Posts: 20
Joined: 1/18/2002 From: Jefferson City, MO, Status: offline
Hey guys, A partner and myself are building a Ziroli B-25, my partner of course doing most of the building. However I have a dilema, I am really confussed on which motors to use. I am not a big fan of the G-23, however I want to stay gas...... Any ideas or have you all tried something else?.....We are also looking for wheels and brakes that will fit nicely with the Robart retracts as we have them already....Any ideas here? In building the rudders has anybody eliminated the bellcrank system that Ziroli lines out?....... If so what did you do?......
Anxiously awaiting answers so we can get this bird ing the sky by July (hehehe)
I have a Ziroli B25. I originally built it using a pair of Kalt 22's that I had laying around. They are similar to the G23, but not as powerful. I found that they were inadequate power wise. Bear in mind I live in Southeast Asia, and the humidity levels here usually necessitate a bit more power than you would need. I re-engined with a pair of G38's. The plugs stick out rather a lot and impact the scale appearance of the plane. The engines are effectively overpowered, but that just means lower throttle settings. If I were to do it again I would probably use the Brison 2.4's, better fit and plenty of power. If I lived in a less humid climate I might be tempted to try the RCS 1.4's although I have heard mixed reviews on these. The bellcrank system on the rudders was certainly sloppy. I ultimately created base mount hatches at the stab fin joint, and used voltz micromaxx servos with the push rod exiting on a very short throw to the rudder. I covered the pushrod with a scale type fairing cover. I was a bit worried about torque with this servo, but it turned out to be fine. I have about 12 flights on the plane. You need to use rudder and reasonable differential on the ailerons or there is a tendency to skid in turns. Otherwise it flies great. Landings require a bit of practice to make sure you use adequate flaps to slow down while maintaining power to ensure control. I am using robart metal wheels. They came out with these last year and they are reasonable like and look scale. Glennis makes a scale wheel which is probably a bit heavier, they also have brakes for their wheels. I don't know if the glennis brakes would be compatible with the robart wheels. I am not using brakes. We fly off grass and it tends to slow the plane down after landing. I am able to get an idle low enough that the plane will sit after taxi prior to take off.
Good luck with the project. Mike
< Message edited by mselby -- Jan 30 2002 3:31AM >
Posts: 1811
Joined: 1/19/2002 From: Apple Valley, MN, USA Status: online
A friend of mine has Q-42 (now US41's) installed, They are nice because the muffler mounts on the back side of the cylinder almost hiding it. You do see a little bit of the head bottow, but this is a trade off for better performance, wiothout a muffler sticking out the side. I have seen them with G-38 also, which also has mufflers on the back of cylinder.
Posts: 3182
Joined: 12/18/2001 From: Arlington, TX, USA Status: offline
The one that I built and flew was way overpowered by two G38s. I would recommend the G23s. They are plenty powerful enough and probably have less vibration. With both G38s running, I sure had a lot of vibration in the ailerons. Had to go to metal geared servos. Ken
Posts: 20
Joined: 1/18/2002 From: Jefferson City, MO, Status: offline
Mike, Thank you for your excellent insight on the issues I have raised. I like your idea of mounting micro servos in the tails to eliminate deadband in the control surface. Could you mount them servos directly into the inboard side of the vertical stabilizer?.... Has anyone tried this?... I have heard alot of pilots talk about the finished weight of their bird?... Any idea where yours has come out at?... I am seriously thinking about using the RCS1.40, it is a lighter motorand just slightly a bit more power can be achieved with the 1.80, or willl this be too much for that?... We are after a truly scale model here so let me know? We have looked at the Glennis brakes and wheels but are not sure what to do yet, do you like the performance of the Robarts? Our stip is 575' of asphalt any pointers here...should I be worried about the landing approaches?
Posts: 20
Joined: 1/18/2002 From: Jefferson City, MO, Status: offline
I am thinking that by using such larger motors one would have to compensate by adding tail weight, was this true? I want to keep her as light as I can but, I want authority as well! 2 Q 42's seems like an awful lot of motor for this bird considering that it is recommended to use 23's. I am looking for good motors with low vibration any ideas????
The width of the servo is problematic for a proper mount inside the vertical fin, the fin is too thin. I put the hatch and mount at the base of the fin partly in the stab. Also be careful on the hinge method on the rudders. I changed it from Nick's plan. I used pieces of brass tube in alternate placement between the rudder and vertical stab and then went through with a music wire. Nick's method was too soft. you can get away with a heavier bell crank arrangement with the servo mounted inside the stab. This allows for a larger servo, and if the linkages are short you would be ok. I thought about this after I had done the other arrangement. Some reinforcement of the nacelles is also desirable. I used a carbon kevlar layup to reinforce inside. There is a lot of potential vibration as well as shock on landing. I am unsure of the weight on my plane. It has a lot of scale detail so I am sure the weight is up there. With the G38's the plane takes off in about 75 feet at 2/3 throttle. It would lift a lot faster if I really ran the engines up. Since you are going for scale, give some careful thought to the gear doors in the nacelles. The curvature is heavy. You will have to use large u shaped hinges. Mine are home made. You need a fair amount of offset from the nacelle as the door opens. flaps can be set up as pseudo fowler using robart hinges. It gives a reasonably scale effect without the headache of making and tweaking a fowler mechanism. Otherwise Wayne Siewart at Aerotech, makes a fowler mechanism for his P47 that can be adapted if he will sell one without the kit. The problem is that you would need 2 per side. Your strip is more than adequate. I was flying off of 350 of less than pristine grass. A hot landing will take up a fair amount of the strip. landing too slow can cause a tendency towards a wing over. I suggest a few practice approaches and you will see what I mean. The plane is by no means difficult to handle. Please let me know if you need any other info. Mike
In reply to your letter about the B-25.. I am not blessed with the answers but have 4 close friends each building four huge B25's at the present time.. I would like to direct you to this enclosed web site as they possibly could be of some help to you.... Wingman..
Posts: 108
Joined: 1/26/2002 From: Livonia, MI, USA Status: offline
I've had my B25 flying for 3-4 years now and It is a *****cat to fly. So much so, in fact, that it rivals a trainer. Now, mine is not tricked out and it only weighs about 30 lbs with G23's. I will admit that more powerful engines could be more fun for this bird, but it flys very well on the G23's and is a good trade off for the weight. When you use the G38's o(or bigger) you just add weight, vibration, and poorer flying characteristics. What's the benefit here? Maybe just speed. Also, the nacelle is not that large and only has ample room for about a 16oz tank.
This thing is so easy to fly, that I can hold the nose gear off the runway on touchdown for several feet. And I'm not that good of a pilot! Really take another look at the smaller engines. I think you'll be happier. I'm including a pic which shows the downling camera that we used a couple of years ago to get some great video. We also mounted is on top of the fuse and aimed it backwards. The video is really a neat addition to the normal library of pictures.
Posts: 20
Joined: 1/18/2002 From: Jefferson City, MO, Status: offline
Jim, that is an excellent shot of your bird! I thank you for your input on the engines! What type of wheels did you use on yours? How did you setup the rudder controls?
Posts: 108
Joined: 1/26/2002 From: Livonia, MI, USA Status: offline
Thanks, for the compliment. By the way, this is the 101" version and not the 118 ". The wheeels are just byron 5.25" they are narrow and fit nicely into the nacelle. I unfortunately built it to the plans and used bellcranks. Although I find this a bit sloppy, it works well and is dependable. I used a giant servo driving the nose gear and the rudders works just fine and has plenty of authority. I use a small amount rudder in making a turn as well. Like most B25's, the tail wants to drag a bit.
Believe it or not, this has been my most dependable plane for the last few years. The robart gear even hold air for several weeks.
Here is another pic taking off with the camera installed.
Posts: 20
Joined: 1/18/2002 From: Jefferson City, MO, Status: offline
I want to eliminate the bell crank driving the rudders, any ideas? I see you are flying off of asphalt as well as I will be, are you using any brakes? If not what is your touchdown to roll-out distance? Can someone still get the Byron wheels?
I am looking at a set by Glennis now but man they are $$$!
Lastly, if you were to change your model at all what would you do differently?
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