Hoerner Wingtip comparison

[kestrel]

I chickened out on doing that type of test for VG's. At the time, I just wasn't 100% certain is was a good idea. Now that I've flow with and without VG's, I'm eager to get around to doing that test. I expect little to no difference in roll and yaw trim, but probably some difference in which when drops and when.

[Nev]

No change to wingspan. Both sets of tips are the same size.

[jaredyates]

Agreed, not a test to be taken lightly, but I'd be tempted in a case like this.

[rodsmith]

I bought the fiberglass tips many years ago, was not impressed with the shape or looks. Sold them to another builder and last year finally made Hoerner tips. Will never know what they did for me aerodynamically, but I sure like the looks of them. They are the hand made parts that I am most proud of. Now I have been debating whether or not to just add VGs before first flight as I am sure I will end up with them. Think I will wait so I can see what difference they make.

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[kestrel]

Jared, if you are responding to my comment, I was specifically referring to the change in IAS error due to AoA is likely not measurable. I wasn't suggesting that the difference in lift or drag was not measurable. But, with that clarified, I think it would be very interesting to check for changes in roll or yaw trim with a different tip on each wing. One would want to be careful doing this type of test as a large difference could result in roll behavior that isn't controllable, but I would be willing to fly this particular tip pairing. Put a stock tip against a 12" extension with a winglet, and I'm a solid "no".

[jaredyates]

If you become comfortable with the idea that the difference isn't measurable, perhaps the most conclusive test is to fly with one of each type of tip to see if your roll or yaw trim situation changes.

[kestrel]

Weight should not effect "position error" as it doesn't change the AOA at stall. If the new tips are improving performance, they are increasing the effective span. A higher aspect ratio wing will stall at a _lower_ AOA an so should have less "position error". I doubt that the differences in IAS error are measurable.

[Nev]

Nice, now you're seeing stall speeds more consistent with what I expected.

Nev Do you know what your overall wingspan is now?
Or I suppose, wing area would be of more interest.

The wing area is unchanged as the hoerner tips are the exact same area as the kitset ones. So the span is exactly the same and I think it gives a pretty good "apples with apples" comparison. However the upper surface of the Hoerner tips theoretically contributes to the overall lift. If my maths is correct (and it's a long shot ) I'd say a 4% increase in the theoretical upper wing area (skylight excluded).

Also worth noting is that the speeds are IAS and therefore specific just to my aircraft, and just at those specific weights and set of conditions, and I'm assuming that position error has increased at these low end speeds. But it is very useful as a "before and after" comparison. It's possible that if I now reduce the aircraft weight to say 1850lbs I might see another 1-2 kt drop in IAS at the stall (although largely unusable unless I'm by myself). But I'd expect a higher amount of position error as the speeds get lower. I'll see if there's any meaningful AOA data on the download.

[svyolo]

Nice data. I have no idea what wing tip works best for what we are doing. I have Bob's CF tips, which fit up similar to the FG ones. If I try something different down the road, it might be Wittman style. Just to try something different.

I also just got lucky and I think I scored a local hangar. I have been actively looking for a year.

[Battson]

Nice, now you're seeing stall speeds more consistent with what I expected.

Nev Do you know what your overall wingspan is now?
Or I suppose, wing area would be of more interest.

[Nev]

Here is the data showing a comparison of the Hoerner tips to the kitset tips. These wingtips are the same size as the kitset ones.

For consistency aircraft weight was 2265 lbs and 17" CG. I used a mid CG for the stalls, so I could be certain that it was the main wing stalling and not just the elevator losing authority. I used 1000ft density altitude (2200ft). This was repeated as exact as I could make it with both sets of wingtips.

There appears to be one outlier in the flaps up stall speed that I've highlighted in red. However overall, for normal cruise speed there was no change. There did appear to be a small speed advantage at higher power settings. This was difficult to observe, but was repeated several times with the same result.

The main gain appeared to be a reduction in stall speed. It's difficult to test for position error at these speeds and there is a chance that some of the observed IAS reduction could be attributable to a higher AOA at the stall. However a higher AOA would also imply a lower stall speed.

Overall, no negative traits were apparent.

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