My Latest Q500 Design
 

Well guys, here is one of my new designs. Been out of work several weeks due to some surgery and finally decided to finish her up. Slightly modified 66-012 wing, shaped 3/16 tail and the key feature is an air foiled fuselage. What do you think??

My next goal is to figure out these skinned hinges. I’m doing something wrong and they are coming out too stiff. Maybe Vicman can show me his secret.

I did use the Mylar sandwich technique that Randy Etken developed on the wing and it worked out great!! Saved much time and I believe came out lighter.

Bob Harris

RE: My Latest Q500 Design
 

To quote Freddie Prince......"Looking Good"

RE: My Latest Q500 Design
 

>>>My next goal is to figure out these skinned hinges. I’m doing something wrong and they are coming out too stiff.<<<


Bob, experiment on some scrap balsa or now that you know there to stiff,,, go a little lighter on the next one:D


BV

RE: My Latest Q500 Design
 

Whats a "Wham Bop Special" ???

Looking very nice. Great job.

RE: My Latest Q500 Design
 

Dave, John Gibson came up with that name!! He flew the first prototype last year and it flew very well. I told him he could name the model so he came up with it!! Lost her due to a takeoff accident.

Bob Harris

RE: My Latest Q500 Design
 

I like it, whats with the nelson?

RE: My Latest Q500 Design
 

Well Randy, I kept 1 SS Nelson to use as a practice engine. It appears by my conversations today everyone will eventually move over to 426 Sport Jett. We have the Old Julian Airport Race this weekend and I was out helping. 26ea 424 entries with 16ea 428. Not sure about 426 or 422 as they will run those tomorrow. I can't see spending $450.00++ modifying the SS to LS when the Sport jett at $250. The 426 class is still pretty fast!! Hope to try her out soon. May want to talk with you about a few wings too!!

Bob Harris

RE: My Latest Q500 Design
 

After yesterday it's obvious I need a new kit. When can I get one as well as wing templates to cut out :D

RE: My Latest Q500 Design
 

Bad day yesterday, Vic?

RE: My Latest Q500 Design
 

Nah. Great day! I just stuffed my Holeshot 10' from the finish line. I still had a blast.

I have this strange problem that just when I get a plane flying hot and on the rails I catch myself watching the plane and forget to fly it. This is the second time I've blown one into the ground enjoying the show. Personally I'd rather they go in a race than suffer some stupid hangar damage. It makes things easier to swallow.[8D]

RE: My Latest Q500 Design
 

Nice plane.
Sorry for my ignorance, which is this mylar technique?

RE: My Latest Q500 Design
 

I'll jump in here since it's been a few days. I hope Bob doesn't mind having his thread hijacked for a minute. ;)

If I understand the question correctly, the "Mylar technique" you're interested in is a finishing method for wings and tails in which the base coat of paint is applied to a sheet of .014" Mylar, and then the Mylar is pressed against the balsa with epoxy resin and light fiberglass cloth in between. If the balsa skin is smooth, and if uniform pressure is applied to the Mylar sheet (as with a vacuum bag system), the finished wing or tail panel comes out looking as smooth as a porcelain dish. You can then apply your trim colors and a clearcoat if you want. Think of it as the poor man's billet mold.

Tricks and traps I've discovered:

1. Klass Kote paint is the best paint. It's a 2-part epoxy that sprays easily, cures very hard, and can be painted over with urethane, enamel, or pretty much anything else.

2. Use PVA as a release agent on the Mylar. You can wax it first with Johnson's Wax, but don't rely on wax alone. The solvents in the Klass Kote will compromise the wax barrier. Spray the PVA on, let it dry, spray the paint on, let it dry, GENTLY sand off any dust particles or bugs with #400 sandpaper, then apply wet epoxy resin and 3/4 oz. glasscloth over that using a squeegee or an old credit card and slap it on the balsa wing panel before it starts to cure.

3. Prime the balsa with nitrate dope if you have some, and sand lightly using #320 sandpaper on a sponge block. This reduces the amount of epoxy resin that will soak into the grain of the wood. My wings always came out heavy until I started doing this.

4. Also prime the balsa with a very thin coat of wet resin just before applying the Mylar/paint/glasscloth to it. I know it sounds like a contradiction of step 3 above, but the last thing you want is little "voids" of unsaturated glasscloth between the balsa and the paint. Most of the excess resin will squeeze out around the edges when you press the parts together. Obviously a vacuum bag will give more squeeze, therefore press out more of the resin, but you should be able to get acceptable results by setting the wing panel in the foam "shucks" it came from and weighting it down with paving stones or a small car or whatever.

Those are the basics. Someone could probably write a book on the topic, and maybe they have. But I hope this at least answers your question.

Cheers,

Duane

RE: My Latest Q500 Design
 

Bob,

FWIW, I'm having good luck with two layers of 2-oz. cloth, cut on the bias with the fibers at 45 degrees in relation to the hinge line.

Duane

RE: My Latest Q500 Design
 

Duane, I had a problem with the glass breaking down over time and have started using kevlar for the hinge area. Under the glass using the method you did such a nice job describing.

One difference is that I only use .75 cloth.

RE: My Latest Q500 Design
 

http://www.rcuniverse.com/forum/fb.asp?m=3421160 using mylar and fiberglass for foam/balsa wing.

RE: My Latest Q500 Design
 

Looks like all was covered. Sorry for taking so long to post I was trying to find Randy's thread!! I am going to attempt the gapless hinge with the 2 oz cloth. I tried Kevlar on my tails but it was too stiff!!

Bob Harris

RE: My Latest Q500 Design
 

Vic,

If you crash as often as I do, that's not a problem!

0.75 oz. or 1 oz. Kevlar would be great, in fact I have some, just hate to work with it because it's so beastly hard to cut. But if you were going to use it on anything, encapsulating it in a wing skin would be ideal since you'd never have to sand or trim it after that.

Cheers,

Duane

RE: My Latest Q500 Design
 

We use Kevlar in our boat construction, and it is challenging to say the least. For long term use, Fiskar scissors reground to a 80ish degree angle with a 80 grit belt sander is the trick. For smaller batches as in hinges the dollar store throw away serrated shears work fine. You don't want to have to sand the stuff, it will fuzz horribly........hide it between layers of fiberglass is the real solution. Tough stuff, worth messing around with. Bob- you might try a piece at each end on the tail surfaces, will act as a hinge and won't be near as stiff as a full run.