drob

Hi all. This is my first time as a contributor to this thread although I have been following it closely for some time now. Thank you Brad for starting it off and to you and all others who have offered such useful advice. I am now on my second Tiger Cat, the first went in on the second flight partly due to my then less than accurate balancing method. Total destruction! Tiger Cat II is flying well powered by two LASER 150 4-strokes running 15x8 3 blade props (cut down from 16x8). Once I perfect the landing technique it will be even better. The sound of those Lasers is something else again. Take-offs are in a word, brisk. No flaps needed or advised.

Here are some of the mods I made.
Main Landing Gear: Made a big enough boxed hole in the wing to accommodate the 'paddle' and wheel. Put wedges (about 2mm at the high end) under the retract mountings to tilt the wheels just that little bit deeper into the wing and thus clear the closed doors. To allow the gear doors to open fully unhindered I filed the doors to create a straight edge between the hinges.

Nose Gear: I ran the pull-pull wires through plastic tubing to protect them from the retracting strut. The tubes are fixed along the rear half of their length to allow some flexing at the front. I use a separate servo for steering which is mixed with the rudder servo. To give more clearance for the 15" props I replaced the nose wheel strut with a modified mains strut from my sadly departed ASM A26 Invader (seniors moment! (71 years young)). This is 20mm longer that the supplied strut and gives an additional 10mm clearance at the props. It also gives the Tiger more of a nose high stance we see in the full size aircraft. I would suggest that a longer steel plug at the top of the strut would achieve the same result. While this did require a lengthening of the wheel well hole the resulting extra length required for the gear door wire loop means that the door is less likely to foul with the wheel on full deflection of the strut.

On the subject of deflection of the gear struts, I found that when the weight of the plane was put on the my ASM Invader mains that there was excessive sideways play with the wheels. This was becoming evident with my Tiger Cat so I have replaced the main struts with the Robart units I had installed in the Invader. Having wider hinges, these are more resistant to movement. Incidentally my system holds pressure for at least 7 days.

Fuselage: I glued birch ply doublers along the entire length of the existing longerons. Also installed the doublers described in post 385 making them as high as I could and still wangle them behind the former. I had the benefit of a template former taken from my first Tiger. Also ran CA along the join in the ABS plastic at the trailing edge inside and out. This was also a weak point on the Invader. One rather hard landing with the Tiger, bad enough to break one of the main gear bearers, resulted in no other discernible damage or movement in the airframe.

The engines are mounted inverted. To give extra cooling egress I removed a portion of the fire wall at the bottom and fabricated ABS plastic to create exit shoots. The air bottle is installed under the wing with the A123 battery above. No extra weight was necessary to achieve balance at around 88mm.

I hope that my contribution is found to be useful. I now feel part of the Tiger Cat 'family'.

drob

Oops, one photo I forgot...

Staggerflyer

drob, welcome to the thread.

That looks very well done. A real good idea on the nose steering cables. Thanks for the tip.

Enjoy flying her, and get some video! [sm=thumbup.gif]

drob

Thanks Staggerflyer. I might also mention that the weight is 9.6 kg. I'll have to get my brother into gear with the video.

elojim

Hi Drob,

good advices !

I've just starded the construction of mine and the first thing I build is a support to hold the aircraft and able to work comfortably :

drob

Hi Elojim
Can I suggest that you leave installation of the 'tail feathers' until you have finished with the front end of the fuselage.
Also install the stabiliser first, before the tail/rudder. This will allow you to epoxy the stab from the inside of the fuselage.

One thing I meant to mention in my earlier post. Wing Tubes: I cut a section length ways out of short pieces of aluminum tube
which allowed me to squeeze/ram then inside the wing tubes to the point where join between the wing sections occur. These then gave
a thicker section for me to drill and tap for 4mm cup head bolts. The bolt on the center section just squeezes between the
engine cowl and the outer wing rib which makes it easier to assemble/disassemble the wing. The wing tubes can then be
permanently attached to the outer panels. Some packing is required here to avoid collapsing the wing surface when tightening the bolt.

Enjoy the build!

David

drob

Silly me! I just noticed that you have already done the tail end. Nevertheless it might apply to others just starting.
When doing a second build we always figure out better way to do things.

Rocketman_

drob,
Welcome to the Tigercat thread, young man (71 years young).
I agree and I'm sure others will agree with your modifications to the longerons and formers. I feel that those mods are mandatory but I also agree with some of your preferential mods such as lengthening the nose gear and the wheel well opening to accommodate it. My preference was for a slightly higher nose also. The picture shows the wheel well opening extending well past the red stripe and nearly to the aft former.

My wing tubes are left permanently in the outer panels also. I've read about some concerns that the wing tube screws might unscrew from the aluminum but mine are tightly threaded into the hardwood that is provided inside the wings and don't depend only on threads in the tubes.

Your choice of the Laser 1.50 4-strokes shows that you don't like to be short on power .
I chose the OS 1.20AX 2-strokes for my F7F and they also provide for a quick take off and I can do an axial roll on take off. I take off without flaps because I tried flaps once and the model leaped into the air unexpectedly.

Staggerflyer

My tubes are also permanent in the outer wings. I just use the kit supplied setup, using a long phillips screwdriver with a GOOD tip, to screw the inner screw in/out, which I leave in the wing, only removing far enough to let the tube by, 3-4 turns. There is no sign of stress to the tube hole as the screw goes into another piece of wood above the tube also. Just snug on installation, I do not "tighten" it.

Flaps are not needed on take-off, nor suggested. This aircraft leaps off the ground much sooner than expected, with authority, without hardly any noticeable elevator input. My two Rimfire 1.20 electric motors on 6 cells lipo each also give very strong climbout power, allowing a roll on take-off.

drob

Thanks Rocketman.
Age is a state of mind. I plan to live forever...so far so good!

elojim

Hi Sterling,

you're talking about the new OS 91. This engine is no longer available. Are you using the new OS 81a ?

elojim

Hi Drob, you're right and i should have done like that !

I start working on the nos gear and i noticed several things as you can see on the photo attached.
does anybody have the same and how did you proceed to screw the gear ? (i plan to insert two small strip of wood to fill the gap).

Thanks for your help,

Elojim

drob

Hi Elojim
I used temporary packers to ensure that the gear went in straight.
There is probably no real benefit in making these permanent. The downside
is that it would be more difficult to remove/install the retract with a permanent fix.
David

Rocketman_

My Tigercat came with the hardwood nose gear mounts spaced too far apart also. The bolt holes in the nose gear mounting flanges are spaced 40mm apart but that wasn't wide enough. I wanted to use socket head screws and blind nuts to mount my retracts and when I drilled the holes large enough to accommodate the blind nuts they were in danger of breaking through the inner sides of the hardwood. Also, the flanges of the blind nuts hung over the edge of the mounts. Adding birch plywood to the side and the bottom of the mounts was an easy fix and it did not hinder installation or removal of the retract assembly.
The thicker plywood was added to the bottom mainly to make the nose of the model stand a little taller on the nose gear.

Staggerflyer

I like the idea of raising the nose slightly via the nose gear. I may do that to mine, altho I have no problem rotating and lifting off. The other problem with the higher nose is keeping it on the ground during landing, especially in the wind, as the wing is at a more positive angle of attack, ie, it wants to keep flying. Just a thought.

elojim

Mounting the nose gear, i notice that there's a loose at the axis. I do not know how to fix this problem or by replacing the nose gear strut.
Nobody has had any problems during the retraction of the nose gear ?

Staggerflyer

Yes, it is loose. Other than making sure that all grub screws are lock-tited, and then using a drop of oil on all pivot points, everything will work fine. The main thing is using something to keep the steering cables up and clear of the axle, so it doesn't catch them when extending. The small springs are supplied for this. You have to do some engineering, but they will work fine if attached to the former immedietely behind (to the rear of) the wheel opening.

silver.kiwi

Elojim,

I have a caution on the nose strut. When inserting the strut into the retract mechanism, I recommend that you remove BOTH grub screws from the retract mechanism first. The instructions say only to " push the strut into the unit firmly. Then tighten the large (both are the same diameter) socket-cap screw against the nose gear strut". I would remove them both so you can look into the holes and check alignment of the screws and the groove/slot that is cut in the strut that mates with the screws. This groove/slot does two things....it allows the strut to rotate and keeps the strut from falling out when the grub screws are tightened. The reason I emphasize this is the strut is made from very soft steel and it is very easy to gall (ulcérer)the groove/slot if the screws are out of alignment when you tighten them. The resulting galling will cause steering headaches and a sloppy fit.

Silver.kiwi

Staggerflyer

Silver is right about the very soft steel. That is why I recommend the lubricant after the lock-tite has cured, in order to lessen the fast wear on any and all moving parts. It also helps the retraction cycle be more positive, in both directions. I have not had any more nose gear down lock failures since applying the oil. The main gear up cycles lock better, closing the doors more positively since oiling, also.

drob

After the heavy landing I wrote about earlier, a distinct hesitancy in the steering was traced
to the fact that the steel pin had bent. I had my brother turn up a replacement from 'good' steel
to which I applied a film of grease (automotive axle grease) before installation, partly to stop
the possible seepage of lock-tite when I screwed in the grub screws. I also smeared the other
moving parts of the mechanism with the same grease.
This has resulted in a very smooth operation all round.

By the way, my landings are getting better!

Brad330l

My Feedback: (1)

Hi guys, I am back from overseas and in my shed there is a big box with Tiger # 2 in it.
My feet still have not really touched the ground yet so it is unopened as I am catching up on everything here on RCU and the other real world.
Good to see you came along to join the family drob. I like the mods you have done and the will look at doing a couple of them in the very near future.

Keep em flying gents. I'll be watching.

Brad

Lebus1

I've got about 4 flights on my Tigercat and 3 hard landings. Take-off is sweet 1/2 throttle and she is up and away and an awsume sight in the sky. Handles great no tricks at all except the landing part. I seem to come in too fast even though to my view it dosen't appear to be. She just seems to come in and land heavy. I'm not "dropping" on the field it just seems to fly down to ground and bend my gear. I'm going to take it to a local field and have a more experianced pilot try or give me some insight to what I'm probably doing wrong. DB

Staggerflyer

Sounds to me like you just aren't flaring soon enough. Or you are coming in to steep. This plane needs to be flown in, low and level, not dropped from high up at a steep angle. The lower and flatter you can be over the fence, the better. What would seem fine for a trainer/sport type aircraft is to steep for this one, mostly because of the wing loading.

Brad330l

My Feedback: (1)

Yes this model can get a good descent rate going when the power comes off. I have just managed a couple of times to literally yank full stick just in time to avert a heavy arrival. (negative ground effect??)
A good approach will generally lead to a nice landing. Practice flying it down the slope with different power and attitude settings until it looks good. If you have to extend your downwind leg to fit it all in then do it. Don't cramp your self up and get all excited in the most dangerous stage of flight. My worst landings with my Cat apart from the engine failures were when I didnt follow my own plan and was a bit rushed.

Good luck mate and keep at it.

Brad

drob

Hi Guys. Here is something to give you a warm and fuzzy feeling whilst throwing your Tiger around the sky with gay abandon.
After two normal relaxed flights this morning with the Master Airscrew 15x8 3blades (cut down from 16x8) I decided to try it with
ASP 16x8 2 blades. The difference was fantastic. I now have no doubt as to the superior efficiency of decent 2 blade props
verses passable 3 blades. I was now able to confidently do nice wide loops, axial rolls, barrel rolls, half Cuban eights that I was
not really game to try before. Really great fun.

After landing I decided to charge up the RX battery before another fun fly. You can probably imagine my shock when I removed
the fuselage top to see a gaping slit across the entire center section if the wing. I did notice an odd exit from the full Cuban eight
I did just prior to landing. I had assumed, as you all probably do, that there is a nice strong continuous main spar in the wing. Wrong!

As you will see from the photos, there are two 'flimsy' spars up front that are butt-jointed to the central rib with a length of carbon fibre
rod to give lateral support. The rear section relies solely on the tenuous glue joint of the balsa sheeting to the central rib. I say tenuous
because on my wing there is a 1mm gap between the two sides of the sheeting with filler to fill the gap, top and bottom!

The left wing was being largely retained by the dowel at the front and 4mm bolt at the back. The carbon rod had apparently separated
from the right wing. There was no cracking on the underside. When I contemplated what could have been I was grateful that I had gotten
off so lightly. I'm not yet sure how to fix it but will probably try to wangle in a decent spar and wrap glass fibre around the center section.
Another option which I am seriously considering is to build a new, strong, center section. I don't think I could confidently fly they way I want
with a 'fix' to the existing wing. I will have to sleep on that.

I was intending to recover the wing anyway to replace the cheap covering. The ease at which I was able to remove the original covering
was testament to the quality. Oracover Corsair Blue seems to be a good match against the painted fuselage.

By the way, the extra length in the nose strut along with Rocketman's suggested packing (post 439) gives adequate ground clearance for
the 16 inch props. I now have an extra 25 mm length overall in the nose strut.

Have a nice day guys.