ColdChuck

Hello,

I am in the middle of building Hobby Shack SST 40 trainer plane. It is not very good kit if you ask me. Anyways, the fuselage is little twisted at the rear toward to the left (as viewed from the front) (it can be said its twisted counter clockwise if you're looking from the front toward the rear). It has not been sheeted top and bottom yet. The twist is quite apparent when installing the stab on the fuselage. the left side of stab is about 1/4 inches lower than right hand side despite the fact that the mounting surface are equal.

Any recommendations? Can I make it straight by forcing it while gluing down the top and bottom sheets to the fuselage side? The fuselage is rather flexible - meaning I can untwist it by hand but it wont naturally stay that way.

For more info, the sides are two piece long sheet of balsa glued together lengthwise (top glued to bottom part entire length). I might post photo if need to.

Thanks!

Chuck

Mode One

It is important that the twist be removed! Yes, un-twist and determine a way to hold the fuselage in this position, while you plank the top, then the bottom. Fuselage building jigs are very handy and in some cases necessary to build a straight and true fuse. When building a fuse. I make referance marks on the inside of each bulkhead and on the fuse planking, which are used as alignment references during building.

If all else fails and the fuse. ends up with a twist, all is not lost. Just make sure the horizontal stab. is aligned with the wing and the vertical stab. (fin) is perpendicular to the horizontal stab. There is way more information you need on alignment, which I would hope is in your building manual and plans. However, if you get stuck people here can help you, or email, or PM me nd I will try to help.

Mark DeSchane, AMA 59157

ColdChuck

So, should I tape down the stabilizer parallel to the table and then tape/weight down the nose and the middle of the fuselage prior to sheeting the rear part of the top? Or should I start with front top sheet first and work my way back to the rear? The twist is limited to about rear 1/3 to 1/4 of the length. The front 2/3 to 3/4 is appear to be OK. How about using a steam iron application?

No, I dont have building jig and yes the formers are marked in the center (as close to 1/16!QUOT! of difference). I suspect the problem is the balsa was slightly warped when I was assembling the sides together.

By the way the sheeting as called out in the plans are 3/32 balsa sheet to be laid 90 degrees perpental from the fuselage sides (grain not running same direction as fuselage). Is there a problem with that that might compound twist even more?

Thanks!

Chuck

ECM

Well, if it's like most trainers with a square fuselage, it's a lot easier to straighten than a wardbird or something with a bit more complicated fuselage.

If you lay it on the table and press down, will it remove the twist in the tail? If so, simply weight it down with some sandbags (1 gallon ziploc full of dirt work for this) or some books... and glue the seeting in place. Usually, the sheeting adds enough rigidity to remove all or most of a warp in a situation like this. Just be sure it's straight before you go gluing the sheeting on - it's going to be much harder to straighten after it's sheeted.

SST

My Feedback: (2)

You're going to love that plane when it's done...I have the 1/2a, .09. .25 & .40 sizes, and am currently building an 8-footer. MikeSell is building one with an 80" span. My .40 size has a K&B .61, and gives unlimited vertical. I have also removed the tip blocks and installed tip plates, and converted to taildragger gear. These planes are basically sticks with style, but they fly better...

Mode One

If the fuse. at the tail is a basic box shape, then yes, most of the times the sheeting will run across the fuse. and it stiffens the fuse. As someone mentioned, sand bags are a good way the weight all down, when attempting to straighten. The stab should be parallel to the table top; but, more important in the same plane as the wing. Does the plane have instructions? These should lead you through this process.

ColdChuck

Thanks guys. I will do it tonight and report back as soon as I can.

I am using Elmer's ProBond wood glue throughout the constructions along with epoxy where needed and quick CA to tack parts before using wood glue or epoxy.

ECM: Yes, it is square shaped fuselage.
SST: thanks for warm comments. I dont think the Hobby Shack kit is top notch well thought out. I had to do several modifications to build it properly. For instance, the plan calls for using hard wood strip to connect two elevators together. Well, I had to cut a notch in the fuselage to allow that wooden strip to pivot properly without binding. Nothing in the plans shows that. Its just one of many "headache" of problem solving sessions.
Mode 1: No, the kit didnt come with instruction manual. It was given to me by my brother who looked into it and had a case of heebies jeebies. He claimed that it never got one although there is "generic" assembly instructions printed on the plans.


Regards,

Chuck

SST

My Feedback: (2)

Is this your first plane?

ColdChuck

SST,

No, it is not. It would be my 3rd. 1st one was a Gentle Lady glider (still have it and only flown once- too hard to find thermal) and 2nd one was one of those mustang warbird that I never finished [sm=stupid.gif].

Chuck

SST

My Feedback: (2)

I didn't mean your first build, but do you have a trainer plane under ( flying ) your belt yet? This is not a primary trainer, though a decent instructor should be able to teach you to fly on it. It's not self-correcting like most trainers, and it's semi-symetrical airfoil makes it quite aerobatic. It responds fast and is pretty steady in windy conditions, and with a hotter engine than the suggested .40 ( which will fly it quite well, there's no real need for more motor, but it's fun with it! ) It's a pretty hot number.

Mode One

I looked through my Hobby People catalog and can't identify a SST .40. Seeing how your calling it a Hobby Shack model, it must be pre Hobby People. I have no knowledge of this plane at all. However, it still needs to be built as straight is it can be.

SST

My Feedback: (2)

They were sold in the 70's in 1/2a, .25 & .40 sizes. Global brought out the .09-.15 size ARF 4-5 years ago, but since they were priced at $90, they didn't last very long. Here are my white/purple 1/2a, my red .09, and my white/transparent red .40. I just got a NOS .25 that I haven't built yet, and my 8-footer is still under construction.

ColdChuck

Okay here is the update...

The twist is pretty much hard to tell now after sheeting top and bottom (measured the stablizer to the table - 1 to 2 mm difference at the most).

SST, yes, you're right this would be my first trainer and yes, I need to seek services of a instructor (ANYONE LOCAL??) for this preflight inspection and eventual training. Yes, the airfoil is semi-symetric rather than true flat bottom. I suppose that is why it is called "super sport" trainer. It is would be ideally suited as 2nd trainer perhaps. I was told that it is little harder to fly but not impossible (with instructor of course).

Mode 1, I believe this kit was made/sold through Hobby Shack years ago and no longer made. I understand that Hobby People now replaces Hobby Shack. I could post photo of carton to show you if you like.

My plane is most similar to your "kendall" plane (white with red transparent) without the wingtip and mine is tricycle landing gear out of 5/32 mains and 5/32 nose. I think I might as well forgo that 5/32 main gear for aluminum version on account that it is easy to bend after not-too-soft landing. I assume that you perhaps converted yours to a tail dragger and added the wingtip to the wings. Otherwise, it looks identical to mine under progress.

Engine is .40 Magnium ABC. Break in procedure is little different than what I am used to. Any comments? I havent done ABC engine before.
Radio is HiTec AM 4 ch. standard generic. Nothing fancy.
Hardware is Goldenrod (red) that is supported several times. along fuselage.

Now, I didnt buy whole thing like I said before it was given to me. It is just bit more work than usual because of the quality of the design of this kit.

Perhaps, I should look into a "true" trainer?

Thanks for responses, SST and Mode1!!

Chuck

ELTIGRE

Global/Hobby Shack/Hobby People kits are usually very good . I have 4 other kits & one of the SST .25 but never went through it much. it looks like it would do fine as a trainer WITH an instructor.reportedly its a groovy flyer.

ELTIGRE

for an ABC type motor you want to use the same diameter & pitch prop recommended for flying.
also, DO NOT run it "SLOBBERY RICH" like the older steel sleve cast iron piston motors. dont let it over heat either but, slightly rich is ok.
reason is ; the way overly rich mixture will cool the cylinder sleeve while the piston gets the heat of cumbustion. being of different materials , they expand differently & it is possible to break the rod due to the piston becoming too tight and straining the rod. Its not hyper-critical but dont over do it. you may find it easier to start using an electric starter on ABC .

ColdChuck

ELTIGRE,

When you mean by "groovy flyer", do you mean its quite challenging (bit too much fun?) to fly?

Thanks for the info on ABC engine. I will be asking more info on the procedure soon. Fuselage is about 80% done and needs to be covered up. I had to install elevator on stablizer due to hidden pivoting connecting part inside the fuselage. Covering will most likey be bit more tougher to install.

Next up is the wings. I got two steel dowel rods and bracket to make wing jig. I need to drill two holes for the dowels. I dont think the wing will take as much time as the fuselage took me alone.

Hope ya'all have a nice weekend!

Thanks!
Chuck

ColdChuck

By the way, I forgot to ask SST about his wing tip. I am wondering what is the function of adding a "wingtip" to the wings? Will it make it much more "controllable" or something? Is it something I should consider doing it to my plane now? I did few modifications to the frame, mostly additional bracing to the rear section after seeing how "thin" the balsa sheeting and didnt want to take chances of it coming apart. But I didnt want to "overbuild" it too much on account of weight.

Thanks!
Chuck

SST

My Feedback: (2)

Tip plates improve stall and low speed handling characteristics. Ailerons remain more effective at landing speeds. I use them now on most of my planes unless they're scale models.

ColdChuck

Thanks, SST! Now, another question... how do you know what size of wing tip to be effective? Is there a mathematical formula or just plain eye-balling it? I might do it the same.

Thanks!

Chuck

SST

My Feedback: (2)

Nope. just eyeballed it, and tried to make it look decent. The leading edge is flush, as the important part starts behind the spar as the wing thins out. It's probably .75"-1" above and .500 below the wing at the TE.

thegreek45

My Feedback: (2)

Do any of you have the cinstrstion manual for the SST 40?

John
​​​​​​​text me at 310-346-2108
​​​​

jester_s1

You may not have realized it, but you just posted in a thread that is 12 years old. You might try contacting the manufacturer though, or if it's a build related issue maybe just posting here with some pictures of your problem.

GallopingGhostler

John, PDF plans are available at https://outerzone.co.uk/plan_details.asp?ID=8975