Tigercat RC pylon racer build project

Wow Andras, my heart skipped a beat and this image popped into my head when I saw this post.



The F-7F Tigercat. I climbed all over one sitting in a row of F-4U Corsairs at Airman Prep school in Norman Ok back in the mid fifties.

Looking forward to reading about your build.

Bob

George, Bob,

thank you for your answers. Yes, the Tigercat is a really nicely made kit, very gorgeous bends and smooth surfaces on its fuselage and wing.

It has a single engine though, Bob, unlike the F-7F fighter plane.

I am currently doing the cutouts on the fuse for the tail section, and for the single nose wheel and electric micro switch, then will think about the aileron setup....the wing halves have been built with the aileron areas still to be cut out and the torque rods to be hidden. These are the most intricate parts of the build, the dihedral sending into the wing halves included.

It has a single engine though, Bob, unlike the F-7F fighter plane.

Yes, I know. A rose by any other name....

Bob

The real Tigercat.


Photo from https://www.hepper.com/tiger-cat/, cropped and resized.

what a beautiful project friend!, congratulations on your acquisition!... it will be a pleasure to see it in action!

Looks like the box has some age Andras. 30" span it's no little guy.



Some issues are yet to be sorted out, like finding the proper epoxy-based spray paint for the fuselage, etc., but the project will launch soon.

Epoxy paint doesn't fade and lasts forever. My Hobby Poxie painted scratch built C/L made about 50 years ago still shines like new.

Good luck with your project.

Thanks Mauricio  and Bob. I enjoy building this racer with my modest handskills and tooling.

Some of the steps I thought were most critical are done: Fuse cutouts for the tail section and nose wheel bay done, with no cracks left along the cuts on this near 50 years old fiber reinforced epoxy fuselage. Nose wheel copper bushing and shaft done. Ailerons cut out from wing, torque rods installed...torque rod cover panels look a bit creased but are sanded  smooth in reality..Wing assembly to 3/4" total dihedral will follow tomorrow.




My epoxy spray paint will be delivered from a webshop on Monday, fuse color is "Honda yellow" whatever it means, I chose this color because my small Honda MSX 125 Grom bike is also yellow and I love that bike and color...will be easy to keep track when airborne....I mean the plane..

The Tatone aluminum mount is bolted to the firewall in metric threads cut in the epoxy/plywood combo bulkhead that I do not really trust..this is just too soft to anchor a TeeDee into, I will add real nuts to the bolts...I ordered a small socket head wrench with extension to reach the nuts I will add from behind the firewall, deep in the tank compartment, without access with fingers, let alone wrenches..I would hate seeing the TeeDee shake itself free mid-air, the bolt and nut is the dependable way to go.. ..

More to follow..

I promised my aching back that I stop and
continue tomorrow, but could not deliver my promise...wing assembled, dihedral set:







...

Andras, congratulations with the find and good luck with the build. I found this article here on the forum

https://www.coxengineforum.com/t11587-1-2-pylon-article

It says:"The text has a lot of good advice about how to make these small models really perform", not that I underestimate your talent and experience!!

Thank you very much Lieven, every advice is welcome...I have built quite a number of COX powered RC planes in the past 12 years, but you always learn with each new model...the 3 pages build instruction tells only about the build sequence, but the tricks of making your model really efficient and safe is learnt from articles like the one you referred me to.

Watching from the sidelines , is that a solid wing sure is thick looking .

Thanks, Eric, well, yes, this is a balsa sheeted foam core wing from the pylon racing design schools of 70's--- designers today would probably make it thinner, with carbon reinforcements etc included...anyway, given that I am an amateur RC  "recreational" flyer, maybe the ultimate speed of a pylon racing plane of modern design would surpass my piloting capabilities,   ?

getback wrote:Watching from the sidelines , is that a solid wing sure is thick looking .

Back in the day, proportional R/C gear along with batteries, although more compact than in the 1960's, was still heavier than today. Aircraft needed to develop sufficient lift for the payload.

It is still an improvement over 1959.

https://www.coxengineforum.com/t6494-1959-berkeley-impulse-single-channel-pylon-racer-build?highlight=impulse

The Tigercat build project continued, with the fiber reinforced epoxy fuselage sprayed in epoxy paint, the tray for the elevator and throttle servos prepared, and the aileron servo embedded in the bottom wing center. Next will be the coverage of the wing and tail section in heat shrink foil, then final fitting of the elevator/throttle tray in the fuselage bottom.




I have limited experience with fiber reinforced epoxy fuselages from the point of view of engine vibration propagation. I know that rubber grommets in the mounting holes of servos will mitigate vibration effects, but my prior experience with the all-epoxy VooDoo racer powered by a TD049 were not all that positive despite the use of grommets: servos in the VooDoo often died due to engine vibes.

The fuselage of the Tigercat is wider and more robust than the VooDoo, plus the wing is made of balsa, so at least the aileron servo will enjoy better vibration mitigation in the wing, but the elevator and throttle servos, fixed to the fuse bottom,  are still exposed to whatever vibration the fuselage propagates from the TeeDee in the nose.

Anyone has a proven tip on how to mitigate engine vibration impacts on the servos in addition to the grommets?

Thank you.

balogh wrote:

Anyone has a proven tip on how to mitigate engine vibration impacts on the servos in addition to the grommets?

Thank you.

Hi András, vibrations are a trigger for micro servos.
Some time ago I posted here, how I do with my servos, because I can't find where to post exactly, but I'll explain; It is about disassembling the servo and placing silicone on the loose cables, making them firm and held by the glue (silicone), then a few drops of oil or Vaseline are placed on the servo cover, and it dries, this is for that when closing the servo, the lid is not stuck with the silicone. That's the ultimate solution, but you have to go to the trouble of disassembling the servo and carefully placing the glue inside. I'll see if I can find any photos.
The vibrations also destroy the eyelets where the servos are held by screws, so what I do is place some Orings where the servo remains floating, it is not always possible to achieve it since the spaces are very small and the servo remains trapped in the structure itself, but if you do the previous step (place silicone), you will ensure that your servos do not lose connection due to internal cutting of cables in their welding.

I dont have a lot of experience in this and dont claim to know if this will work, but it occurred to me that maybe if the vibrations could be stopped or limited from the engine in the first place then vibration management would be easier for secondary systems. I dont know how to do it, as I haven't thought it through, but if the TD could be mounted so it was still fully functional but on a mount that incorporated rubber sections like engine mounts in a car that may help make the problem with the servos easier to manage, by resolving the problem at the source.

Yabby

Yabby wrote:I dont have a lot of experience in this and dont claim to know if this will work, but it occurred to me that maybe if the vibrations could be stopped or limited from the engine in the first place then vibration management would be easier for secondary systems. I dont know how to do it, as I haven't thought it through, but if the TD could be mounted so it was still fully functional but on a mount that incorporated rubber sections like engine mounts in a car that may help make the problem with the servos easier to manage, by resolving the problem at the source.

Yabby

Placing an engine on a rubber block does not guarantee to limit vibration. These motors are extremely light (they do not have a proportional hub) and in relation to this they have a high rpm, two factors that add up when generating vibrations.
Different is the gasoline engines that have a high hub with respect to the rpm they generate and then the rubber pads are more applicable there. The same goes for a 4-stroke engine.
What sums up the issue is that the TD engines have many laps and it is from there that the vibrations arise.
The breakage or cut of connections hold from 15000 rpm, that is why it is more common to cut cables with a TD and not with a Babe Bee.
The size of the aero models also help to absorb vibrations, that is, the larger the model, the better it will withstand or absorb vibrations, it happens that, in most cases, a Cox TD engine is applied to a slightly small model and light for high displacement speed and the little hub of the engine, plus the small size of the model and the high rpm, all these factors add up in favor of cutting cables and connections, for all the aforementioned, it is best to glue the cables with silicone.
Of course, one factor that must be taken into account is to control and balance the propeller, this is essential when there are high rpm. This will also help reduce vibrations.
You can place an electric motor of more than 30,000 rpm and it will only depend on the good balance of the propeller, then there will be no vibrations. But an electric motor is not the idea of use in this case.

Thanks Mauricio.

As the plane currently stands, I expect its all-up dry weight to end up less than 16 ounces versus the advertised weight of 20-21 ounces with heavier radio gear in the 1970-s, so the weight factor will not help much to mitigate impacts from engine vibration, even if my prop is well balanced.

I will see how I can add thin rubber pads under the ears of elevator and throttle servos, that may help a bit...I am less concerned with the aileron servo sitting in the middle of soft, balsa sheeted foam wing that will better attenuate engine vibration.

My concern with  engine vibration inflicted occasional servo failure prompted me to repurpose 2 party balloons, and cut their neck piece with the twirled, thicker lip on top, and pull them on the servo bodies .





Now the servos are sitting on the soft, thick lip of the balloon neck, and their body is wrapped in double layer of balloon rubber, and the vibration will be partly dampened. The servos are totally separated from the tray by the rubber, only the servo screws may transmit some vibration to them, but the servo ears sit on thick rubber..

I am not saying this is totally vibe-proof, but trust will save the servos from detrimentally shaking.

The Tigercat is almost ready. I need to swap the stock TeeDee needle valve with a thinner one, and add a smaller, plastic fuel filter, the current aluminum filter is a bit bulky for the cowl..

The tail wheel block is still to be added.

The all up weight is 18 ounces I.e. >10% lighter than the 1976 build instructions say, thanks to the light radio gear of nowadays- even though I have a 700mAh NiMh battery on board- and the feather weight party balloon light tank.

Maiden flight is scheduled in a week. A very  shapy pylon racer, I am thrilled to see how it will fly. I find the inverted engine a bit vulnerable for landing on rough terrain even if in a cowl, but trust the CG properly set will prevent it from hitting the ground head first or sommersaulting..

Beautiful color Andras, super low drag must be a winner. Are you going to dress-up the wings/tail a bit?

Enjoyed your build.

Thank you, Bob..
I also like this plane and I have spent quite some time building it, even if it was pretty pre- built..honestly I made so many mistakes that the cosmetics took almost as long as the build itself,and the reason I did not show details mid-way was not to show all those frustrating errors and inaccuracies.
But finally my salvation efforts worked out quite well...I will add some ornaments of some sort to the white tail and wing, though the orange color of the fuse is restricting the choice for the third tone to only a few.

What color would you choose for decoration? Maybe the yellow or red side of the spectrum, but certainly not on the blue or green side?

Your, or all other CEF friends' opinion would be highly appreciated..

Somehow your going to have to pick up on that beautiful body color Andras. As I have mentioned before, I have no talent in that regard. My go-to guy for this advice is Levent. Without him I'm a lost puppy in the woods.

Bob