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ASM F-7F Tigercat

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Old 08-31-2011, 03:51 AM
  #451
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Default RE: ASM F-7F Tigercat

Good Grief!!
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Old 08-31-2011, 04:12 AM
  #452
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Default RE: ASM F-7F Tigercat

Yikes!![X(][X(]

Wow, I see a winter project there. A box or two with either one piece or laminated spars, or drilling and installing wing tube kits. Either way, going to be a little work.

Not saying this is how everyone should fly, but I do try my best to keep my flying style to the type of aircraft I'm flying. Scale. I love going to airshows, and/or watching videos of the real aircraft to see how they are flown, and emulate that with the type of model I'm flying. Warbirds are not 3-D, or Aresti type fliers. Big, open, low G type manuevers.
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Old 08-31-2011, 04:40 AM
  #453
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Default RE: ASM F-7F Tigercat


Quote:
ORIGINAL: Staggerflyer
Not saying this is how everyone should fly, but I do try my best to keep my flying style to the type of aircraft I'm flying. Scale.
Drob's maneuvers are scale for the F7f Tigercat.
Google "Steve Hinton Aerobatics" or go to the link below to see full scale F7F maneuvers.
http://www.youtube.com/watch?v=MBzif...eature=related
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Old 08-31-2011, 04:57 AM
  #454
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Default RE: ASM F-7F Tigercat


Quote:
ORIGINAL: Rocketman_


Quote:
ORIGINAL: Staggerflyer
Not saying this is how everyone should fly, but I do try my best to keep my flying style to the type of aircraft I'm flying. Scale.
Drob's maneuvers are scale for the F7f Tigercat.
Google ''Steve Hinton Aerobatics'' or go to the link below to see full scale F7F maneuvers.
http://www.youtube.com/watch?v=MBzif...eature=related
I think you misunderstood my statement. I never accused him of anything. I only stated how I fly. No one else. I know how Steve Hinton flies the Tigercat. It's how I fly mine. There are others here who have mentioned doing 3D with theirs. And those of us who have been flying for a long time, as in many, many years, well over 30 in my case, often see newer pilots try to fly all types of models in the same style. Some are just not designed for it, was all I said.
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Old 08-31-2011, 05:04 AM
  #455
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Default RE: ASM F-7F Tigercat

Wow drob what a spin!!![X(] I am very happy it hung together for you so you got it down OK.
I have been inspecting my Cat and have found a couple of joins that are not glued at all and a couple with glue that are not strong at all. I will spend a good few hours going over it and beefing it up where you guys have that is for sure. Looks like a wrap or two of 2oz glass will be going around the center section join as well after your report. Man that is such a spin. I knew the sheeting on the wing was quite soft but no spar???? It is such a shame because it is a wonderful model I reckon. A bit of quality control and better engineering would have been nice.

Funny thing is, after my # 1 Cat went in, the center section was still in one piece and it hit wing tip first in it's death spiral.

Please post all repair pictures and any else you have of the internals.

Cheers,

Brad
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Old 08-31-2011, 07:47 AM
  #456
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Default RE: ASM F-7F Tigercat

I wonder if your idea to wrap the center section seam with fiberglass will be enough. It just might do the trick without further beef up. If it opened at the top and not the bottom then I'm guessing that it was stressed in the negative or inverted.

I have this bird still in the box so I'm hoping you find a reasonably easy fix.

Good luck,
Mike
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Old 09-01-2011, 03:04 AM
  #457
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Default RE: ASM F-7F Tigercat

Hi guys. Here are some more pics. I removed the top sheeting from the Tiger #1 wing so I (we) could see what was underneath.

I too try to fly scale like. My Nitro Cessna 310 is capable of loops and rolls but I choose not to do these maneuvers as they
are out of character for the 310. I have downloaded the Steve Hinton video and often go back to it to work out a matching
routine. My one indiscretion on that last flight with the Tiger was the Cuban Eight. I was enjoying the new capabilities of the
Tiger with the 2 blade props so much I thought I would try a Cuban. I won't do that one again! But the others are so satisfying.

When I analyze the flight, it was at the end of the Cuban that I believe the wing failed. I thought I had lost the Tiger at that point.
Once I managed to get it back on an even keel it behaved normally. The landing gave no indication of any abnormality.
Fortunately it was possibly the smoothest I had managed so far! I guess that the upwards pressure on the left wing held it in the
correct position. It was when the weight was taken off the wheels that the wing dropped.

The weak point (in the already weak wing structure) was the carbon fiber 3mm tube which on the Tiger #1 wing transverses the
entire center section. On the Tiger #2 wing however, two tubes had been installed, joined by a wire insert as the first photo shows.
Had the wire been glued into both tubes this reprehensible action may have gone unnoticed. It would seem that it is on this one
measly carbon fiber tube that the strength of the wing mainly relies. Unbelievable isn't it?!
I wonder how many other wings have a similar 'fix'.

As indicated in the other photos, I plan to insert a carbon fiber tube (16mm diam, 1mm wall) that will extend out to the third last
rib on either side. I have removed a section of the top sheeting equal to the width of a sheet of balsa to gain access. This will be
replaced with one sheet that will extend out to the second last ribs. I also plan to add a glass fiber bandage around the join in the
wing halves. I may also consider a second, shorter tube towards the trailing edge.

Please feel free to comment.

David
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Old 09-01-2011, 03:09 AM
  #458
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Default RE: ASM F-7F Tigercat

Woops! where did the pics go?
I forgot to click the OK.
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Old 09-01-2011, 03:37 AM
  #459
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Default RE: ASM F-7F Tigercat

One thing I had meant to mention. On further examination of the wing I found that the 'spar' does in fact continue
through the center rib. It is slotted from the top to half way down to accommodate the slotted ribs. You will see
from this photo that it a snapped at the bottom.
David
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Old 09-01-2011, 04:41 AM
  #460
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Default RE: ASM F-7F Tigercat

David, interesting photos, there. We have all been noticing a major lack of good glueing in the factory assys. I would say it appears that may have contributed in your case. A Cuban Eight, properly flown, is not out of character for this aircraft. Nor should it have caused your problem. A warbird style would have you rolling rightside up on the top of the downline, instead of waiting till the center of the downline. Putting that aside, it would still seem that something was terribly wrong inside your wing from the start. I've noticed a lot of terrible wood used in mine, and I'm sure the same goes for all of ours. A total lack of gussets to spread the loads, also. Your tube idea looks like a great fix.

You mentioned wing#1 and wing #2. Do you have two wings, or is this meaning left and right??

Mine has been upside down quite a bit, including a couple outside loops, very large, low G, but definitely negative, with no noticeable looseness in the center section. Hope your fix works.

Went back and studied your pics, you do have two wing assys. I see the difference, now. I can definitely see where some strengthening could easily be done while the sheeting is off.
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Old 09-01-2011, 06:34 AM
  #461
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Default RE: ASM F-7F Tigercat

Hi David,

your photos are very interresting and will be very usefull !

One thing : don't you think that to use such powerful and heavy engines as Laser 150 can contribute to cause such damage (given the poor quality of the kit) ?

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Old 09-01-2011, 07:00 AM
  #462
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Default RE: ASM F-7F Tigercat

drob,
Thanks for letting us see what's inside the Tigercat wing. Again, it is the same old ARF story, the lack of glue, the lack of sufficient glue and the lack of epoxy in high stress areas.

Their butt joined plywood spar reinforced with the carbon fiber tube may be a workable design if glued properly, especially if accompanied by a fiberglass wrap around the wing center. Sparless foam wings coverered with sheet balsa or Obeche work well when reinforced at the wing joint with fiberglass. Even butt joined built up balsa sheeted wings with no spar joiner are usable if the center section is fiberglassed. That said, I'm a spar man, I like wing spars with a hefty dihedral brace.
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Old 09-01-2011, 07:20 AM
  #463
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Default RE: ASM F-7F Tigercat


Quote:
ORIGINAL: elojim

Hi David,

your photos are very interresting and will be very usefull !

One thing : don't you think that to use such powerful and heavy engines as Laser 150 can contribute to cause such damage (given the poor quality of the kit) ?

Unfortunately this latest incident confirms what none of us have been willing to readily admit. The quality of the ASM kit is very poor. When I bought mine I went for the cheap price and that's exactly what I got. The construction materials were poor quality, engineering flawed, and quality control nonexistent. While the finished product looks great (a testament to the original) and the flight characteristics good, none of that makes up for the poor quality.

Elojim, I believe you are correct to question putting more power in this flimsy airframe. Mine flew (past tense) very well on two .91 Magnum four strokes, just not very well on one.
That was pilot error. Besides more power on one engine only leads to thedeath spiral sooner. I suppose it is possible the strengthen this kit to make it exceptable but that just shouldn't the buyers responsibility. I will wait for a better quality manufacturer to produce the Tigercat before I try again.

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Old 09-01-2011, 02:31 PM
  #464
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Default RE: ASM F-7F Tigercat

Staggerwing, as I said in my first post, #1 went in on the second flight. Bring a gluten for punishment I immediately
purchased #2. #1 continues to be useful as you can see!

In answer to other posts, yes I readily agree that the extra weight of the Laser 150's could have contributed but then
I didn't anticipate that the wing structure to which they are attached would be so badly constructed. As to the extra
power, the Laser factory recommends a 150 when a 120 is called for. Why use them? I know they are very reliable.
They don't stop until told to is my experience, which is a useful trait where twins are concerned.

I have a theory that manufactures deliberately understate the required engine size(s) for their wares. The Australian
distributor for ASM products Model Engines (who incidentally, were involved to some extent in the development of
the Tiger), used OS 110 Alphas in their model. I feel the extra power allows the aircraft to be flown excitingly 'scale like'
and not boringly scale like as I do my Cessna 310, which now has the Laser 70's used originally in my Invader.

After my experience with the ASM A26 Invader (gone to dust) and my more recent experience with the Tiger Cat, I
doubt very much that I would even contemplate another ASM product. I agree, it really is a case of you get what you
pay for. It has been suggested to me by fellow club members that perhaps the ASM B17 or Lancaster might be my
next model.

NO THANKYOU!!!

If Tiger #2 meets an untimely demise (just don't think about it David) I would consider the PrecisionCutKits version
as a replacement. I would then know exactly what I am dealing with. The Tiger Cat is a beautiful aircraft. I put it up
with the Spitfire for looks.

David
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Old 09-01-2011, 02:34 PM
  #465
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Default RE: ASM F-7F Tigercat

Sorry Staggerflyer fo the Staggerwing thing.
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Old 09-01-2011, 04:14 PM
  #466
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Old 09-01-2011, 04:20 PM
  #467
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Default RE: ASM F-7F Tigercat


Quote:
ORIGINAL: drob

Staggerwing, as I said in my first post, #1 went in on the second flight. Bring a gluten for punishment I immediately
purchased #2. #1 continues to be useful as you can see!

In answer to other posts, yes I readily agree that the extra weight of the Laser 150's could have contributed but then
I didn't anticipate that the wing structure to which they are attached would be so badly constructed. As to the extra
power, the Laser factory recommends a 150 when a 120 is called for. Why use them? I know they are very reliable.
They don't stop until told to is my experience, which is a useful trait where twins are concerned.

I have a theory that manufactures deliberately understate the required engine size(s) for their wares. The Australian
distributor for ASM products Model Engines (who incidentally, were involved to some extent in the development of
the Tiger), used OS 110 Alphas in their model. I feel the extra power allows the aircraft to be flown excitingly 'scale like'
and not boringly scale like as I do my Cessna 310, which now has the Laser 70's used originally in my Invader.

After my experience with the ASM A26 Invader (gone to dust) and my more recent experience with the Tiger Cat, I
doubt very much that I would even contemplate another ASM product. I agree, it really is a case of you get what you
pay for. It has been suggested to me by fellow club members that perhaps the ASM B17 or Lancaster might be my
next model.

NO THANKYOU!!!

If Tiger #2 meets an untimely demise (just don't think about it David) I would consider the PrecisionCutKits version
as a replacement.
I would then know exactly what I am dealing with. The Tiger Cat is a beautiful aircraft. I put it up
with the Spitfire for looks.

David
Yes, I've been contemplating the same thing, going back to building my own. I get to choose the color scheme. Been looking at some Ziroli models, I really want a Twin Beech!! NOT CHEAP!! The Precision Cut Kits Tigercat does look nice.
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Old 09-01-2011, 10:50 PM
  #468
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Default RE: ASM F-7F Tigercat

Work In Progress
Thought I would let you see the repair prior to fixing the carbon fiber tube. I may not bother with the as yet
'empty' ribs. I would say that once the epoxy sets the wing will be substantially stronger than before.

Getting the tube in was a bit of a squeeze. Anything larger than the 16mm tube I used would be much more difficult.
Tip: If you intend to do the same, measure for the length of the tube at the bottom of the ribs, not the top.
I cut mine just over 2mm shorter to allow me to slip in the 2mm birch ply plates. I am using 2 of the end plates
at each end of the tube and one either side of the center rib. I should have fixed these before adding the fillets.

You will see some staining around the nacelle fillet caused by fuel seeping under the fillet. Something I will be
addressing before recovering.

As an aside, I was at one of the hobby shops I frequent this morning and was told that the Tiger Cat is currently
on special. Just over half what I paid for #2 at AUS$285. How does that make you feel Brad?
Seems Model Engines, the Australian Importer/Distributor is trying to clear their stock.

David
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Old 09-02-2011, 12:33 AM
  #469
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Default RE: ASM F-7F Tigercat

David

Looking at your wing it is clear the model was never intended for negative G loads, which is poor really. But for your repair i would have been tempted to cut a 1/8 slot between the ribs and current spar about 20cm either side of the middle, i would then make a pair of 1/8 birch ply dihedral braces and sandwhich when current spar between them (lots of epoxy here) i would then use epoxy to glue the ribs to the new spar (they should have been a tight fit) and then use 3/8 inch balsa triangle on all of the spar to center rib joints, resheet the wing and use at least 6'' wide glass bandage around the whole thing. The reason i would do it this way and not with the tube is because the loads from the outer wings are in the same line as the current spar, also the deeper the spar the stronger it will be.

In any case its clear the model is not designed for the power it has been fitted with, i did warn you when you ordered the engines although i expected flutter, not structural colapse!

Keep me posted on the fix

Jon

Also the ESM tigercat is a good one if you do require a new one at some stage!
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Old 09-02-2011, 03:59 AM
  #470
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Also i saw posts talking about the quality of ASM models overall and i must say that my eperience of them is poor. I bought a 2nd hand but never flown asm hercules, i flew it 3 times in total and it started falling apart. The covering wrinkled up, the abs fuzelage cracked all over the place and the harware began to wear. It was a shame because the model flew brilliantly. I sold it in the end as it was to much of a pain to carry about. Even ESM models have isses with poor quality wood and a lack ofglue,its a real shame the artf builders dont sort out these QC issues because they would sell far more kits
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Old 09-03-2011, 06:10 PM
  #471
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To my mind extra power does not necessarily equate to higher speeds. Is a model that cannot execute a smooth wide loop overpowered? Is a model that does not encourage big wide barrel rolls or half Cubans overpowered? I think not. Such was the case with my model with the 15x8x3 Master Airscrew props. I don't use the extra power to scream around the sky. Speed is so low on my list of priorities as to be non-existent. The ability to emulate the flight envelope of the aircraft upon which a model is based and to execute maneuvers with a smooth transition from one to the next is much more satisfying. That's what mean by exciting.

The take-off for that last flight was achieved with less than 3/4 throttle and with a purposely shallow climb out. Most of the flight was done with this throttle setting or less with near full throttle used on the upwards segment of the wide loops and half Cubans. I have just viewed again the video posted by Staggerflyer (Post 399/P16). Mine did not seem to be as fast as Staggerflyer's appeared to be flying but the authority in the maneuvers was comparable. The pulling power available with the ASP 2 blade 16x8 props over the 15x8x3 props was very evident. Three blades look terrific for a static display but in my experience cannot match the performance of 2 blades.

A point that seems to be overlooked here is that the carbon fiber tube in my model's wing, the same as those 3mm tubes used in the fuselage, did not do, rather was not capable of doing its job. It seems obvious to me that the designed purpose of the tube is to handle the down load on the wing center section. It is glued to the bottom of the outer ribs and the top of the center rib and to the intervening ribs where it touches. I'm no expert here but that set up would resist a down load on the wing. Negative G??

How much emphasis do I need to put on the fact that in my wing (and hopefully no others) what should been one carbon fiber tube was two. The left tube extends to around 30mm into the right wing. The tubes are joined at this point with a wire insert which itself is glued only to the continuing tube in the right wing. In effect the load that was intended to be taken by what should have been the one continuous tube relied upon the one spot of glue either side of the center rib. I have no doubt that no effort would have been made to prepare the surface of the carbon fiber to accept a positive adhesion given the poor quality of assembly in the airframe overall. It gave way leaving all the load to be taken by the lower half of the equally questionable quality 3-ply 'spar' which snapped downwards.

Some pertinent facts are called for here. Brad's model with OS 75 AX 2 strokes weighed 19.4 lbs. Rocketman's model with OS 120 AX 2-strokes weighs 18.7 lbs. Staggerflyer's model with its Rimfire 120 electrics and 4x 5000ma 4 cells weighs 21.25 lbs. Mine with Laser 150 4-strokes weighs 21.16 lbs. The total weight of my model at take off would of course be higher than that of Staggerflyer's model, but the weight would obviously reduce during the flight as fuel is consumed. Staggerflyer's flight envelope appears to match that of mine. Consider the following.

Laser 150 - 900 grams (31.7oz)
Full Dubro 16 fluid ounce tank - 430 gms (15 oz) approx
Total 1330 grams or 47 ounces

Rimfire 120 - 400 grams (14oz)
Two 5000ma 4 cell batteries - 1200 grams (42oz) approx
Total 1600 grams or 56 ounces

I believe my figures are close to correct here. The point is that Staggerflyer's model has more weight in the nacelles than mine with those BIG HEAVY Lasers.

The Tower Hobbies site states the power output of the OS 120's in Rocketman's Tiger to be 3.1 hp @ 9000 rpm I don't know the power output of the Laser 150 but I do know that the Laser web site clearly states 'Always use the LASER-150 if a 120 is called for'. I am guessing that Rocketman's OS 1.20 AX 2 strokes would be delivering more power than my Laser 150 4 strokes. The Lasers with higher torque, indicated by the bigger recommended props, would probably have more pull. The factory recommend props for Staggerflyer's Rimfire 120's is 16x6 to 17x6. Laser recommends 16x8 props for the 150. Staggerflyer uses 14x9x3 props. My model could not come close to Staggerflyer's model with the 15x8x3 props I was using. Go figure!

Was excess power the cause of wing failure on my model? I don't believe so. Was the inherent weakness of the faulty carbon fiber wing reinforcing in my model exacerbated by the weight of the Lasers? Possibly. Or was it just an accident waiting to happen.
Would we be having this discussion had my wing not failed? Probably not. We all would probably still be blissfully ignorant of the abysmal construction of the ASM Tiger Cat wing.

After my last post I had already decided to additionally add a reinforcing dihedral brace to the existing spar extending it to the first ribs out from the center rib. I will replace the fillets and add others where I can after this is installed.

Knowing what I now do, if, IF I were to be starting a new model I would first be stripping the crappy covering from the wings (and elsewhere), at least install a dihedral brace, fuel proof the exposed balsa (I am now using diluted PVA wood glue for this purpose) and recovering with good quality material. I will be using Oracover Corsair Blue. Power? I still like the big Lasers with their great throaty 4-stroke sound.. $285 for a new kit is tempting.

This is my solution to my problem. I am not dictating what others should do. It is your choice. It could well be that what I am doing is over kill but I know that I will be able to fly 'Steve Hinton style' with a reasonable degree of confidence as a result, something I am eagerly looking forward to. Have a great day guys.
David
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Old 09-03-2011, 08:01 PM
  #472
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Default RE: ASM F-7F Tigercat

drob, very interesting, and mostly correct dissertation.

I'm running 2x3 cells (6S) per motor, lebus1 is running 2x4 (8S). His E-Flite 110 motors are higher voltage than my Rimfires. However, the weight you list is pretty close.

As for the reason I can get the performance out of the 3 blade props that you don't is rpm v torque. Electrics turn slower rpms than fueled motors, but have GOBS of torque! Thus, we can turn bigger props at lower, more efficient rpms. According to my logs, my max rpms are 9921 for an instant, dropping to an average of 9100 rpms thru the full throttle run, which on the longest period of the log I checked, ( I keep them all) was exactly 10 seconds long, which would have been a full length high speed pass.

Glow motors turn much higher average rpms, especially 2 strokes, but have much lower torque than the electrics. 2 blade props don't cavitate at higher rpms, like 3 blades do. Thus, more performance. After rereading again, I think I see where your lack of power was... To big a prop. Drop one inch, to the 14 inchers, and I think you would have been there. Mine did not like the 15 inchers either. I did switch to 5 cells, which lowered rpm, because 6 cells caused to much amp draw. The performance was a very noticeable drop with the APC 15x13.5x3 props. (These are listed as a pattern type prop by APC.) Top speed was lower, vertical was terrible.

You are also correct about larger engines do not necessarily mean more speed, just more vertical capability. Some extra speed is a given, as the extra power helps overcome drag, but in straight and level, the difference is generally only a few mph. That's what throttle control is used for. Unfortunately, I find more and more of our newer pilots in my area are not being taught proper throttle control, thus we have more crashes of new planes, lately. Which is to bad.

Overall, I think you hit the nail right on the head as to the cause of your wing's failure. As well as the poor design details you list.
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Old 09-03-2011, 09:01 PM
  #473
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Default RE: ASM F-7F Tigercat

Me again.
Something that might be useful to you Brad and others. Page 5 of the instructions says where to position the Flap control horns, left and right. Seems they got it back to front. If you want to make use of the ply inserts to secure the horns, the RIGHT WING panel horn needs to be approx. 140mm from the root end and the LEFT WING horn 160mm from the root end. As you can see here, I followed directions (for once) and missed.

Staggerflyer, I have just noticed your response. My Laser 150 4strokes were turning around 8900rpm on the ground at max throttle with the 15x8x3 props. The 16x8x2 props give around 8500rpm. Both figures are within the 8000-9500 'useful' rev range for these motors. I think I will stay with the APC 16x8x2 props thanks.
David
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Old 09-04-2011, 01:46 AM
  #474
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Default RE: ASM F-7F Tigercat


Quote:
ORIGINAL: drob

Me again.
Something that might be useful to you Brad and others. Page 5 of the instructions says where to position the Flap control horns, left and right. Seems they got it back to front. If you want to make use of the ply inserts to secure the horns, the RIGHT WING panel horn needs to be approx. 140mm from the root end and the LEFT WING horn 160mm from the root end. As you can see here, I followed directions (for once) and missed.

David
Thank you for that drob and I too will seriously be looking at a dihedral brace as well as a glass wrap around the center join.

Cheers,

Brad
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Old 09-05-2011, 03:23 AM
  #475
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Default RE: ASM F-7F Tigercat

I agree totally that the poor construction/design is the real issue and not the power of the engines or your flying style.

Sure the higher weight adds to airframe loads but 20 odd lbs for a model of that size is not overweightby any great amountand should not be a problem for the airframe, my ESM La7 is 81 inch and 17lbs (others are flying upto 23lbs without issue) andif you are flying it ina scaleway, which you are, thenthere should never bethis problem. Indeed i have see asm hercules models looped and rolled and they didnt fall apart, i didnt do it with mine though!

Also regarding the HP of the laser 150 if you are using 16x8 apc props at 8400rpm then you are looking at about 2.2hp. Now that is useful hp atthat rpm and not max hp as quoted byOS. In any event you will probably be flying slower with the lasers due to lower revs compared to a two stroke, however you will have alot more power in climbs due to larger props and can keep speed down on downline maneouvers due to propeller braking, something two strokes are not as good at.

With the two 150's using the props/rpmsaboveyou should get approx:

27lbs static thrust
63mph max speed in level flight

If i can get rpm and prop info on the other engines used i can get the numbers and do some comparisons

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