<snip...You can bring the fairings down to 1 inch or less from the ground and contour the lower surface aft of the tire upward and then back to reduce the scoop effect. As far as the fairing assembly screws are concerned I agree with Alan - just drill out the outer surface holes to 3/8" and use flat head screws and dimple washers to replace the round head screws.
Some things I learned as I worked on my subfairings may be of interest to you in you post racing season work in this area.
- If you bring the edges of the fairing opening around the tire down low the interface is changed in an interesting way. The tire changes shape when weight is placed on them. The change in shape increases the gap between the tire and fairing opening if the opening is below the swell point of the tire. I jacked my plane up and down and measured the gap all around to verify this. I thought I reported the numbers in this forum when I was developing my current subfairings. The effect is similar to the old fixed gear with clam shell wheel covers idea without the mechanical baggage.
- The rotating tire in the fairing that extends down to around 3/4" or 1" above the ground only has a serious interference problem at the rear of the opening and that can be eliminated if the shape of the fairing in this area places the surface tangent to the tire diameter instead of "edge on" into it.
- If the front of the fairing lower surface is brought down to the tire 3/4" or 1" above the ground it is an inclined plane relative to the ground and even in the event of a bad landing it will deflect the airplane away from the point of hard impact rather than digging in. It will scrape the paint if you do it on pavement but no one will see it until you remove the fairing. Been there, done that.
Bob Axsom
Bob - this is a really interesting observation. What kind of tire are you using? I would guess that this might make a difference in how it deflects when loaded.
Looking more closely at the photos I'd agree that Bob's fairings are mounted a bit high (although the trim around the tire looks pretty tight).
My tires are McCreary Air Tracks I believe. The amount of deformation will vary with tire design I'm sure but the distribution of the distort away from the point of contact with the ground will have the same characteristics.
When I said to bring down the edge of the fairing closser to the ground that may have given the wrong impression. I ment build up a mold with clay on the bottom of the fairing to the tire and lay up fiberglass on it which will change the shape and volume of the fairing. Bob Mills observed that he has the fairings rotated back too far and I agree with that but his vertical area seems to be pretty full of tire. That could be wrong and if so, when he changes the mounting that should be addressed as well before the new fiberglass effort.
Bob Axsom
Thanks guys...I'm feeling pretty special...post a couple pics and get some awesome professional consultation!! And I almost understand it!
I highlighted a couple areas, and let me see if I do get the gist.
I, of course, get the tinnerman/countersink recommendation (makes good sense, and I have lotsa those!!) Add 471 tape, and off we go! I'll either do that, or fill the holes, beef them up and go with countersink screws only. The former will be quicker, but my glass maestro is a craftsman, and may not "allow" me to opt for the quicker solution, if you know what I mean!
On height (the blue words), I think I understand that to mean to lower the bottom of the fairing to below the fattest bulge of the tire as it sits on the ground. In my pics, I'm about an inch above that, where the tire nears the wheel outer circumference, and thus gets narrow. Under Bob's guidance, that edge would drop to below the bulge, and closer to where the tread contacts the ground. I might be able to accomplish a little of that by raising the hole the axle nut goes through (lowering the entire fairing if the wheel has room on top...I think I have a little to work with), and the rest would have to be with a build up of glass. Since my fairing sides are somewhat flat in that area, it may take some careful glass work to add some curve to that area (to get it around the tire bulge).
Any lowering would have to be combined with rotating the fairing forward, to keep the trailing edge off the ground. Bob, I'm trying to visualize what you meant by the red words (I liked picture books as a kid!
). Can you clarify the recommendations that include "contour up and back to reduce scoop effect" and the "tangent versus edge on"? HAving trouble picturing what you mean. And what do you mean by scoop effect...the lower lip acting as an air scoop and thus causing drag?
Finally, the forward section discussion (in magenta). I think you mean that as long as there is some upward tilt of the forward part of the pant, even if its low, the pant will deflect up, and that incline will make for a glancing blow, and some scrapes...is that right? Then again, why would I worry about a bad landing!
(Oh yeah, I'm a Navy guy...flare to land, squat to...
)
OK, so you guys are gonna have to start charging me for this, and the OP is gonna kill me for thread drift! Perhaps we can talk about this in Taylor, and maybe even ask Mark if he can bring a pair of Rocket PR pants, and then compare SJ, -8 PR, and Rocket PR pants in person (by looks). I'd love to run a side-by-side test of all three and add real value to this thread...but my bride says I'd need a little sponsorship to do that...especially when I start negotiating for a BA prop!
(Side note, I'd like to run a side-by-side-by-side test of my D-twist vs. the BA vs. Paul's Ellipse prop...but the CFO says I need to get a
lot of sponsorship to do that...and the crankshaft work to swap from CS to FP and back intimidates my banker too!...but I digress...again!)
Ah, those Sunday musings! Thanks again for the discussion!
Cheers,
Bob
