A while back I saw a post where the bottom couple of inches of the wheelpants were removed and a rubber mold was made and installed to the wheelpants to prevent any serious damage if the wheelpants came in contact with the ground. Of course now that I want to try this I cant find the post. Has anyone seen this or done this and can give me any feedback how its working? Thanks
Van's Air Force
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Help finding previous post wheelpant rubber
- Thread starter Doug94
- Start date
Works great.
This is about 200 hours of wear. These pants are mounted lower than average. Right behind the tire the rubberized fabric only clears the ground by about 3/4", so it drags on hangar door rails, steps in the asphalt, etc. The fiberglass has been removed under the rubber almost to the tail of the pant.
This is about 200 hours of wear. These pants are mounted lower than average. Right behind the tire the rubberized fabric only clears the ground by about 3/4", so it drags on hangar door rails, steps in the asphalt, etc. The fiberglass has been removed under the rubber almost to the tail of the pant.
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Dan, why so low? More speed? I am working on my wheel pants and I was thinking of cutting them higher to avoid problems with bumps or snow.
Yeah, drag reduction. I have no quantitative way to tell you if it's worth it.
Three details....
A-model clearance is less critical. Tailwheel models put the ventral section of the pant close to the ground while A-models maintain a more or less level waterline.
Here's the pant being fitted on the bench, level waterline. If I recall correctly there is a 3/4" spacer block on top of the tire for this fitting. Plenty of clearance under the pant, right?
However, load the tire with gross airplane weight, set the tailwheel on the ground, and this is the real clearance:
Neal Willford wrote an excellent series of design spreadsheets in Sport Aviation. One dealt with landing gear design. It included a calculation of tire compression for a given weight, landing G load, and air pressure. Most owners would be really surprised to learn how much the tire can be compressed during a firm arrival. The numbers suggest the average RV is grossly under-inflated; I run 50 psi. In addition to maintaining wheelpant clearance I believe it also greatly reduces stress on the tube.
The rubber is cut so it almost touches the tire sidewall, another attempt at drag reduction. Might not be such a good idea with an A-model, as it limits airflow for brake cooling. For sure I'd want viton caliper o-rings and MIL-H-83282 fluid.
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Toobuilder
Well Known Member
A buddy installed rubber rub strips all around the tire opening to completely seal it off and says it was worth 2 knots. This is on a Rocket with already tight wheel pants.
direction post
Dan,
Did you post the instructions at one point on the procedures to do this? I'm just curious if the glass is completely cut off and what type of rubber mix is used that will form up firmly before I cut the pants down. I actually read the posting about a year ago but just can't find it now of course. Thanks
Dan,
Did you post the instructions at one point on the procedures to do this? I'm just curious if the glass is completely cut off and what type of rubber mix is used that will form up firmly before I cut the pants down. I actually read the posting about a year ago but just can't find it now of course. Thanks
Walt
Well Known Member
I have found/fixed quite a few RV wheel pants, 95% of that damage I suspect was caused by firm landings with under-inflated tires. I would say the majority of RV tires I check have around 25 psi in them. I always pump them up to 45 psi which gives a little "stiffer" ride but is much better for the tires and will protect your wheel pants.
Plenty of clearance under the pant, right?
Just a little funny side note. See that work bench that Dan is working with the wheel pant on. It is the perfect height, for a giant! When I bellied up to it, I was definitely the toddler at the big boys table
. This isn't you're standard EAA shortie.
rvmills
Well Known Member
Dan, Looks nice...and much like the bottom of my wheel pants get after a while. Of course, mine are still fiberglass
, so I'm also interested in the process, if you can provide a pointer to where the info on this is...thx. I actually did a re-work of the angle of my pants a few years ago, as they were really low-riders. Now they sit about where yours are.Michael, Coach showed me those rubber strips on his Rocket pants at Reno a couple years ago. Actually I heard them rubbing on his tires as we pushed it out to the line, and asked about them. They are 1/16" baffle material, RTV'd to the inside of the wheel pant and extend out of the cavity just enough to touch the tire. He told me the same thing...2-3 knots. My gaps may not support having the baffle material there (too tight on the inside), so this rubberized material is interesting.
Neat thread, thanks for bringing it up Doug!
Cheers,
Bob
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It was here:
http://www.vansairforce.com/community/showpost.php?p=554319&postcount=11
..but like most of my experiments I'd do it slightly different next time. Here the rubber-impregnated fiberglass cloth was draped over the wheelpant belly for cure. Next time I make a set of galoshes I'll mold them over the top of the pant....which will round out the tire area rather than having the flat spot.
I'll also take more glass off the belly. If you wanted to push the idea I suspect the whole lower quarter of a wheelpant could be rubber....maybe two plies of 9oz and shore 80 urethane?
When first installed the galoshes were a single ply of 9oz plain weave. At 100 hours there were holes worn in a few places. Look at the photo in post #2 and you can see where I added a two ply patch behind the tire and a strip along one edge.
Fabrication technique is same as here:
http://www.vansairforce.com/community/showthread.php?t=43391
Smooth-On sells a two-part urethane adhesive which worked well to glue the rubber to the wheelpant.
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Toobuilder
Well Known Member
Dan,
Do you shoot for zero clearance with the rubber/tire, or do you leave a gap?
Do you shoot for zero clearance with the rubber/tire, or do you leave a gap?
Just hacked out a hole. It's not zero.
I like it. Nothing to compare it with however.
Thanks. They are also at 2-1/2 years and 200+ hours now. Still doing fine, although I note they don't like water immersion. Same would be true of the galoshes, but hey, it's not a seaplane.
rvmills
Well Known Member
Dan,
I like your idea of the galoshes fairing to the tire at a tangent. Contemplating this on a pair of James pants. They're less rounded that your PR pants, so top overlay may not work in my case. Maybe a clay mold to fill the gap between tire and pant...might be space constrained and fighting gravity during the layup if trying to do it on the plane...hmmm. Any thoughts from the Horton Skunkworks?
Re-read the previous threads as well. Thinking about using this as a skid plate and sub-fairing in one...suffer through a couple Q's?
Did you add the pigment, or did the product come in black? If the former, think it would take red...or d'ya think that would yield pink or orange?
Would the urethane-impregnated cloth bond to the pants, if appropriately roughed up, or is the adhesive required? Thinking about feathering it to the pants to avoid a ridge, by making each subsequent layer 1/4" longer, maybe using real lightweight cloth as the top layer for the feather-edge. Not sure if that thin layer would glue well though (thus this bonding question).
Would peel ply help to smooth the finish at all (or would it just stick to the rubber)?
Last one...why remove more glass from the pant? Just more clearance for all-terrain work (and hangar tracks). A fairing with a lot of give?
Thanks very much!!
Cheers,
Bob
