lorih

Hi YumaMike. Very sorry to hear about your loss. I am currently putting together a red/white Senior Telemaster and I'm concerned about the strut issue.

The one thing I cannot figure out is what stresses could possibly have caused the wing, WITH STRUTS even, to fail in nearly level flight. You said you applied slight elevator, but still, that is near level flight.

It would take some serious stress to cause a catastrophic failure such as this. For the struts to be pulled out of the wing, some force must have been transfered to them. At least in my mind I see it that way. Is it possible that there was a loss of some, or most, of the rubber bands? This would have transfered most, or all, of the wing load to the struts.

I have witnessed a rubber band break on the ground that caused several other bands to pop off the wing without breaking, so I know this is possible.

I also know that the rubber band dowels on the Senior Telemaster are rather short.

What are your thoughts? What size and what number of rubber bands did you start with?

The reason I'm asking about the rubber bands is that they carry, or should carry, ALL the load in level flight. The struts should just help prevent wing flexing under load. That wing should not have come apart WITHOUT the struts in level flight.

Cliff

YumaMike

Thanks for the reply:

I also lost a aileron at the same time. When I moved the elevator to correct the nose down attitude we all heard a loud POP then a number of loud POPS as the wing started to come appart. After air got into the covering from the HARD SPOT being riped out of the wing and taking a large amount of covering with it, and distroying the ribs and support. After all the loud noises the wing came off the plane and the fusealage came down with the wing seperate but stil attached to the other wing with fiber tape. The GLUE on the HARD SPOTS was very sparce and only two sides attached, one to the ply covered spare runner and the cheap balsa rib. The Glue points on both HARD SPOTS gave way at the joints. I would redo the hard spots with epoxie and more support. I would redo the screws in the control surfaces by removing the screw and drop some thin CA in the screw hole to wick into the Cheap Balsa and reinsert teh screw again. Thats all that would be needed to correct the problem.

Find below a RC Universe forum comment back in 2007.

RE: Hobby Lobby Sr. Telemaster ARF - 10/16/2007 3:47 PM

I just wanted to pass on an experience I had last season with the Hobby Lobby Sr. Telemaster.

Due to a bad experience with Hobby Lobby last season, I am avoiding buying their kits at this point. Last year the first Senior Telemaster I had came with the hinges very tightly in place........so I thought. The manual said to glue them in place, but they were too tight to remove. So I called Hobby Lobby and they assured me that the hinges had been glued, and that there was an error in the manual.

I was on my 10th or 11th flight, straight and level, in cruise, when all of a sudden there was tremendous flutter either from the ailerons or elevator. The plane became uncontrollable, and I totaled it. Inspection of all servos revealed they were all working and no gears were stripped. Upon inspection of the now cracked-open hinge lines I noticed that THERE WAS NOT ONE DROP OF GLUE ON ANY HINGE ON THE AIRPLANE!

I reported this to Hobby Lobby, and even sent them the wings, elevators, and rudder. They didn't believe me, and gave me a bag of crap. The support guy I talked to was skeptical and arrogant. Later a manager called and said "What can we do for you?". I said I was just letting them know that there is a major flaw in the kit which resulted in my loosing an airplane. I was hoping they would fix the flaw so that other pilots would not have the same dangerous experience I did. They thought they could shut me up by sending another Telemaster, at no cost, which hey did. But they never agreed to acknowledge the flaw in the kit, nor did they assure me that it would be corrected.

They sent me a new Telemaster, and upon close inspection of its hinge lines, I noted that NONE of the hinges were glued again. But they were tightly held in place by tiny 1/8 inch wood screws under the covering material! I called them again just to warn them, and to suggest they leave those stupid screws out of the kit.

They ignored me. I cut through covering over every screw, removed them, and have epoxies all my hinges. But I will probably never buy another plane from Hobby Lobby because of this experience.

PLEASE BE CAREFUL, LOOK FOR THOSE SCREWS, AND GLUE YOUR HINGES!!!!!

Dick Byrnes

lorih

Well YumaMike, you've inspired me to take a look at my wing. Sure enough, no glue at all on the hinges. They do seem like strong hinges. Look like polypropolene or similar and each side of each hinge has a screw installed. Still, I think I'll change them all to the same size CA hinges. I'll install the hinges dry, put the screws back into place, then CA the hinges into place. That will give a stronger hinge mount and the CA will soak into the balsa making it stronger as well.

I'm also going to cut the covering around the hardpoints and reglue them. It isn't a big deal and has to make things stronger.

Really sorry to hear about the loss of your plane. I still cannot visulize what caused the failure though. Maybe control flutter? Rubber bands breaking....something weird to cause the failure in basically level flight.

Your loss wasn't in vain though. I'll heed the warning and do some beefing up on the wing.

Cliff

cadconversions

My Feedback: (21)

I've currently have stripped off all the covering on the ARF and recovering in better covering and to fix a few of these issues. Nice plane but not much to boast about in the cosntruction quality. I would for sure recommend the kit - the 12' ARF scares me to death if it's built in the same factory.

lorih

I've finished cutting into the wing to strenthen the hard points. I did find the hard points to be well glued in my wing. I went ahead and epoxied some triangle stock to the hardpoints and soaked the surrounding wood with thin CA just in case. It only required a 3 1/2" by 3 1/2" hole at each hardpoint and wasn't too difficult. Shouldn't have to do it, but that is the way it is.

Also replaced the hinges with CA hinges. I reused the screws for the hinges to hold the CA hinges in place while glueing. The original hinges had no glue at all, just the screws to hold them in place.

cliff

lorih

I finally got a break in the weather and was able to perform the maiden flight.....plus 4 more. What a beautiful, graceful plane this is. Take off was a half throttle affair with only 1 click of right aileron trim required for trimming the plane. Rolls were slightly barreled as would be expected with a top wing plane. Loops were large and graceful. The entire flight was like watching a full size plane go through its routine.

All takeoffs and landings were with a 7-8 mph direct crosswind from a grass runway with no problems. Ground handling required low throttle and full up elevator as the slightest throttle wants to lift the tail, and tail wheel, clear of the ground. That was the only surprise of the day.

My plane is way over powered at 900 watts, but that is okay.

Seeing the plane in the air almost brought a tear to some of the clubs old timers. The ST isn't a 3-D or a pattern ship....she is just a slow, graceful, majestic flier. You just sit back and relax while watching her fly.

Cliff

jongurley

My Feedback: (29)

Anyone running a gas engine on this telemaster,,

cwharper

Gas engine, yep!!! RCGF-20cc-B

But you gotta reinforce the firewall and all the bulkheads with strips of fiberglass. I've been running it for about three months now and it seems to hold up. One thing though get some heavier duty control horns and clevises than what is supplied in the kit, especially some metal clevises.

Eplane65

My Feedback: (16)

4130?? You are going to rip the wings off!!

jongurley

My Feedback: (29)

Anyone care to elaborate or preferably have some pictures of converting this wing to a bolt on instead of this rubberband stuff..

Telemaster Sales UK

A customer of mine has fitted one of those new Saito petrol (gas) fourstrokes to his model. I've had no bad reports.

lundb

I don't like ARF's as I don't know what is inside. I did the Senior Telemaster Kit. I do not like struts so I reinforced all wing spars with carbon fiber, and cap stripped all upper wing ribs. Underwiung fuselage area has 3 detachable pods that slip/bolt in place. (candy bomber/Video camera/Flag or Glider tow). Fuse stricture was also reinforced.and wire braces installed on fin/stab. Power is CX50-L-380 (2Kw+) with a pair of 5000mAh LiPo's, 80 Amp ESC, and 17x8 Electric prop. It jumps of the ground (take-off run less than length of fuselage) and has unlimited vertical, but is more fun just flying around doing mild aerobatics. No flaps but raduio can pe programmed for flaperons. (slows down and lands nicely so flaperons are not used). All up weight is 10.19 lbs with a wing loading of 18.03 oz per ft sq. Wing was modified with 4 attachment bolts, 2 front and 2 rear.

Telemaster Sales UK

Nice job lundb! I'm building an STM for a Laser 91 using the old German "Barn Door " wing with inset ailerons. I was thinking of fitting struts but may be I'll leave them out at least for the first few flights. The Barn Door wing has two sets of webbed spars and I've substituted spruce for the original balsa so that should be strong enough.

2Kw motor eh? No wonder it goes vertical I have a motor which draws 1Kw in my ARTF and that leaps off the ground. Are you running your 5000 mAh LiPos in series or parallel?

fritzdecat

Have you got any pictures of that build?

I am looking to do the same thing, I would like to make a wing that would look like a Fiesler Storch

Spoilers on the front of the wings and Fowler style flaps, which I think is what you mean by barn door flaps?

Hopefully this might allow it some stol characteristics...

Telemaster Sales UK

Hi Fritz and Everybody

Spent much of yesterday afternoon with one of my club-mates, who is far more knowledgeable when it comes to computers than I am, pouring over my computer to get my camera to talk to it, with limited success! I'll try to upload some pictures from the build but I'll probably need his help.

The "Barn Door Wing" is the name given to the wing designed by the original designer Karl-Heinz Denzin. When the RCM plans of the Senior Telemaster were published the wing structure was modified by Joe Bridi to feature strip ailerons and two spruce mainspars.

The original wing, such as the one I'm building, featured inset ailerons, similar to a real aircraft like a Piper Cub. It also featured a total of four balsa spars arranged in two pairs and joined together by 1/8th balsa webbing to produce two "I" spars. I have used spruce for my spars instead of balsa and I am building the wing off a plan drawn up by a club colleague who used the wreckage of my original STM as a pattern.

The attached pictures show the process involved in fitting joiner tubes to make the wing two-piece.

1. Firstly, I selected six wing ribs from the hardest balsa, pinned them all accurately together and drilled two small pilot holes (1/16" or 1.5mm) exactly halfway between each pair of spars.

2. Secondly I unpinned the ribs, set aside two of them and drilled out the pilot holes to the exact size of the carbon fibre tube I will be using. These two ribs are then marked with a "2" as they will be the second ribs out from centre.

3. Select another pair of ribs and drill two appropriately sized holes 3/16" (5mm) above the pilot holes. Mark these as "1." These will be the centre ribs.

4. With the last pair, drill the holes 3/16" lower than the pilot holes.

5. By arranging the holes in this way, you should end up with stock dihedral of 3" (7.5cms) below each wing tip.

You could extend the same principle to incorporating the fourth and fifth wing ribs but I've found that three is sufficient especially if you fly gently and fit struts. With the Joe Bridi wing the second tube may be positioned 4-5 inches (10-12cms) behind the main spars, the distance is not critical.

I intend to make the wing bolt-on and will show you the structure when I have completed it.

Fowler flaps are totally different to the arrangement I shall be using. As far as I understand it Fowler flaps are pivoted in such a way as to increase the wing area once deployed.

fritzdecat

Thanks for posting that following this wing build with interest

vmsguy

In case anyone is interested...

I did a build thread on a scratch built Senior Telemaster...

Electrified, of course...


http://www.rcuniverse.com/forum/m_9917705/tm.htm