Impact Airfoil

I just finished the Mr. Hyde. You might have seen it, I posted some pictures. This design started out life as an Impact, even though the only thing left that is Impact is the wing and flaps.

My last airplane was an UHP Impact kit (Shear Panic).

I have several versions of the Impact plan, including the FM, Steve's UHP plan and the Pat Johnston CAD plan. Now I ordered foam cores from Randy for the Mr. Hyde, they were cut by Aerosmith cores. Randy said they were original cores, same ones that Paul used to win the WC.

Anyway, the cores are different than all of the others. The UHP and PJ versions are the Patternmaster shape exactly. The foam cores have the same high point, but thin sooner toward the front and have a much more elliptical leading edge.

Just wondering if there were any thoughts.

HAY Lizard, Wasn’t there an article a few years back In Stunt news that had the Travail Pursuit, Pattern Master and the Impact ROOT and WING TIP out lines, and a lengthy article about the shapes of them and the difference’s? All of mine stunt News is in storage so I can’t look it up. If any one has this article it’s a good one.

Scott (need to build an Impact) Riese

snip...snip

Randy said they were original
>cores, same ones that Paul used to win the WC.

snip...snip...

Sorry, but the facts are not correct. I did use a Randy Smith foam wing on the very first Impact (used at the '90 WC's, 3rd place). That is the only one I had a foam wing on. All others were built up. The plane that won the W.C's was an "I" beam, carbon fiber spar arrangement. If there are differences, I don't know why. I have my templements and they are all "very" close. Copier problems???

Paul,

Is the Impact wing template the same as the Patternmaster?

Godzilla,

If I have just enough information to screw things up even more, apologies are extended.

Both of my Impacts have been built from the plans published in Flying Models.

As it happens, Pat Johnston gave me a set of his Impact plans and a whole sheet of plotted rib shapes.

PJ's airfoil DOES NOT match that shown on PW's plans.

>Is the Impact wing template the same as the Patternmaster?

Don't know...I don't have a PM airfoil!

LAST EDITED ON May-15-03 AT 07:47 PM (CDT)
 
>
>>Is the Impact wing template the same as the Patternmaster?
>
>
>Don't know...I don't have a PM airfoil!

Don't feel bad. Just consider yourself fortunate that you randomly stumbled on the "right" design....

I was suprised to learn that *I* had also copied the Patternmaster aerodynamics for the Infinity. Must have been through telekinesis or remote viewing, since I haven't ever seen plans for a Patternmaster. I also heard I copied the Trivial Pursuit, which is interesting since the cores for the Infinity were cut and sheeted before Ted had put pencil to paper.

One time, I mentioned that I drew around my shoe to get an airfoil. I subsequently got a whole bunch of questions as to *which brand of shoe* and *what size*.

Brett "'Walk-over' brand leather wingtip, size 9, B width" Buck

Godzilla,

I remember some time back when you were discussing various airfoils and had come to the conclusion the Impact uses the Pattern Master airfoil. I didn't think so at the time, but was not sure of my facts.

If PJ is in fact using the PM airfoil, and PW has never had an example to copy, and PJ's material as submitted to me does not match up to PW's plans, we are simply going to have to find out why I used so many "P_" abbreviations in this sentence.

> One time, I mentioned that I drew around my shoe to get an airfoil.

> Brett "'Walk-over' brand leather wingtip

Is that why they're called wingtips?

>> One time, I mentioned that I drew around my shoe to get an airfoil.
>
>> Brett "'Walk-over' brand leather wingtip
>
>Is that why they're called wingtips?

Why ARE they called "wingtips"?

LAST EDITED ON May-16-03 AT 08:11 AM (CDT)
 
>snip...snip
>
> Randy said they were original
>>cores, same ones that Paul used to win the WC.
>
>snip...snip...
>
>
>Sorry, but the facts are not correct. I did use a Randy
>Smith foam wing on the very first Impact (used at the '90
>WC's, 3rd place). That is the only one I had a foam wing
>on. All others were built up.

How did you like it?

I actually like the "look" of the foam core the best. The root is .25" shorter, making the whole package higher AR.

The wing does not appear so chunky either.

We will see how it works.

I like it also, looks wise. It also isnt quite as big as the others. We set it next to my Beo Bolt wing plane adn you could see a difference in size. I hope it works good. I dont see why it wouldnt. We havent been able to fly here for a while so it is in waiting. But the chord is short and it looks like it will turn on a dime. Cant wait to see it fly.

I have the Ultra Hobbies kit, a set of FM plans, and a set from "Heart Beat Models" plans. All are slightly different. Kinda like the three Noblers, 4 Stilettos, and three Cobras. No two are ever the same. Maybe that's why we love these things, they're just like wimmen. They are all the same but just look different. Do ya think??

'zilla

This is where if you actually had been a PAMPA member you could have saved a question on the net. Tom Morris, published in Stunt News an article detailing the similarities and differences in the Pattermanster, Trivial Pursuit, Impact, SV and the Cavalier airfoils. I believe that was sometime in 1999 or 2000. Anyway, there are subtle differences in the root airfoil shapes of the TP, PM and Impact. Where I see the major difference is in the Tip airfoils. The TP being somewhat less percentage wise than the PM or the Impact. Get someone (Doug) to find that article and you can see the differences/similarities.

Jim Pollock

From somewhere inside Kazakstan, actually the Baikonur Cosmodrome.

The article that I know about is Issue 1, 1998 and the comparison was Patternmaster, Trivial Pursuit and SV 11. If any more has been published in Stunt News, I've missed it.

GOOD JOB GEOFF.

Scott(this will answer your questions) Riese:7

this is where Igor Burger should chip in and compare all these airfoils to the optimized airfoil he uses, using Xfoil or whatever he used to analyze the airflow. Knowing radius's thickness percentages, etc. doesn't mean beans if you can't evaluate how the air flows over the wing. Having PW fly the plane doesn't work either. He can make anything look good.

Wrong again, ferocious breath.

I have it on good authority that when PW snapped the outboard wing off his 2003 Miss America he couldn't fly it worth a lick. Level flight only, what a wuss...

Recently saw the (now repaired) model in action. A whole slew of you guys are in big trouble, even if you don't know it yet.

DAN...Should we bring helmets???or trees

>DAN...Should we bring helmets???or trees

Scott....I can pretend YOU are a tree!!!

I stand corrected, but I'm disappointed. I would have thought half a wing would be plenty for Paul to do a decent pattern.

LAST EDITED ON May-17-03 AT 07:05 PM (CDT)
 
>I stand corrected, but I'm disappointed. I would have
>thought half a wing would be plenty for Paul to do a decent
>pattern.

The problem is he couldn't start the pattern correctly. He could only do half a wing over. (Half a wing over. Get it?)

Sorry, Paul, they shouldn't get me started. I am glad your plane is OK and flying good (according to reports). It will be interesting to see it at the Nats.

snip
>
>The problem is he couldn't start the pattern correctly. He
>could only do half a wing over. (Half a wing over. Get
>it?)
>
>snip

Well...The fact is it would do a full wing under!! (It's my turn for the bad puns!)

But Paul

Is there a correct Impact airfoil out there and if so, which of the several is it?

geoffgg,

Paul's busy. Something about making sure his wings won't fall off eight days from now.

I would think PW's plans, as published in Flying Models, to be the best source.

All this discussion concerning accuracy of airfoils and such reminds me that when Bruce Hunt (Heavy Stunt) built his foam-winged Impact last winter he was at one time quite concerned the purchased wing was too small. It most definitely did not match his FM-supplied plans.

Later, much later, having built all the rest of the model "per plans," he thought it a good idea to slap a 6-inch rule up against the scale on the plans. His wing was the correct size. But he had built a slightly larger model around said wing.

Flies great, please do not poke him with sharp sticks. Although a nice supply of 6- and 12-inch rules, one for each set of plans he owns, might well be a nice touch.

LAST EDITED ON May-17-03 AT 10:27 PM (CDT)
 
I was at a friend's house today, and he cut's his own foam. I had his aluminum plates in my hands for several wings. You would be amazed how close the PatternMaster and others are, even the Trivial Pursuit, except the TP tapers more to the tips.

But the really scary eye opener was the SHARK45 AIRFOIL!!! A little smaller at the main rib, but not a lot and very similar in shape! Man, that plane was ahead of it's time.

Tips ribs vary more than the root ribs on these that I compared, but I was amazed at the similarities I did see in several airfoils.

LAST EDITED ON May-18-03 AT 09:42 AM (CDT)
 
I've also noticed, and mentioned to several folks how similar many airfoils are. I've also noticed, that for the most part, Patternmaster type airfoils seem to be most popular where there is more wind and turbulence. When drawing these airfoils, I've found it convenient to use the NA63a airfoil, and modify it by adjusting the location of the high point. It can come so close to most of these that the differences are pretty minimal.

Although there are probably minor differences, I've found that many of Windy's designs, Randy Smiths, Bears, Pw's Impact, and surprizingly, Jean Pialets Skylark, Pegasus, and Zephyr all share very similar airfoils. Quite differnt from the NACA 4 digit airfoils used on many other designs.

Though not necessarily exactly the same, they are close enough that they should all perform about the same way, at the sizes we build.

4 digit airfoils, those often seen on our models, tend to be blunter at the leading edge, even though the extreme thickness at the high point may be identical, between the two styles of airfoil. It's my belief, purely from my own speculation, and not backed up by anything other than my own observations, that when the airfoils get progressivly thicker, over 20%, the blunt leading edge doesn't penetrate as well, and may contribute to an earlier stall, especially with the power off. GMA's Nobler uses a thinner 4 digit airfoil, about 14-16% range, and doesn't suffer from this effect, at least as far as I've observed.

I am not sure this is totally accurate, but I have been told, and tend to believe it to be true, that the most important feature of the airfoil, at our sizes, is the entry, or leading edge to the high point. What happens after the high point, within reason, really doesn't affect our models very much, considering symetrical airfoils.

I'm not surprized to hear that many of these models show the most variance at the tip.

I've never checked the Shark 45, but I'm not surprized that it may indeed share a similar airfoil with the patternmaster.

Not to denigrate the Patternmaster, a well proven set of numbers for sure, but Pailet and others were using a very similar airfoil somewhat earlier. Oh, the evolution of the Cl stunter, a long and interesting journey for sure. I wonder if the makers of those tennis shoes weren't really the ones we should thank. (Tongue firmly planted in cheek)

I'm wondering why everything is spinning around?

Not tennis shoes, but Red Wing engineers boots. Thicker life time soles and better curves.

LAST EDITED ON May-18-03 AT 07:12 AM (CDT)
 
Hi Dan

Thanks for a great laugh.

I understand exactly where you are coming from but the anal retentive analytical that lurks inside this somewhat gregarious engineer likes to nail down the detail before allowing for reasonable manufacturing tolerance.

I will compare the FM plan with the Pat Johnston drawing as they are what I have.