Question on wing tips. I am finishing up a wing kit started in 2001/// The kit has the older droop wing tips in the kit. I could not find a reason for changing to the current wing tip on the 7 wings.
Does anyone know why? Was it a performance issue? A cosmetic "eye of the beholder" issue? I called Van's asking but got no answer of why (they are slammed busy).
I'm asking myself is it better to get new tips before I work though mounting the original tips?
First this is an old thread, 16 yo. I can help but not sure what "droop wing tips" are? I think you mean the "Batwing tips".
So lets go back in history. Van made 3 wing tips in their history up to the RV8. They all physically fit on a RV3/4/6/7/8 wing. The wing cross section is the same. The RV9/10/12 have different airfoils so their wing tips are different.
Just for discussion the first type was the 415 wing tip for RV3/RV4/RV6/RV8*, pre RV7. This is a "Horner Style" wing tip (a standard term and used on all kinds of aircraft). The cross secton of the 415, inboard to outboard is flat on top and curved on bottom.
The other wing tip was the 715 and 715-1. The 715 came out with the early run of RV7 kits. Later it was changed to then 715-1. It is unlikely you have the 415 unless the original builder requested it or traded wingtip. The 415 was not the standard for the RV7 kit as far as I know. The RV8* I believe started with a 415 and later went to the 715/715-1.
Van produced the 715 and later a modified version 715-1 which became standard. The 715 was discontinued. It is likely you have the 715 which came out with the early RV7 Kits.
Both 715 wing tips are identical for the most part. The 715 cross section is symmetrical from top to bottom surfaces unlike the 415. It came with a pocket/recess for Nav/Strobe in the front outboard corner, with a Plexi cover. The most distinct and obvious difference of the 715 to the 715-1 is the 715 trailing edge (TE) is flared out. The slight radiused curve resembles the TE web of a bat wing, thus the name. It is not especially a large flair but you notice it if you are looking for it, because it is not straight inline with trailing edge of wing. Beauty in eyes of beholder.
The 715-1 is identical but they made the Nav/Strobe pocket larger so fitting a landing light in there was easier.
The other big change is they got rid of the flare on the trailing edge and just went straight across in line with the trailing edge.
Which one is better? Performance wise no one knows. It is unlikely there is any significant difference one could measure accurately that makes real world difference. I am not saying there is no difference in performance, but you would be hard pressed to measure it. Also if you gain something with a wing tip it is likely you also lost some performance at the other end.
Is 415 better than the 715 series? Some say yeah some say nay. Is the 715 better than the 715-1? I don't think we know but people make claims. The 715-1 looks better? Really beauty in eyes of beholder. I know some loved the 415 look and put those on their RV7 just for looks. I think they look old fashion but the aerodynamic principles are solid. Some report better performance with the 715-1 Bat wingtip. When talking better the numbers are so small it is always hard to determine "micro knots". I am guessing Van got some complaints about look and felt the performance gain was so small a straight trailing edge was better.
The other "issue" is the Nav/Strobe. The 415 I recall came with no place for a Nav/Strobe, no recess. So it was standard to mounted them externally on the edge of the wing tip. This really is proper to get required coverage and with rear facing white NAV lights on the wingtip you don't need a NAV light on the rudder. However there was a kit for the 415 where you could cut the wingtip recess in and lay up new recess with lens, to fit a light and Nav/Strobe.
The 715 came with the pocket but is was smaller than the 715-1, which made fitting both the NAV/Strobe and a Landing/Taxi/Recognition light in there a bit of a challenge. I have the original 715 on my RV7 and have Nav/Strobe and Landing Light. With the advent of smaller powerful LED lights it was not an issue. However the 715-1 is a larger pocket/recess. That is no reason to change. The down side of the 715 are the lens covers I recall were out of production and hard to find. The 415 asymmetric shape lends it self to a bigger recess (with the add on kit). The symmetric 715-1 even though it's bigger recess than the 715, it still does not have as much space for a landing light as a modified 415. The shape of the wing tip has less cross section area for a recess.
Back to Performance. Does that Bat flare help? Some say yes. There are many people who have modified the Bat wingtips further and report some improvement.
ai
Are there other wing tips out there? Yes other folks make wing tips. One post in the last month from VAF Forum member made smalllose out. That has Pros and Cons as well. A wing tip is not going to make radical changes in performance, no night and day difference. However lowering wing area will increase stall sf
Over all a well build RV that is in rig, good fit finish, tight engine cowl and baffling, kept light weight will perform very well with any of these wing tips. If I were you I'd use what you got (still not sure what a droop is but assuming Batwing). You can always drill out the fasteners and put a new wing tips on.
If you don't like the Bat flare you can trim it and glass over it.
PS I assume your wing tips are Gelcoat? I know Van gel coated most of his fiberglass stuff, including wing tips. Not sure if he ever stopped as he did with his cowl layups. Gel coat adds weight and can telegraph surface cracks (not structural) into the paint after many years. If I were you I would sand most of it off. You don't have to sand off every square inch just most or at least reduce the thickness. Sometimes Van's gelcoat was thick which is more likely to crack with heat and vibration, which was a factor with cowls. He did stop gel coating the cowls. However my 715 wing tip came with gelcoat.