Question 145: "Twinman: I purchased the VQ P61 for a future project. Have a little question. When the plane did lose one engine was rudder used at all or did the plane land without there use. Thank you. Jerry"
Twinman: "Hi Jerry, I cannot push or emphasize enough that you MUST learn to use rudder to safely fly twins........Any twin!! You MUST use it all the time. You cannot learn during an engine out!!!
Try to imagine....you are flying the only example of this prototype anywhere in the world and one engine dies. You know that this is almost certain death on a P-38.
The rudder on this P-61 is extremely effective and I had already tested it. Panic, as a word, does not really do this condition justice!!!!
Could I tell you exactly what I did?,,,probably not. If you use rudder all the time, the reaction to unexpected yaw is instant and automatic or the plane will die.
It was really a non event and handled well, but I was not about to test single engine performance beyond flying 100 yards the wrong direction, getting it turned 180 degrees, and down.
What did I do upon landing???? Shook so bad that I went to one knee......after I was sure it was safe.
Please do not take this answer as talking down to you or anyone else. That is NOT what I am saying or trying to do.
I have made most of the mistakes possible learning to fly multi engine planes. I do not want others to follow that frustrating, heart breaking and yes, expensive learning curve.
Good luck and keep us posted on your progress.
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Question 146: " Hi, I have an Expert On Board Glow driver but before I install it and set it up in my plane which is a single engine I would appreciate an expert to tell me the proper wiring/schematic to use to do the job correctly? Thanks, Lee"
Twinman: "Hi Lee, I would really suggest that you go back to Expert for an instruction manual. Most glow drivers use a "Y" to the throttle channel and allow the driver to come on at a preset throttle setting. Example, below 25% throttle the glow driver is on. Most wiring is simple, but I am still saying to check with the manufacturer. Two wires the engine, one to the plug and one to the crankcase for ground. The other wires are positive and negative to a
large,,,,1800....2400 ma single cell battery. Some drivers also have provisions for an outside charger for the driver battery. Do not attempt to recharge the battery via the glow plug, unless you are sure this is allowed. Good Luck,
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Question 147: "Hi, i am a huge warbird lover and i my dream warbird is a P-38 and i was woundering where i could get the plans or even a kit. Thanks Mike "
Twinman: "Hi Michael,
At the extreme risk of raining on you lofty goals. I really do not suggest a P-38 for a first twin warbird. They are very unforgiving with engine loss.
Consider to get twin experience with less highly loaded twins and less expensive.
Do you ALWAYS fly coordinated, by that I mean do you always use the rudder with the ailerons. If not, learn. You need to be able to do that INSTANTLY with a twin and the P-38 is the most demanding. I am not talking down to you. Been there done that ....don't!
I do understand you dream of the P-38. I am flying two right now. One at 108" and the VQ ARF at 84", but there have been four others leading to this point.
Consider a twin fun fly like the Cedar Hobbies Twin Ugly stick, or bash a large single into a twin. Twin Mustang, comes to mind.
OK, still not convinced and demand a P-38.
There are actually a lot of them available via ARF's such as the KMP, VQ and even one from Robart. You can see my review of the VQ in this forum and the VQ compared to the KMP at RCU in the twin forum.
Plans, can come from almost any major kit cutter, Zeroli is the most well known.
P-38 lover?......my kind of guy!!!! You want composite type kit? Besides above, the only other ones that fit that bill that I know of are Robart at http://www.robart.com/ kits /images/index.htm and Yellow aircraft at http://www.yellowaircraft.com/prop/index.htm. For built up kits that you can build or customize, here are two more. G&L Hobbies at http://www.glhobbies.com/P38%20LIGHT/1_6P38.htm or get the VQ as a non covered version at http://www.vqmodelaircraft.com/ There is another kit at G&P Sales at http://www.rcairplane.net/ Aero Tech in the UK makes a "Quick Build" with much plastic at http://www.atimanufacturing.co.uk/ American Eagle at http://www.flyrcmodels.com/ I would also suggest that you go to the associated site for RCU at www.rcwarbirds.com There is a whole section on just the P-38 's.
PS Did I miss one? Yes, Wing Mfg at http://www.wingmfg.com/ opps one more.... http://vicrc.com/P38-Lightning.htm PPS Currently own two out of five total have owned. Got it bad.......I need a life!!! Sorry if that is not enough.......is my best shot.That should keep you going for a while. Keep us posted.
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Question 148: "Twinman, I've been bitten by the twin bug! Help!! I'd like to use a Sig Kadet or an Eagel II as my first twin (bash). Do you have any proven techniques for bashing? Thanks!"
Twinman: "Hi Larlee,
Here is a reprint of an old post I did here at RCwarbirds some time ago.
Hope it helps, or consider a twin engined Ugly Stick ARF from Cedar Hobbies for 40-45 size engines. Quick and simple to get into and a blast to fly.
Subject: Kit Bashing a Perfectly Good Plane into a TWIN!!!!!
There are very few multi engine arf's and few kits, compared to the single engine types for the modeler to choose from. If you want to get multi experience before the bank is broken on that multi engine war bird, consider "bashing an ARF" to a twin. Yes, the Hobbico Twinstar is good, is coming back, and an excellent flyer, but small compared to the larger war birds..
Ugly Twin Stick
One way is to find a long fuselage single such as .60 size ugly stick, put nose cone over the center engine mount and add nacelles to the wings. Warning, the wing loading skyrockets!! Forties will not fly this well. Go to two .60's, add 8" to the wing and add wing plates on the end. The result flies well and was the subject used for my experiments with various ideas with twins.
Ultra Sport 1002
Got an Ultra Sport 1000? Need a twin? Create the US 1002. Put an eleven inch tapered nose cone over the original engine mount area. Suggestion, the fastest way is to use four 1/2-balsa triangles, glued to a point and shape as needed with sanding wheel. (Remove the original engine first....Let's not go crazy!!)
I added wing plates to the end of the wings that extend 3/4" outside of the airfoil. This is necessary to compensate for the additional weight of the two engines. Make nacelles of 3/16" balsa with 1/16" ply reinforcement inside the vertical walls. Use Grappner 14 oz. square fuel tanks. The recommended engines are healthy Super Tigre .90's with ASP 108 Carburetors and Master 14x6 propellers (Or equivalent). Enlarge the rudder to roughly two times the original size and go to pull-pull on the rudder control. Enlarge the ailerons to two inches and full length. I added carbon fiber cloth, from Dale Brown, to the top and bottom of the wing to reinforce the wing structure. It will be necessary to increase the servo power to at least 100 oz or go to two standard servos per aileron ( Which I chose). The plane can go so fast in a dive, aileron flutter will result!!! Yes, you will do it!! Sealing the control surface gaps is highly recommended. The elevator is split for more roll response. Total 10 servos.
This plane will go straight up and flat spin like you would not believe, as well as knife edge all day. You will also wow the crowd if you can learn to hover the plane.......a twin!!!
Twin Long John
Another way is to create a "100 foot stand off-scale" F-82 twin mustang. Yes, World models makes a F-82 ARF, but is still smaller than 80" and lightweight.
One plane that works well is to take two Long John 40's, combine the wing to 82", two fuselages side by side. I set my engine spacing at 12.5" to use 12x4 props, and a single horizontal stabilizer. You must make a brace, to hold the fuse's inline for transport, to take the place of the wing and support the two fuselages. I learned the knife-edge circle with this one and still fly it today with two Super Tigre .45's. Instant "Twin John".
Due to the smaller size, I used one servo for the rudder and connected the other one to the master rudder with streamline tubing. Two tail wheels are necessary. I also only used one elevator servo. This is a risk, and must be evaluated on each conversion. This is not a high-speed model, so to reduce weight; I tried it and was satisfied. Total 6 servos.
Again, a brace to go between the fuselages for transport and bolted in as the wing replacement, is necessary or the elevator will be broken during transport.
Twin Fuselage Ugly Stick
Still another conversion, that flies well, is to use two Ugly stick .60's and build the plane with two fuselages, as the Twin Long John. Take the arf's wing halves and glue the center joints, as normal, then shorten the center joint, which is the outer of each wing assembly, four rib spaces for only one new joint. This yields a fuselage spacing of 20" centers. The joint should be strengthened with fiberglass cloth. It is also necessary to sheet the center area of the wing, so that the fuselages will be supported from front to rear when bolted to the wing. This yields around 86" wing span. I recommend adding carbon fiber strips to the top and bottom of this wing to reinforce against the newfound power and maneuverability. Two .60 two strokes fly it well and now flying with two Super Tigre .90's (More power ARGG ARGG!!) Pin the firewall with epoxy and tooth picks to stand the added forces.
The horizontal stabilizer is formed using the original stabilizers shortened in the middle. Cut the two elevators to match the fuselage spacing that you have chosen. With this type of two-fuselage system, you can either put the receiver on one side and battery on the other, or can practice the concept of two receivers for redundant control. Again, must build brace for transportation to hold the fuselage's in alignment and not break the horizontal stab.
To keep the model interesting I inverted the fuselages to make a low wing model. One problem with this modification was that with such a large wing, so close to the ground, ground effect really comes into play on take-off and landing.( Did not plan on that one!!)
I added one more "Small Modification". I had extra elevator material left over, so I used it on the wing between the fuselages as a kind of extra flap for more lift during maneuvers. This "Flap" is mixed into the elevator for more response.
This plane is fantastic as far as aerobatics are concerned. The more you mix the engines to rudders, the more fun.
The two fuselage conversions should keep the props almost touching for better engine out characteristics. My twin Ugly stick is not close. The centerline of the engines is 20" for more practice similar to a P-38 with wide engine spacing. Engine out is good due to the long fuse and larger rudder.
Used separate servos for the two rudders and two to a single elevator. Total 9 servos
Tips for Twin Conversion
1. The nose of the fuselage (Where the former single engine once stood) needs to covered. Fabricate a pointed nose cone, in whatever shape you desire, and cement or fasten to the former engine mount area. Using a solid small block of balsa, sanded to shape and hollowed, is the fastest method (Let us not discuss tri-motor idea at this point...Two motors will be enough problems at this time.)
2. As a general rule, make the engine nacelles out of 1/4" balsa, and reinforce on the inside with 1/16 plywood in each side (On the inside) of the nacelles.
3. Use two servos, one on each engine, and "Y" harnessed together and connected, to the receiver. Mixing of the engines comes later.
4. Due to the increased weight of the additional engine and fuel tank, the wing loading goes up quickly. It is advisable, unless you are planning to practice war bird flight characteristics, of high wing loading, to lengthen the wing span by 10-15%. This will reduce wing loading and make the model fly similar to the original plane...except now the model has more horsepower, weight, and feel...ect.ect.
If, after the wing is lengthened, you still feel the wing loading is high, or the plane seems to fly "Heavy", then the addition of wing "Plates" to the end of the wings is advised to provide additional lift.
5.The once open area of the wing that will be covered by the nacelles, should be sheeted with
at least 1/8" balsa or 1/16" ply, prior to the installation of the nacelles to provide additional area to glue the new engine nacelles. Additional triangle stock inside of the nacelles to additionally mount the nacelles to the wing, is not out of order. Now you can go find fuel tanks
that, ideally will fit between the firewall, nacelle sides, and the mail spar. You might want to check Hobby Lobby and the Grapner line. They have high capacity square tanks that seem to be shorter than competitive tanks. This lends itself to this modification.
6. The wing stress climbs quickly due to the additional weight, twisting loads, forward mounting of the engines, power, increased speeds, ect. The wing should be reinforced during the conversion process to be able to stand the additional loads and stresses of flight. Do not cut the main spars for any reason!! Carbon fiber cloths or strips work well for this applies directly to the main spares. This is more important if the wing is lengthened.
7.The rudder size should be increased by up to 50% to aid in the single engine out condition. Similarly, the servo for the rudder should be increased in power, or go to 6 volts from 4.8. Remember that the battery for the plane will be drained faster than the old 4.8-volt pack due to higher current flow and additional stresses on the servos due to the extra power.
8.Now is also a good time to seal the gaps on all of the control surfaces. Due to the additional potential speed, flutter could rear it's ugly head, from where is has been hiding while using the lowly single engine.
9. Make the nacelles overly long to the front of the wing, but do not mount the engines at this time. Bolt the wing to the fuselage for a completed flight assembled plane. Make sure all servos and batteries are installed. Mount the engines to their individual firewalls. Using rubber bands around the freestanding nacelles, hold the mounted engines inside of the nacelles and move forward and backward until the plane is balanced. This step reduces the need for additional weight to provide the proper model balance. When the plane is balanced, similar to the pre-conversion setting for CG, then glue, and I suggest pin, the firewalls in place.
10. The radio installation, on twin fuselage planes, involves putting the battery and servos on one side and the receiver on the other, to maintain some degree of lateral balance. You will need quite a few extensions. Or you could practice the concept of dual receivers at this time. One receiver for each side of the plane....Even split elevator is possible. I suggest using two servos for the rudders, and elevators, due to the higher forces and longer surfaces on the elevator. One servo on a 12" elevator, mounted on one end is inviting flutter!
11.Whatever you do, have fun with it, but practice before the first twin warbird on a cheaper alternative. Been there, didn't do that..don't do that!!!
12, One other good trick is to mount the engines using the propeller bolt to a steel or aluminum flat bar. Now, you can install the engines and make absolutely sure that they are straight.
Good Luck, Twinman "
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Question 149: "Hello Twinman, I have just purchased the TwinStik ARF from Cedar Hobbies. I am trying to decide which engines I would like to use on the model. I have a pair of Evolution .45's (similar power to O.S. .46FX, and I have a pair of Thunder Tiger .42's (bushing motor similar in power to O.S. .40LA). I would like to use three bladed props. I could use the three blade Evolution prop (approx 10.5x4) with the Evolution engines or I could use 9x6 MA props on the Thunder Tigers. I think that the Evolution motor/prop combo would be more than enough power and the low pitch prop would hopefully keep the
airspeed reasonable. I don't think the Thunder Tiger's would have the torque that I would want for the Evolution props (they have very wide blades for their
size) but I am concerned that the 9x6 MA props may make the plane fly faster than I care for. I could always use throttle management, but 2-stroke sound
and perform so much better at or near full throttle. Unfortunately there is little variety in three blade props and I have yet to find a lower pitch prop that would work well with either motor, the Evolution prop being an exception. Any suggestions? I will also be doing some modifications to the model... The rudder will be redesigned and will have more surface area. I will be converting to a tricycle landing gear and using a Hangar 9 .60 size aluminum gear for
the main and a Eurokit shock absorbing nose gear. All other modifications will be cosmetic, that is unless I decide to make more changes in the building process. Any comments and/or suggestions are greatly appreciated. Thanks Dan Willis"
Twinman: "Hi Dan, I really like my Cedar Hobbies Twin Stick, Suggestions. Make sure your re-epoxy the firewalls. Some of the kits were not glued
enough and a bit extra helps. All sticks are a little weak where the push rods for the elevator and rudder come out. Those holes weaken the tail area. Not just Cedar, but all sticks. I am flying mine with 15% nitro, two ASP 45's and 12x4 two blade props. The larger diameter increases thrust which is really what you want on this bird. If the Thunder Tiger are similar in power to LA 40's, it will fly, but it will NOT BE FUN!!
I am afraid that I have not experimented with the three blade props, so you will be a bit on your own there. Sorry, if I have not done it, I don't talk about it.
I like the tricycle conversion idea. Much easier for the take off and landing than a tail dragger. On the rudder, it is effective now, but I did once do a kind of Ultimate Bipe rudder for more area for knife edge. If you plan knife edge, consider to mix the engines to the rudder for easier knife edge and better spins. Remember on the spins, to get out, just reverse the rudder and the differential thrust reverses. Make sure the mix only works above 50% throttle or taxi can be dangerous. I would build the wings with no dihedral, it is not needed. Single engine flight is no big deal, including loops........but make sure
you are good with the rudder before you try that. Yes, you can do a single engine take off...with powerful engines, but again,,,,let that one wait a
while. Have fun and keep us posted........now what is next??? Was flying the VQ P-61 this morning and had a blast.
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Question 150: "Hello George, a while back you gave me some advise relating to a twin trainer - the twin Ugly Stick from Cedar hobbies - I recall during our discussion that you indicated you had extended the wingspan of such a model to 80 inches. Question, did you extend the wing length from the root, the tip, or a combination of the both? Thanks Tony "
Twinman: "Hi Tony, The Cedar Hobbies twin stick is already extended. The plane I was refering to was a twin fuse conversion I did, using two GP ugly stick 60's..Kind of like a P-82 twin mustang. Sorry for the confusion. Twinman"
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Question 151: "do you have any information on who to contact to purchase the bobcat's from texas twins you mention in your twin guide? thanks..."
Twinman: "Hi, Yes, I do know what happened to Texas Twins, but you will not like it. It was sold to the company in Florida that produce or produced, the Long John. It was on the net as Texas Twins, but I cannot find it now. Unfortunately the new company never put the planes back in production. A shame as I had the largest of three sizes and liked it. Sorry about that. Twinman"
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Question 152: "Hi George, What do you know about the CBA P38? Scale outline? Flight characteristics? Thanks, Dave"
Twinman: "Hi Dave, I know from a friend who owns one that it is pretty scale, but mostly out of production. It is 120", but he has not flown his yet, as he is getting Fox to build him a counter rotating engine. Good Luck, Twinman"
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Question 153: "Hi George, My name is Andre, I stay and fly in Singapore. I have now for quite some time planned to get a P38 and I was quite impressed with the kit from VQ after admiring it at my local shop. Now, I have not flown a twin
and for sure not a warbird twin. What is the wing loading of this beauty and how would you describe the flying characteristics for this bird? Would you think that 2x70 four stroke is enough to fly her with authority? What is your estimated chance of survival if the P38 is used as a first time twin? I loved your shoot out article and I am therefore also looking at the KMP model. Any strong reasons why KMP should be preffered? Thanks a lot for you help, Cheers"
Twinman: "Andre, The VQ in my opinion is far more scale than the KMP. The actual working fowler flaps put it almost in a class by itself. Now, that answers the model question. At the extreme risk of sounding like I am getting on a soapbox, PLEASE do not do a P-38 for a first twin!! The Great Planes profile, maybe, The wing loading of ANY P-38 is very high...over 30 oz per foot in most cases. The engines are very far apart, which leads to very large asymmetric thrust, which leads to a snap roll if an engine fails. The rudders are small. This does not give good authority for engine out. The distance to the rudders is realitivly short, which again leads to control issues in the event of engine failure.
Get some type of twin engine light wing loaded trainer, or do a conversion as I have detailed before. Learn to fly coordinated at all times. Engine out, is NOT the time to learn rudder control.
Been there, done that...don't do that. Learn to fly twins with engine out and THEN progress. The P-38 is the most beautiful and distinctive plane in the air, but IS NOT a first twin.
Even the VQ-61 is MUCH easier to fly and control than a P-38. Get good on that and progress.
Good luck, Twinman"
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Question 154: "Twinman, I read in several of your posts that you recommend 2-axis gyros for the P-38. Im not familiar with the available gyros. What specific gyro(s) do you recommend and do they come with adequate instructions for setup? James "
Twinman: "Hi James, Based upon your job at Lockheed, I am humbled for your question. The problem, in my opinion with the P-38 model is engine out. We are not in the seat and so, must react,,,after the trouble starts. Lose an Engine on a P-38 and a snap roll is almost always the result. Heavy wing loading, snall rudders, wide engine spacing will get you in trouble quick.
I use one gyro that has a single input and output for the rudders, this to reduce yaw on engine out. Unfortunately, the control surfaces are too small on a P-38,,,or at least the model, to handle differential thrust from engine out. The gyro reduces yaw to a rate that you have time to react, but the rudders cannot alone handle the tendency to snap roll.
I personally use another gyro in the ailerons to reduce the wing from rising on the powered side. As I tend to use one channel for each aileron, I must use a gyro that has two input and two output channels. The extra wire is used for rate control of the gyro. Hobbico used to make such a gyro, but I understand it is now discontinued. Was called the Aero gyro. Both Futabe and JR also make such gyros. I do not recommend helicopter type heading hold gyros.
Good Luck, Twinman"
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Question 155: "Hi George; Ive bought a KMP B-25 plane and will begin construction over the winter. There has been a lot of discussion over the building of this bird along with your input on twin engine considerations. My question, however, is more on the electronic side of things. The plane boasts a regular servo count of 13 and 1 more for a bomb bay door. I see that many builders of large scaled warbirds are implementing 2 receivers, possibly 2 battery packs, and maybe 2 switches. Since I am new to this type of configuration, can you advise or point me in the direction as to what is the normal servo setup for a 2 receiver/battery/switch setup? The KMP B-25 has 2 servos for left/right ailerons, 4 servos for flaps, 1 servo for elevator, 2 servos for rudder, 2 servos for throttle, 1 servo for nose gear steering, 1 for retract control, and a final one for bomb door actuation. Thanks for any input you can provide! Great article on twin engine airplanes, too. Daryl."
Twinman: "Hi Daryl, The idea of two receivers is not new and is used much in three D flying. Basically you split the plane into two separate parts that is controlled by two separate receivers. The idea being that if one system fails, you still have half the plane to work with for control.
You MUST use two separate switches and charging jacks any time you use two batteries or the batteries will not charge correctly.
In this case you would also need two servos for the elevator to maintain control in the event on one system failure.
The receivers must be of the same design and manufacturer and needless to say the same frequency.
How to split the control up with a twin...up to you. There are many combinations on this and not sure I want to get into the "Best".
I supposed the engines should be on one receiver, perhaps PCM and set the dead man setting to low idle or kill in the event of system failure.
I personally have not done this, but have experimented with it. I really think one good receiver..that HAS been used before ( DO not use a fresh receiver right out of the box for this project. You want to be sure it is good, so test it on a cheapie.) and two batteries and two switches would be the best solution.
Good Luck and keep us posted. We WILL need pictures.
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Question 156: "Dear George, I have just dusted down a project I started some years ago and would appreciate your advice. The model in question is the G&P Sales, Grumman Albatross, 81inch wingspan and weighs around 15 lbs. The power recommended is 2-.40 two strokes but I would like to install two OS Wankels that, according to the spec.sheet develop 1.27 BHP at 17,000 rpm. This idea goes back to an article in the MAP magazine, dated October 1991on Amphibians and Flying Boat set-ups which show the the Model powered with engines that appear to be Wankels. Talking to my clubmates they reckon that I would be better going for 2-40 two strokes or 2-70 four strokes. The latter is out of the question as the engine centre line would have to be moved out by an inch and I have already committed to the position stated in the construction manual. Another option would be to use RCV 58 four strokes but the prop size would only give a 0.6 inch clearance between the prop tip and the fuselage. Question, Is there a minimum clearance that should be maintained between the prop tip and the fuselage on twins?. Ideally for appearance I would prefer the Wankels as they would be totally enclosed in the cowl. I would appreciate your thoughts on this. Many thanks
Twinman: "Hi Alex, My personal favorite engine are the Super Tigres'. Let's look at the ST .40 which develops up to 1.15 HP verses your proposed OS Wankels at 1.27 HP. Now neither of these will actually wind to the astronomical figures listed, but it does indicate relative performance, which would be very close. The only problem with the RCV in your application is the relatively low prop shaft RPM for these engines. They need large diameter props and you cannot do that. The OS FL 70 develops 1.1 HP and the FS at 1.2 HP. Clearance to the fuse is not an issue,,,unless the covering near the tip is loose or can come loose. My two cents is go with the largest prop possible for thrust and modify from there. I do not want the plane to be set up for High Speed and loose thrust...particularly in the event of engine out. You did not mention about what size you are going with on the props. The scale appearance of the Wankels sounds great. MAKE sure of reliability. If on board glow is necessary for reliable idle do it. If it is any help, check out the thrust calculator at http://www.lcrcc.net/thrust_calc.htm.
Send pictures of your project. Have a good day. Twinman "
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Question 157: " Hello, As far as Twins go, Double your pleasure, double your fun, get yourself two engines instead of just one!
My flying buddy and I have flown Midwest TwinSticks and Hobbco Twinstars for a number of year and with various engines. What do you think of the TwinStick from Cedar Hobbies with SuperTiger 34's ? Larry"
Twinman: "Hi Larry, The Cedar Hobbies Twin Stick is a blast, but larger and more maneuverable than the twin stick. While it will fly on the ST 34's, it will not be as much fun as the plane is capable of providing. Mine has two ASP 45's and is a blast to fly. Use 12x4 props for thrust.
Mix the rudder to the engines for hammer heads, knife edge, and flat spins. Note, do not mix the engines too aggressively on the flat spins. Personal experience, it will spin so fast that the fuel is pulled away from the engine spinning backwards in the spin and die...NOT FUN to get out of that situation. Good Luck, Twinman"
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Question 158: "Hello George, i am from Germany and about to finish the Yellow Aircraft p-38. It has Zenoah G-38 engines and about 33 pounds of weight. As you own som of these, please can you recommend position of C_G, as well as Aileron and Elevator throws? I found that C-G moves about nearly one inch when operating landing gear, so what is the right point? I believe that with gear up, C-G is exactly in the position of the forward Aluminium wing connector ( which I replaced with a 30 mm Aluminium Tube). What do you recommend? Thanks for your answer
Twinman: "Hi Detlef, It has been some time since I built my Yellow. Always follow the instructions for CG, but you must balance with the gear Up not down. If you balance with the gear down and raise them, as you say, the CG shifts back and that is dangerous. As for throw, I set the elevator at 1.25" or 30mm, but set the rudders for ALL YOU CAN GET. They are small and really not as effective as you might think. You will need them in an emergency...I pray you do not need. Now, you have Gas engines and you feel safe. DON'T. With two helpers, bring the engines up to full power and get your helpers to CAREFULLY hold the plane vertical and listen for any change. IF the engines change..even a little readjust. P-38's DO NOT FLY WELL ON ONE ENGINE. These have been lost on maiden flights when the supposedly reliable gas engine failed.
Good Luck, Twinman"
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Question 159: "respected sir, all of write ups have given me fantastic info on my twin experience i am on the verge of completing my 2 nd twin which is a kmp p-38 with os fl-70's regarding the use of gyros i have both futaba 350 and 351 gyros with us i am using two servos on the ailerons and two for the rudder. i would like to know if i can use the 351 gyros using a Y- cord on both the channels . the gyro has the capability to take 2 channels would really appreciate a reply regards puneet "
Twinman: "Hi Mr. Puneet First of all, these gyros are also able to operate in the Heading Hold or as Futaba now calls it, AVCS mode. DO NOT USE THIS MODE FOR AN AIRPLANE!! You can operate these gyros as normal, and they will work fine, but in heading hold, the control surface will basically stay where you put it. YOU DO NOT WANT THAT.
You are going to use these gyros to assist or slow down unexpected rolls and yaw, that is associated with an engine out on a P-38, not to control the plane.
Note, as with any gyro and good flying technique, you MUST use rudder coordinated input on all turns, and more so with gyros or the gyro could fight your turn. Inputting a turn or roll over rides the gyro, until you release the control. It in interesting, that during input, such as a roll or turn, any unexpected outside influence, such as wind, is also handled instantly.
Futaba has an excellent section on the use of their gyros at http://www.futabarc.com/faq/faq-gyros.html#q340 and I would suggest reviewing it.
As far as the 351, DO not use a y cord, put one channel into each input of the gyro and one of the outputs to each aileron servo. The gyro is installed in series. This way, no functionality is lost and all the benefits of using two channels are maintained.
One other word of caution about the KMP UP-38. Check the incidence between the wings and elevator. Most of them are produced with a Positive 5 degrees of elevator pitch. This means that the plane will climb or fall, depending upon speed. I personally own the VQ P-38, but that does not mean that the KMP is not a good plane. Per correspondence on this incidence problem, you will have to cut the elevator loose from the booms and rotate downward. Then repair the modification area.
PS Remember to always use a helper with any twin and ALWAYS do the vertical test before ANY and ALL flights."
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Question 160: " Hi Twinman , Love you advices on all the Twins i just got my 1st Twin plane , Need your kind Advice , 1, As i just got my Air retracts , but there is 1 problem with the nose gear , when the nose gear is up , for steering How can i connect to the servo as there is no guide on the instruction manual ? 2, Will saito 82 over kill it ? 3, Will you advice to install gyro on this plane since this is my 1st Twin , Many thanks for you Kind advices . Cheer Eddie ( S,pore )"
Twinman: "Hi Eddie and Happy New Year. Ok, if the retracts are Spring Air, there should be a link like used on regular nose steering gear on fixed nose gear. It should have a large hole in the center for the nose gear wire and a hole on each opposite end from there to connect pull pull cables from each side of the steering nose gear. Make the cables Just Barely snug, so that the nose gear will still lock when down. The cables will relax, and make sure they do not tangle when the nos gear retracts. I make a loop of the wire and crush brass tubing to hold the wires. Make centering adjustments at the servo. The servo shows in my review at http://www.rcwarbirds.com/review1.htm look down near the bottom for the inside view. The lower servo to the left is for the nose wheel.
The Saito 82's, yes is a lot of power, but if that is what you have, suggest go to three blade props. Looks more realistic and reduces thrust slightly.
DO NOT DO A POWER DIVE!!.
A gyro. Well, let's see, do you ALWAYS fly coordinated aileron with the rudder for ALL turns? If yes, then the choice is up to you. If the answer is no, then absolutely do install a gyro on the rudder. I have flown both ways on this plane and one time without a gyro and one engine. Not recommended, but it will do it. Always do the vertical test EVERY time you fly.
Good Luck and send pictures.
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Question 161: " Dear Mr. George Lumpkin, Am I building in Brazil and am I projecting two plants one of a cessna 150 high fin with 94" of span and a Saab 90A Scandia with 110" of span, and will the construction be balsa and ply, which could find out the engines that I should put in the prototype? I am drawing only the external lines in the autoCad and the internal part of construction am doing the hand, because in the close future I intend to put the plant of Scandia for sale. Thankful for the attention, and good flights"
Twinman: "Hi Sérgio, Your English is MUCH better than my Portuguese, so you are ahead of me. I fly a Foker F-27 in the Golden Knight paint scheme at 120", retracts and flaps and am very happy with Magnum 91's four stroke and 20-20 fuel. Now at that power, DO NOT ATTEMPT a loop..Did that...WON'T TRY IT AGAIN!! Take off is very good, as is climb out. Will roll fine, but DO NOT LOOP!
Hope this helps. Twinman"
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Question 162: "Twinman, Ive picked up two ARFs of my favorite twin warbirds. I have a VQ A-26 Invader and a Aerotech International Mosquito T-111 (71 wingspan, 9 pound flying weight). Can you recommend a source for retracts for these planes? Thanks Warren"
Twinman: "Hi Warren. Spring Air is the official supplier for the VQ A-26 and could help with the Mosquito. If you really want the maximum in realistic gear, I would suggest that you check with Sierra Products at http://www.sierragiant.com/products.html.
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Question 163: "twinman what would happen if the engines were facing angles outwards. my thery is that if one goes deadstick it will fly in a reasonably straight line."
Twinman: "Hi, There are many opinions on the subject of outward thrust settings. One is that due to engine torque, the left engine should be angled out and not the right. The Profile P-38 angles both out, for just such reasons as you are proposing. The final truth, to me, is that, no practical engine angling out will prevent the plane from yawing and trying to spin without that addition of rudder control. Learn to fly coordinated rudder at all times. Personally, my engines are placed so that the engines face straight ahead on all my planes.
Good Luck and get to flying. Twinman"
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Question 164: "Mr twinman what brand of on board glo for a Saito 180 would you recommend or what mfg.'s name do you use. I would appreciate your answer,thanks. T.M."
Twinman: "HI TM, There really is no stand out on board glow of one over the other in my mind for the currently available on board glow systems. If you decide to make your own driver using a microswitch, be careful about arcing causing radio interferance. Use a capacitor across the wires at the switch. Some on board systems use 1.2V nicads and others use 4.8 receiver batteries. DO NOT use your on board receiver battery to drive you glow system. I guess I prefer the systems that use the 4.8 batteries as you can quick charge using you field charger between flights.
Good Luck, Twinman"
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Question 165: "I am thinking about getting a larger P-38, I currently have a Wing Mfg. Lightning. What would you recommend? Yellow (100)? Ziroli(114)? Others? Thanks for your time. Bill"
Twinman: "Hi Bill Which P-38? Ok, first my usual questions How big can you move,afford, store and carry? The next logical step up is the KMP and VQ sizes at round 84" and an ARF. You can see my two cents on these two planes compared at the comparison site here are RCWARBIRDS. The VQ is a built up scale type plane and the KMP is a composite, more of a sport scale. I own the VQ myself and am very happy.
I have owned the Yellow and it also is a quick build, but now you are into very expensive retracts and larger expensive engines.
The Zeroli unless you go to ROBART for the arf is a kit of large scale that will take a long time to craft, but has no limit as to scale details you wish to include. The larger the plane, the somewhat easier to fly, as the wing loading goes down and the plane is easier to see.
Good Luck, whichever you decide. Twinman
PS Send pictures to RCWARBIRDS"
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Question 166: "Hi Im flying a trainer and I am building a p-40 from rc store I would like to start flying with a twin. I want to start with an ov-10 bronco would this be a good idea and when do you think I should start building. "
Twinman: "Hi Ben. While I really understand your desire to get into multi-engine planes, I would NOT suggest the OV-10 or any warbird as a first twin.The engines are very wide spaced, which is not good for engine out and the wing loading is MUCH higher. This also is not good for engine out and means much higher landing speeds and a good possibility of stall induce snap roll.
Let me ask this. Did you instructor teach you to fly coordinated movements for the rudder and ailerons for ALL turns? Do you use the rudder for all turns? If the answer to either question is no, learn to use the rudder for ALL turns now. You really have no business flying multi-engine planes if you are not AUTOMATICALLY able to use the rudder and warbirds are worse than sport planes due to above reasons.
Lose an engine and the plane starts to yaw...NOW, then the wing, on the still running engine, raises and the plane rolls over and spins in to a crash. Learning to use the rudder to hold the plane straight as it rolls over is not an option. It must be automatic.
If you are planning a OV-10 using 40-45 size engines could I suggest that you consider either converting your trainer into a twin, using the various procedures I have outlined before or go to something like Cedar Hobbies twin stick.
Get experience with a twin before the warbird and you will be MUCH happier...and keep that special warbird much longer.
Good Luck and send pictures of you project.
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Question 167: "Wonder'n if you've heard anything about the Eurolite B-25 ARF, quality, construction, etc. I was think'n two Saito 100's would pull'er nicely. I'm here in Germany and its availble to order thru a local hobby shop. By chance do you now of any 3 Blade props for a Saito 100?
Twinman: "Hi Breck, Master Airscrew makes a line of three blade props from 6" to 16". I use the 13x8 on a 90 two stroke for my VQ P-38 and P-61.
Perhaps the 14x7 or 14x9 would be better for the Saito 100 due to slower rpm. Grapner also makes a line if three blade props and those should be available in Germany. I am not familiar with the Eurolite B-25, but it might be the KMP sold in the States, but not sure. You might ask our ARF guy about the Eurolite kits?
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Question 168: "Hi Twin man I did fly my first Twin stick today, with excellent results. Very smooth and stable. Open it fully and it really performs!!! Twins sound so nice!!!Everybody were congratulating me with the first flight! What a nice feeling!! Thanks for all your advice and help!!!!!!!!!!!!!
I followed your instructions, and it went well. My plane is the Cedar Hobbies version I powered it with two 46 LA's, with more than enough power. There were a few problems with the kits shipped to South Africa. The fuel tanks leaked, and I found that the firewall were not that properly glued, as you mentioned. I also found the undercarriage to be a bit weak, as it bended on my very first excellent landing.(It was really a perfect landing) To
solve the fuel tanks, I used Great Planes 10 oz tanks, but I then had to move the ply stiffener into the leading edge of the wing. The space provided
for the servo's were also not sufficient for almost any servo. I did cut it open and glued two pieces of balsa inside and then mounted two standard 3003 servo's for the throttles. The engine mounting space is to small to mount two 46AX's which I did break in for the purpose.(The fire wall is made very small and with the mount in place space is to limited, as I see it) I then decided to get two 46LA's as the mounting space or engine width is less than that of the 46AX.(I will be using the AX engines in the DC-4 - will then need two more) As I've said, I think power is enough.
The good news about the Douglas DC-4 is that I will soon be in for the plans of the DC-4. Again thanks for your excellent advice!!!!!!!Best regards and happy twining Hennie"
Twinman: "Hi Hennie, You are just getting started with the twin stick. Now begin to mix the rudder to the engines for better knife edge and spins.
Cedar Hobbies has now bought a factory in China, so no longer only imports a kit but designs them also. I will pass you comments on to them, as they are
interested now in really producing a quality kit. Pictures?
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