Multi-Engine Guy

I'm new to rc u but have been flying model airplanes for over 25 years.In order to keep my interest in the hobby going strong I decided to start flying multi-engine aircraft. I started with a scratch-built F-82 Twin Mustang, which I still fly. I then Put together a V.Q. Models A-26 Invader and I am currently working on an old Royal B-17 (About 85% finished). I'm debating on which medium I should use on the fiberglass cloth for the finish(Epoxy vs. Zap) I'm leaning toward zap to keep it light. If anyone is interested in Pics of it let me know.

jrlingrel

Iwould love to see pics fo the A26. I worked on the real airplane in Thailand back in the 60s and have often considered building one. Ieven had a chance to get a flight in one for a maintenance check, what a rush when he fired the 8 50 cals in nose.

John

jaka

Hi!

Keep it light!
When I built my Marutaka DC-3 years ago I decided to lighten it in every possible way. Because light planes always fly better (Slower, more scale like)
That meant hollowing every balsa block and replacing every heavy item with lighter ones and only using small mini servos and the lightest covering available and still be "scale like".

I decided to first cover the fuselage with 25g glass-fiber weave and 24 hour laminating epoxy to have a though surface and then sand it to a smooth finish and cover it with small strips of Oracover chrome plastic film (wet sanded on a piece of glass).

Ca glue is fine for building (use it most of the time when I build ) but would not do when covering with glass-fiber.

I-fly-any-and-all

My Feedback: (1)

pictures! pictures! pictures!

Avaiojet

Jaka,

Great looking model!

Isn't this stuff adheasive backed? "Oracal." One of the vinyls I use offers a "chrome" vinyl. Could they be the same?

Good idea the wet sanding. 400 or 600?

Multi-Engine Guy

Hey jaka,
Sorry it's taken so long but here are some pics of my Royal B-17 build.
I'll post more as my build progresses.

______________________________
Jon

Multi-Engine Guy

Iguess I tried to post too many pics..... I'll try 4 at a time.

jaka

Hi!
Nice plane!
Four 2,5cc two strokes (OS LA .15) and 8x5, 9x3 or 9x4 APC or RAM props would be perfect for it!
I would replace the standard servos with Hs 85 servos on throttle and side rudder and use Hs 225 on elevator and ailerons.
I would also recommend using separate tanks (4oz) for each engine.

Personally I would not use Sullivan golden rods for throttle linkage, it's heave and flex! I would either use separate 10g servos (Like Hs 50 or 55) or using 1,5-2mm carbon fiber rods and bellcranks which will be lighter and give a more accurate movement. I use "Blue Bird" 9g servos for throttle in my DC-3.

I mostly build all my models with Ca glue. But Ca glue is not working with 25 glassfiber cloth. For covering a fuselage or wing with glassfiber use 24 hour epoxy, like West systems.This is the preferred method. Not Ca glue!!! Easiest to use though is polyester resin.

Oracover is a very good covering plastic film, called Ultracote in the US. I mostly use a covering iron to fasten it.

I-fly-any-and-all

My Feedback: (1)

please do yourself a favor and save the headache. go with one servo per engine, it will be very frustrating to set up all the throttles with out the binding and having slop with one servo.

and here are the real retracts air powered for your royal b-17 http://centuryjet.com/product_info.p...roducts_id/209
I knew someone made them.

Multi-Engine Guy

O.K. Here's the deal, first and formost thank you guys for your concerns
and insights. As far as the throttles, I left a space behind each nacelle
for a mini servo in case the one servo set is a failure(Which it probably
will be). I'll just need to cut out hatches on the bottom of the wing over
each area and cut and use the nyrods to actuate the throttles.

I am not going to use nyrods or bellcranks on the ailerons as it is already
set up for two servos. And thanks Jaka, I will be using new good Quality
servos all around onthe B-17, and all of my planes, as I almost lost my
F-82 this weekend due to an old/weak servo(A Futaba s-148 with about a
bazillion flights/crashes on it, which dated back to about 1987/89.....How
could it have possibly failed?). Hey, I know, but Ibuilt the F-82 back in
1999, and it's had a ton of flighttime puton it over the last ten years,
so I should have expected it. Thankfully, I always do a preflight before
each and every flight...... sure has saved a lot planes!!

Thanks again, Jon

I-fly-any-and-all

My Feedback: (1)

good no I'm at ease. did you see the retracts for it in the link?

Multi-Engine Guy

I fly any and all,
Yes I checked the c.j. Retracts, I wasn't aware that they were
still manufacturing those units, I remember seeing those years ago.
Very sturdy looking gear, although a bit on the pricey side for me at the moment.
I am looking at other gear options, but will probably stick with mechanical units
if I can't get the homemade jobs to function(They go up and down and lock just fine,
beyondthat, they're weak and sloppy) adequately.

I'm putting a lot of time and effort into this project and I like my planes to performwell
and last a long time (Ihate crashing). So IknowI will want to go with a sturdy and
reliable retract system and will definitly consider those if can'tfind anything better.
I really like how the struts areat the proper angle and it travels at about 80deg.
and the fact that I can slow down the retraction time.



~Jon~

Multi-Engine Guy

I've got the wingtips attaced and shaped. Next step is to glass
the wing.

~Jon~

jaka

Hi!
I would not recommend glassing it! Too heavy with 25g glass fiber and paint ! Use Oracover instead (Ultra cote to you Americans)! This is a small plane and it will fly like a pattern plane if built heavy! -Do you want it to be such a plane ???
Have a goal to have the plane weigh around 3,5kg ready to fly!

I-fly-any-and-all

My Feedback: (1)

glass glass glass! are you using finishing resin with filler mixed in or polyurethane?

Multi-Engine Guy

Jan,

I’mpretty sure I’ll need to glass the wing to strengthen the

Structure. The manual states that the wing is “weak” and “should be

Fiberglassed. Adding to this, is the fact that the original builder removed

Most of the #1 rib(center) and mainspars out to the #2 ribs for a working

Bombay. Not wanting a Bombay or a foldable wing, I opted to scarf back

in the #1 rib and wingspars with some reinforcement added.

This area will be glassed with some heavy cloth top and bottom, with the

Rest of the wing being glassed with 3/4oz. cloth.

As far as the ultracote goes, I have been using this and the Ultracote Plus

Exclusively on my models for the past twenty years. I have mostly flown

Small scale models and this stuff does keep it light but at a cost.

My problem with plastic covering is longevity. It just doesn’t hold up over

Time and it only re-shrinks so many times before it begins to deteriorate.

Fuel creep, wrinkles, bubbles etc. And once fuel gets under it, it becomes

A problem keeping it in place. Most of my planes have been flying 7-10 years.

All are covered in ultracote and all of them need to be recovered (after I dry out

Fuel soaked areas)

Bottom line is, I’m pretty sure I’m done with Iron on covering, especially as I

Begin to get into larger more scale like planes. No, I don’t want my B-17 to

Fly at supersonic speed, but I am used to flying small scale planes with high

wing loading and can fly them at fairly realistic speeds, albeit carefully.

I’m planning on powering the B-17 with O.S. fs-26’s inboard turning 9-6

3-bladed props. And O.S. fs-20’s outboard turning 8-6 3-bladed props.

Or maybe four O.S. fs-26’s .

My question Jan, is, how do get your covering jobs to last, avoiding the

Problems I have encountered. How do you prep the wood etc.

~Jon~

Multi-Engine Guy

I-FLY-ANY-AND-ALL

I am going to glass the wing and more than likely
the entire structure. but JAKA is right, this will be
heavier than iron on covering, so I'll want to keep
it light. For the last 25 years I have flown small
scale(.20-.40size) planes, kits, scratch-builts
and ARF's. All of the ones I've built have covered
with iron on coverings. This will myfirst complete
glass job on an airplane (I repair and Restore
old classic surfboards- using polyester resin and
much heavier cloth).

I thinking of using the Z-Poxy finishing resin.
What filler are you referring to?
anybetter resin?

~Jon~

Multi-Engine Guy

Jaka

Here's an example of my use of Ultracote. This is a
House of Balsa .20 size P-51D. I applied large
pieces of covering(standard application). then I taped off
and scotch-Brighted each panel, with a very slight overlap
to leave the panel lines. This plane has been a regular
flyer since 2002. It takes alot of maintanence to keep the
wrinkles at bay. This covering is pretty much "dead" as
some wrinkles refuse to re-shrink for very long.


~Jon~

Multi-Engine Guy

The pics wouldn't post,here they are I hope......

I-fly-any-and-all

My Feedback: (1)

I'd try west systems e-poxy its a 1 to 1 mix and they have a few different fillers aka micro balloons that I would mix in if it were me.
how about four o.s. .20 four strokes? you could try http://mecoa.com/ for engines.
Now lets see if I have this right, you placed new spars in the areas where someonbe had removed them and replaced the center rib as well?
If so then you did a fine job but also you will want to double the spars up in the area where the old meet the new.

Multi-Engine Guy

Mecoa sells the old O.S. fs-20's? wow, that would be cool, I'll check
it out. As far as the wing spars are concerned, I did double the area
where they join, but I still plan on laying 4oz. cloth over this area,top
and bottom. I have four .26's, but feel this will be overpowered.
I had seen at least two royal B-17's in r/c magazines back in the late
80's/early 90's, that used the two .26/two .20's set-up. They claimed
that it worked great. If it doesn't work great I'll go with four of one kind.
Four .20's would be ideal!

Thanks, Jon

Multi-Engine Guy

Hi Jan
I have been weighing(Literally) covering options,
and after carefully reading your first post on this thread,I see that
you glassed,but did not paint, you just used the oracover.
After checking out a lot of other Royal B-17's, I've found they
all seem to have one thing in common, THEY"REALLOLIVE
DRAB!!! And after having stared at your awesome looking
DC-3, I've come to realise, I want an aluminum looking B-17!
So, I'm going to glass it, But I'm not sure what would work best
for me, the flite metal type covering(which I know nothing about),
ormaybe the they way you apply oracover(Ultracote).
Any way you could fill mein on your technique?
and would it be okay for a weekend flyer? Wouldit hold up well
with regular use?

Thanks, Jon

Multi-Engine Guy

Jan
One more thing, I definitly want to keep it as light as possible,
after having watched a number of videos of royal B-17's that were
flying WAAYYY too fast!

Jon

jaka

Hi!
My DC-3 fuselage is first covered with 25g glassfiber using professional 24 hour Epoxy resin...not the hobby stuff variety.- There is a huge difference!
The epoxy I use get glass hard after 18-24 hours,but is easily sanded.

After I covered the fuselage I spray painted it with Sikkens Autocryl 2 -part primer filler, then sanded it to a smooth uniform surface so that the wood grain would not be seen through the plastic covering. Then small stripes of Chrome Oracover was placed on a glas surface and wet sanded with 1200 grade wet/dry sandpaper.
Each strip was then placed on the fuselage and fastened with an iron.

On places with dubble curvature such as the rear most end on the plane and on the wing fillets , I used pieces of aluminium duct tape (first wet sanded on piece of glass).

Oracover fastens very good to a sanded glasfiber surface, soo you don't have to be anctious that plastic film loosens over time.
The only Oracover film that does not like to be strech repetadly is the "silver" variety.That's my experiance!

I would stronly advise you to put in a wing spar in the wing and not only rely on a glass covered surface. Using a thin spar is both stronger and lighter than a glassfiber covered wing and will also give a more ridged wing, which is good.

OS FS .20 will give plenty of power and is a good choice I think.
If you want I have scale, carbon fiber, 3-blade, "Hamilton standard" typ props for the OS .20 and .26. which will perform equall or better than the best 2-bladed props ( RAM or APC.

It's a very common misstake by newcomers to twin engined planes to over motorize them! Saying: "Better to have much power than too little...I could always throttle down" Sorry to say but saying so only reveals how little they know about twin engine flying and how to build.
It's much better to use as small engines as possible and build as light as you can. That way ,if everything works out as you have planned, you will have a smoth, easily flown airplane that behaves like the full scale plane in the air, not like a pattern plane!

I-fly-any-and-all

My Feedback: (1)

I'd use the hp .21 http://mecoa.com/hp/vt/21.htm
no neccessary adjustments on the valves!