
Marcos Quito's Avatar
Big concern is related to resistance, rigidity, because of 2400mm.
That´s why I choose 1 big central wing and 2 tips.
Center with 1000mm, and 2x 700mm tip.
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Sep 05, 2016, 07:41 AM
HerkS's Avatar
Very interesting project - looks good - keep it going
Sep 05, 2016, 10:13 AM
less is more
Knoll53's Avatar
Nice build log Marcos! I like the close up shots of the spar construction. Bamboo and lots of hot glue. It looks like a winning combination. Airfoil accuracy looks good.

Will you have a blunt trailing edge as shown in the photos? Will you add a shaped balsa trailing edge? I was thinking possibly a scarfed joint with the depron skins.

At this wingspan, this structure should be plenty strong. Will you use hot glue to attach the depron skins? Sounds tricky.

Sep 06, 2016, 05:56 AM
Plank addicted
Marcos Quito's Avatar
Hello Kent, thanks for the positive words !!!

Trailing edge : I should use double depron sanded till 2mm.
The skin finishes on 10mm thick.

Skin is not with depron sheet. It s with very low density foam. That s why I had to strengten BEFORE covering. Cover has almost no resistance.

Forbidden words : more depron and Balsa sheet. Both are too very expensive.

Skin is glued with liquid foam glue, demands 10 hs to dry. Enough time to place everything in place.

Moving sorfaces will be on depron (double).
Sep 06, 2016, 08:06 AM
Registered User
Glad to hear from you, your build looks great.
The foam ribs and structure are very durable and will take a lot more abuse than a balsa structure. I did very much the same on one of my projects. That airplane survived some nasty spills that would have shattered a balsa structure.
Keep up the good work. I am looking forward to your flight reports and as to how well the airfoil works out for you.
Sep 08, 2016, 01:41 PM
Plank addicted
Marcos Quito's Avatar
Small changes after start building :
Center panel : 1000mm long.
Tips : 700mm long.
Total the same 2400mm.
Biggest cord 350mm.
Tip cord : 300mm.
Comand surfaces : 60mm cord.
Botton Hinge.
Sep 09, 2016, 05:29 PM
Plank addicted
Marcos Quito's Avatar
More pictures.
ATTENTION : in case you try doing the same, the process of SANDING the EPS sheet is VERY important, otherwise nothing will glue on it.
This EPS sheet has some very small edges, so you need a very thin sand paper to pass entirely. It´s easy, only a bit, enough to break that small edge.

The feeling you have to have with your hands is type "babe face", that´s it.

Take a look to the glueing process of the outside sheet - due to the top camber line of the airfoil - it´s reflex. I had to put a stick, and the wing upside down. See pictures.
Stick will be removed, it´s only with tape.

I´m very happy with the end result : strenght is exaclty what I wanted !
Sep 10, 2016, 10:49 AM
less is more
Knoll53's Avatar
good photos Marcos. the reflex support stick worked out pretty well.
Sep 25, 2016, 08:57 AM
Plank addicted
Marcos Quito's Avatar
More (slow) progress :

Reinforcing 'D" box with hard paper (kraft paper they call here in Brazil).

White glue with a little bit ot water to make it more liquid.

The process : pass a lot of glue and wait untill paper is very wet, so it can curve and follow all surface. It s just not to pass glue and put in place. What I usually do is : put glue in two pieces of paper, that s enough time to place the first piece in place.

Care must be taken to the drying process :
Paper is very strong and SHRINK a little.

Avoid sun or heat : if one side is heather than other, paper will shrink this size first and will curve your wing.

Best process is keep piece under shadow, and both sides away fron other surfaces.

Keep an eye on it and change position of the piece, if possible, during drying. 1 overnight is enough.

Well here at D box there s no shrinkin because structure is strong. Trailing edge is the worst case.
Sep 25, 2016, 09:05 AM
Plank addicted
Marcos Quito's Avatar
Wing tips, same process :
1, Ribs (more complex due to taper wing,
2. Sanding ribs
3. Glueing to longerine,
4. Gluing "shear web" (please correct me if this word is wrong : that sheet between ribs and longerines).
5. Covering

Still need kraft paper in wing tips D box.
Sep 25, 2016, 12:25 PM
less is more
Knoll53's Avatar
The kraft paper over the white foam looks to be the perfect combination. That kraft paper will add a lot of durability at the wingtips, where it is needed for landings. I can see that the trailing edge would be a challenge. I wonder if Minwax Polycrylic would also be a good glue. It looks like you are able to lap one piece of kraft paper over the next so as to create a continuous skin.

Your use of shear web is correct. The spar is made up of spar caps and shear webs. Longerons are on fuselages.

Looking forward to seeing how you do the trailing edge.
Sep 25, 2016, 10:49 PM
Plank addicted
Marcos Quito's Avatar
Now, a new headache : Eagle with eggs in the airfield :

Name of eagle : Geranoaetus melanoleucus / Black-chested Buzzard-eagle (English) / Água Serrana (portuguese)

Ataque Águia Serrana a planador RC (1 min 44 sec)

Take a look in the dive !
Always before the dive you can hear his "shout". In the video there are 3 atacks (one is repeated).

I´ve saw it before, but neve so angry.
Oct 25, 2016, 04:50 AM
Plank addicted
Marcos Quito's Avatar
Video shows the PAPER TECHNIQUE :
Técnica papel dobraduta e cola branca (1 min 48 sec)

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