An odd question...

[ajreynolds]

I've got a bit of an odd question that just popped into my head. How does surface stickyness affect drag and other factors?

Say you've got two identical airframes and the surfaces are identically smooth. If one is sticky honey and the other slick like oil, would that affect the performance in any way?

I know, "where did he come up with a question like that???" Too much Monty Python I guess... :D

Andy

[ciurpita]

somewhere i recall seeing an article about why some pilots (sleger, agnew ?) liked a particular airfoil (e387?) despite the wind tunnel data at uiuc. i think the reason was the wings with the airfoil were sheeted with veneer which had a rougher surface than monokote (or fiberglass) that the uiuc wing test were. in this case, it changed the performance of this airfoil (for the better, on those planes).

[ajreynolds]

I can see how different surface textures would change performance, turbulation, etc. But given two surfaces that have the same smooth texture, but one is sticky and one is slippery, would it make any difference?

Andy

[vintage1]

1/. Two surfaces one of which is sticky and one of which is not, are not identical

2/. The one covered with honey will attract dirt, flies and wasps, which will become micro turbulators.

This making it even less identical.

[ajreynolds]

1/. Two surfaces one of which is sticky and one of which is not, are not identical

2/. The one covered with honey will attract dirt, flies and wasps, which will become micro turbulators.

This making it even less identical.
True enough. I'm being hypothetical here... The whole point is, does being sticky or slippery in itself affect the performace in any way?

andy

[BMatthews]

Air doesn't stick like your fingers do. If they maintain the same surface smoothness without the coatings migrating or collecting bugs then they will fly the same. But let the first bug land and not be able to take off and all bets are off.....

[Jurgen Heilig]

Well, you can do a little experiment here. Take a fully moulded GRP/CRP glider model. Now spray the leading edge of one wing half with some hairspray and watch the models reactions thoughout the speed range.

:) Jürgen

[vintage1]

Well, you can do a little experiment here. Take a fully moulded GRP/CRP glider model. Now spray the leading edge of one wing half with some hairspray and watch the models reactions thoughout the speed range.

:) Jürgen

Better still, watch the reactions of the club members downwind.....

[MarkusN]

Well, you can do a little experiment here. Take a fully moulded GRP/CRP glider model. Now spray the leading edge of one wing half with some hairspray and watch the models reactions thoughout the speed range.
Not being serious, are we? Hair spray is well known method to create a rough surface / turbulation. It was one of the popular remedies for birds that wouldn't fly when covered with monokote, when the same design had worked well with paper covering.

[ghoti]

It is all in the boundry layer, if that. Bill

[John O'Sullivan]

Come to think of it we have a lot of birds around here from eagles and ospreys, gulls, crows, jays and finches etc. Never seen one covered in monokote. Im sure if I tried it I would have some protests, both from the birds and enviro-terrorists.

Seriously though, for models, most properly designed and built models will fly better without honey, treacle, peanut butter or asphalt for turbulator.
Turbulators may show subtle improvements in a wind tunnel at specific Reynolds Numbers , but real life gusty wind conditions have no respect for uniform Reynolds Number conservation.

John