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Venus II

Old 08-21-2013, 01:16 AM
  #1776  
cmoulder
 
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IMHO the first step toward sorting out any of these issues is to move the fuel tank to the CG, or as near as possible given the present problem. The CG changes - annoyingly! - every flight as fuel empties. Mine flew much better and the constant elevator trim adjustments were eliminated, although unfortunately it died in a mid-air shortly after my refurbishment project, detailed somewhere earlier in this thread.
Old 08-21-2013, 03:56 PM
  #1777  
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I agree having the tank on the CG is preferable, but it requires a major rebuild of the airplane. It is not that difficult to move it back a bit into the next bay rearward but it will still not be on the CG, and will require a pump. My Focus Sport was easy to set up with the tank on the CG but this one is a major effort. I even looked at putting the tank in the canopy. I'm not looking for the best-trimmed plane, but rather the best I can do within the constraint of sticking with the current tank location. I know it is not ideal but...
Old 08-21-2013, 05:37 PM
  #1778  
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anyone know if there are any Venus II around for sale? I know Tower no longer makes them.
Old 08-21-2013, 09:27 PM
  #1779  
Jetdesign
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Tank on CG is not a major rebuild at all. There are lots of postings in this thread. Yes, it needs either a pump or a YS, but that and a little ply and you're on your way. I played around with both of those options, but I was new and impatient and didn't get very far. Once I started flying pattern I quickly came to dislike the change in balance. Lots of guys have no problem with it, and probably get into a rhythm of when to compensate with a click of elevator here and there.

I have to go back and see what 'issues' you're talking about though I remember adding positive wing incidence to my plane, and I believe a little change in engine thrust as well. I don't remember all the details other than knowing there was a washer under the engine mount, and a Popsicle stick under the wing saddle.

I have another Venus I will be converting to electric. Should be my next airplane project over the winter. I am going to research a little - want to make the canopy hatch very nice and clean, and am considering at least a little recovering, if not major. It will be fun putting this plane together knowing what I know now
Old 08-22-2013, 04:37 AM
  #1780  
cmoulder
 
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Agree, relocating the tank is a relatively simple project. See posts #1162 and 1166.

I was using an OS 1.20 4C with a Perry Oscillating pump and it ran better than ever with no in-flight leaning. I remember having such a problem on outside looping segments.

Having the tank on CG also makes problems (leaks, tank clunk/plumbing) easier to spot and provides much easier access for repair.

Last edited by cmoulder; 08-22-2013 at 04:41 AM.
Old 08-22-2013, 03:42 PM
  #1781  
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Thanks, Joe and Bob. I went back and looked at those posts and see how to do it. I do have a pump (the previous owner had one mounted to the firewall but it was not connected) and I have plenty of ply available. I'm sure I don't really notice the change in trim during an 8 minute flight, unless the cg is back of the most rear range! What I find confusing is that, when I tried moving the CG back (finally to 3/4" back from the mid point) I saw no change in the elevator deflection needed to trim to level flight at 3/4 throttle. Yes, I refilled the tank before each test. The stability changed but the elevator position did not. I went back to the design CG and tried shimming the rear of the wing. I even took a Popsicle stick! (5/64") A 1/16 shim made a noticeable improvement in the trim, so I tried the Popsicle stick and the 1/16" shim for a total of 9/64" which got the elevator to almost the neutral position. It seems that 5/32" is needed. This seems a lot. I'll borrow a friend's incidence gauge and see what the angles are. BTW, I did the inverted 45 degree test for CG and noted that, as I increased the shim size, the indication was more nose heavy. I'd appreciate your comments on these results.

BTW, I do very much appreciate your help with this. I'm told the Venus flies even better than the Focus Sport and I loved the way that plane flew, so I have an incentive to get this one tweaked to where it needs to be.
Old 08-23-2013, 11:41 AM
  #1782  
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I may be over-thinking this issue but I'm a little confused by what happens to the design CG when I move the tank. You adjust location of weights with an empty tank to get to the point designated. Now, with a forward tank, this location presumably takes into account the effect on the flight CG of some percentage of the fuel in the tank. In other words, the designated location would be aft of the desired flight CG. It seems to me that with the tank "on the CG", you would end up being tail heavy if you balanced at the design point. For those who have moved the tank to the CG, where is the new balance point?
Old 08-23-2013, 06:02 PM
  #1783  
Jetdesign
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RC_F:
Actually the first thing I want to say is: if you don't think you notice the change in balance much with the tank forward, I recommend (for most people) not changing it and messing with a pump. I really enjoyed flying the plane with tank at CG, but I did not enjoy the issues that come with running a pump with a motor that is not designed to do so. If you are a seasoned glow engine guy and have experience with pumps then this probably doesn't apply to you. But if you are looking to get the most amount of flying in and not worry about tuning and dead sticks, fly electric - uh I mean keep it simple and forget the pump

The one place where you went wrong is
with a forward tank, this location presumably takes into account the effect on the flight CG of some percentage of the fuel in the tank.
The design point for the CG is with an empty tank, or tank on the CG itself. When you fill the tank and fly, your CG is forward of the design point and the plane is nose heavy. If it were the other way around, the plane would be tail heavy when the tank is empty and could be trouble for a lot of pilots.

When I had the plane without a pump, I had the plane balanced so it felt a little nose heavy at takeoff, and a little tail heavy at landing. I don't know if that was the best thing to do, since I think the change from slightly nose heavy to slightly tail heavy could be more noticeable or drastic than always having a nose heavy feeling (probably very subjective though).

There are a few things that could be working on your trim 'issue': it could be the thrust line of the engine (extra down thrust would pull the nose down with power), it could be that the horizontal stab was glued in with a little positive angle (acting like down elevator), or maybe it could have something to do with the speed at which you fly and trim the plane. There are trim charts to work on this stuff, but if the only thing that you are noticing is where the elevator is trimmed when you land, then don't worry too much about it. What matters most is how it flies. I do agree that the amount of shimming you added is a lot.

The 45deg inverted test: if you are adding shims to the rear of the wing, you are making the wing generate more lift when upright. When you roll to inverted, up is now down and the added incidence can cause the plane to pull toward the ground. If it is that noticeable I have a feeling there is something that you are working against (stab angle or thrust line).

Yeah, the Venus is a great flying airplane. I sold mine to buy a Sebart Wind 110 and regretted it ever since. I really liked flying the Venus a lot more than the Wind. I am very fortunate to have come across another Venus and am excited to have it as my backup plane.
Old 08-24-2013, 07:52 AM
  #1784  
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Thanks, Joe. Some excellent advice. I think I was getting ahead of myself in trying to futz with the plane instead of flying it. Time to step back from that and fly it until I do notice the differences. I do have a trimming chart so will try that with the plane as built then, when I can tell the difference from full to empty tank, I'll move tank to the CG. I'll also look at some of the things you suggest as I recall seeing some had to add a washer for down thrust.

I had a pump on the Focus Sport which seemed to work okay but I had too many dead-sticks where the engine died in level flight at half throttle with no warning. Fuel system checked out but I still wonder about the pump. As for going electric, not likely! I love the sound of an engine. I just wish the plane came with a 4-stroke as I love the sound of the Saito 100 in my chippie.

Thanks for the help from all on this thread. Time to fly it for a while but "I''l be back."
Old 08-24-2013, 08:02 AM
  #1785  
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Hey guys,

Just wanted to let you know about a carbon fiber gear I found. The web site is www.graphtechrcshop.com. Here is the gear that will fit the Venus II.

Grap1204 | #1204 Hangar 9 Showtime 4D Main Landing | $49.95

The struts are a little thicker than the metal gear so I had to use these:

http://www3.towerhobbies.com/cgi-bin...?&I=LXD823&P=7
Old 08-24-2013, 08:21 AM
  #1786  
Jetdesign
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Corwin, thanks! I want to get a set of gear from Graphtech. Can you post a pic with the gear on the plane?

RC-F, I had similar experiences. I had a dead stick on one of my best contest flights with the Venus. I spent the whole contest behind the pits with some guys trying to get it running right, couldn't seem to get there. And this is with guys who have been successfully running pumps in contests for years.
Old 08-24-2013, 08:51 AM
  #1787  
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gaRCfield......just got them but I will soon. Debating on whether or not to put the wheel pants on.
Old 08-24-2013, 09:07 AM
  #1788  
Jetdesign
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Thanks :0

I have never had an issue with wheel pants, once I started mounting them how I do now. There are probably a few ways to do it, but the key point is that the axle bolt goes through both sides of the wheel pant. I use plastic spacers to keep the wheel in place. The wheel pant gets clamped to the landing gear with one nut. Second nut either on the inside of the gear if you started the bolt from outside the wheel pant, or second nut goes on outside of wheel if you started the bolt from inside the gear. I don't use any pins to keep the pant in place. So the wheel pant is prevented from being pulled off to the side, and free to rotate to absorb energy.

I haven't tried using plywood (or carbon) blocks inside the wheel pants yet, that could work too, lots of guys do it. I think one killer for wheel pants is that they are often secured to the gear on one side, the opposite side is not secured, so the wheel pant flexes and all the load goes into the one side that's clamped to the gear. I have destroyed plenty of sets of wheel pants until I started running the bolt all the way through. It looks best with a stainless button head screw from the outside.
Old 08-26-2013, 12:50 PM
  #1789  
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Having made the decision to "just fly it" for a while, I couldn't resist a couple of measurements. Empty tank balance at 6.45", full tank (take off) balances at 5.6" and after an 8 minute flight it balances at 6.0." This seems like quite a large range, thus the desire to move the tank to the CG (one of these days). From start of flight to end, I did need to re-trim a couple of clicks for level flight. The other test, from one of the many trimming articles I found, is to trim for level flight at full throttle, fly a distance at full throttle, then cut to idle and see what happens. I did this early in the flight; the plane continued straight and slowly lost altitude. To me, this would indicate that the downthrust is about right.

Comments?
Old 09-02-2013, 03:25 AM
  #1790  
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Thrust test sounds fine to me.

For the mid-flight trim changes, you might put them on a 3-position Tx switch so that you don't have to 'fish around' to find them, and also remove the guesswork when returning to normal, full-tank trim...
Old 09-02-2013, 10:54 AM
  #1791  
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Originally Posted by cmoulder
For the mid-flight trim changes, you might put them on a 3-position Tx switch so that you don't have to 'fish around' to find them, and also remove the guesswork when returning to normal, full-tank trim...
Sounds like a good interim approach. I'll be having knee replacement surgery in a month or so and will likely tackle the "tank on CG" rebuild then until I'm mobile enough to go flying again.
Old 09-04-2013, 07:25 AM
  #1792  
corch
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I was able to move my tank to CG without using a pump. Keep the midline of fuel tank even with midline of carb. I did install a small shelf with some scrap lite ply and popsicle sticks. I'm running a 1.20AX 2 stroke with a 15-10 through a 16-8 prop. No pants
Old 09-05-2013, 09:09 AM
  #1793  
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Doesn't the engine lean out on long uplines?
Old 09-05-2013, 09:33 AM
  #1794  
corch
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Not one bit. And with a 15-10 APC it has unlimited vertical.
Old 12-03-2013, 06:41 AM
  #1795  
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If you find a few for sale please let me know. This by far was... my pride and joy till my (Hobbico HD switch failed) There is not much on the market unless you want to go Elec. I have a good motor sitting around waiting. Thanks!
Old 12-03-2013, 07:50 AM
  #1796  
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I'm still flying mine (knee replacement delayed) and love it more every time I try a new maneuver.
Old 01-01-2014, 06:31 PM
  #1797  
Jetdesign
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I have been studying options for an electric conversion and would love some feedback if you have any. It is looking like a 6S setup, and probably a Hacker A50. I'm a little confused because people are using the same setup on "50 size" planes like the Sebarts, at only 6lb but using small props. However Sebart suggests 6S for the 125-size Mythos, so maybe it's based on new technology. 6S is also used on ~8lb planes by 3D Hobby Shop and the like, so that's where I came up with this (also some experience by others with electric Venus planes). I also came up with 6S because I have 3S packs to run in series. This will be a backup plane when my 2M is ready, so I don't want to buy 4S/8S packs that would only be used in this one airplane.

My research has pointed me toward these motor combos:
Hacker A50-14S (425kV) and 15x10 (63A/1350W), 15x12 (71A/1500W) or (16x10 75A/1570W).
If the calculator is right or on the conservative side I could try a 16x12 (84A/1750W) or a 17x10 (87A/1800W).

Alternate is a Hacker A50-16S (365kV) and 17x12 (71A/1500W) but it seems I'd need this much prop for power and speed but can't fit bigger, so that's a concern.

The other alternates are the RimFire 1.20 (462kV) (seems like it would turn a 16x8 similar to the 120AX or 16x6 or 15x10 similar to the YS110, but that wouldn't make best use of electric efficiency I thought). It's also a heavier motor, but that usually means better capacity to handle heat.

I suck at making decisions.

Last edited by Jetdesign; 01-01-2014 at 06:38 PM.
Old 01-02-2014, 10:12 AM
  #1798  
Jetdesign
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I sent an email to the USA Hacker distributor and got confirmation that the A50-14S is 'perfect for this application' and that 16x10, 16x12, and 17x10 are 'right on the money'.

Well that wasnt so hard
Old 01-02-2014, 11:02 AM
  #1799  
Jetdesign
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I learned an important lesson when experimenting with my Wind110 power system. When choosing an electric power system it is critical to ensure the ability to prop up or down if things don't work right. I found out the hard way they don't make many/any 14pitch props under 19". I really needed an 18x14to get the performance I wanted with that motor.

The A50-14s should work well on 16x10. They do make 16x12 and 17x12 if needed, and the plane flies well with 15-17" props so there is room either way.

Last edited by Jetdesign; 01-02-2014 at 11:10 AM.
Old 01-03-2014, 04:53 AM
  #1800  
wildwillie3
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Joe, would that be used with 5S packs or 6S?

I still have mine and would keep it if it was a easy change over to electric.

Bill

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