Rocketman_

Hasn't it been established that 3-blade props are less efficient than 2-blade props on model airplane engines because the blades follow too closely in the wake of the one preceding it at high RPM?

Staggerflyer

I'm not going to say no, due to the fact I haven't read about it. On the smaller diameter props on high rpm engines, definitely a possibility. But 4 strokes turn lower rpms, and electrics can be slowed down by lowering voltage, while still having lots of torque to turn bigger props. Ck the kv rating of your motor choice, that gives the rpm per volt (unloaded) of the motor as wound. APC's 15x13.75x3 is listed as a pattern prop, while the 15.75x13x3 is just listed as a 3 blade.

I pulled my logs on the Tigercat flights, and they claim I turned a max of around 9500rpm. Interested in what's going to show when I get the APCs and 16" MAS props cut down.

Rocketman_

Whew! Those OS 4-stroke engines costs piles of money and you'll need two of them. Expect to pay more soon. I went to my local hobby shop today to pick up more "stuff" for my Tigercat and had a conversation with the owner who was busy updating his website. He was marking up his prices after a recent price increase on engines from Japan. He said there hasn't been a price increase in quite a while but he thinks that quantities are limited now. His prices are generally the same as Tower Hobbies on all items.

That O.S. 110FS-a w/Pump costs a big $479.97. The powerful supercharged Y.S. 115 FZS costs "only" $429.95.

Staggerflyer

We fixed the torn up petromat runway at our club field Wednesday evening. Had enough people present it only took a little over an hour. Then it was flying time. Got one more in on the Tigercat. Take off was just about half the runway, which is about 120' long, using half throttle. I didn't throttle up till after about 10-15 of roll. The roll was straight ahead, even though we had a quartering crosswind at about 10mph. Did a few high speed passes, it didn't look as fast as I thought it would. Since I was the only one up at the time, couldn't compare it with anything. Have to remember, this is a big plane, it has to be going really fast to look fast. Hope to get the bigger props cut down this weekend, as it's supposed to rain all weekend.

I did get to try out full flaps, once I read the manual on how to adjust the mix on my new Spectrum 8ch. Have 10% and 22% down elev mixed in, with a 3 sec actuation time, no ballooning at all. Landing was noticeably slower, rollout on the petromat was maybe 50ft. I did do a small bounce, just a few inches, because I got it to slow before touchdown, but it never dropped a wing. The crosswind did not bother it at all, either. I'm liking this plane more and more all the time.

picked up a new radio on/off switch from MPI-Maxx with the built in charge jack and led battery indicator. But found I have to dissassemble and remove the cockpit floor to get to the original one. Bummer, this could take awhile.

Staggerflyer

OK, for you guys interested in some scale details, found this pic posted on one of the MSFlightsim forums I belong to. Great photo pass showing the top of the wing and fuse, pics that have been hard to come by. You can see how the air scoops/intakes are supposed to be, (the two in the kit are for the OUTER ones, out side the nacelles,) and where and how the two duct outlets should be in flight. Notice the exhaust stains, also.

Brad330l

My Feedback: (1)

Cool mate, that is exactly what I have and yes on some passes I see a door hanging a bit I just get some height and go inverted and push a little to get some neg 'G' happening and it is closed for the rest of the flight. One thing for the door set up is have the model right way up to make adjustments. I did all mine at initial set up on its back and was all pleased with myself but when I turned it over and checked they hung down a bit from the slop in my actuator rods so I had to spend time adjusting it all. Now they are nice and tight. Still spins me out when one hangs a bit as my retracts lock up just fine. Like you said,, must be the air flow.
That is cool about the nose door too. If I break mine I will see how it goes.

Cheers,

Brad

Staggerflyer

Yes, I did an inverted half loop, and noticed that one set of doors were closed for the rest of the flight. The warped set still won't stay closed. I did do the adjustments from right side up, as I noticed the same thing you did when I would turn it over and try them.

I replaced the broken off tabs on the nose door, but I shortened them a little to get more glueing surface, and to see if I could get the door to close more closely. I had drilled my hinge pin hole slightly out of position, and the door wouldn't close completely. Didn't want to bend wire, yet. Found that with shorter tabs create a problem, they restrict strut compression movement. Since you cannot see the door not being closed tightly in the air, I'm going to trim the wire to allow it to be quickly disconnected for flight, but connected for display/storage, since when showing off the retract sequencing, just leaving the door hang doesn't look good. [&:] My system looks neat during retraction, as it just turned out that while all three start going up at the same time, they go into the wells one at a time. Coming down is just the opposite. Both mains open the doors, then fall just out into the airstream, then the nose opens 3/4, the mains lock, then the nose locks. Does it in the same sequence each time. No, I don't have any restrictors in the lines, I just have the newer Robart valve block with the adjustable bleeders. And two air tanks for more sequences and higher residual pressure for the first couple sequences. I don't have any major leaks, yet. They will hold pressure over night. Have tried the overnight test in both up and down conditions. I pump them up to 100lbs psi each time.

Supposed to be a very windy week this coming week, so I'm busy trying to get the rest of my fleet ready for the season. All of them have something major I want/need to do, so I'm busy. Luckily work has slowed down for a short while so I have some time. Have one done (BH .90 size P-40,) and am working on building new motor mount for the GP P-6E Hawk now. The stainless steel one I originally used, (can't remember brand right now,) bends to easily on nose-overs, which this plane does constantly, every time it catches a large tuft of grass or rough bump. That is it's only bad trait. Going with either a HobbyKing aluminum or may end up making the wooden stand-offs like I did on the Tigercat. This plane has an E-Flite power 110 for motor, and it sets 3 3/4 inches out from the firewall. That's a lot of weight and distance. I'll figure it out.

Rocketman_

Pneumatic retracts. Never trusted them. I don't believe that I've ever been to an event where someones air retracts didn't malfunction. Well, I'm stuck with them now.

My retracts are installed and all lines and fittings are connected (I substituted some Robart parts) and they actually work fine on the bench. Well, they worked fine for 3 or 4 cycles until one of the plastic Robart quick disconnects popped loose and emptied all the air out of the system. I prefer the threaded Chinese disconnects shown in picture #1. I have considered that I may not have snapped the Robart disconnect properly but it still left me with an uneasy feeling. I used Robart disconnects in the nacelles to facilitate easy removal for maintenance.

After reconnecting the quick disconnect I re-pressurized the system to 100psi and continued cycling the gear. The pressure dropped by 10psi for each up/down cycle. There was no measurable loss of pressure when the retracts were left alone for 5 hours.

Picture #2 shows the two air pumps that I used. I'm a retired man enjoying the easy life and I just found that skinny Robart hand pump to be too much manual labor so I went out looking for "easy". I found it at a local Harbor Freight store in the form of a little $7.99 12 volt air pump. It will pump the retract air tank from 0 to 100 psi in 19 seconds using my field box battery, picture #3.

There must be a substantial mark up on prices for retracts from China. There is obviously a profit being made when a retract system complete with struts and aluminum wheels continues to be sold for $169.00. It has to be a really sweet deal for those who are selling Chinese retracts between $300 and $400. Pictures 5 and 6 show just two examples of a number of retracts available from China.

angel18

Yeah I like it your post....Thanks for informations.

elojim

You should go to e-retract.com !

Rocketman_

Thanks Elojim, I have seen the Lado retracts.

Brad330l

My Feedback: (1)

Well I got two more flights in today (34 and 35) but only after TWO engines that just would not start.[:@]
Works out that my sub trims on the throttles were way out and way low so the engines were not getting anything. I played with the flaps last week after that episode where I wiped the models memory and must have adjusted the settings for the throttles.
Man I was angry and happy all at once for 1 doing it in the first place and 2 for nutting it out[:@][:'(]
Any way I was trying 12x9 two blade props so had to retune the engines and works out I went a bit lean on the left. In a hurry to get a couple of late afternoon flights in I continued the flight noting that my usual nice exhaust streams were not present. During the first flight I did a pass at about 3/4 throttle and it (the left as it works out) was surging a bit so I worked the throttle a bit in the hope of clearing it up, climbing out and away I heard it wind down till there was only one exhaust note and it initiated its own left turn. It turned way over 90 degrees in an instant and headed down so off came the power on the live one and I headed for home in a glide with gear down and full flap in the decent as I knew I was high and scooted past myself to a beaut cross wind landing finishing up about 150 meters away from where I was standing.

Flight two was 5 clicks richer and no problems except that the 12x9 props didnt have the performance I thought they would. 13x8 two and three blades are the best so far for this ship.
Also I did a pretty tight right level turn during flight two and the fuselage cover from the top of the wing departed company. ( Hmmmm, fuselage twist or warp or something???) It was all ok when retrieved and the landing was uneventful. Another 10 minutes that went oh too quick.

So that is two more chalked up and # two engine failure. (again,, my fault)

Cheers,

Brad

Staggerflyer

Wow, that's great, Brad. Glad to hear everythings ok.

I got two more flights in last Tuesday, the 12th. Found that with almost no wind, the elevator becomes extremely sensetive just at flare point. I think I touched the tail on second landing. Need to set on position on dual rates at less elevator and remove all expo on that setting.

I was also able to try out the 15x13.75x3 APC props on 5 cells. Did not seem as snappy, and was definitely slower. Log readouts showed I was still pulling a lot of amps, also, but within burst specs.

Had to redo strut mount tightening on mains. I had forgotten to locktite one of them. Also found out that when the air cools down alot, like almost 20 degrees F from when you pump up the retracts, there is not enough pressure to get the nose gear to lock. No damage, and at least with electric, the props are not continueing to tear up the ground.

Don

Rocketman_

Interesting prop data. It seems certain that both of you are close to determining the optimum prop for your respective power plants.
My Tigercat was up on its wheels recently (on the bench) and I had 1.5 inch clearance with a 16 inch prop. That's a little too close so I'm going to try 14 inch 3-blade props to begin with but its good to know that I can increase the diameter a little if it becomes necessary.

Its good to hear that your Tigers were unscathed after an engine out and a nose gear collapse. I read a post in the ESM Tigercat thread where someone had a nose gear collapse and the props never touched the ground. I guess it pays to have tall landing gear.

Staggerflyer

Rocketman, I don't think the 14 inchers would have touched, but I had the 15 inchers on. Also, I think the APC 15 inch 3 blades are designed for more RPM, as hey are listed as a pattern prop. The blades are fairly narrow, not wide like the E series, nor are they the same shape as the 15.75 3 bladers. The 15.75 has much more blade area, and are a totally different shape. I'm going to cut them down to 15 in for first test, then 14.5 if they are to close. My .90 size Black Horse Models P-40 is powered with a Scorpion 4025-12 440kv motor on 5 cells, and it turns the 15.75x13x3 with authority. I wanted to use that motor in the F7F, but they were on a long backorder. If that doesn't work, hopefully the MAS 16x10x3 cut down to 15, or 14.5, or even 14 to get the performance I know is there. Heck, the 14x9s pull it great, it just looks slow. Need to get a radar reading on it.

Brad330l

My Feedback: (1)

Well I suppose if you fly a twin engine aeroplane you have to expect the odd engine failure,,, but not two in two flights![&o]
Yes it did happen (and rather slowly) I had an engine quit on me right after rotation and yes I tell the truth I did hear it sag just before that point. I elected to continue as I have experienced this a few times before and the engine has cleared nicely and away I have been. This time it ( the left engine) quit at 10 feet and I was climbing away slowly to the East and turning ever so slightly to the left. I got to about 30 feet and got the gear tucked away still on full throttle and then I must have got too slow as I gracefully winged over and headed for the hard stuff. Full right aileron and throttles closed had it go in nose down and left wing down. It didn't even get to cart wheel,,,, it just crumpled and bounced and sat. You know I held it nice and straight with rudder during the take off roll (I pride myself with a nice straight take off and strive to make it happen every time) but I know I didnt hold any right rudder during the 'flight'. All I could think of was to keep the nose down, wings level and when I thought I had it,, get the gear up and start turning right. NOW I know I should have made sure I was at least turning a little bit right the whole time but it didnt happen. When I had my first engine out at height I noticed on downwind in the circuit that I had to fly good engine wing low to maintain some assemblence of control and I had dialled in a heap of rudder trim.
OH well, I think it is repairable. It did go in hard and the fuselage is snapped clean in two but I think it will fly again. I will soon break it down to single components and fix each of them. Just hope my engines are ok. I will thoroughly clean and inspect them before I attempt to turn them over. They look fine though and went in on idle. I did break a prop.

So Does this make me a twin pilot now or just a dumb bunny? I have learnt some thing but also crashed my model.
I feel ok, I'm not in this great hobby to get all sad and messy.
I will set it aside for a few weeks though as my Spitfire is almost ready to go so will be test flying that for a while.

Cheers,

Brad

Staggerflyer

Brad, That's just sickening to see. Doesn't look super bad, but still.

Did you dissassemble the nacelles from the wing, or did the crash? I hope it flies again. I think you learned that if there is still some runway under it, shut it down as soon as it sags, no? Otherwise setup for a belly landing immediately.
Now you know why I've gone 100% electric!!!

Still to windy to fly here in central US. Have 4 flights total on mine, won't get another for at least 2-3 weeks according to long range forcast. Wind has been 20+ form all points of the compass for almost a month, except the one day last month when I got to fly. Supposed to continue for 2-3 weeks more. We even had snow last week!!

Don

Rocketman_

Ugh!! Man! Brad, that's a horrific sight. I'm so sorry to see you lose your Tigercat. I was expecting to continue reading your accounts of your experiences with it for a long time. Crap, that's discouraging and just reinforces my apprehension about flying mine. My Tigercat should have been completed before now but maybe I was just dragging my feet.
Yesterday, I was wondering if I would buy another one if it suffered the "engine-out-death" so I checked the Hobby People web site and found that the ASM F7F has disappeared. They still have the retracts though.
I just got home a few minutes ago and decided to checked this thread before I go out to the yard to start my engines for the first time. Now I'm not so enthused.

Brad330l

My Feedback: (1)

Hi guys, yes as you see it in the back of the ute (recovery vehicle) is how four of us picked it up and brought it home to the pits.
Unfortunately Don I didnt end up having too much runway left after rotation as we were set up to fly east and were taking off at the edge of out field. Yes I do agree though I should have cut it there and gone into the weeds and small (burnt out) shrubs. This would have resulted in a damaged UC and covering and possibly a break or two only. Ah,,,, hindsight.
It was such a beaut afternoon, not like your howling winds. Hope you get some fair weather soon.
Rocketman do not dispair my friend. All is not lost and you shall read more of my Tiger flying,,,, just might be a while though.
There are spare kits over here still available but with postage reach the $600 mark so I will rebuild.
Now stay enthused and and learn from my mistake, I did not follow my own run up procedure and didnt get it on the ground quick enough after it happened thinking I had it under control and ended up paying the price. I have had such a great run with this model and the engines that I got a bit too comfortable.
If you dont run it up and just go do it you will never know how good it is to fly.
I'll post the repairs, the first bits being the fuselage. If that can be fixed the rest will be easy.

Cheers,

Brad

Staggerflyer

Brad, chin up, Mate. At least you've got a good winter project, now, no? Engine out on take-off is the biggest fear of all twin engine pilots, real and R/C. I'm sure she'll fly again. I think that is one advantage of the design. It's easily fixable, just takes some techniques we're not used to using. That Spitfire should keep you happy till flying season ends down there. Do you have a build thread on it?

On a side note about the F7F, I found another thing to watch out for. On one of my main gear mounts/rails in the front of the nacelle, I found the plywood split/separated. The glue joint was still good, but it was only on one side of the plywood! The side you could see! The side where the fuel tank mounts on yours, there was no glue. So just the one side of the plywood was taking all the fore/aft load. And the sheeting separated. Some thin CA glued it back in place, then I removed the nacelle and dribbled glue in the front side, also. Did it on the other one, also. Just a heads up to everyone.

Good luck on the maiden of that Spitfire, Brad. [sm=shades_smile.gif]

Brad330l

My Feedback: (1)

Yeah mate I will just take my time and hopefully make it as new as I can with out too much weight added.
The gear rails I think I did a long time ago when the nose rails let go and were able to slide back and forwards in their mounting formers. (a few pages back now) and I had a flap servo tray come loose as well. I actually think in the crash the glue letting go in some places has saved the airframe from more major damage. Not a bad idea.

Yes onto the Spitfire now. Here is my build thread.
http://www.rcuniverse.com/forum/m_7644110/tm.htm

After I fly it I will fix the Cat and put my ESM BF109 together.

Cheers,

Brad

Lebus1

I've been reading this thread for some time but now I need to post some questions. This is mostly for Staggerflyer as he has setup his F7F the way I wish to. Could you post more pictures of your battery mounting and how is that working out for you? I am planning to use the E-flite 110 motors with four 4s/5000mAH batteries (same setup as Bluenose P-51 so I can use the same batteries). Do you think that this will be too heavy? I also wish to use the E-flite 120 size electric retracts with a nose retract using 102 degree extension. What is your opinon on that? I am not able to find oleos to fit the wire yet (5mm mains 4mm nose). I see that HobbyPeople and the US distributer has dropped the F7F. I hope we don't have an orphan. I may need parts. If you wish you can PM me at [email protected].

Staggerflyer

Lebus1,

Hi, welcome. Go here to see more pics of mine as I built it. http://public.fotki.com/modelrdh/rad...-f7f-tigercat/

The E-Flite 110 is an excellent motor, I have one in my Great Planes P-6E Hawk swinging a Mejslek (spelling?) 18x10x3 prop on 8s (4sx2) 5000mah batteries.

Don't know about the E-Flite retracts, as I didn't know they were out, yet. Last I checked they were still developing the 25 size. As for struts, I really don't know, sorry. All my add-on ones are Robarts.

Yes, at present it seems this plane is an orphan, for now. If Hobbypeople ever had major parts available anyway, I missed it.

As for extra weight, I don't think this plane will notice what your planned system would weigh.

Lebus1

Thanks for the info Staggerflyer. Did you glue the battery boxes to the formers in the nacells?

Staggerflyer

Yes, they are glued to the formers that they set against, as well as the firewall. The outer pieces are made after the boxes are in place, as they are just for mutual support.

It is best to split the batteries like I did for balance and so the firewall is not overly weakened.

After you cut the firewall, go thru the holes and glue every joint you can see and reach, as that is the biggest problem with this model, the factory joints are only glued on one side, if at all, and the loads cause the plywood to split/separate it's sheeting. Other than that, it's pretty straight forward. Oh, and make sure you make the full length doublers for the main fuse as Silver.kiwi suggested. Doing it as you build is easier than after. Mine are 24" long, from the rear bulkhead holding the nose gear rails to just in front of the rear wing mounting.

My setup required zero balance weight when 6S are in each nacelle. With 5S it could use a touch in the nose, as it is sensitive to pitch at low speed. For your setup, the 110 motor is slightly heavier than the Rimfire 120, I think, plus you will be having 2 more cells in each nacelle. Yours might come out just a touch nose heavy, but I think that will actually be better. I'm thinking of adding a couple ounces just to tame down the pitch sensitivity on landing.

Good luck, and post picks.

Don