Zobec(ov) CAROBNJAK!

[Bozo]

6 g:

DVE pobede, za redom!!!

[bbjurek]

nice weight, I wonder if a very slender wings?

[Bozo]

Yes, it is!
Special if you know it is some variant of DK-models...
(maybe Zobec does not think so...)
Wing - same,
Vertical Stab - bigger...
Horisontal Stab - without V ...

[bbjurek]

everything is correct but the weight ...
unrealistic for me

[vilim]

I got nothing to hide, like most of them here, this model is close to DK 29 planform. But this one is carefully planned and built, with best materials I could find.
Don't worry, the weight is closer to 7g. Original weight was 6,4g but I started to break stabs. I was short of time so I just put stiffer and heavier tail feathers. That put some 0,5g to the model. Till then I had no ballast on the nose, i fact, I was trimming the front of the tube to get balance .

[vilim]

I forgot to say that these two wins were made with heavier incarnation. I'm still not completely comfortable with this model and the tail is little too heavy, so, hopefully, there's more to come

[bbjurek]

Vilim, thanks for your clarification
of my estimates suggest that the wings weigh around 4g. It is an art to make such a light wing. You are using balsa 3 or 2.5?

[Laca]

Iskreno, oduvek sam se cudio tezinama od 6 grama za tako veliki model.
Istina, uspevao sam na "MRAK"-u da dobijem tezinu od 5,9 grama ali je to model raspona 580mm a dubine krila 96mm. DK-29 ima bar 25% vece povrsine, pa mi je tezina od 6 grama stvarno neverovatna. Realno, takav model mora imati najmanje 7-7,5 grama.
I ja sam koristio laganu balzu, 70gr/dm3, ali trup i rep moraju imati najmanje 2 grama. Karbonska cev 1,3 gr, horizontalac i vertikalac 0,3 gr, parasol i balast 0,5 gr.
Ispada da su krila 4 grama ?
Odgovorno tvrdim da takva krila moraju imati od 5-5,5 grama.
Ko je vest matematicar neka pomnozi specificnu tezinu balze sa zapreminom krila, doda na to lepak i karbonske trake i videce da je 4 grama nemoguce.

[bbjurek]

Hello Laca,
I agree with you,
even 7.5 gr is very difficult to achieve for DK-29

[Laca]

Stanov "Slow pocker", koji je za 10-15% manji model od DK-29 je bio tezak 6,7 grama, ali sa balza trupom, oblozen trakama karbona duzine 480mm i tezinom od 1gr. Repne povrsine su mu bile teske 0,25 gr.
Verujem da je Stan koristio najbolje moguce materijale, koji se mogu nabaviti u Americi.

[bbjurek]

Laca,
it's all true what you write,
Vilim probably doing a very delicate and very slight wings.

[vilim]

Front part is 3mm to 1mm where flaps begins. Whole wing is 4,64g heavy, without pylon. Fuselage with stabs were originaly 1,75g (0,23g for tail) but later I shortened front part by 50mm to get balance. Than I decreased incidence and finaly changed stabs. I can't remember the weight of pylon. Now I'ts 6,97g.
Laca, gornjaka se može brusiti i konkavno da se izvadi još materijala. Ja to nisam radio, ali bih, da sam morao. Za opstrujavanje nema veze, ionako je laminarno kod ovako malih Re brojeva. Nekada treba imati i sreće. Mogao sam staviti šest kepova na krilo, kako se to inače radi. Međutim meni su ostala samo dva (laminirana u kalupu u V) pa sam ih raskolio po pola da imam dva gore i dva dole. I pokazalo se da je to sasvim dovoljno a da se flaps jako fino ''prebacuje''.
Nije lako napraviti lagani model. Polomio sam ja i trup i rep, flapsovi su se izbacili, još prije nego sam složio model. Brušenje ne završava kada kažu vaga ili šubler, nego kada se obje strane krila jednako savijaju, kada flaps jednako prebacuje, kada se trup jednolično savije. Nijedna komponenta ne smije biti prečvrsta u odnosu na ostale.
I da se ne zanosimo, nije ovo najbolji model na svijetu. Uhvatio sam Dlaku na lijevoj nozi dva puta zaredom i to je to. Nekada je mogao imati loš dan pa opet pobijediti ali sada sam ja ''vrebao iz busije''.

[bbjurek]

Nov 20, 2012 14:17:42 GMT 1 vilim said:

Laca, gornjaka se može brusiti i konkavno da se izvadi još materijala. Ja to nisam radio, ali bih, da sam morao. Za opstrujavanje nema veze, ionako je laminarno kod ovako malih Re brojeva. Nekada treba imati i sreće. Mogao sam staviti šest kepova na krilo, kako se to inače radi. Međutim meni su ostala samo dva (laminirana u kalupu u V) pa sam ih raskolio po pola da imam dva gore i dva dole. I pokazalo se da je to sasvim dovoljno a da se flaps jako fino ''prebacuje''.

Gentlemen, you're cool but you have such a difficult language
I know, I know, this is my problem

[Laca]

My friend Jurek,

We say, speak croatian-serbian and the whole world understands.

Vilim, sad mi je malo lakse, 7 grama je vec moguce.
Poceo sam da sumnjam u sebe kao modelara.
Licno mislim da se ne dobija previse sa povecanjem nosa trupa. Smanjuje se balast ali karbonski trup u svom najdebljem delu ima svoju tezinu.
Koristio sam Korejanske vrhove za pecanje (koji su po mom misljenju najbolji) a najlaksi trup duzine 500mm, mi je bio 1,2 grama. Balast 0,35 grama i rep 0,25 grama a parasol 0,1 gram. To je 1,90 grama. Krila su mi bila 4 grama. To je vrh koji sam postigao ali sa manjim modelom.

[vilim]

Eto Laca, vidiš da tu nema čuda. Jedino što sam u taj model uložio dosta truda. Radio sam ga dva mjeseca. Kada nisam bio raspoložen ili vidim da mi baš ne ide, ne radim. Puno više planiranja i gledanja nego rada. Rezultat je model koji se lako reglira i nema bubica. Najveći je problem što sam ja loš bacač .
And now, for You Jurek. I was writing directly to Laca because he was sceptical about weight. In my opinion we all know how good model should look like. Also, I think that airfoil isn't that important (except curvature) because of low Re numbers airflow is laminar so it is possible to make upper surfice concave to remove excessive material and save weight. Also, I mentioned that I ran out of V-shaped capstrips for root reinforcement. Usually people put six of them but I had only two so I spliced them and made four but it turned that it is just enough and I saved weight.