kochj

I may add a allum. shroud that goes over the engine heads (like the Piper cub)
and paint it red.... so when viewing from the side, you can't see the engine sticking out....

???????????????????????????????
Good Idea or bad????

hpergm

Dear Kochj,

If you got'em....flaunt'em!!

kochj

LOL.....

Had a 1.4 32 spark plug fall apart!..... weld failed? anyhow.... a had to use glow plugs.. instead//

Funny thing is... I had to INCREASE the VOLTS to like 3.2 to get them to glow bright orange!....
No WONDER WHY I had such a pain in the arse it was, to get enough juice to power the five glow plugs on my radial..!!!!
It Needs more amps AND volts, to get it to burn bright and start....
I was using my VOLT out on my associated charger, to run both glow drivers... so the Numbers were exact....

kochj

Going to try to get this bird flying today.
5mh winds....and sunny...
I am running to large of prop right now, and transition is still bluberry rich .... even with carb set correct (old airbleed style)....
This was with the gas tank inline with the carb (had to drop it lower than stock no issues though)

I think it balances spot on with the NEW balance point.

rafeeki

My Feedback: (11)

Flaunt it and be proud

rafeeki

My Feedback: (11)

Erric, are u using a glow engine in yours? I am using a Saito F 180 4 stroke in mine. Tried to get the engine strated than it dawned on me that the fuel tank was way too high relative to the carb.... flooding the engine and making it impossible to start the normal way.
Did u run into this problem? If yes how did u get around it? Do I have to butcher the tank location to lower it? I need to lower it by approx 1 1/2".

OR

Could I run the fuel line from tank to the carb in a raised loop that goes above the top of the tank to prevent it from feeding by gravity?

Any help would be appreciated.

Rafeek

rafeeki

My Feedback: (11)

Dale did u decide to go with a glo engine? I did and found after all was completed the fuel tank was too high.... Do u have any suggestions other than butchering the holding formers to lwer it??

Thanks

Any help would be appreciated

Rafeek

hpergm

Dear Rafeek,

If your engine is mounted with some sort of stand-offs (or a long beam mount), then you can simply loop the fuel line on one of the mounting beams - see pic. This stops any gravity-induced flow from the high tank to the low carb.
Note: This will for sure work with gas/walbro-type of carbs (i.e. pumped). For glow, you would need to test...

rafeeki

My Feedback: (11)

I suspect that once it starts drawing fuel it will continue to drain even if I shut the engine down, that is how siphoning works. However that would be the easiest test before I butcher the interior to lower the tank..
I am not planning to get into gas at this point as my whole hangar consists of OS glow engines
Thanks for your input

rafeeki

My Feedback: (11)

Kochj,
I have been having a problem with my 1.8 cu in Saito 4 stroke (glo) in my Moth. Turns out I inadvertantly didnt pay any attention to the position of the fuel tank relative to the carb.... it was over 1 1/2" higher than it should be. So the engine is giving me fits and wont start as it is flooding. Now I am working on lowering it but would require major re-work...
However your dilema with your Gemini is similar to what I tried to avoid in my H9 1/4 Cub with the Gemini engine. Had to lower the tank.... to prevent flooding and siphoning of fuel even after it shuts down.

I thought I would point this out as it doesnt seem from the pics I saw that you have modified the position of the tank...
Best

Rafeek

rafeeki

My Feedback: (11)

In case u havent realized there are more than 1 link to Tiger moth, this is the other.

abelard

I'll have you know we observe the Hydrostatic Paradox on this forum.

rafeeki

My Feedback: (11)

This is addressed to anyone who would like to chime in pl feel free to do so.
Today I took out my Moth for a maiden flt which I had to abort as the wind picked up.
I realized that the included wing jig intended for transporting the wings leaves a lot to be desired as it slips off the already slick covering.....

If you have any tips on improving it pl. share it with the rest of us as the gears in my head are already overheating...
Thanks

Rafeek

foundryratjim

My Feedback: (93)

Look at post #141

hpergm

It's all in the small print: if the friction of the longer/looped line is overcomes the hydrostatic difference (potential energy) plus there is a diaphragm valve in the way in a Walbro carb, the loop helps.

rafeeki

My Feedback: (11)

Once it dawned on me that the upper jig support was at the wrong incidence angle I modified it to match the wing as assembled. It is now glued in the correct position, will add screws later.
- With that done I can now slip the jig into place with the wing still attached to the fuselage.
- Added some thin shock cords instead of the original rubber bands.
- Pulled the wing assembly out.
- Inserted a vertical piece of a "Lowes" yard stick with small block spacers pressing against the jig to prevent it from slipping out of place. I also slid a wire push rod throught the tab holes to keep it in place.
- Needless to say I also added the wire cross rigging at the wing struts which are not in the picture and were pointed out in post #141.

The pictures are self explanatory but your comments would just make it better.

Rafeek

RCPilotSteven

Can you please show me the photos of your muffler and engine install for OS GT22?
Thanks
Moe

Planejaw

My Feedback: (53)

I don't have any photos close by of the installation of the GT-22 without the cowl on, but here's a photo of the left side of the airplane. You can see just to the left of the "59 on the cowl, I had to cut a rectangular(ish) opening to clear the cowl. Not very obtrusive. I also added a silicone exhause extension to clear the bottom of the cowl. The combination seems to work quite well.

rafeeki

My Feedback: (11)

Beautiful. I see u now have a militery version instead of the trainer.
Is that a Xoar prop?

kochj

I haven't seen anyone on here in a while.....
Just a update....
I found out why my engine wasn't running very well....on transition.... The IGNITION MODULE is bad!!....
It is an OLD C&H ignition and they had a few bad parts, that went in (back in the 80's) and were fixed.....
I am going to send it in. and see what can be done... The OS 1.60 twin would idle all day but transition was blubbery....and now I know why...
LOL....
I haven't flown it in a long time..... I am tempted to place the Saito fg36 that I have...(weight is good on this plane) but not sure yet...
I have a super chipmunk , staggerwing, or a Waco that the twin could go into... I would like it in the chipmunk, but I really don't want to have to move things around...
The good thing is that the os twin was ALREADY in the chipmunk..... Just have to do some painting on the chipmunk and good to go.

kochj

The NGH GF-38 4 Stroke Gas Engine would work great in this plane as well...
Cheap and reliable...

rafeeki

My Feedback: (11)

Thought I would share some of my findings with you and others.

The Saito FA-180 (inverted) is now tamed with the help of a perry pump. I am flying at %50 or less with an APC 18x6, nor daring to go much higher I suspect resonance may cause some issues.

Now with the 11 oz of ballast attached + cowl, the engine shimed for some downthrust and the front of stab shimmed up by 1/8" it flies well up to 40% throttle. If I increase throttle it will climb. So I keep it at the 40% setting. Landings are tricky as it is floating in I have to add down trim.

Found out the cross braces under the dummy tank pulled out of place and two of the end eyelets broke off. Have to revise that setup.

One other thing I did was replaced the lower member of the landing gear with a J-3 Cub "O" ring held strut that I had lying around from a Robart set. Some other beefing up of the front from inside the box and now I have a working landing gear that is working really well, less bounce on landing.

hpergm

Some findings from my side, to complement Rafeek's above.

Anticipating the zooming behavior, I took care to set about 2.5-3.0 degrees of Down on the new firewall (OS GF40, had to move the original back about ~1 inch).

Also, and because this is a slow biplane, I fitted a MAS 20x6 to the GF40; the big prop disk means I can adjust the thrust and not so much the speed.

The combined effect is a plane which is very close to neutral trim at most speeds, using the stock decalage. I trim at about 40% throttle as well, but find I need no downtrim all the way @ full throttle. I still need to hold a bit of up in idle/approach. If I gun it on takeoff without holding up until some speed is reached, it will bite the dust (effect of increased downthrust + LG position close to the CG).

Turns need a bit of rudder to look good, although I have dialled in a lot of Ail Diff (ailerons hardly go down, most movement is up).

The GF40 will hover the plane (which weighs 7,150gr empty) but I found it to get extremely hot; I cannot touch the spinner at the end of a flight! It has also flamed out on me on a couple of occasions during summer.

For this reason I have improved the cooling flow inside the cowl, by putting up a close-fitting baffle around the engine fins and also louvres on the bottom of the cowl to create some suction under speed. I also found that the rear-mounted carb of the engine sits rather high in the engine compartment, at a place where there is no air circulation. As the flight progresses, the temperature in the breathing plenum around the carb throat gets very hot, and the engine tends to flame out near the end of the flight. For this reason, I beat-up some vents out of lithoplate, to allow fresh air circulation in that part of the cowl as well. Time will tell.


Finally, I too have faced the broken eyelets - these are just electrical wire eyelets, you can buy better quality ones from a hardware store (1$ for 100?) and fix the problem. Another story is the fliyng wires which tend to break at the pass-through in the brass mounts - obviously out of vibration/abrasion. One trick there is to fit a thin heat-shrink to protect the wire a bit more at that place.

rafeeki

My Feedback: (11)

Wow now that is what I call input.
I have few random questions to make sure I understand u better.
1. While measuring the thrust angle what was your reference datum?
2. U did not prop up the stabilizer?
3. The cross braces broke and pulled out of place on mine probably due to a lateral movement of the wing support structure. I was thinking of revising the anchoring ends back to the bottom of the verticals. Not sure yet.
4. Flying wires are a pain in the neck. They loosen after each day of flying. Thought of attaching springs at ends instead of clevises.
5. The red rods helping to keep the flying wires in place create a lot of drag... I was thinking of eliminating them and use a zip tie to keep the one set of wires together.

Again thanks for your and any input.
Enjoy your blue skies
Rafeek

hpergm

Refeek - to answer:

1. Datum is the stab @ horizontal. Stock angle - as set per factory. So, if stab is @ 0.0deg then the engine sits @ between -2.5 to -3.0. Now, remember the decalage is quite "agressive" on this plane, at least it seems so. Actually the plane is a trainer and is designed to fly at a nose-down attitude so that the student's vision is not blocked by the engine cowling. So, in the air, the engine will be sitting @ -5 degrees down or more (undercambered wings will fly @ -2 to 0 degrees).

2. No, not needed. At least at the speeds I fly it!

3. I find that the metal strips holding the top tank are quite sturdy. I still think its vibration. If it were stress, the wood where the cross braces are bolted on (front turledeck = just balsa!) would tear out first...

4. If you want to dump some cash into the bird, go for the Proctor turnbuckles...:
http://www.proctor-enterprises.com/p...rnbuckles1.htm

5. Drag is the name of the game with this bipe - it begs to fly slow. That's why it also has the undecambered airfoils... Try as a low pitch/high diameter prop as possible to keep thrust up but speed (scaled to the square for drag) low! The only bummer with these rods is to figure out how to install them (also after a cut wire...!).



BR,
Hector.