Bryan Wood

Bryan Wood

Well Known Member
I ran into Earl Hibler Saturday at the local airport. For those of you unfamiliar Earl races a Glassair fixed gear taildragger at Reno. While talking about his plane we got into speed mods and some of the ways he was able to squeeze extra knots out of his airplane. It is powered by a 300hp IO-540 and has a propeller worked up for him by Sullivan Propeller at Hayward Airport, CA.. His prop was modified by twisting it to a "D" and then flying it and sawing off the ends and then repeating the same. By doing this he gained 18 knots. The goal that both Earl and Brian Sullivan had agreed on was to stop cutting on the prop when or if they could reach an "Indicated" airspeed of 270mph. They achieved that goal plus a little and stopped. I have no idea what altitude that was at and didn't think to ask.

What caught my eye though was tape that he had on his airplane. Every gap was taped with some kind of teflon type tape. This included the flaps and ailerons both top and bottom, the same on the elevator and rudder. The wing tips were taped to smooth the transition to the wings. He said the cowl is taped the same during races. The tape being used as gap seals intrigued me so we looked at my RV to see where it could be used to improve it. The ailerons and flaps are not able because of the hinge and the way the aileron leading edge drops below the wing when the aileron goes up. So we looked at the tail and he told me that using the tape on there would "Wake it up dramatically."

So the purpose of this post is to let folks know tricks that are being used to make planes go faster by the serious speedsters. I've seen Lancairs taped at Reno also and it blends in nicely. He mentioned the supplier which makes this product for sailplanes but this has also slipped my mind. :eek:

So where is this going? I'm wondering if anybody has tried taping on an RV and what the results are. And secondly, Mr. Bob Axom if you are reading this send me a private e-mail because I got Earl's card for you and he is receptive and anticipating a call and talking turkey with you about how to go fast.

Best,
 
Ailerons a no no....for tape

Great post Bryan, but I'd like to add a safety factor into this on the RVs as the Glassairs/Lancairs are totally different birds than ours. I'm not trying to knock anything as I believe that tape and sealing things up is very important to going a little faster.

I've heard that taping the gap seal on the lower portion of the ailerons is a NO NO on RV's, I have not done this or used any type of tape/sailplane strips on my RV, so I can't give an honest opinion, but maybe I'll try a little tape here and there someday. I only mentioned the ailerons because after visiting with a few other RV'ers that tried it were shocked with mixed bad results and were trying to get back on the ground and land quickly as their aileron controls were cut in half, or something like that. I'm talking about the underside of the aileron where air is needed to make the aileron work. Just a warning from what others have told me as I don't have first hand experience at this, just from other sources so be carefull. I'm thinking safety for first timers thinking of taping up the gap on their ailerons on an RV. Hopefully someone else can chime in on this.
 
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Some Comments

I will send a private message about the prop. My instincts tell me the prop is a place where performance could be gained with my airplane. I also know that this is an item of high risk. I have a Hartzell non-blended airfoil constant speed prop and the spinner bulkhead markings show that there is no more pitch available without altering the twist of the blades themselves.

I have seen RV taping in the races this year by John Huft, Tom Moore and Mike Thompson. Mike and I are competitive with each other and I did not see that change as a result of his spending time carefully taping in preparation for the Rocket 100 in Taylor, Texas last month. John and Tom are enough ahead of us that a knot or even two would not be noticeable from our perspective. With the baffling I have added in the lower cowl of my airplane the cowl joints are already isolated from the cooling flow air. I have give thought to removable multi-piece screw mounted covers for the tail surface hinge access cutouts. John has his aileron hinge & bracket hardware faired in and the holes around them covered. These are things I think you go after when there is nothing else left to cleanup in the belief that any possible improvement is worth the effort. That point is getting nearer for me as well but I'm still looking for silver bullets.

(John Huft - Since I retired I always wake up in the middle of the night like this but it is better when I'm away from home and computer.)

Bob Axsom
 
Nothing Learned so far

Bryan I do not have your e-mail address and the profile on this website denies e-mails for you. I sent the private message and I am extremely interested in getting the card and talking to Earl. I will do this if I can do it in a professionally controlled maner that does not require me to go through the twist then repeatedly cut and try to the point of deminishing returns then buy new blades and twist and cut to the experimentally determined optimum. I can't afford that. When Earl was developing his race prop it would be very interesting to see the modifications and speeds that could be placed in an excel spread sheet with the chart function used to plot a line through all the test speeds and get a sense of the correlation between cause and effect.

When I called the company some time ago the lady I talked to said that any qualified prop shop could do the work and didn't seem to think it was a big deal. I STRONGLY disagree with that point of view and I would not think of going into a prop shop and propose that they do this pitch increase and diameter reduction. I do not want to provide someone's education at my risk. I'm sure prop shop techs know the theory but I need first hand experience, desire and ability to do the job right on my prop. It seems to me that a Hartzell non-blended airfoil prop optimized for speed could be developed for any RV model that is better than a generic hartzell blended airfoil propeller and a market wouild be created for that product. This is a win-win for the producer and the customer supplying the original prop. Given the right situation a reasonable deal could be worked out I'm sure.

Bob Axsom
 
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Props and tape

On props...

Other than an inflight fire, a prop failure is the worst thing that can happen to a flyer. The loss of even part of a prop blade can cause an imbalance bad enough to tear the engine off the front of the airplane. The resulting weight and balance problem can easily kill you. This is why Reno racers are required to have safety cables holding the engine to the airframe.

After my prop failure and subsequent emergency landing, singing pigs will be flying over a frozen you-know-where (how's that DR?) before I let anyone put my prop blades in a vise and twist them.

As a data point, you might ask ole Earl how many RPM he is turning during the race...I would guess 3500.

On gap seals, I have added some words and pictures to my web page at
http://lazy8.net/speedmods.htm
because it is easier to post pictures there. Page down.

Have fun!!
 
I love your web page John - thanks for sharing the fruits of your work with everyone! Makes some great lunchtime reading for us aero engineering types....;)

Paul
 
The Word

I talked to Cris Ferguson about Sulivan Propeller a few months ago and he said that they have a tech there that knows his stuff about these prop changes and has successfully made the changes for racers at reno. Cris won the biplane gold race this year although he was using a paul Lipps designed prop made by Catto. I am still cautious but willing to look into it further.

Bob Axsom
 
John,

Yeah, many thanks for your site and posting that info. I just recently changed to the James cowl and Larry Vetterman's 4 pipes. Gonna take a side look at the cowl like you suggested...and all your other mods.

I'm sure not racing; but why not slick up the ole girl???:p

Really do appreciate you sharing your work, good luck in your racing.

Deal Fair
RV-4 flying
George West, TX
 
Spitting erosion strips

Nuisance said:
On props...

Other than an inflight fire, a prop failure is the worst thing that can happen to a flyer. Have fun!!
Click to expand...
That is not the only brand or prop to lose a bonded on erosion strip or some kind. I have heard or seen the after affect of spitting strips off on both constant speed props and fixed. No engines where lost fortunately but damage to the plane has happened.

Bob you are right Props do represent more speed. They operate in the low 80% range show you are throwing away almost 20% of you HP! Dave Anders who has the Cafe Foundation Tri record beating a Harmon Rocket II by a large margin. He did special things to his Hartzell prop, like new twist distribution. May be too much for the average person. Also he turns at 2,900 rpm and overhauls his prop ever few 100 hours.

For us the best thing to do for your prop is make sure it is smoooooooth. No little bugs, nicks or bumps on the leading edge or faces (especially aft face) or pealing paint or finish anywhere. Than wax that baby like there's no tomorrow. There is mph or two there. (Geee I am giving away secrets). The leading edge must be mirror smooth.

Bob when are you going to get the James Aircraft Cowl?


PS: Gap seals make a small diff but hard to measure. As John said they are a little pain and can cause some paint rubbing. Van's aircraft did a good job with the basic design. There are gains there. When I raced I taped all kinds of things with "speed" tape including the flaps which I did not use for landing. Cowl gaps, fuel caps, seems on fuselage all where taped over.
 
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Eval

John I read your document again and I agree on some points.

First hand observations:
- Your basic tandum taildragger airplane design is faster than mine.
- Your engine and prop give unquestionable speed advantages.
- your lower cowl is slick as glass and has a minimal surface area, cross section and volume and the extension back under the fuselage over the exhaust makes the 3kt gain believable.
- There are conflicts on the cooling air inlet outlet effects in your package.
- The ECI Cold Air Intake and Sump section does not apply directly to my existing system but I think there is something in the idea that is useful. This goes along with a redesigned cowl that I am thinking about. Chris Zavatson provided information sometime ago on his intake that has the airfilter in a box in the cowl cavity below the front of the engine in front of the sump. I would like to retain the carburetor fed O-360-A1A but eliminate the the center protrusion under the cowl for the filter airbox and cooling air outlet. This arrangement forces exit air to exit through the nose gear structure on an "A" model. Anyway, the induction air system could be improved I believe.
The 3kt gain you saw is inspiring.
- Your Exhaust pipe findings are exactly the same as mine except my soot level is apparently less than yours.
- I simply do not believe that gap seal tape adds a thing and you do not provide any test results to change my mind on that. About the vinyl tape adhesion - I used it to make up numbers for several races and it just comes off. A guy with a F1 Rocket at Memphis used it for his numbers and it partially came off during the race. I do not know the reason but I now use Contact paper shelf liner to create my race numbers. It is very thin and does not come off during a race unless I get sloppy on the installation. apparently the boundary layer is thinner than supposed. I have thought of putting Contact Paper over the cabin vent NACA scoops but did not do it this year. Need to test. I do not believe there is attached air flow on the upper surface of the wing back at the hinge line and I would not expect a great deal of speed impact from taping the wing to flap and wing to aileron interface on the upper surface. I would expect an effect on the lower surface but the aileron is dangerous to tape according to the recognized experts and the flap interface is a pretty smooth piano hinge.
- closing the access holes to the attach bolts for the elevator and rudder and ailerons holes and gaining 2 kts is amazing! I trust you completely so this is something I will have to do. That is amazing. If someone else had said it I would have run up the BS flag.
- the engineer's perspective is just a lot of self indulgent technical narative with nothing concrete. The assertion that you have to do everything and do it to perfection is simply a back door for escape if some one tries to use his words and is not successful.

Your package is stimulating but it does not get down into the technical details that make the difference between success and failure. I know you are much deeper than that and the quality of your work is outstanding. It is financially impossible for us to interact in a way that would allow me to reach your level of excellence but the interchanges we do have and the competition at the races is pulling me up slowly but surely. In the last race your speed over mine was down to 21.23 mph from a 28.27 mph difference in the AirVenture Cup race (it's my wingtips).

James cowl - It looks good but I am considering making my own

I'm still waiting to hear from the Prop folks.

Bob Axsom
 
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Nuisance said:
On props...



As a data point, you might ask ole Earl how many RPM he is turning during the race...I would guess 3500.
Have fun!!
Click to expand...

I did ask Earl and he runs at 2850 during the races.

Bob, I see your private message now and will call you Saturday.

Best,
 
The metal prop.... Smooth or rough?????

Someone mentioned about keeping the prop polished as smooth as glass. Look at the fast Reno racers and look at their props as the winning planes did not have polished metal props, but were stripped of paint on the front side and painted black on the back side. I talked with a few of the pilots asking why there props were so dull looking and they told me that there props work better if left with a 45 degree crosshatch pattern on the front side by block sanding them with 280/320 grit sand paper and leaving them semi rough. OK I thought about this for a minute and the light bulb came on as to why they did it.
I understand the concept after studying up on this, but I'm going to leave my prop polished for appearance reasons. John Sharp won the Sport Reno race with a scuffed up prop and his friend Kevin Eldredge with the same type of plane came in second with close to apples and oranges airplanes. I'm sure there are suttle differences between the two airplanes, but Sharp blistered the field and it sounded like his engine was turning some VERY HIGH RPM's!!!! Kevin told me he wanted looks and not the extra speed, go think. Showplane or Raceplane?????? :rolleyes: For those of you wondering about a light textured surface over a polished surface on a prop, go study up as there is some benefit. It's very similar to dimpling the first 1/2"-3/4" of the leading edge on the prop.
 
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