Those Steps! Speed Mod?

Bob Axsom · #1 03-29-2008, 08:40 PM

On 8-17-1997 my wife and I riveted the steps in place on both sides of our RV-6A. I just looked at the photo that shows 21 big round head rivets permanently anchoring each one in place. Since I first flew the plane in March of 2004 I have made MANY modifications to increase the speed and some have actually worked. We are not spry young kids anymore and the steps work wonderfully to help us board the aircraft but when I stand back and look at what's left to clean up and buy a little speed it is hard to ignore thos steps. S-o-o-o-o, tonight I thought why not change the installation from riveted permanebt to screw mounted removable? I would have to drill out the pop rivets in the baggage floor, and replace them with a screw and platenut installation. Then drill out all of the step flange mount rivets and replace them with a screw and platenut installation. For a race preparation then, the steps could be removed and a cover plate installed. I know how to do this and I may or may not do it over next winter but I think you folks that are yet to complete the step installation may want to think about this.

Bob Axsom

hevansrv7a · #2 03-29-2008, 08:44 PM

Bob, my wife couldn't use those steps anyhow because she needs to be even closer to the wing. I use the folding wooden stool from Sporty's and it works very well. Take them off! Just my 2 cents.

While on the subject of speed, did you ever verify a speed gain from opening up the rear bulkhead inside the wheel pants?

n5lp · #3 03-29-2008, 08:55 PM

I don't know how easy it would be to retrofit, but some people go the retractable route. http://www.vansairforce.com/communit...tractable+step

Bob Axsom · #4 03-29-2008, 08:56 PM

I have no bulkheads in my fairings. I added them, they slowed the plane down. I took them out and the speed was restored.

Bob Axsom

Ron Lee · #5 03-30-2008, 06:54 AM

My questionable guess is that changing to flush rivet heads will not make any difference. I would also ask if you have made the changes that "may" make huge improvements like the plenum and cowl with round inlets (can't remember the name).

Bob Axsom · #6 03-30-2008, 09:20 AM

The cooling drag possibilities have been worked severely and I did gain 4 kts there but the popular techno talk magic bullets do not produce the kind of automatic improvements you may expect. The super fast airplanes have super power and efficient propellers in addition to cooling drag improvements. I have not gone to the smaller volume hard topped plenum yet and do not plan on it at this time in spite of the popular support for this mod. I have tried several inlet configurations, outlet configurations and internal flow baffles and surface smoothing plates. Many lower cowl baffle configurations slow the plane down, the suface smooting plates did nothing, the inlet changes varied CHT with no change in speed. What worked for me in this area was to build a complex curved baffle from the rear of the engine to the bottom of the plane; add two angled side plates to direct the lower cowl air to the width of the outlet on the curved baffle and finally add two horizontal baffles one each side of the engine just below the lip of the cowl to restrict the cooling air flow to the lower cowl forward of the previously described lower cowl baffling (these last horizontal baffles made it all work together - previously the other baffling had reduced the speed 2 kts and these little beauties brought back the 2 lost and added 4 more). The cowl is essentially isolated to three zones - inlet plenum, lower cowl cooling air flow path and a non-cooling airflow zone outboard of the plenum and aft of the engine forward of the firewall. I have tried many other speed mods that do not involve the engine cooling air as well but the most effective by far is the 3" wing tips you saw at Memphis which added 3 kts over my traveling configuration that includes 9" (each) span adding tip tanks and 12" span adding stock tips. I have made many other mods but the gains were small with the possible exception of the nosewheel subfairing accurate results have been elusive due to windy conditions but it appears to add around 1 kt.

Are we going to see you at Texoma (Sherman, Texas) on the 19th of April?

Bob Axsom

Norman CYYJ · #7 03-30-2008, 09:26 AM

Bob have you thought of removing the steps and then installing bushings in the holes. Modify the step to insert into the bushings and then use a pin to stop the step from rotating. This way you could remove them for racing, then when needed just reinsert them and drop the pin in.

N941WR · #8 03-30-2008, 09:38 AM

Bob,

One local builder installed his step plates on the inside of his plane. The step still sticks out but not that ugly plate. In addition, he didn't install the right side step or stiffener plate on the wing. All in an effort to reduce his weight.

That said, I do like the idea of of removable steps.

Bob Axsom · #9 03-30-2008, 10:59 AM

Quote:

Originally Posted by Norman CYYJ

Bob have you thought of removing the steps and then installing bushings in the holes. Modify the step to insert into the bushings and then use a pin to stop the step from rotating. This way you could remove them for racing, then when needed just reinsert them and drop the pin in.

That is a clever idea. It reflects the kind of innovative thinking you see in aircraft assembly especially aftermarket developments in the field. You have given me another approach to consider.

Bob Axsom

Christopher Murphy · #10 03-30-2008, 11:19 AM

Bob,

I am very satisfied with my stock RV-4 cowling I think there is little to be gained with an aftermarket cowl. That being said, I think the area aft of the plenum down to the cowl exit area has improvement potential. If you have photos of what you have done in that area would you be willing to post them? If not, you might see me peeking under your cowl at Texoma.

Chris Murphy RACE34