Hello,

I am in process of building Hobby Shack Super Sport Trainer 40 (SST 40). I am trying to finish this.

Wing is pretty much built. Only things left is fiberglass center, covering and installing aileron. I have Airtronics DSM8000 2.4ghz radio (no servos or RX yet) as per earlier review in this forum. I would like to have dual servo setup for aileron for ease of trimming.

I am debating how I go about this.

Option 1) install 2 servos in the center of the wing and box the opening and run torque rods to the ailerons.
-problem with torque rod that came with the kit is too short by at least 1 inch. I will have to build it out of music wire.
-problem is that there is a possibility that its too sloppy and be warping the surfaces.
-cutting a hole in fiberglass seems introduce a weaker area? How to resolve this adequately?
-it will be a cleaner install with no exposed opening and thus no exhaust gases going into this.

Option 2) install servo further out in the middle of wing under a hatch with arm sticking out. Run linkage to aileron directly
-problem is that more weight out the outboard creates possibility of added stress to diehedral area.
-problem is exhaust gas can go inside the opening where the arm sticks out
-it will be more crisp control -no fluttering.

Option 3) install servos in center like option 1 but use bell crank in the middle of wings like option 2.

Option 4) forget all others and just drop in 1 servo and use torque rods as called for in the plans.

The aileron will be hinged with CA hinges and pinned. Another thing... when I put the wing on built fuselage - I noticed that the trailing edge of the wings are sitting on top of the fuselage by 1/4". The wing does not touch the fuselage saddle anywhere from leading edge to trailing edge. It looks like I will have to do some trimming either to the top sheet of fuselage or the wing to allow the wing to sit in saddle correctly. How important is the angle of the wing in this trainer? My plans did not call for the angle of wing at all. I will do epoxy the wing saddle to fit the wing better later.

Thanks.

Option two is probably the best way to do this. It is also the way most are done. Also if you go ahead and install the torque rods and a servo in the center, build a "Y" rod connector cut the ailerons and you can have flaps too. Unnessisary but mildy cool

It's a trainer. Go with Option 4

Dual servos will not give you better trim adjustment... or anything else for that matter.

On a trainer, you will never see any difference whether you have one servo or ten.

Keep it simple and wait till you move up to an airplane that will benefit from two servos (in fact, MOST of the planes on the market today that use two aileron servos don't need them).

There is nothing wrong with using Dual servos and there actually is one benefit when compared to strip ailerons used with a single servo and torque rods. You will get a more slop free System by nature of the short pushrods and virtually zero torsional flexing of the rod and aileron itself which often there is with a poorly assembled/built airplane using torque rods.

This torsional flexing and aileron bending (because it is being moved on the inboard bitter end can an many times is a conributor to aileron flutter. Now granted we are talking about trainers where flutter is rare but when we get to many sport aerobatic types using torque rods then this is an issue such as some older pattern types.


Its great that you want to experiment, Thats a good thing and what this hobby/sport is all about. For wing mounting servos in a trainer wing or any built up wing its not really neccessary to to use the buried servo mount system with a plate. If one cares to do just a little covering film work its very, very easy just to do a surface mount and all thats neccessary is a few sticks glued in to form a box and have someplace to stick the covering to. These have the tremendous advantage of allowing adjustments done literally in seconds rather than requiring disassembling a servo plate. The first two are full surface mounts with the servo lugs directly on the wing surface and the third yellow wing had the top of the servo lugs flush with the wing surface.

The one thing I would not do is use two servos in the center as you remove none of the torque rod/aileron flexing that way.

John

Experimentation is great ........... but ....... this is in the beginners forum and its a trainer.
I also think option 4 is the best way to go.
There will be very little benefit of having two servos, unless the extra weight and the extra current draw are considered benefits.
As far as it being easier to trim (what I think you really mean is to set the end points) you will be better off if you learn to do it mechanically instead of doing it with the TX.
Getting that accomplished is not hard to do either and there are plenty of us here to help with that if you need it.

Ok then I'll go with single servo in the middle

Should I fiberglass the center section first then cut a box for the servo or cut the box first then fiberglass last?

What adhestive should I go for center section fiberglassing ? 30 min epoxy or polyurethane or resin type?

I will head to store and get music wire to build as torque rod - what size should I get?


Thanks all for the answer.

Fiberglass center section first. use either epoxy or an aliphatic glue such as titebond. i have used both in past. titebond is more sandable than epoxy, but has a longer cure time. if you haven't chosen an engine yet, i would go with a good 45 size class engine. this gives you more options for the next plane. you can always throttle it back, but you can't add power!

For the torque rods, you could get this:

http://www3.towerhobbies.com/cgi-bin...&I=LXD946&P=SM

I have never used Titebond as glue for fiberglass. I always thought it has to be even stronger glue such as epoxy and fiberglass resin. Bu lately, people are suggesting using polyurethane (Minwax brand) because of ease of application and ability to flow through the weave.

I am using Titebond II as primary glue when building the plane. In center joint - i used 30 min epoxy for dihedral joint. For fiberglassing I guess I will have to nearly empty the Titebond II bottle to do center section (the length of chord is 6-8 inches I dont remember). The plans calls for 4 oz 3 inch wide. I think I will go for 5 inch wide (3 inch wide and overlap 1 inch in the middle so the rubber band does not cut into it and eventually will switch to bolt on version (I have Dubro heavy duty nylon wing bolts kit. But for now, I think I am better off using rubber band if (or when ) I have hard landing, there should be a give in wing to reduce severity of damage if any. I have this already: [link=http://sonictronics.com/xcart/product.php?productid=16137&cat=275&page=1]sonictronics[/link]

The engine I am using is what I already have - Magnum GP 40 ABC that was bundled with the kit. Its new in box. Eventually, I might upgrade to 60 version for 2nd plane (I would like to stay within 40-60 class as any larger I would have a storage problem with monster plane). I dont have a link it.



MinnFlyer - thanks for the link to the dubro aileron strip torque rod. The aileron strip is very long (from tip of wing to maybe 1 inch away from fuselage). Im sure it will be more senstive so there is perfectly good excuse to buy a Airtronics RSD8000 tx so I can put in some expo or other stuff to limit excessive travel. Based on this review, I believe that this radio even its 8 channel will allow me to grow.

I went to LHS and they did not stock this specific part so I ended up buying 3-32 music wire and 1/8" brass tubing. I will make torque rod out of it. At least I am trying to support my LHS anyways (its more geared toward RC cars and static models than anything else).

At Home Depot I bought a spray can of water based Minwax polycrylic in gloss to "prime" the wing first. I also bought a can of same to do fiberglassing the center section of the wing. Am I doing right thing? This would be my first "deviation" from epoxying the fiberglass in the past with both epoxy and resin based methods. [:@]

Thanks for the support/comments.

I only wish to commend you on your ability to accept these replies and your choices of how to do things as stated. Although all of my aircraft use bolt on wings and have for many years what you have said does make some sense. Also your choice of purchaseing a 2.4 computer radio is also good. I use Jr Spectrum and have used Jr for many years but cannot knock Airtronics, very good buy. Hopefully you belong to a club and have the help of an instructor for your beginning flights. Good luck.