It is my understanding (subject to rebuttal from those in the know) that the RV3 and 4 spar design are the same with the 4 being stretched "just a bit" due to "market requests" to shove a second person in there if they are not too big. Then "market pressure" to have everyone in the front seat, or "my wife does not want to sit in back" or I want a two place plane that is actually more capable of two people than the RV4 which is sort of a one and a half person plane brought about the side by side RV6 but except for the width of the fuselage (and some changes to the stick/control arrangement) the design remained virtually the same.No, I did not understand the RV-6 wing attach. I have seen several RV-8 and then a few sailplane style install. That the RV-6 is quite different from the RV-8 is a bit of a surprise. I have only seen a couple pictures of RV-6 wings and the spars looked long enough to cross the whole airplane...The butted spars with some steel straps bolted through the caps always bothered me - the caps loses section area and straps have to carry all of the moment across the gap. That makes it essentially a one piece wing with the bolts near the wing roots carrying all of the lift but not bending, and the straps carrying all of the bending.
In this case, total lift reacted at the root fittings has to be adequate for carrying total lift, which should be OK. With a one piece wing or a two piece wing with overlapping spars (sailplane style) the bending moment at the root is the bending moment between the lift bolts, and the strap system must carry the bending moment at the root. More span is more moment is maybe the stock straps and bolts are OK, and maybe they need beefup for longer wings. Either way, you have to do the check ...
OK here are a few photos in no particular order. If someone is curious about a particular element I can likely dig up some pics in response.Please post photos when you can.
Ahh the eternal question. My wife and I differed on the answer and after the first plane she left. Now the answer is settled, I have a kitchen in my shop. Good observation Jedi.One question. Is your shop in the kitchen or do you have a kitchen in the shop. Either way its a nice setup you have.
I vacuum bagged them down around a piece of PVC pipe. I had to experiment with a couple different sizes of pipe to "suck them down around" until I got a radius that worked out pretty well. This process does not make them fit precisely around the nose of the ribs (the same I believe is true of a Vans kit, at least for the RV4) but puts a roll in them that allows them to contour nicely to the ribs when pulled around them. Trying to wrap an "untreated" piece of aluminum around the "nose" is NOT something I was able to make work. Since the wing is tapered and the radius changes it turned out that I was able to find a size of pipe (I don't recall what that was right now but it is in my notes) that worked for the main tank. For the aux tank I had to use two sizes of pipe and "step" them as the same size from root to tip did not allow for a nice wrap around the leading edge at both ends. I was able to do this with a simple standard shop vac. The entire tank skin is enveloped in a plastic (painters drop cloth) envelope that uses a bit of duct tape, and then the vacuum is attached to the end of the pipe to suck all the air out through a hole drilled in the PVC pipe which it is all being sucked down around. If this is not clear I can likely find some pics of the process.How did you roll the leading edges?
All those comments on Van's history are well and good, but do seem thread drift. The rest of the comments support the notion that a tapered wing of more span could be a serious add to the Van's airplanes. I would like to have seen flying reports on davefried's plane, and look forward to them on Fenix's plane.It is my understanding (subject to rebuttal from those in the know)
Anyway, Billski, in regard to "....maybe the stock straps and bolts are OK, and maybe they need beefup for longer wings. Either way, you have to do the check"
I think I have done that check in the engineering report for my wing. Not asking you to do any work for me for free, but if you'd like to see the report for your own benefit, curiosity, interest, or whatever I'd make it available to you for all the effort you've put into helping others here at HBA, but I can't do so for a couple months until I am re-united with the report.
This is how I plan to do the big fuel tanks (75 inch skins) on the Rocket, but I have never done it before. I'd sure like to shortcut the learning process and see pictures. Do you clamp the pipe to the aluminum to keep it in position on the LE, or something else?I vacuum bagged them down around a piece of PVC pipe...
... If this is not clear I can likely find some pics of the process.
Billski,All those comments on Van's history are well and good, but do seem thread drift. The rest of the comments support the notion that a tapered wing of more span could be a serious add to the Van's airplanes. I would like to have seen flying reports on davefried's plane, and look forward to them on Fenix's plane.
There are quite few kinks to learn about this process and you will learn them all on your first attempt. After that it is quite easy. I'd be happy to discuss all of this with you in advance and you could probably save yourself ruining the first piece of tank skin (like I did). Not sure how the PM message works here but if you sent me your email that way and I found it I'd be happy to send you a degree of detail that most here don't want to read.This is how I plan to do the big fuel tanks (75 inch skins) on the Rocket, but I have never done it before. I'd sure like to shortcut the learning process and see pictures. Do you clamp the pipe to the aluminum to keep it in position on the LE, or something else?
I've also done the math on this (link to the spreadsheet I used in this post from a former taperwing RV thread). I have a -8 not a -4, so aimed on having the same bending moment at the attachment to the center section. Using Shrenk's approximation to calculate that moment. What I find is that with taper you can get more span. But not very much. By my math I can increase the span from 24ft to just over 25ft with a taper ratio of 54% or so.The concern that I had raised had to do with the OP concluding that the basic structure was OK because his MAC was in the same place as the stock bird. I have pointed out that the real max bending moment does increase significantly when span is increased even while tapering the wing. Now maybe the existing structure had enough excess in it that this does not seriously compromise strength, but communicating that a proper check should be performed was my point.