RE: Advice on engine choice
 

Anybody using CF rods instead of 4-40 steel rods ? What diameter of CF rod is suitable ?

RE: Advice on engine choice
 

I am. I used the 1/8 rods, titanium ends on mine because I had some left over from a 35% project. If I had it to do over, I would use the Hangar 9 Titanium rods - about the same price or even cheaper, way easier to set up, likely stronger, and just as light.

RE: Advice on engine choice
 

For a 35%, 1/8" is mighty small, perhaps 5/32" or 3/16" ?

Can the titanium rods be joined to obtain "in-between" lengths ? Just concerned that it will be more difficult to get the exact lengths as they are supplied in fixed lengths. Also, I notice that there is a hex in the middle of the rod. What is that for ?

One concern with CF rods I have is that in the event I want to re-use the titanium ends, it will be kinda tough to remove JB weld ?

RE: Advice on engine choice
 

1. 1/8 is plenty strong for short lengths (less than 6 inches), the CF is <very> strong.

2. Titanium rods cant really be joined, but they do come in several lenghts. Just measure the distance and buy the appropriate length rod.

3. The "hex" in the middle of the H9 rods is thier beauty - they are reverse threaded on one side so you can adjust the length by turning them one direction or the other without removing the clevis from the surface. It makes setup a snap.

4. Its not a big deal to remove the ends from the CF, they arent very strong laterally and you can break off the CF rod from the length and clean off the glue fairly easily. Actually I was surprised how easy it was to chip off the CF and remove JB weld with a wire brush on a dremel.

RE: Advice on engine choice
 

I'm having problems with my engine leaning out in a hover. I was told an "oscilating pump" made by perry would help, if not solve the problem. My tank is in the original position, so it's not like the fuel has a long way to go. Does anyone have any suggestions/experience with perry pumps?

RE: Advice on engine choice
 

Try setting your high end richer by 300-400 rpm, and tune your engine at half tank or slightly below.

RE: Advice on engine choice
 

Ah, I forgot to mention that I tried that, and while it helped, it still looses power. Is it the variation in air/fuel volume in the tank that would cause it to tune differently at different fuel levels? It does seem to get progressively worse as the fuel runs out. In fact, it actually stalled/went dead stick, this afternoon. I assumed that the fuel starts to foam pretty badly at lower levels. This, in conjunction with the low RPMs I typically have it floating around on between hovering attempts.


Aside from that, I'm having a blast with this thing.

RE: Advice on engine choice
 

What type of engine and muffler setup do you have ?

RE: Advice on engine choice
 

The amount of fuel pressure you can get may decrease as the tank level goes down. A perry pump would definitely solve the problem and you'll end up with a bulletproof reliable engine.

RE: Advice on engine choice
 

O.S. 91 4-stroke, stock muffler. It now has a 15 x 4 APC, and it's running on 25% pro pattern cool power. I went down in diameter from a 16 x 4 to get faster spool up, and a little more rpms. It tached out at 9,300 with the 16 x 4 on 15% cool power 4-stroke formula. I used a buddy of mine's digi tach, so I can't wait to see what it's doing now. It is making a bit more thust, but not much.

Good to hear about the Perry. Last I checked they were in the neiborhood of $30. Very not bad...

RE: Advice on engine choice
 

Try running an APC 15 x 6 prop on your .91, I liked it best on that engine in the UCD. If your not running a pump of any kind your going to have issues with fuel delivery in the UCD because the tank is mounted so high in the nose in relation to the carb which is very low on a 4 stroke. You are probably setting it overly lean to compensate for the high tank siphoning fuel at low throttle while the plane is horizontal. Once the nose goes up then you are way lean and the motor gets hot and loses power.

A pump will help with this problem but I think a regulated fuel system is a better approach. I put a Cline on my plane and it solved ALL of my fuel delivery issues, also allowed me to place the tank back over the CG which makes a HUGE difference in the way the plane flies.

RE: Advice on engine choice
 

Thank you, and I may go with a 15 x 5, because I had been running a 14 x 7 when it was on the pattern ship. It was pretty fast, wich is something I don't want to happen with those huge control surfaces. Could you tell me more about the Cline system? What powers the pump, and how much weight did it add?

I've been reading about moving the tank over the C.G. I even downloaded the pics so I could do it later. I still need to add some down and right thrust. It is of course, an on-going project, wich is half the fun. Thanks for the help ;)

RE: Advice on engine choice
 

The Cline or Iron Bay regulator will work great. Here is the info you need:

http://www.billsroom.com/pcfs/

http://www.ironbaymodelcompany.com/

Good luck !

RE: Advice on engine choice
 

Thank you.

Fuel tank on CG
 

Hello!

For those who've put the fuel tank on the CG could you post a picture of how you fixed the tank in? I went thrugh this who thread yesterday (3 hours!) and could only find a coupla pics. I'm just finishing off my UCD and using a YS91FZ. I've cut out the ribs in the centre section and the tank fits in nicely but I'm not sure the best way of securing it. Maybe silicon sealant?

Andy

RE: Fuel tank on CG
 

Velcro, Fuel Tubing or Zip Ties should work really well. I assume you installed a pump?

RE: Fuel tank on CG
 

After reading about the Cline/Iron Bay regulator options, I'm still curious as to wich would help more. Wouldn't the Perry work best, as it pumps fuel to the engine? Or is it the regulator, wich means to me that I would re-adjust the mixture, and in theory, it would have the right pressure all the time? But what about when I throtle down a bit, will the lack of pressure leave the regulator starved for fuel?

RE: Fuel tank on CG
 

I ran a 7-year old Cline (not used for 5 years) in my UCD60 with Saito 100 all season and worked excellent till October. Very frustating when these darn things don't work! I removed it, readjusted the needles slightly, and I'm living with the static fuel-flooding problem. I dissassembled the Cline and found no apparent problem or debris, other than the diagphram is maybe stiff. Anyhow, my experience with the Perry pressure pumps was the engine(s) always loaded up a mid throttle settings. I had to keep the engine on the lean side at full throttle to correct the loading at midrange - not good. I did not try the Perry on the Saito 100. The Cline or Iron Bay regulator makes the engine run flawlessly (after proper low & hign needle adjustments) at all throttle settings ... until the thing fails.

RE: Fuel tank on CG
 

Throttling down with a regulator installed does not lead to an instantanious decrease in pressure. The pressure will decline over a period of time, but in my experience I've never seen it happen to the point that the engine stops. I heard someone mention a few years ago that he thought it would take at least 2-3 minutes of idle before the pressure decreased enough to make an engine die. I have a Cline regulator and i've seen my plane sit there idling on the tarmack for several minutes without skipping a beat. And I have the tank placed near CG.

As for the Pump vs regulator debate it's been going on for years. There are varying opinions, and I've admittedly never used a Perry pump. But from everything I've seen a read a regulator does a better job at delivering a consistant amount of fuel to the carb. They are not finicky to adjust like most pumps. They allow what is demanded by the engine and thats all. There is no adjustments on a regulator like there is a pump. But thats just my opnion. I'm sure there a lot of pther people that will prefer pumps.

RE: Fuel tank on CG
 

What were the symptoms of a failed cline? How did the engine act?

RE: Fuel tank on CG
 

The engine ran perfectly until one day on the first start it wouldn't start. Head pressure in the tank was good - I used the Fourmost check valve in the UCD. It seemed like I ran my electric starter forever and continued to check the tank pressure whenever I stopped crankin'. When I did get it started, after much fiddiling (removed cowl, fuel filter, replaced glow plug) it wouldn't accelerate past mid throttle. It was always too lean. I guess the Cline wasn't allowing enough fuel through it. I removed the Cline, readjusted needles and flew many uneventful 3D flights. I haven't replaced the Cline yet and probably won't. I wonder, can you buy the diaphragm? I fly the UCD46 with an inverted Surpass .70 (my winter flyer on skis) and deal with the flooding issue. Engine/plane combo works great for me....although the Saito 100 would really be awesome in the little UCD.

RE: engine choice
 

Im runing a apc 16x6 on my ys91ac works out great....

RE: Fuel tank on CG
 

Hi Andy,

Here is a picture of the tank in my UCD which also is using a YS 91FZ. I just used a support against the back of the tank (to prevent it from moving backward) and one over the front (to hold it in place). I think that these pieces of wood were included with the plane (to hold the tank in the "stock" location?). Anyway, this seems to work just fine.

By the way, you will *love* the plane with that engine!

RE: Fuel tank on CG
 

Cline sells new diaphragms for about $6 a piece. He will even tell you that these need to be replaced periodically to ensure proper operation of the unit, something like every couple of years if I remember correctly.

RE: Fuel tank on CG
 

Robert,

Thankyou! Just what i was after! I've taken heed of what was said earlier in the thread and wrapped the tank in the tape that came with my zagi (the reinforcing stuff) and used silicon sealant around the neck too. I agree with what you've done - front and back supports are the best way to go but mu throttle servo will go in front of the tank. I'm *so* looking forward to flying this - just need some decent weather. Much abliged sir!

Andy