Wednesday, August 6, 2014

Goldguy Is Right: Round Flies Better

It's a Nutball without the polyhedral. It's a round Pizza Box Flyer. It's the USAF UFO.

I'm a big fan of the Pizza Box Flyer, but I'm not a fan of the pitch sensitivity. I wondered what it would be like to fly a round one, and I recalled that on the All Things Round thread I'd seen something called the USAF UFO, by the always excellent GPW. Pardshaw built one and loved it. I built mine along his recommendations:

24 inch diameter

1300 kv Blue Wonder

500 Mah battery

He recommended huge elevons, but what does he know? I scaled mine up from the 21 inch plan provided by GPW. I'd show him.

It flew really sweet. It climbs at half throttle. It has a very low wing loading so it's very floaty, but with the throttle up it gets fun. Which was the problem. The roll rate with those little elevons was slow, too slow to get out of hairy situations before smacking grass, and the whole reason you build something like this is to get into and out of hairy situations.

I cut the old elevons out and installed bigger ones. I measured 6 inches up from the rear, drew a line straight across (leaving a 2 inch strip for the tail) and cut new surfaces to fit. The throws are maybe 35 degrees and I've dialed in 40% expo. And the result? Amazing.

It has all the benefits of the PBF without the pitch sensitivity. It's smooth, in a dive or a climb, but it still loops in almost it's own length. It's just as wild as a PBF but it's easier to fly. I love it. Don't think I'm going back.

Pardshaw raves about it, and I think I recall Goldguy saying that "next to a UFO, the PBF" provides the most fun-per-buck. I think I agree.

That huge tail is odd looking but MAN does it keep this thing straight, even in wind. I bet the Pi Yak is a hoot (it's this thing with a fuselage and a functioning rudder). 

The only problem is that when you see it in profile all you see is tail. The wing turns invisible. It's a little disconcerting if you're far away.

Very pleased. It's my new favorite.

* * *

PS: The fuse and tail are all one piece and L-shaped. The fuse on mine is 1.75 inches tall. The tail is 9 inches tall and 4 inches wide. The whole thing is 12 inches long. 

PPS: Built it out of Model Plane Foam, which I love.

Thursday, July 17, 2014

Hobby King's Nutball

If you're into scratch building little foam RC planes you know what a Nutball is. For the uninitiated the Nutball is arguably the most significant design to come out of our branch of the hobby. Goldguy knocked it out of the park with this design.

The support thread over at RC Groups is on page 834 and counting for good reason; this is the perfect first build. You don't have to worry about elevons, it has very few steps in its construction, and its polyhedral tips give it a huge amount of stability and thus make it easy to fly. Dial up the rates and you can do silly things with it. A pilot who is bored with Nutballs is a pilot who is bored with life. These things don't get old.

I first encountered the design at Flitetest:

I've made several. Some I've crashed because I wanted to see how far I could push them, and some just plain wore out. I've passed 3 of them along to newbie pilots to use as their first planes. Every one of them has flown great.

Say you're new to the hobby don't want to scratch build it? Getting the new plug and fly version from Hobby King might be a good option. Like scratch Nutballs all of the components are exposed; you can see how everything is put together and what everything does. Even if you didn't build it from scratch you still get some experience learning about what makes an RC plane work. Just glue on the tips, attach your receiver and you're in business. Also consider the fact that HK's version only weighs 100 grams ready to fly (3.5 ounces!) and it's made of EPP, which means it will be crash resistant.

$50. It doesn't get a whole lot cheaper than that, folks. I haven't bought it, so I can't review it, but I like it. I might have to get one for the sheer novelty of ordering an ARF Nutball. It's also smaller than the Nutballs I have known, having a span of just over 18 inches. The original design calls for 20, and that's the only size I've ever flown, but the way this one flies seems very familiar to me.

Here I am with my buddy Albert in some Nutball versus Pizza Box Flyer combat (my Nutball is squarish... I haven't found that the shape matters very much). With the rates up this thing is very agile; with the rates dialed down it's a sweetheart.

So build a Nutball, or buy one. Everybody should have one.

Wednesday, July 9, 2014

Model Plane Foam

Time flies! It has been too long. Life gets busy.

I just got a load of Model Plane Foam's A-grade stuff, 16 sheets for $60 shipped, and I'm very happy with it.

Lets compare it to Dollar Tree's Adams Redi Board:

Surface Area: Adams =  600 square inches  per 20x30 inch sheet, while MPF has a surface area of 1152 square inches per 24x48 inch sheet. For all practical purposes MPF sheets are equivalent to two sheets of Adams.

Price: Adams costs $1 per sheet, while MPF costs $1.88 for an equivalent sheet if you buy the A-grade stuff ($60/32).

The Foam Itself: At first blush I like MPF better. It's maybe not quite as stiff as some depron I've ordered, and it certainly isn't as stiff as Adams, but there's no paper on it.

Thickness: Both are 6mm thick, so plans designed for Adams ought to work with MPF.

Weight: Adams weighs .19 grams per square inch (source), while MPF weighs .14 grams per square inch.

To calculate MPF's weight we take the retailer's figure of 2 pounds per square foot of density (a 12x12x12 inch cube) and divide by the total number of 1 inch square cubes in that large cube, which is 1728. Then we divide that by 4, because the stuff is 1/4 inch thick. We get a weight in ounces of .005 per square inch of material. This converts to .14 grams per square inch.

Conclusion: MPF has no paper to deal with, it's strong but not as stiff, and it's about 25% lighter. I'm liking it so far... I'll build a plane with it and report back.

Tuesday, September 10, 2013

RC Groups Park Jet Thread

Here is a link to the park jet thread. It really is a subculture unto itself. Lots of interesting stuff.

Tuesday, September 3, 2013

Standard Park Jet Power System

There is a strong subculture of park jet enthusiasts which I have only recently stumbled upon. They make their jets out of 6mm depron and they use this standard power system: 2200 kv motor, 30 amp ESD, 1600 mah 3 cell battery and a 6x4 prop. Tis setup will power large models (though not overly large) very handily. It is the best of all worlds, the sweet spot, for park jets.

RC Powers has a parts list and links to suppliers. Dave and Scott also have well researched designs and will sell you the plans for a very fair price.

A huge number of plans can be had for a small donation at park A favorite seems to be the Alpha Jet (a very modernist take on the biplane).

Monday, September 2, 2013

The Cheap N Easy by Rcrich

I built this foamy to test its feasibility as a trainer. I am thrilled with the results.

What do I love about it?

  • This thing can fly SLOW.
  • It's easy to slap together. Build it like Goldguy's Nutball... the only real complication is the prop-and-slot pusher motor configuration.
  • It's a Rudder, Elevator Throttle style plane that can do axial rolls.
  • It's a larger plane but it still uses the standard Blue Wonder motor, 1000 mah battery and 9 gram servos that EVERY Flitetest aficionado already owns.
  • It is STABLE. The Cheap N Easy wants to fly straight and level. I flew mine in high wind with no problems.
  • It will hover even on a calm day. You can land it straight down if you get your high-alpha angle correct.
  • It literally turns in place.

Here are some points to consider:

1. Rcrich has us balance the plane at the back edge of the prop slot. This is fine for experienced pilots, but I suspect that a beginner will want a more forward CG... perhaps in the middle of the slot, or at the front.

2. The large control surfaces can make the plane squirrely if you don't tame them with exponential. I have 60% expo on the elevator. Of course you could just reduce the throw, but what fun is that?

3. I've used bamboo skewers as pushrods. Take pieces of wire and heat shrink them to the ends. I like to add a dab of CA to the end for added insurance.

4. I've also rubbed Minwax Oil Based Polyurethane into my plane with a paper towel. First I taped all the control surfaces, then I added colored sealing tape, and finally I minwaxed it. I'm very pleased with the results. It's a durable finish and it adds a lot of strength.

5. I wonder if the Cheap N Easy could be included with the swappable series? It flies like an extra stable Nutball, and I think might make a decent first plane.


My video really doesn't do the Cheap N Easy justice. To watch its designer put it through its paces follow this link:

Time to build your own! Check out the plans at: