Test005

Just wanna ask you twin guys on any tips for changing a standard glow trainer into a twin airplane.
Curious on how to build the nacelles in the wing and the do's and don'ts.
I have a LT40 with an OS.52fs and this thing flies great, it's my everyday cruiser and I really like it.
Sometime I'd like to try out a twin and perhaps a trainer like this would be a good start for conversion...?
For engine's I figure 2 * .30-fs would be good? (fourstrokes are prefered)

Any build-alongs, links or tips you can share?

jaka

Hi!
Well it's an easy fix.
All you have to do is to make two rektangular boxes from balsa and plywood, and then glue them into the wing.
Then remove the amount of area you feel necessary in the wing to have these boxes fit.
You mount the engine up front using a plastic engine mount (best is Dave Brown)and inside the box you mount the tank and mount the throttle wire (I prefere thinnest Sullivan wire). Best way to mount the engines is side ways. That way it is easier to line up the tank and carb.
No side trust is needed, mount everything 0,0,0 degrees (engines, wing and stab)
For your model twin .30 fourstrokes would be fine, or .20-.25 twostoke engines.

Regards!
Jan K
Sweden

Test005

I belive those boxes, (engine nacelles) need to be of the same width as the bay between two wing ribs in order to have somewhere to glue them?
Any plans available on the Internet do download for building these boxes?
For trottle linkage I think it would be easiest to use two separate servos or are there and good ways of linking two trottle pushrods together?

csandt051196

My Feedback: (35)

I took an old Midwest twin stick and made a tri-engine plane out of it. The original kit had two engines and the nacelles were mounted between two ribs. The only angel was the firewall and it was mounted at 20 degree (I think) out thrust. Make sure you build your nacelles big enough for the tanks you want to use. I made my wing 6" longer just because it is carrying more weight. I wish I would have made the rudder and elevator bigger. I would suggest making your about 20% bigger just to have the larger throws. No matter what it will land heaver and faster than you expect it to. If you search for Midwest tri-stick you will see a picture of my bashed kit and you can see the engine set up.

I am surprised Twin-Man has not responded yet.

Good Luck!
Scott

BillS

Maybe pictures will spark your imagination.

The bathtub nacelles have been on three different trainer wings prior to the Kadet Senior. The Cherokee is an unfinished current project.

Bill

Test005

Thanks for your answers guys.
I have no current plan to gut my LT40, it's new and not crashed + the .52fs is a great power plant.
Wanted to get my head around how to get into twins and thought a trainer would be a good way to start...
I figure any low wing sport plane als o would be suitable for conversion...? Let's see if I try to get into twins sometime soon, looks fun& definately sounds great (2x fourstrokes )!

William Robison

My Feedback: (3)

OK, one more time.

This airplane, which I call the "C-3/10" was originally a Hobbico HobbiStar 60.

Granted, a major bash from stock, but it's an example of what can be done.

"Before" picture atrtached also.

Bill.

Test005

Wow, that's a pretty amazing conversion, looks great! I was more in the line of:
-Take a chep trainer or low wing sport plane
-Attach two engines to wing
-Go fly

donniercjet

My Feedback: (10)

i just built a twin out of a trainer what i did was cut the l.e. out between 2 ribs take some cardboard paper and copy the rib from the l.e. about 3/4 back making cut outs for the spars take your template and set on top of another piece and trace it using the tracing draw out your nacelles to your liking(mine looked like the twin star nacelles) as long as there not taller as the ribs are wide test them to make sure you can lay them in sideways so that you can roll them in place and lock into the spars once your happy with the finished template copy it to 1/8 ply make 2 and glue them to the ribs now your locked into the spars build your firewall use 3/16 balsa stripes and glue them to the inside top of your nacelles so the top piece will screw into to hold the hatch use 3/16 for the top hatch and sand it so it has a nice arch to it same thing to the bottom but i used 1/8 balsa for the floor and fuel proffed the snot out of it i was able to put 6oz. tanks in the nacelles on mine....... good luck donniercjet

twinman

My Feedback: (2)

Hi Test 005
Here is one of the articles I have posted on this subject in the past.
Hope it helps.
twinman

Subject: Kit Bashing 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 engined war bird,
consider "bashing an ARF" to a twin.Yes, the Hobbico Twinstar is good, and
an excellent flyer, but small compared to the larger war birds..
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.
Sheet under the new nacelles. Now, one idea that has worked well for me,
on this conversion is to make the nacelled longer than necessary. Mount
the engines to the firewalls, that ARE NOT mounted to the nacelles. This
allows the engine assemblies to me moved forward and back to get a
better balance and reduce extra weight. Once you find the best balance, them glue in place.
Warning, the wing loading sky rockets!! 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.
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. ( 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. 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 for 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. The plane can go so fast in a dive, aileron
flutter will result!!! Yes, you will do it!!
This plane will go straight up and flat spin like you would not believe, as
well as knife edge all day.
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 light
weight.
One plane that works well is to take two Long John 40's, combine the wing to
82", two fuses 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 that one and still fly
it today with two .45's. Instant "Twin John".
Still another is to use two Ugly stick .60's and build as with two
fuselages,as the Twin Long John. Take the arf's wing halves and glue as
normal, then shorten the center joint four rib spaces for only one new
joint.This yields around 86" wing span. I recommend adding carbon fiber
strips to the top and bottom of this wing to reinforce against the new found
power and maneuverability. Two .60 two strokes fly it well and now trying
for two .90's (More power ARGG ARGG!!) Pin the firewall with epoxy and tooth
picks to stand the added forces.
Sheet the center section joint, and glass for additional strength.The
horizontal stabilizer is formed using the original stabilizers shortened in
the middle. 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.
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
center line 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.
Whatever you do have fun with it, but practice before the first twin war
bird on a cheaper alternative. Been there done that..don't do that!!!

Twinman

Rcpilot

My Feedback: (78)

If you want to bash an LT-40 into a twin, simply order a wing kit from Sig or Tower and build a second wing with the twin engine on that.

Then you can swap between single engine and twin by simply changing out the wing and removing the front engine. I'd cut the stock cheeks off the front. Then make/buy a cowl that can fit over the front end. Attach it with a few screws into the firewall when the front engine is taken off. Instant twin.

Or, leave the front engine on and you got a triple engine. Ya might want to stretch that wing a bit though.

twinman

My Feedback: (2)

Here is a twin Kadett that was done exactly like the above suggestion, but the wing is 8" longer. The owner did change fuse's to get the tri-engine combination and it flew really pretty well. It did not stop there, though,,,the five engine version was..........a .........Bit much!!!
Twinman

Boomerang1

Hi Test 05, I converted a Sterling Gazariator (old shoulder wing model) to a twin & then a four engined model & then back to a twin. I made the nacelles strap under the wings with rubber bands, a dowel through the front of the nacelle & a single dowel at the back facing the rear. I put some notches in the ailerons to let the bands go through. There were locating pegs to stop the nacelles floating around on the wings & the fuel tanks loaded from the top through the hole in the top of the nacelle. Worked great, the model was eventually retired due to old age. - John.