Has anyone built an Oly III with a removable full-flying horizontal stab?

[rogerflies]

The idea of having to carry around a plane with that large a non-removable tail isn't very appealing. A protective tote-box would be nutso cumbersome.

Has anyone has tried kit-bashing the tail of an Oly III.

Roger

[seanpcola]

Good question Roger. I'm building one right now for a buddy and have been staring at the rear fuse for a couple of days thinking about the very same thing. Shouldn't be hard to do. Only drawback I can see is added weight which can be overcome within reason.

Sean

[rogerflies]

I'm thinking that it might be easier to put the stab a little lower so the pivot pin goes through the very top of the fuse. That might leave enough room at the bottom for the bellcrank that drives the stab. A little bulge on the bottom of the fuse might be necessary, but it needs a skid-point anyway.

Putting the brass sleeves in the solid sheet stab might be a little tricky, but a little local reinforcement could be blended in over the area.

An alternative might be to make the fin and rudder removable, and use a shallow tote box that's wide enough for the fixed stab, with the wings alongside the fuse.

Roger

[FoamCrusher]

Funny you should ask...I have one under construction right now using a set of DynaFlite Bird of Time stabs.

The stab is operated by a pushrod that works a X-servo horn on an axle with two arms at 90 degrees removed. A short threaded rod with two clevis connectors work the horizontal rod that lifts or drops the LE.

In order to be able to adjust it after flight testing, one side of the tail is removable. Right now it is held in place with four small screws, but once the adjustment is correct I will glue it in.

The horizontal tail volume (Vh) comes in at 0.55 which is just a little on the positive control side of neutral. I would like it higher, but the stabs were already in my spares. Even though I made the fin a little larger so the vertical tail volume (Vv) would be correct for the larger plane (132" wingspan vs. the BOT's 118") it still comes in a bit on the small end of the acceptable range.

Yeah, I know the tail is overbuilt and may be heavy, but this plane is going to be electric powered with a Mega 16/15/3 in a 5,2 GB with 3S2P 2100 mAh lipos (400W and 87W/lb), so according to my balance calculations it should about even out.

Beyond the tail what concerns me is that the calculations and my TLAR engineering says that the dihedral is too small by about half, at least by today's standards. When compared to a Bubble Dancer or Ava, it looks positively flat - almost like an aileron plane. Changing the 1.75" and 5.75" lifts at the panel breaks to 3" and 11", it calculates about right.

Can someone who is flying one with the stock dihedral assure me that I don't need to increase it?

FC

[Mr. Kite]

Here is some other ways that work Mr. Kite

[rogerflies]

Oh, my. I may have finally found a use for the 1/16" endmill I've got. I can use it to mill the slot in the bellcrank so the drive pin won't bind as the stab moves.

Looking at the photos of built Oly IIIs, I'm now wondering if it might be possible to lay the wings tips-forward alongside the fuselage with blocking under inner panels just in front of the fixed stab. The roots don't look like they'd stick out past the tips of the stab, and they might be about even with the top of the fin.

Since the custom tote box needs to accommodate the bent wing panels, the fuse and fixed stab might fit.

Anybody with an OlyIII reading this thread? How about posting a picture with the wing panels alongside the fuse with the roots propped up over the stab?

Roger

[atmosteve]

Rodger i built my fuse to accomodate a removable tailfin, but didn't follow through. Basically it involved four 3mm countersunk nylon bolts going small spruce blocks and blind nuts in the back of the spruce blocks within the fuse. dwells (Don) is building his as a removable setup featuring a V groove seating to locate and align the fins, but thats all I know. Sounds interesting anyway.

[atmosteve]

Oh, my. I may have finally found a use for the 1/16" endmill I've got. I can use it to mill the slot in the bellcrank so the drive pin won't bind as the stab moves.

Looking at the photos of built Oly IIIs, I'm now wondering if it might be possible to lay the wings tips-forward alongside the fuselage with blocking under inner panels just in front of the fixed stab. The roots don't look like they'd stick out past the tips of the stab, and they might be about even with the top of the fin.

Since the custom tote box needs to accommodate the bent wing panels, the fuse and fixed stab might fit.

Anybody with an OlyIII reading this thread? How about posting a picture with the wing panels alongside the fuse with the roots propped up over the stab?

Roger


Ok I just tried this on the bench, as you described it. it turns out to be a very neat fit, the wing roots will come within the tailfins when the wing tips are inline with the nose of the fuse, and with the standard polyhedral the inner wings sit about 3/5 of the way up to the rudder fin. My wings are a little longer than specified, so the standard wings will fit well within the fuselage length. It'll all fit neatly in a tote box as far as my eye can see.
Sorry no pic, but the idea will work all the same.

Steve.

[rogerflies]

Thanks, Steve. That sounds good.

Roger

[efowlerpreston]

I have an OLY III in Valdosta if you want to see or measure one in person. I built it stock except for flaps and the motor in the nose.

[FoamCrusher]

I built it stock except for flaps and the motor in the nose. In my post above I said, "Beyond the tail what concerns me is that the calculations and my TLAR engineering says that the dihedral is too small by about half, at least by today's standards. When compared to a Bubble Dancer or Ava, it looks positively flat - almost like an aileron plane. Changing the 1.75" and 5.75" lifts at the panel breaks to 3" and 11", it calculates about right. Can someone who is flying one with the stock dihedral assure me that I don't need to increase it?"

Since you are flying a stock plane, can you comment on the dihedral? Does it turn easily enough or would you increase the dihedral and if so by a little or a lot?

After playing around with the calculations a little more, it looks like 2" rather than 1.75" at the first break and about 7.5" rather than 5.75" at the tips gets the values in the ranges recommended by Mark Drela. That's quite a change and while I like mathematical models, I don't want to muck things up if the stock values work well.

FC

[rogerflies]

Just looking at the pictures of the OlyII and OlyIII on the Skybench site, it looks like the tip panels on the III are larger in proportion to the inner panels than on the II. I don't see much difference in the dihedral in the photos.

The original II turned well with stock dihedral, so I'm thinking the III with proportionally larger tips will also turn well.

Roger