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May 08, 2007, 09:31 AM
gpw
gpw
“There’s no place like Foam”
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Build guide on a 4 piece plane ....HAHAHAHAHAHAHAHAHAHAHAHAHA... !!! Now that's Funny !!!
Latest blog entry: Lost plans
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May 08, 2007, 09:31 AM
Registered User
skotman's Avatar
Quote:
Originally Posted by gpw
She can fly it !!! Now all we have to do is negotiate for a build ... Why don't we do a really light 36" and call it "Big Pink".. 60's
Sure...I'll pick up the foam, I have enough motors and radio gear to outfit it. I just need your building expertise.
May 08, 2007, 09:34 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Scot, MS is on the way over with plans for the 150% dart ...39" WS ... looks like a lunchtime build session ... probably will make 3.. one for the Domina and one for MS and me ...I guess you'll want one too eh ???
Latest blog entry: Lost plans
May 08, 2007, 09:40 AM
Registered User
skotman's Avatar
Of course lol, man I need to find a job like MS' where I can go build airplanes during my work day.

Can't wait for our order to come in.
May 08, 2007, 10:30 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Skot , call MS on his cell...
Latest blog entry: Lost plans
May 09, 2007, 09:33 AM
low tech high tech
vtdiy's Avatar
Springer,

though not pink foam, I have about 60 flights on a twin boomer (Foamflyer SO style) similar to yours.

Of interest to you possibly -- I used only a single rudder, on one of the vertical stabs. This really cuts down on lingages, and tail weight and complexity.

Rudder authority is excellent and you can put it into a spin with the single rudder fast (if you want). It turns nice sharp corners inside my short tree-lined field on the way up. For sizing information, my rudder is 1-1/2" wide by 6" tall. Rudder throw is 3/4" either side of neutral.

The horizontal stab is 4" wide and 12" between the booms (plus 3" total boom overlap). The elevator is an additional 2" wide strip. -- I don't have a big throw on the elevator.

Wingspan for comparitive purposes is 40" by 7".

Maybe this will give you some relative dimensions to go by.

It is an excellent and precise flyer -- self recovering, and does very well with a J250 with a 9070 GWS prop on a GWS B drive using the same Hobbico 7 cell pack you are using.

I practice loops (sloppy ones after a dive because of the polyhedral and low elevator throws) for awhile every flight, then fly around for what seems like 10 minutes or so on that Hobbico pack practicing approaches and turns.

The sizes of power, battery, and plane match well.
Last edited by vtdiy; May 09, 2007 at 10:52 AM.
May 09, 2007, 01:41 PM
treefinder
springer's Avatar
vtdiy: Thanks for the dimensions, and more ideas
Interesting idea about a single rudder w/ dual vert stabs. I always figured each fin should have a "turning" mechanism - guess not. My center mount rudder was 3 1/2 tall, 2 wide and it seemed to turn the plane well enough - unless it was too small for the windy, slightly gusty condition when the plane did the vertical dive. I thought my wing might have been too long (20" mid section, 7" extensions) but yours is longer and looks narrower. Seem to remember an aspect ratio discussion in prev. threads. Ah well, the guts are in a just finished stealth sport, but I'm waiting for more servos from UH. anyone know how long it takes for airmail to get from them to Michigan?
May 09, 2007, 02:21 PM
low tech high tech
vtdiy's Avatar
Springer,

Seems like you might have just stalled in after a short gust took out your forward speed -- kinda wondering about that wing section with the step on the top surface. Maybe it makes for a sharp or unpredictable stall break?

Seems like that could really give you some eddies behind the step -- maybe in combination with a gust you lost a lot of lift suddenly.

You could just try a curved plate section like GPW shows on Trainer One.

Are you doubling up the wing surface to get stiffness?

A curved plate will give you form stiffness without doubling up -- at least in this size range.

re. A/R Nothing wrong with the aspect ratio aerodynamically other than requiring slightly more stiffness in the wing.

It might give you slightly flatter glide and better climb on lower power. But 39" by 7" is quite moderate AR for a conventional design. It shouldn't have affected anything the way you experienced it.
May 09, 2007, 02:36 PM
treefinder
springer's Avatar
vtdiy: I "thought" (famous last noob word) that I was high enough that it should have pulled out with up ele, but (it all happened so fast! ) seemed to just go straight down, no spin, no ele reaction - actually now that I think about it, I wonder if the wing broke first then it dove? I'd patched the fuse just fwd of where the wing is glued several times, maybe the joint was cracked without being obvious.

The top step was a copy of Dritch's KF wing on his slocat. I think I might do step on bottom next time. I find it does strengthen/stiffen the wing nicely. The top step worked well too, though - maybe build one of each!

Do you have any thoughts on the foam booms vs skewer/stick?
May 09, 2007, 02:40 PM
treefinder
springer's Avatar
Also was gonna add, there was a period about a month ago, when the air was perfectly still just after dawn. All my flights were good then (well, almost all), but recently there seems to be no time when there isn't 5+mph winds.
May 09, 2007, 03:03 PM
Registered User
DRITCH's Avatar
Thread OP
I haven't tried the foam booms yet. They look weak, but then so does the skewers and hot glue. Never had one break yet. I believe mine was overpowered and had 3d size controls. I really like the way it flew. It would float flat to the ground with power off and full up elev with no stall.
May 09, 2007, 03:05 PM
I hear you...I seem to fly great when the air is dead calm...but even light winds play havoc with these <10 oz planes.

jasta
May 09, 2007, 03:10 PM
treefinder
springer's Avatar
And today it's been pouring all day! Oh, well, got to finish the SS, think I'll get offline and go cut foam for the next cat. Let's see foam or stick, topstep or bottom? too many options!
May 09, 2007, 04:03 PM
low tech high tech
vtdiy's Avatar
Springer,

I think both boom types obviously work -- so you pays yer money and takes yer choice.

We often talk about "strength" when we mean stiffness. Adequate strength means something doesn't break when flown the way you want to fly.

Adequate stiffness means something doesn't bend when flying the way you want to fly.

In airplanes it's often a lot harder to get adequate stiffness than adequate strength.

The plane I'm flying now is probably the stiffest structurally of the 4 I've built so far. It is really tough and stays aligned. I think it flies better because of it -- maybe my imagination.

It's been through a lot. 60 flights in the hands of a newbie -- 4 per day, morning and evening.

I did break the booms once in a straight in dive from about thirty feet ( I had reversed the elevator servo throw on the transmitter for another model, and forgot to switch back -- ). But being foam, I just hot glued them back together again -- and the repair was invisible.

I don't think you should expect any construction to survive a straight in dive from any height -- something has to give -- and in this case it was the booms and fuselage front. The wing and tail were fine.

A stick boom, if broken would probably need to be replaced. Or worse, tear up the things it is attached to, like wings and stab. In my case the booms simply snapped cleanly behind the wing -- they absorb a lot of shock from the rest of the structure and are easily repaired.

I've also been caught in trees and dropped through them without breaking the booms.

The foam booms also give you somewhere to recess your servos -- I like that.
It was also easy to attach the horizontal stab of sheet material over the wide area of the foam booms.

But I will probably also build a stick boom type some time soon. Just for the heck of it. I have a lot of white pine, and I'm trying to figure out how to use some of it in an airplane somehow.

Note that I used bamboo skewer wing struts to add further structural stiffness -- you probably couldn't do this with stick booms as easily. The skewer penetrates the foam boom and glues to either side of it -- same for the fuselage.

Like I say this is really the stiffest plane I have built -- and it weighed 12.5 ozs AUW in its original configuration with a 180 direct drive motor, 650 mah 6 cell pack and 5x3 prop. Flew fine for a trainer that way.

Quite a bit hotter with the geared J250 now and AUW around 16 oz.

PS go here to see the 150 planes Foamflyer has built and many foam boom types included -- see the Project History section.

http://www.qnet.com/~skif/rcmain.html

See also the plans for the SO type twin boomer at the bottom of the page.
Last edited by vtdiy; May 09, 2007 at 04:31 PM.
May 09, 2007, 08:34 PM
Registered User
DRITCH's Avatar
Thread OP
I hear ya about stiffness. My next build is qoing to be a laminated fuse and laminated wing with a small carbon rod inside. Figured if I build something for some speed it better bea able to hold up. I do like the way my light planes flap though.


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