Dave Kovensky

My Feedback: (3)

I just finished de-coring the bays between the capstrips of my Stinger 120 wing and thought that the actual weight reduction would be of interest to builders of this model. I used a "hot knife" to remove the styro foam and weighed all the foam blocks. It came to a total of 8 ounces! Since lightness seems to be an issue for this model, I think that the trouble of removing these chunks of foam is well worth the effort. Also, since there have been reports of wing failures in flight, I am installing a 3/4 inch wide carbon fiber tape on the area over the main balsa spars instead of replacing them with hard wood to keep weight down. The strip of carbon fiber will run span-wise from tip to tip upper and lower surfaces.

TerrellFlyer

Hi Dave, unless you are inverted the carbon strip on top of the spar isn't helping much,compression isn't it's strong point,add top and bottom of spar or front and back of spar, I fly a stinger built in 92,after the three inside ribs I cut the foam away from the open areas and added spar weds

Dave Kovensky

My Feedback: (3)

Hi Terrelflyer,

Thanks for your reply. You are absolutely right about carbon fiber not having any compressive strength! I DID intend to fly inverted however and in this mode, the carbon fiber strip on the top wing surface would now be in tension. By the way, I modified a 30 watt soldering iron into a "hot knife" by installing a ground-down long two inch long machine screw. This does work, but not too well. Is the X-Acto "hot knife" any better? Or, are there any other commercial products that would be good to use to remove the foam between the cap strips?

Tx_RcFlyer

My Feedback: (7)

try one of the 100 watt weller soldering guns. Use 16ga copper electrical wire for your bits. With this setup, you can make many diferent hot wire designs. Also use wheel collars and 1/8" ply as depth stops when cutting spar slots or servo wells.

TerrellFlyer

Hi Dave ,mine is a giant stinger,I used a soldering gun then used 14 ga copper electrical wire as a cutter,my gun is 140 watts so when hot had to cut fast or would melt more foam than I wanted removed,mine now is at 17.25# with g62,even though I fly other planes the Stinger is a blast to fly,then land and take off better than some trainers I've seen. Hope you get as much pleasure from yours as I have.

Dave Kovensky

My Feedback: (3)

Hi Tedster,

Many Thanks! Will try the 100 watt gun with copper wire.

Dave Kovensky

My Feedback: (3)

Hi Terrellflyer,

Many thanks for your advice. Will try a 100 watt gun with wire.

SVFlier

Two questions, guys:

1. Did you build the wing at 80", or at 72"? (I assume you are doing a kit, not "bashing" an ARF).

2. What size glow engine would you recommend (I'm not yet ready to go to gas)?

Thanks, SVF

Dave Kovensky

My Feedback: (3)

Hi SVFlier,

I am building the kit version of the Stinger 120 and am making the 80 inch wing. I want the airplane to have as low a wing loading as possible, so have elected to use as many square inches of wing area as possible. Also am trying to eliminate as much un-needed weight as I can without compromising structural integrity.

I will power my model with a Zenoah G26. As far as glow is concerned, I decided against it as the cost of fuel would be much more than gasoline and glow fuel is much more messy than gas. If I had to use a glow type engine, it would be as large a four stroke as I could afford to buy. I want a lot of thrust with a large low pitch prop so the Stinger will be able to flow relativly slowly but still be aerobatic.

Hope this will be of help.

SVFlier

Thanks for the reply, Dave. I am still exploring options, as I have a fair number of planes in the repair que, but I am looking towards a Stinger 120 or a 72" Edge for the future. Perhaps I should consider the Stinger 120 ARF, which has a built-up 80" wing? SVF[8D]

Dave Kovensky

My Feedback: (3)

Hi SVFlier,

Have no experience with the Stinger 120 ARF. If it does have a built-up wing, then it should be a good candidate. I have been building and modifying the foam wing in my kit and believe me, I would have preferred a built-up structure! Removing the foam was a real messy job even with a soldering gun to melt out the chunks between the cap strips. After they were removed, I had to sand down the foam that remained and supported the cap strips. The only redeeming thing about this type of construction is that it lets you end up with a warp-free structure. Anyway, good luck with what ever you decide on for your "big plane" project

Dave K

Dave Kovensky

My Feedback: (3)

I just finished applying Dave Brown Products Carbon Fiber Tape on the sheet balsa leading edge to add strength in this area as there have been a number of reports warning that the wing is subject to failure during high stress aerobatics. Anyway, applying the tape according to their instruction sheet did not reflect the "easiest way". They advise applying the epoxy first to the sheet balsa and then "carefully" laying the tape over it. tried this and it was a mess!
The tape began unraveling despite my efforts and I had a Hell of a job repositioning it to show a semblence of neatness. I used the following method of my own devising on the other side of the wing with much better results and thought I would share it with anyone trying to strengthen their Stinger 120 (or equivalent) wings:

1. Carefully lay the carbon fiber tape on the sheet balsa and use masking tape on both ends
secure the tape in place. Don't try to rearrange the tape to make it look good. It will only
get messed up and unravel. Strength is the only important issue to be concerned about.
2. Get drywall adhesive fiberglass tape from Home Depot or any hardware supply outlet.
(This is the same stuff that was recommended in another write-up to strengthen the Stinger
120 plastic cowling, turtledeck, hatches etc.)
3. Apply the fiberglass tape over the carbon fiber tape and adjacent sheet balsa leading edge.
4. Now mix up some 30 minute epoxy and thin slightly with lacquer/epoxy thinner to facilitate
application with a brush. Apply the epoxy with a throw a way brush and keep working the
liquid into the fiberglass/carbon tape layers. Use enough epoxy to saturate the glass/epoxy
and adjacent sheet balsa wood leading edge.
5. Allow to cure for 24 hours. Then LIGHTLY sand to dress up the surface. Remember, you will
be covering the wing with a plastic heat shrink film or fabric and though the undersurface
may not be beautiful due to the fiberglass tape, the wing will be strong and that is what is
important!

Hope this will be of help to anyone wanting to stregthen their Stinger 120 wing>

fwman1

My Feedback: (22)

Most failures I've heard of from Bubba Spivey had to do with the LE of the ailerons being smaller than the TE of the wing. This induces flutter. When you have already removed max foam and overpower the plane, it doesn't take long to explode a wing if you don't mind your throttle.

On mine, I thought that was an awfully long and wide aileron to drive with one servo, so I glassed mine and repositioned the aileron servo a bit further out. This, and extra hinges were all the mods I made. The glassing ensured that the LE of the aileron was at least as thick as the TE of the wing. I have seen guys make up aluminum control horns with a counterbalance forward of the LE of the aileron to balance the aileron. Looked pretty simple to do in this scale. Good luck.

Dave Kovensky

My Feedback: (3)

Hi Fwman1,

Thanks for your comments regarding aileron flutter. For the past ten years or so, I have used sewn "X" type gapless full length fabric hinges. Also, I have always matched the width of the wing trailing edge and the aileron leading edge as it is a common sense thing to do. Another measure that is good to avoid flutter is to make the outboard 3 to 4 inches of the aileron a fixed portion of the wing trailing edge. In as much as I have not read of any serious flutter problems associated with the Stinger 120 design, I went ahead and made the ailerons full length as called for on the plans. (Hope that I won't regret that decision!) Since I am powering the Stinger 120 with a Zenoah G26, I don't think that this model will be overpowered. Anyway, I do really appreciate your suggestions as every idea can only help make the model that much better! Thanks to you and the other modelers that provided me with their suggestions, I am confident that my Stinger will be a great flying plane.