I have experienced crashes due to inflight skin separation of the stab and fin. Since the skin provides most of the tensile strength of the structure, when the skin delaminates from the foam the structure fails. With fin and rudder separation there is no directional control. With stab failure and separation there is no pitch control. The cause is accumulative stress due to normal inflight loads. If the skin stayed stuck to the foam then delamination would be minimized. The carbon fiber (CF) strips do little for bending or torsional loads.

Alternative tail parts could be stronger if constructed from balsa, ply, and fiberglass. However an easier way is the objective. I've seen pilots add struts to the stab and fin. This keeps the structure from flexing but adds extra drag and looks out of place.

The goal is to make a stab and fin that is no more than 150% the existing weight.

Existing weights are: stab and elevator=44 grams
Fin and rudder=30 grams

A similar thickness of Depron foam was cut out using the stock stab and elevator. A CF tube is planned for a spar at the hinge line. This combo weighs 24 grams leaving 20 grams for covering and hinges. I've been using a similar Depron fin and rudder with 20 X clear tape. This mod is stronger and lighter than the stock parts. Adding a second elevator servo
will increase weight but save a crash if and when one elevator fails. In the pics you can see that the elevators are not connected. Each elevator will have its own servo, pushrod, and control horn.

Today, 04:39 AM
#15 Report
VicT
Registered User
USA, FL, Safety Harbor
Joined Sep 2000
406 Posts
Blaze : programming the old DX7S tx for Lemon......
I got to set up Mike's new Blaze using his DX7S TX and Lemon (LAYMOAN) receiver. Like the instructions indicate setting up the V tail for rudder can be tricky as left stick gave right rudder. Of course we tried the easy way of TX reversing rudder....or ruddervators and that did not work. So we tried reversing plugs in the receiver and that DID work! Probably why many pilots deny v tails! I like them because they are less drag and weight, don't damage on landing and are unique looking.

I chose flaperon for the DX7S wing type and opened up the flap menu. Guessed at values for spoilers at 0, +20, + 40 % and had to reverse the sign from + to - to get spoilerons to reflex up. Guessed at elevator compensations for the 3 positions with 0 having 0 compensation.

Hand launch at 3/4 power IAW manual then full power for vertical climb for 10 seconds....power off, trim for level hands off flying. It took 35 up trim clicks for hands off elevator and this must of been because of the 3S 3000 pack ( its the only battery Mike had). This is with the pack all the way aft so I know now why folks are using lesser weight packs like the 1800 and 1500 to get CG aft. Oh well I flew her down to about 50% capacity remaining and was very impressed at the low power consumption for the 20 or so 10 sec climbs and power off dives. Will try a new...Continue Reading

Recently I maidened and trimmed out a new member's Beaver. I had not flown one for a few years and was reminded how nice she looks and performs. More scale looking than the Apprentice and Timber designs and stock performance almost as good as he Timber. With a larger prop and ESC she could probably hover but I was able to slide off grass with the floats pretty easy and this was enjoyable. I decided to resume mods on my own Beaver that I started some time ago.
I wanted to install an Apprentice receiver so cut out a top hatch and left door for access to the elevator and rudder servo area. I glued a plywood floor between the servos to support Dual Lock fasteners for the receiver. I learned after testing Beginner mode that the servos needed reversing. I could have used servo reversers but chose to reorient the elevator and rudder servo output arms instead. While the arms were removed I moved the pushrod locks to the outermost hole for more mechanical throw. See first photo.

The flaps are very scale looking but the max flap angle is not enough so I opened up the bell crank area and re positioned the bell crank for more throw. The long bell crank arms travel further to achieve a greater flap angle now. On one wing panel I drilled another pivot hole and this helped increase flap travel. I had to cut foam and Dremmel some plastic to reduce binding of push rods.