When tossing my plane the Vtails flutter/vibrate quite badly (whole tail, not just the ruddervators), Pretty sure that this is my throwing style, and that I just need to practice, but I'm concerned that something will break before I figure out how to prevent it.

It is built as a V tail, covered with ultra cote lite transparent. I used Scotch vinyl repair tape (~ 1.25" wide) on the "outside" surface of the tails, becasue I couldn't figure out what scotch 600 was. I didn't put any on the inside of the surfaces due to the weight. Covered the fuse with ultracote opaque hoping that it would inpart some strength, as I am pretty new to this hobby. I'm also thinking that the little extra weight will help penetration, and allow me to fly more frequently.

Your FAQ describes using a Javelin style toss. I seem to get less flutter if I point the nose of the plane upwards, with my arm behind me and then leave my arm stiff, with no elbow bend when throwing. The throw is in an arc. I am comcerned that this will put some downward pressure on the wings as I attempt to Follow thru, as with my arm straight it seems to be best to release it at the top of, or just very slighty past the arc. I'm not seeing any flutter in the main wing at all.

From : Don Stackhouse

I'd be careful about throwing in an arc like that, the downward pressure you're worried about has broken MANY, MANY wings! Notice how the upper spar cap has a doubler at the root, but the lower one doesn't? This means that it only takes about ONE FOURTH as much downward load (compared to the critical upward load) to break the wings!

The reason you're getting less flutter from the upward launch is because it's a less efficient throw. You're getting less speed, so you get less flutter. You also get less launch height. BAD tradeoff! We need to fix the flutter problem (more on that in a moment).

The best throw is the one that gets you the highest speed, but with the least stress (especially upwards, downwards and sideways) on your model. Properly done, the javelin style throw with a good follow-through seems to do the best at that for most people.

Is there something obvious that I am doing wrong to cause the V tail flutter?

Keep reading, the key to this one is in your question #2.

When putting downward pressure on the ruddervators with my fingers, they seem to deflect pretty easily, due to movement of the control rods in the fuse. Maybe 1/4". Should this be a concern, or could it be related to the above mentioned flutter?

Yes, most likely the CAUSE of the flutter.

The flex and/or slop in the linkages allow the ruddervators to flutter, which puts air loads into the tail assembly, which causes the tail to twist back and forth on the end of the tail boom.

We occasionally get questions about tail flutter, and in almost all cases it can be traced to slop or flexibility in the control linkages and/or hinges (of course, technically the hinges are part of the control linkages, both from an engineering standpoint and from the point of view of the air molecules).

I have the conrol rods running straight down the sides of the fuse. ie. the right hand servo connects to the right hand ruddervator. Would having them cross in the fuse provide a little bit of resistence to movement/flex?

Probably not. You need to make sure they're as straight as possible. Make sure you've avoided kinks in the ends as much as possible. The other thing I like to do with mine is use F3 as a support. I let the glue-stiffened thread wrappings on the end of the pushrod act as a drill when I put the pushrod through F3, so they make a hole just slightly larger than the 1/8" dowel pushrod midsection. The dowel can slide easily through the hole, but can't flex very far before the side of the hole in F3 stops it.

You can also put in a second support about halfway down the tail boom. Messy to do now, since your model is already assembled and covered, but it can help in extreme cases. Carefully cut a hatch out of the bottom sheeting with a razor blade (cut at a angle to the surface so the joint will be stronger when you glue the piece back on, and try to avoid cutting into the spruce longerons!), then use some balsa sticks to box in the pushrods so that they can't move around too much. Leave just enough clearance that they don't bind on the supports when they move. Once you're done, glue the balsa hatch back in place, then patch over the edges with some lightweight glass cloth or nylon (pieces of nylon stockings will do) and epoxy or white glue (cyano-acrylate will work, but tends to be more brittle). Iron a patch of covering over the repair and go fly!

The other areas to look at closely are the pushrod ends. Make sure the holes in the control horn and servo output arm are a good fit with the pushrod end and the clevis. If the servo output arm hole is oversize you'll need to drill a new hole or replace the arm. The control horn can be repaired, just plug the hole with cyano-acrylate glue, then use a piece of pushrod wire (with a chisel-shaped end from being cut off with diagonal cutters) as a drill to make a new hole. By the way, the hole in the horn can sometimes wear larger after a lot of flight hours, in which case you can use this method to repair it again.

I started out with right at an Inch of travel ( 1 up and 1 down above neutral), and have reduced it with the epa adjustment in the Flash 4., in hopes that less control surface travel would smooth out my flying some.

If possible, try to use the full travel of the servo. Reduce the travel of the control surface by making the horn longer. First make sure you have the pushrod on the opposite side of the control surface from the hinge, that's worth 3/32" of effective control horn moment arm. If worse comes to worse, you can make your own horns from 1/32" or 1/16" plywood. Glue two pieces of ply together with rubber cement, cut them out and drill the pushrod holes with them stuck to each other, so they come out identical. After they're done, peel them apart and rub off the rubber cement.

Keeping the control horns as long as possible will increase the effective stiffness of the control linkage, which will improve your flutter problem.

The other thing to check, as I hinted at above, is the stiffness of your hinges. By this I don't mean their resistance to changes in control surface angle (that would just feed a bunch of loads back at the servo), but rather their ability to keep the control surface from moving bodily up and down or forward and backward at the hinge line (not the control surface trailing edge). This kind of hinge flexibility will also reduce your effective control linkage stiffness. Taping the hinge on both top and bottom (so that the two pieces of tape meet each other at the hinge gap on the upper surface) will help this considerably.

By the way, 3M 600 is nothing more than vinyl-type Scotch Tape. Look in the tape section at any good office supply store, such as Office Depot or Staples.

You can also use iron-on covering for hinges, instead of the Scotch tape. It's a little stronger, stiffer and more durable, but more trouble if you need to remove or replace the hinges for maintenance.

3rd Question... I read the FAQ about tuning V tails and nose down/up in turns. Mine is nosing down quite a bit. I checked washout and it was just barely the 3/32" recommended. I heated it again according to the instructions, but havn't gotten to fly it again to see how much that helped.

3/32" washout on the inboard panels should be fine. I don't think the washout is your problem.

First of all, regarding differential in V-tails: It's really very simple. There is a mutual end-plate effect between the two panels of the V-tail, but for a rudder input those effects are often not equal between the two sides. Although different designs see differing amounts of this, in general the up-going ruddervator sees more end-plate effect than the down-going ruddervator. If the deflections of the two ruddervators are the same (i.e.: zero differential), the up-going ruddervator will therefore generate more lift than the down-going one, which will tend to pull the nose up. By adding just enough differential to cancel out the unequal end-plate effects, we make the lift of the two rudders once again the same, so there is no change in pitch when you make a rudder input.

Get your model flying directly away from you in level flight, preferably at close to eye level if possible. Now give it a big rudder input and watch for any change in pitch as it begins to yaw. If you see a significant un-wanted pitch change, then you need to adjust your V-tail differential.

In addition, some folks feel more comfortable with a model that tends to drop its nose a little when entering a turn. They add just a little extra differential to get this effect. It's entirely a matter of personal preference. I, for example, prefer my models to be exactly neutral in pitch during a rudder input. You should set you model up in whatever way is most comfortable for you.

However, if it's a sustained nose drop during the turn (rather than a momentary drop as you roll in or roll out of a turn), this isn't a differential problem. There are several other phenomena that could be involved in your turning problem:

1. A circling airplane is using some of the wing's lift to counteract the centrifugal force from the turn. This leaves less to hold the airplane up. The airplane naturally starts to descend, which increases airspeed and/or angle of attack enough to provide the necessary extra lift. A too far forward C/G will tend to increase the amount of nose-down pitch change that results from this. A touch of up elevator to increase the angle of attack (assuming you aren't too close to the stall angle of attack to begin with) can provide the extra lift, without the nose-drop. Just be careful, there are limits on how much angle of attack you can impose on the wing before it gets mad at you and goes out on strike. In a turn, your stall speed goes up.

2. In a steep bank, the yaw resulting from a rudder input into the turn will be directed partly toward the ground. This is a quirk of airplanes that don't have ailerons. A little more up elevator and a touch less rudder can help in this case.

What is the MAX amount of washout that I should put in this wing, before I start looking elsewhere for "problems".

As I mentioned above, I don't think washout is your problem. I fly mine at 1/16" to 3/32" washout on the inboard panels, and it does fine. 1/8" is more than enough. Just make sure it's uniform over the inboard panels, the outer panels are both flat, and above all, that both wings have the same amount of washout.

I don't think that I have much, if any, differential adjustment available to me with the FLASH 4 radio. I'm using the Elevon mixing, and the EPA's just don't seem to let me adjust in any differential. Actually my Ch 1 adjustment won't let me adjust different end points for each direction. It uses the same setting for both directions, so maybe there is a problem with my radio, or possibly it is related to the mixing.?

Some radios just don't have a programming adjustment for this, in which case you get to do it the old fashioned way. For more downward differential, just re-mount the servo arms on your servos so that at neutral they lean towards the tail a notch or two on their splines, then re-adjust the clevises on the pushrods to get the control surfaces back to the correct neutral position. This will give you more "down" travel than "up".

To reduce the "down" movement and increase "up", move the servo arms so they lean away from the tail a notch or two at neutral. Check to make sure that the clevises don't bind against the side of the servo output shaft when in the full "down" position. If this is a problem, you can accomplish the same change in differential by making control horns that have the pushrod hole moved forward of the hinge line, instead of even with it.

I'm really happy with the durability of this plane, (it looks great in the air too!!) I was concerned while building it that it would be too delicate for someone with my limited experience. Right now I am a little concered about is the covering on the underside of the Poly joint. It's looking kinda bad already due to my not-so-graceful landings, think that I'll try a pair of those plastic wingtip landing skids there.

That will work fine. An extra layer or two of covering, or a piece of Goldberg's "Scuff Guard" tape will also work well for this, and be lighter and easier to install than the skids.

The only other comment I have is that this was my first built up plane, and many of the terms in the instructions were new to me. Some kind of glossary or maybe "ballons" pointing to the parts on the drawing would be nice. ie. this is the longeron, this is the doubler, etc.

Good comment, and we've also heard this from others. We've done exactly that on the 2-meter Chrysalis, the parts on the plans sheets are all labelled with their names and materials. In the cases of strip wood, like spar caps and trailing edges, we've also added a little full-sized cross section silhouette of the material, so you can be sure you picked up the right size piece of wood. I'm hoping to do the same thing to the HLG Chrysalis one of these days, but I still have a few other things ahead of that on my schedule. So much to do, so little time, I need to be twins! Thanks for the feedback, I hope this helps. Good luck with your Chrysalis!

Don Stackhouse
DJ Aerotech