CF & ripstop UL stunt bipe - RC Groups
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Jul 12, 2005, 03:35 PM
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hardlock's Avatar
Build Log

CF & ripstop UL stunt bipe

If you are just seeing this theard for the first time and want all the build information, here's a link to the post with the important information needed:

I mentioned this plane in the 3D section, but it's probably better suited here due to the low wing loading. Here's the specs:

Span 26"
Length 24" (now 28")
Area 2.5 sq ft
AUW 6.5 oz (7-7.5)
W/L = 2.6 oz/sq ft (less than 3)
Motor Westport 20 turn CD-ROM (LensRC 20T, 25T)
Prop - APC 8x3.8 (now using GWS 9x5HD - 8x4HD with 3S)
Bat - ET 2S 700 LiPos (& 3S)
Rec - Plantraco DSP4
ESC - PHX 10
Servos - 2) Waypoint WD-60 (also HS-55s
1) GWS Naro HP (for dual wingerons)

Everything just plugs together for ease of adjustments and flat disassembly.

I'm really needing input as to whether I've got something here or am spinning my wheels considering the Bugz line and Slow Jazz similar designs.

Any comments, suggestions, etc. are VERY welcome!
Last edited by hardlock; Mar 02, 2006 at 02:14 PM. Reason: added link to "index"
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Jul 12, 2005, 05:31 PM
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I like it very much! I love carbon & ripstop models, but most aren't too aerobatic, except my IFOs. This would fit my fleet nicely.

BTW, coventional ailerons would be fine with me.
Jul 12, 2005, 05:48 PM
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hardlock's Avatar
Thanks MKH! Conventional ailerons will be the next thing I try. Hoped to reduce the complexity as well as save some weight with the wingerons as well as increase roll rate. It seems the slower you fly, the less response ailerons have.
Last edited by hardlock; Jul 13, 2005 at 08:48 PM.
Jul 18, 2005, 09:08 PM
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hardlock's Avatar
Lots to learn from this design. I've taken some sweep out and relocated the wing pivot line further aft. Found I was flying WAY too tail heavy. Also in my quest for a truely indestructable plane (I crash a LOT!), I replaced the bowed nose which broke with straight pieces. The next version won't have any bows at all as this a a major beef of mine with the IFO. I like the looks, but if it breaks it requires a major rebuild due to the bow(s).

Here's a couple shots of the new layout for testing. Working on getting a real camcorder for some better vid clips.

First time tear-down without tools took 2 minutes. About 3 putting it together again.

Found out that by just removing the lower wing you get a high wing model. Can be flown as a R/E or full house either as mono or bipe by simply sliding the LG/struts in or out for more or less dihedral.

Once refined, will just need a name. What do you think, kit or ARF?
Jul 18, 2005, 11:03 PM
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Does 'no bows' mean square wingtips and tail shapes? I like the curves, but you're right about breakage. The bows do give some strength though, as the rods are under tension and tend to hold shape. 6 of one, you know? I like carbon-ripstop building, but many do not, so you may want to ARF this model. Either way, I really like it, and will buy one later this year if they're available. I'll need a new project in another month or so.

BTW, an afterthought here, the 3D shockie type crowd will drool over the durability of carbon over depron, but they'll demand crisp responsive handling. Is this model rigid enough for this, as in minimal frame flexing? That's a real problem for alot of people who overpower their IFOs.
Jul 19, 2005, 12:51 AM
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Yes, rectangle wings with ailerons to come. Since unless you make a tear-drop shape, you need diagonals for strength so might as well get the most wing area possible from a given span. I've found that too much sweep (at least with wingerons) causes lots of coupling issues and too little causes some rocking in the hover.

It's a very rigid structure with the dual wing and fuse diagonals all joining at the same point. The all flying elevator needs to have it's pivot back further for better aero-balance and less loads on the servo. The roll rate with the wingerons isn't a fast as I'd expected but considering how slow it flies, maybe I'm expecting too much. Response is very quick however and removing the expo helped a lot also. It will axial roll pretty straight without any input except ailerons.

It KEs well with very little rudder input but I'm still probably running too tail heavy. Inverted is solid with no tendency to want to roll out as my mono-wing does. If I get in trouble inverted, full down and punching it always gets me right back to a harrier in the opposite direction I was going. Loops and 360s are very tight.

I flew it in 5-7 mph switchy winds this evening and found myself just wanting to park it in my face at minimum power and trying to keep it there against the wind. This may not seem very exciting but was very challenging and allowed me to see what was going on with the controls like in a wind tunnel. Some fun!

As to durability, I've dorked it in many times, cartwheeled it, dragged it out of a tree with a rake, and it just keeps going. Except for the front broken bow redo, the only "damage" is popped fittings that only take a sec to restore. The original prop is getting mighty thrashed however from trying to mow the lawn!
Last edited by hardlock; Jul 19, 2005 at 12:56 AM.
Jul 19, 2005, 10:35 AM
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That is one cool plane! What weight ripstop did you use?
Jul 19, 2005, 02:29 PM
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hardlock's Avatar
1/2 oz poly coated. Kinda spendy but real light and slick.

MKH - what do you use to glue your IFO fabric on? Contact cement is quick and tight but you better get it in the right place the first time as it can't be pulled up to reposition if you miss. I'm going to try rubber cement on the next one but not sure it will hold that well.
Jul 19, 2005, 02:54 PM
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So far, only used the recommended Weldwood contact cement. I overlap the fabric about 1/4 inch so the fabric is glued back onto itself. Stays pretty tight, but not flawless. Never tried rubber cement, might be worth a try?

Square tips and traditional ailerons should give your bipe good control. Are you thinking 4 ailerons or 2? They'll need to be big enough for good authority at slow speeds, but I wouldn't worry about achieving a really rippin' roll rate, just fast enough for quick inputs. If it will loop, roll, knife, and invert, in a 60'x80' backyard, it will join my fleet.

Jul 19, 2005, 03:32 PM
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Thanks MKH. My yard is about that and I'm sure the plane will do all of the above in it. I'm not quite good enough (or brave enough) to try them all yet as I have a deep creek canal filled with black berries along one side that is almost inaccessable if it should go in it.

From my calcs, it looks like going conventional ailerons will add lots of parts but might be able to use smaller rods to keep the weight down.

I want 4 ailerons for sure and hopefully will be able to use just one servo for them (Naro size) to keep the load off the ESC. Where to mount it is a problem since the main structure is half way between the wings. Works great with the wingerons driven on the root LEs but dual wing ailerons is a different story.

A single HP Naro is all I use on the "Carbon Snapper":

It's at about 10 oz with 30% ailerons and haven't had any problems with it on one servo. It's at about twice the wing loading as well. Very fast roll rate on it.

Learned some tricks with it BTW to keep the fabric tight on a rectangle wing. Slight bow in LE from levering them over the spreaders really help.
Jul 22, 2005, 05:21 PM
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Am I having fun yet? (video)

Getting to know the plane MUCH better now and learning lots. Also got a new camcorder so not limited to just 30 sec MOV clips from my old still camera.

Here's the "must see" good stuff at the park in no wind. Gee, should I post also in the 3D section, park flyer or here? Maybe one plane can do it all!

Not bad for a stock Westport Go-Brushless CDR motor and only one 2S 700 pack, eh? Got about 15 minutes worth of airtime on that flight.

What do you think?

MKH - Not too happy with rubber cement except that if a rod pops out of a fitting in a crash, the fabric comes loose instead of tearing which can be just pressed back in place. Might be good to use just on the nose where all the crash loads end up but just doesn't stick well enough for use on the wings I don't think. I've heard of clear contact cement but have only seen and used the yellow stuff myself. Ever seen any?

After much designing, I think a rectangle conventional control surface version will end up needing a larger motor than a CDR. Might be cool to develop anyway but with the goal of going for the lightest W/L possible may not be possible with all the additional framework needed to keep it strong and rigid.

Now that I'm getting used to the wingerons, you can't beat them for simplicity of construction. No control surfaces to make, no rear trusses or separate aileron connectors, not even any control horns. Just some short pieces of control rod sleeves lashed to the wing for pivots and direct drive links from the servo to both LEs. I'm keeping them detuned for now but once I open them up we'll see what kind of roll rate I can get from them.

Also I've got a yard video coming showing how really small an area she can fly in.
Last edited by hardlock; Aug 28, 2005 at 09:13 PM.
Jul 22, 2005, 07:30 PM
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KLH's Avatar
Very nice! I'll have to add this one to my fleet. I've flown one of your original CF Falcons all over the US in the last couple of years and it's still going. Looking forward to another great design.

Jul 22, 2005, 08:33 PM
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That's a great video, it really looks good in the air. Hard to tell how axial the rolls are, but if they're pretty clean, maybe wingerons is the way to go. The round tips and tails sure look pretty too. I kinda hope it stays this way, if testing goes well. I have the same Westport CDRom on a Lazymoth. Another motor I love is the LensRC 25 turn slowfly motor. It swings a 10x4.7SF or 10x6HD on 2x730TP pack, or your 700 pack, very smoothly at only 4-5 amps. It gives gobs of thrust but low pitchspeed, which is ideal for my IFOs. Torque is more obvious from the big prop, so it depends on the design and pilot preferences.

Never seen clear contact cement before, only used the Weldwood milky looking stuff.

FWIW, the new Lazymoth from is an updated Butterfly, and the wing and tail rods are now a white fiberglass rod instead of the black carbon rods. This was to help with rods breaking on impact, or from being left in hot cars in summertime. Not sure if you've ever used them before, I had not, but it's an interesting idea. Construction, glue, fittings, are the same as with carbon construction.

The bipe is looking really good!

Jul 22, 2005, 09:47 PM
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theKM's Avatar
Ken, too late to be on the beta crew for this one too!?
Jul 22, 2005, 09:48 PM
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theKM's Avatar
this forum software needs a "follw X" feature... so that anywhere Ken posts, I'll be notified

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