Ojimak F-22 Raptor

**jlcopen** · #1 08-22-2010, 01:49 PM

Here is my fourth Ojimak build, and my second paper model using two coats of Sig Nitrate dope as a finishing agent. I've used dope essentially to condition it better for the rigors of flying. I'm still getting the hang of producing a nice finish, so there are splotchy areas. I used to use dope on balsa model rocket fins, but paper seems a little trickier to get a good, even coat onto.

I must confess that this is an approximate 130% version of Ojimak's design, as I just wanted a larger scale for flight. I hope this isn't a violation of his expressed wishes to "...not modify..."!

These models look sharp and are fun builds, especially for flyable models! Thank you Ojimak!

**thomaswg** · #2 08-22-2010, 06:57 PM

Try something called "Envoirtex" It is a two part expoxy liquid resin system. Mix one part hardener, one part resin, two parts denatured alcohol. Then dip the model in the solution let it sit for a couple of mins. and withdraw. Let it dry on wax paper, but you have to move it several times as the excess runs off otherwise you'll get flat spots on the model where it came in contact with the paper. an alternative is to suppot modlle on upright toothpicks to let it dry, jst make sure you check for drips as well

**wowhaza** · #3 08-22-2010, 09:42 PM

How do you builders read the text in his pdfs? I don't understand his language but his designs look really special, and worth making.

**jlcopen** · #4 08-22-2010, 10:48 PM

thomaswg, thanks for the tip - sounds interesting! Does it not cause any warpage?

wowhaza, you can usually get by without the text part of the instructions, however some of his pdfs include photos of the model's construction in stages, which helps. I'm not actually sure about the placement of the "tail cone" on this model - I took my best guess!

Other posts about using dope cited applying it to the parts before even cutting them out, but I would think that the added stiffness would cause difficulty in shaping parts that require curves. I may try that next, though, then maybe run dope along the seams post-build.

This model turned out a little tail heavy, I believe, as it didn't fly very far at all - it just sort of "floated". Aerodynamics may also be a factor, I suppose.

**thomaswg** · #5 08-22-2010, 11:20 PM

After all is said and done I think you are going to have to experiment with these various methods to find the best solution. You can use the resin method to soak parts first then cut out byut gleuing becomes more problematic, super glue works well though

**papermate** · #6 08-23-2010, 01:17 AM

It seems that you are not building Ojimak's latest version of Raptor F-22. In his improved version, not only the look gets better, but also the flight or glide or whatever you call it. Try that, and you see the difference.

**jlcopen** · #7 08-23-2010, 01:46 PM

papermate - Holy Cow! I completely missed that! Thanks for pointing it out - I'll have to build it now!

**papermate** · #8 08-23-2010, 09:15 PM

thomaswg, I normally use UHU glue which is a non-water based glue to work with Ojimak's planes. After drying, the glued parts become stronger and quite durable to withstand the impact of many flights. Water-based glue will warp the parts you glued. Especially the wing part, I will definitely use UHU. CA glue is more expensive and comparatively more harmful and I use it sparingly. The most vulnerable part is the nose cone. So that's why in Ojimak's recent designs, he would add in a re-inforced nose cone. It would be a good idea to build a couple of extra nose cones - to replace the damage one just in case and for static display after having fun flying it all over the place.

Do they look gorgeous? One tip about the F-20 (the red one). When you fly (rubber-band launch) it, make sure that the ailerons are angled right and that you launch it at shoulder level as it first dives OMG appearing to hit the floor but then it climbs, absolutely fantastic.

**jlcopen** · #9 08-23-2010, 11:24 PM

Papermate, thanks for sharing your methods! I generally use white glue, but I've started to use double-sided scotch tape quite often for wing laminations; it works very well, but isn't too practical. I've used 3M Super 77 spray adhesive for laminations as well, but it's tricky dealing with overspray and oversaturation. I still haven't tried an UHU stick for that, so I may see how I fare with some attempts. Your planes look great, too!

**papermate** · #10 08-24-2010, 12:26 AM

Jlcopen, double-sided scotch tape isn't ideal and neither is spray adhesive as you have mentioned. The UHU glue is in a tube, see photo, and not glue stick. Another method I often use for reason of price is contact adhesive. We have Rubstik and Pattex in HK. What you need to do, especially working on upscaled build is that you apply thin layers of the adhesive on both surfaces, allow to dry, and then simply snap together and that's it.