Bubble Dancer VNE?

[bjr_93tz]

Just a quick one,

assuming a slop free stab mount and linkages and reasonable build quality, just how hard can you push a BD in a dive to get out of lift?

Mine started to dutchroll a few times before I chicked out and slowed it up and put on the brakes. The plan reckons the wing is good for about 150lb of lift at 90mph but 90mph is faster than I'd like to push the rest of the airframe.

Will the elevator rip off before the wings start to flutter or am I just being a pansy?

Brett

[nuevo]

Brett,

I'd say flutter is your biggest concern. Caused by either control surface slop or in the wingtips.

Perhaps a better question is "how do I get safely out of lift?"

travel to a completely different part of the sky. Strong lift can't be everywhere.
deploy spoilers to 70-degrees and then dive vertical. Doing so completely safe, if ample spoilers are deployed. The plane will make a relatively slow descent, and not stress the airframe at all. I'm not sure if this will work for those of you who only deploy spoilers to 30-degrees.

I've done both many times with an Ava.

BTW, these techniques work equally well with a full-house plane. For #2, deploy full flaps, then dive vertical. If you've never tried it, you'll be surprised how slow the dive is.

[bjr_93tz]

Thanks nuevo,

I have the throttle stick set up so that full back stick the plane will float on the point of stall and full forward stick the plane will penetrate on the point of tucking which makes it nice to fly as you use the throttle to trim your airspeed.

Yesterday I was tapping the down elevator a bit as well as full forward stick many times but twice I had to give up, slow it up and apply the brakes.

I have a pair of hs55's on the spoiler and I don't know if they would take a hard dive? My current landing mix sees a "hands off" decent of about 18ft/sec at max braking which sometimes hasn't been enough with me adding a bit of down elevator to help it down faster.

I might program in a "dive" condition so it does a "hands off" dive at about 30-40ft/sec. The reason I need it hands off is I don't believe in putting the brakes on until I "have to" meaning I can't see the blob too well by then.

Cheers
Brett

[OVSS Boss]

No dive required, just go inverted and decend in that condition till you are in a position to roll out and go on your merry way.

Marc

[bjr_93tz]

No dive required, just go inverted and decend in that condition till you are in a position to roll out and go on your merry way.

Marc

Yeah Right,

if I could still see it well enough to fly a RES glider upside down I wouldn't be trying to lose height....

Clocked up an hour flight yesterday of a soggy bungie launch, tried again today and best I could manage was 13 minutes, The damn thing can never find a thermal when I put the Zlog in it. Also tried 12oz ballast for kicks and it flew so much nicer but I couldn't work the little bubbles under 60-100 feet..

[dharban]

I have always been able to get my Bubble Dancers and AVA's down with full spoiler, full up and full rudder. A fairly steep controlled spiral dive can be done when plane is so far away that the plane's exact attitude cannot be determined. When it gets close enough to see more clearly I ease off the elevator a bit and the spiral merely steepens.

Happy Landings,

Don

[FrogChief]

Just a quick one,

assuming a slop free stab mount and linkages and reasonable build quality, just how hard can you push a BD in a dive to get out of lift?

Mine started to dutchroll a few times before I chicked out and slowed it up and put on the brakes. The plan reckons the wing is good for about 150lb of lift at 90mph but 90mph is faster than I'd like to push the rest of the airframe.

Will the elevator rip off before the wings start to flutter or am I just being a pansy?

BrettSoon as you said Vne I thought you MUST be a pilot... :D

[Batmanwpg]

As Don said. Pull spoilers and put the stick in a bottom corner (full up elevator and full rudder) to spiral it down. The plane will never reach a high speed with all that drag. You can get down very fast this way.

[schrederman]

Build a Houston Hawk instead... Properly built, you can point the nose at the ground and bring it down as fast as you want... no worries...

Yeah, I'm biased...

[Mark Miller]

With my Soprano I usually point the nose to the ground usually about 30 degrees from vertical and use full up spoiler. It keeps it from reaching VNE.

I have also done it without spoiler and never had a problem.

Mark

[tonyestep]

A properly-built BD will go very fast without fluttering. For its size, the BD ought to be the most robust design of any built-up plane, because of the careful engineering of its structure. Mine will dive vertically if you really want to, fast enough so it whistles like a moldie -- however, mine is bagged, so I don't have first-hand knowledge of how fast you can dive a built-up version.

As with any RES plane, the controls get twitchy at high speed, so it's preferable to descend in a wide spiral dive at medium speed, or as Marc suggests, fly inverted. When coming down from high altitude, I don't use spoilers -- it creates a lot of load on the battery.

[bjr_93tz]

Thanks for the replies,

I've had a old RES for many years that can be "safely" accelerated until the wings flutter but with the way the BD wing is built I don't think that the first signs of overspeed will be coming from them.

I wonder what speeds you'd get zooming off a winch?

I'll just head out one afternoon and set up a "dive" condition with full brakes and at a safe hands off maximum rate of descent. I've been looking around for a Submarine dive klaxon sound bite to assign to the condition switch and I think I've found it.

http://www.policeinterceptor.com/sounds/688dive3.wav

Cheers
Brett

[tonyestep]

"...I wonder what speeds you'd get zooming off a winch?..."
===============
If you have a Zlog you can estimate from the height gained in the zoom how fast you were going in the dive (from bottom of dive to round-off). Here's a table of theoretical height gain vs speed: A typical BD launch ends up with a dive speed > 70 mph.

Height gained in feet Speed at bottom of dive in mph
------------------- ------------------------------
6 34
31 51
76 68
140 85
224 102
326 119