Well, I posted previously that I was converting my tower voyager ARF to a twin. I am using OS FS30 engines. I have started the project and I have several questions:

1) What do I need to do to properly convert to taildragger? THe plane was a trike, but after I got rid of the fiberglass cowl and tapered the nose down, I lost my front gear mount. I think the plane would look cooler as a taildragger anyways. I was thinking that all I had to do was bend the wing mounted gear forward to make the wheels sit further towards the nose. I shouldn't have to change the CG much if any if I do this right???

2) During the process of getting rid of the cowl and making my own nose, I probably lost about 3 inches of length to the front of the plane itself. I basically started tapering the nose down aft of the bulkhead. The nose only extends about 1.5 inches past the bulkhead now. SHould this be a problem with stability??

3) Should I change the elevator and rudder?? THey are currently one piece 3/4 inch balsa strips. SHould I build out my own larger so that I can make the rudder and elevator more responsive?

4) Finally, I am starting to plan the nacelles and need some advice. Does it matter if the center line of the engine sits slightly above the wing, or would it be better to have the center line of the engine even with the center line of the leading edge? How far forward can I place the engine in front of the wing without compromising stability?

Sorry about all the questions. Thanks

sbaugz:

You might be able to bend the gear forward and get it to sit tail down, but it would be very close to tipping over all the time. If you are set on a taildragger make a new main gear mounting plate to put the wheels approximately straight down from the leading edge of the wing when the plane is level. But I would urge you to keep it as a trike - if the engines don't come up evenly you will find a taildragger twin just about impossible to get off the ground. P-factor is almost a non event with a twin, but uneven power is a large factor. If you have a fair bit of tail dragger time with singles, you might get away with it. But training wheels are a lot easier.

The length of fuselage in front of the wing has no effect on stability. Look at the Grumman Skyrocket - no nose at all. But I would urge you to extend it and put nose gear out in front. See last comment. Only real necessity is being able to balance the plane.

Elevator, no. Rudder? Make it at least 1 1/2" chord. The rudder will become a main flight control on your twin. And if you don't have enough your plane is dead when an engine goes out. Or you manage to chop the other before entering the death spin. My Tiggerkitty has a grossly overscale vertical fin and rudder, as a result VMC is the same as stall speed.

Having the thrust line above the wing tends to minimize trim changes needed from power on to power off, but to make engough difference to notice you would have to pretty high, I don't think you'd see any effect having them 1" above the wing, and very little if any at 1 1/2" above.

Distance in front of the wing? Limited by the strength of the nacelle, the wing, and the attachment of the nacelle to the wing. But I wouldn't put the firewalls more than 2 1/2" to 3" in front of the leading edge. And again, it depends on being able to balance the plane.

Twinman has some good tricks on firewall location. George, want to chime in here and continue?

Bill.

PS: Pictures are the Tiggerkitty, showing the vertical fin and rubber, second is my C 3/10, its firewalls are against the LE of the wing. wr

My ears are burning on firewall placement.
It really does not matter so much on the twins I have bashed. What is important is that you keep weight down. My trick is to build the nacelles less the firewall and build them too long. Install the engines and mufflers on the firewalls and move them both forward and back until the plane balances. Mount the engines in this place. This prevents having to add a bunch of additional balance weights.
My two cents on the landing gear.....if this if your first twin.....keep it a tricycle gear. The engines never come up together and a tail dragger is harder to handle with differential thrust.
Hope this helps. Good Luck,
Twinman
PS You do have to send pictures for the rest of us.

Reference to William Robertson's Tiggerkitty........you ever tried a single engine takeoff with that rudder?
Twinman
PS Wait until I get the video camera!!!!!

George:

Even with the rudder from a B-52 I wouldn't try a single engine flight with the Tiggerkitty. She's a real bear with both turning and burning, when one stops It gets back on the ground. I don't attempt anything but final and touchdown. But it is fully controllable. Main reason for coming down when one quits is lack of power - it wont maintain level flight on one engine.

I have given thought to installing the 0.074 engines, but I have too may other projects under way.

Bill.

Thanks for the great advice.

I think I will try and keep it as a taildragger now.

So, should I rebuild the vertical stab larger too, or is simply making the rudder larger going to be enough?

What is the smallest size tank you would suggest for my OS FS30 four strokes? I want to try and put the tank inside the wing so that I don't have to build huge nacelles that extend halfway back to the trailing edge.

Thanks again. Steve

Steve:

If you increase the size of the vertical fin that will make the rudder effectively smaller. I'd leave it alone, enlarge the rudder only.

You are going to do the engine runi-n on a stand, aren't you? For me two ounce tanks would probably be fine, but if you want 15 minute flights you'll want bigger tanks. You can check fuel consumption as you do the run-in, and size your tanks accordingly.

Bill.

Yes, I plan on breaking the engines in on a stand first. Probably will do it next spring. I will try and take some pics of my project as I go along. Steve

FWIW I've got both the Brightstar and the Twinstar. When they were both NIB I did some comparisons.

The horizontal and vertical stabilizers (and rudder/elevator) on these two aircraft are identical except of course for the color scheme....

This sounds like a pretty cool project. I would like to see those photos as you progress on this modification. I am new to RC flying and just started last fall and have just recently completed the construction of the Tower Voyager ARF as a second plane. I'm sure it is because of my newness to this hobby but I am amazed that some of the creations and modifications I have seen so far even fly!

Good luck on your project.

Sbaugz I guess you didn't want to see my Voyager that I converted to a twin that is in the back ground of my A-26 at Davenports scale meet. Your going to find out that you had better take the advise of twinman and keep her as a tricycle gear. But if you insist at least get some photos of it be for you try to fly. Cause it won't be long before you kit it. Experience is the best teacher not what you think you will like. On mine I left all the control serfaces stock but did bullet shape the nose. And it will fly level on a single engine but throttle down before you try to turn. Then gently throttle up and continue flying. Will not take off with one engine though. Mine has two OS26 fourstrokers with 6 oz fuel tanks micro servos for the throttles.

nchrome: I did check out your pictures of your twin voyager, and yes, I am going to build it as a tricycle gear plane. I took twinmans advice. Unfortunately, that project has taken a back burner to some other projects I have going one right now but I hope to finish the twin by this summer. My Stuka JU-87 has taken priority for the time being.

Glad and pleased to hear that you are going to take some good advise. On your batteries just put them and some foam up where the tank use to be. On new years eve I took mine out and with lites adorned and spot lites handy flew out the old year and landed in the new year. Was quite thrilling to do this and am looking forward to do this nest year too. Flew a total of about 15 mins and landed with no problem. Maybe some time this year we mite meet at an event and compair planes and notes.

To tune the engines just before flying, you should also invest in a tachometer, it would help a lot in getting the engines to run with the same power. Good luck on the project!