IMAC Buff

My Feedback: (8)

Has anyone used a gyro on the Pizza Box? One on the rudder might make it interesting. Not that isn't already a blast!!

Foamguy

Just checking in guys

Saw the article in RC Report. Havent been home too much lately, still in Md. Glad your all still having a LOT of fun


Foamguy

Unstable

you know... i have a pbf that is asking for that .32sx-h ... and since the engine is out of the heli i got a gyro that is just sitting there.. hmmmmmm

Graeme Marion

First let's start with a pic.

Graeme Marion

Sorry I can't do a better post, the forum logs me out after 1min.

I want to build a lighter version of the above.

What should I buy? The plain bearing Norvel.25, or the more powerful and heavier BB Norvel.25

Regards,

Graeme Marion

It seems like I"m on a roll so here goes.

I have two 3lb. FPB's. which fly very well and attract a lot of attention. Both have an undercart, three full size servos plus a mini throttle servo and a 600mah. battery pack. One has a TT.36pro., the other has an OS40FP. I am using Kavan 10X4 props on them both and have yet to break one.

Each has a single nose wheel with a skid on either side for ground stability and a skid / tail wheel at the rear. The effect is like a trike but with a nose high attitude. The landing and take off roll is very short.

I am now ready to build a lighter version. No undercart, smaller servos, a 250mah. battery pack and a Norvel.25 engine.

Which Norvel should I buy? The lighter plain bearing Big Mig.25, or the heavier more powerful ballraced Revlite.25.

Regards,

Dave McDonald

My Feedback: (19)

Graeme,
Your PBFs look good!
And your shop looks GREAT!
(hmmmm......are you related to James Goss?)

Get the plain bearing Big Mig .25. My combat buddies tell me that the ball bearing version just barely outruns the plain bearing version, and isn't worth the extra money.

I've been extremely pleased with my Big Mig .25 in a PBF. It runs great, and it's much lighter than even the 40FP. With a 270ma Ni-Cd or a 700 NiMH battery, you should be able to get your PBF down to within an ounce or two of 2 pounds. At 2 lbs - 1 oz, my Norvel Big Mig .25 powered PBF is one of my favorites!

I wish I could say that! Originally, I ordered 18 Kavan 10x4 props. They all broke as soon as the PBF hit the ground, or even tall grass. I broke one blade off while simply holding it and tightening the prop nut. And Crash99 broke one on a deadstick landing into tall grass.

After my dealer called Hobby Lobby, they agreed to replace nine of them. But even these nine Kavan 10x4 props broke just as easily as the first batch. In fact, I loaned one of the replacement Kavan 10x4 props to my hobby dealer so he could fly his OS 40FP powered PBF. While he was flipping the prop over with his finger to start the engine, he snapped the blade off. I had never seen this happen before even with wood props! Needless to say, my dealer is going to call Hobby Lobby again.

On the other hand, the Kavan 9x4 props that I'm using on my Norvel .25 PBF have proven to be extremely durable.....just as advertised. I will definitely buy more of them when the need arrives.

Graeme Marion

Thanks Dave.

This was exactly the sort of information I was looking for. I will order the Big Mig .25 today.

On the subject of props. I just went into the shed and did a flex test on the Kavan props while still on the models.

My Kavan props will flex until the tips are less than 3inches apart.

Dave McDonald

My Feedback: (19)

I also used to think this was a valid test. I flexed some of these Kavan 10x4 props until the tips would touch.....but they still broke faster than wood props.

I suspect that flexibility doesn't seem to count near as much as impact resistance. But I'm not sure how to test these props for impact resistance other than by hitting the ground.

Take a look at one of my broken Kavan 10x4 props. Notice that even though this prop obviously didn't survive a ground strike, I could literally flex the tip to actually touch the blade.
(After seeing this photo, I also just realized that I hadn't washed my hands after coming back from the flying field!) :stupid:

Fil-Dill

But Dave when I ask your wife about your cologne, she said you usually wore 10-15% premium.

Graeme Marion

I just spent half a day looking for 9x4 Kavan props for the Big Mig 25.

I rang all the major retail outlets in Australia. They all said the same thing. "Kavan props have not been available in Australia for many a long year."

It looks like my Kavan 10x4 props are collectors items.

I have ordered some (Australian made) Taipan 9x4 props. They are a chunky prop with a deep cuff at the root. Beginners use them because of their durability. Taipan props are glass reinforced and tough, nowhere near as flexible as the Kavans.

I'll let you know how they work out.

Regards.

Dave McDonald

My Feedback: (19)

Graeme,
Sorry to hear that the Kavan 9x4 props aren't available in Oz anymore.

If you can find some old Grish 9x4 props, they seem to be the most durable, and they seem to be a more efficient prop than the Kavan 9x4. But you'll have to dig deep to find them.

My next choice would be the Master Airscrew 9x4 glass filled props. They don't really flex......but they're just flat out tough. Hopefully the Taipan glass filled props will be equally as tough as the Master Airscrew props.

On a side note, my hobby dealer recently informed me that Hobby Lobby is going to send me another nine 10x4 Kavan props to replace the last of the 18 original props I bought. But Hobby Lobby said that they weren't going to replace any more of them.

Oh well, at least nine is better than nothing. And at least nine more Kavan 10x4 props will let me fly my PBF for nearly a full evening.

Graeme Marion

What did you just say Dave?

"Nine props , or nine plops , in an evening?"

Dave it just occured to me that plastic and nylon become brittle when cold. How's the weather over there?

Regards,

Mud Duck

My Feedback: (94)

Howdy Folks!!

Well I had the opportunity to spend about an hour with Dave McDonald last Sunday and was able to come away with some more incredible photos and videos of his flying abilities and the PBF.

This PBF has the modified rudder and elevons that improve performance.

If you don't see any others, you must view the video of "2 out of 3 Ain't Bad - IT'S GREAT!!"

I understand that some people may have difficulty viewing the videos and I don't completely understand why. My one suggestion is to try to download the video clip to your hard drive and try to view it from your local drive.

The link to arrive at the new photos & videos is located here...

Click on this line to go to the new page of PBF stuff

Good luck to all with your PBF's and be sure to buy your props in bulk...

Shaun

Graeme Marion

Great video Mud Duck. Thanks.

You have given us all a new trick to try .

Regards,

JoeLang

My Feedback: (1)

Mud Duck/ Dave McDonald,
In what respect do the modified rudder and elevons
improve the performance of the PBF/Stamp? Do they enhance any particular maneuver? What are the new dimensions for the rudder?

And while I've got the forum's attention, I'm curious as to what is the reason my PBF/Stamp does better (tighter) inside flips and doesn't come even close with an outside flip (waterfall?) when I have the same amount of throw, up and down elevator. Has anyone got an answer as to why this might be?

TIA

Dave McDonald

My Feedback: (19)

JoeLang,
The fin/rudder measures 6"x6", with the last 3" being moveable rudder.

On the original PBF, I cut the rudder off at an angle to clear the elevon movement.

About a month ago, I modified the original PBF to keep the full size rudder, and cut a Vee notch inbetween the elevons to clear the rudder movement.

With the whole rudder, the old PBF will now do tighter skidding flat turns than before......almost as tight as a flat spin, but not quite. The missing section of the elevons doesn't seem to matter much at all.

So far, I think I like the full size rudder with the cutout elevons better.

As far as inside versus outside loops, my PBFs also inside loop tighter than outside loop. Maybe the radio gear is interfering with the airflow on outside loops? I'm not really sure though.




Graeme,
Summer just ended here in the middle of the USA, and the daytime temperatures are still pretty much around 90 degrees F (32 degrees C) around here.....which should be plenty warm enough to keep those Kavan 10x4 props from becoming brittle.

JoeLang

My Feedback: (1)

Dave McDonald, I'll have to give the larger rudder a try as you suggest.
I had mentioned to James Goss in another thread that I was thinking about enclosing the radio gear in a simple triangular shaped box using 2 mm Coro to clean up the airflow and give the PBF/Stamp a "stealthy" look. I'm hoping that improves the outside maneuvers. I'll need some more flight packs with some of the ideas that are popping into my head. I've started pulling gear out of planes that I've lost interest in flying since the PBF/Stamp came along.
You guys have created a monster that must be fed! The PBF/Stamp is really great fun and sure gets a lot of attention at the two fields that I fly at. I'm trying to convince a few other fellows that they have to try a PBF/Stamp too. They like the stuff I can do with it, but it's so unconventional, and so I think the purists are having a hard time accepting it as an airplane.

wingspan99

My Feedback: (2)

Ok here's the stats on the PBX-Wing:
Wingspan 24"
Length 24"
Height 24"
Weight 3lbs 8oz
Engine: OS 32 SX w/ Mac's pipe and 10x4.
Control surfaces: Two elevons, two rudderons, four VT's(Vectored Thrust). The VT's are located just behind the leading edge behind the prop, 2" x 5" each for a total of eight control surfaces. The four VT's are cabled together and work off one servo and only to counter the engine torque when in a vertical hover. These are mixed to ailerons. I may try to connect them to each elevon and rudderon later. The rudders work together for standard rudder control, and they also work with the ailerons so I am calling them rudderons. A total of six servos and six programmable mixers are used on six channels including ch 5 and 6. It's pretty wild to see four ailerons and four VT's move together with the aileron stick.
Servos: Four standard Hitec HS-300BB's, one JR 503 on VT's and one RadicalRC.com micro servo on the throttle.
Construction:
Four 12" x 24" coro pieces were used, with 3/16 x 2" dowels holding it all together in the middle. A standard PBF motor mount and spine was used in the middle, and the spine was slotted for the coro vertical. Four 40lb steel cables go to each wingtip at the leading edge and the trailing edges. I plan to add another set of cables in the middle to take out almost all of the coro flex.
Orientation in flight:
I originally planned to have the red side up, then decided I needed the writing to be vertical so the top fin is going to get some yellow paint before flying. I will need to see a distinctive mark at the top of the vertical surface so i will know which end should stay up. I will probably fly it like a standard PBF at first, then graduate to rudder-only turns. Landings will have to be vertical hovers to a touchdown on the coro elevons. I will probably not attempt that on the first flights though, I'll dump it into the 30" tall weeds at the edge of the runway. And I plan on hand-launching it at a 45 deg angle at first to avoid having to trim the machine in a hover. I was thinking about putting wheels at the wingtips so I can do landings on two wingtips, but everything adds weight that has to be hovered. I used a 700mah Nimh battery and FMA 7ch Supreme receiver. It balances just about 5.5" back from the leading edge. I expect it will fly a lot heavier than my 26" PBF that was 3lbs 4oz, but that OS 32SX is very healthy and could yank the 26" PBF vertical when I leaned it against my transmitter case standing straight up on the elevons on the runway.
This machine will be my first attempt at a VTOL. I am already thinking that the next one will be from nice yellow coro or 3/8" extruded foam, about 28" span both wings, and have a YS .45 w/ Macs muffler. The YS yanks a 4lb 36" foam disc vertical. I was originally going to use that YS 45 on the PBX-Wing but I had so much fun with it on the disc I didn't want to take it off that. My 26" PBF was looking so rough from being thrashed 39 times into the ground that I decided to strip it for the PBX-Wing. This is the weirdest plane I've ever built. It has 20 cables. I used pull-pull on each elevon and rudderon, plus the wingtip cables, and the VT cables. It will have 24 cables when I add the other cables midwing for additional stiffness. I hope to fly it this weekend. I will have the video camera rolling to capture it all, and maybe get some stills of it flying. -Tom

Flipper

My Feedback: (3)

ws99, cool idea, can't wait to hear how it flies!

TriadSport

Tom that is one wild piece of coroplast - I don't know how you managed to get all of the mixes to coordinate. I'll be watching the sky this weekend at my house, just south of Winston-Salem in case it gets away from you! - Bob

Dave McDonald

My Feedback: (19)

Tom,
Your X-Wing PBF looks great!

I can't wait to hear how it flys!

KCFlyBoy

My Feedback: (12)

Yea let us know how it flies and how you orient to it.

BMatthews

OK, I just joined up to this forum thanks to this one thread. You guys are having TOO much fun. You gotta stop right now before they start taxing it........

Anyway, I'm going to make my own PBF but I was hoping to just use some of the thinner 2 or 3 mm stuff that I have two sheets of in my shop. What I was thinking of doing was to cut it to 24 x 45 and fold it so the top stops at the hinge line. Then I'd clean up the inner edges and glue it together with contact cement.

Hmmmmmm.... Just thought of something. Since it's gonna be folded anyway maybe I'll add a few ribs about an inch thick and put the gear inside. Nothing fancy, just a simple shape to fatten it up and make enough room to put the stuff inside between the sheets.

Anyone else tried one with an airfoiled wing? I saw some reference tonight about the PBF foil but I didn't see any flying reports.

Of course since it takes little or no time I'll do it and get back to all of ya.

Cheers.....

PS: Ooops.... Should have checked before I typed my big mouth off. I've GOT 4mm stuff. Gotta go clean off the bench now.....

KCFlyBoy

My Feedback: (12)

Welcome BMatthewes. Yes we have to much fun. Why would you use the T word we already pay to many Taxes. If you have 4mm fly it flat the fly great! KBFlyBoy