<span style="font-size: small">Irecently got my first nitro 3Dcapable plane. It's a U Can Do 3D .46from GP. For 3D nitros, what do you prefer a 2 stroke or 4 stroke and why?

I've flown mostly nitro/elec helis and electric planes and foamies.

Aloha,
Les</span>

A U Can Do 3D can in fact do some of the 3D maneuvers. The main reason it isn't an all-out 3D'er is the weight (wing loading).
There are only 3 engines I would consider for it.

I tend to prefer 4-strokes on 3D planes as they get the airframe moving quicker (not talking about top speed). If this was a 4-5 lb bird, it would be good on the .55AX.

1. OS 55AX 13x4 Xoar or APC sport. Would be just enough power.

2. Saito 82 14x6 Xoar or MAS S2. What I would recommend as a first four stroke for this plane.
You could also move this to a profile later on. (Easier to get the needles right than the YS)

3. YS 70 13x6 or 14x4. This is easily the most powerful of the three and would be my choice. It is not necessarily a good first time four stroke though.

Another consideration would be an OS 81 alpha but it's another 2 oz. heavier and every ounce counts.

Keep the stuff you add to it light. Be careful not to add weight to adjust CG. Get that right by motor placement after the other gear is in place.
Decent light servos for it are DS-821 Spektrum or JR on 6V.

The OS 55AX does have a lot of grunt for a 2-stroke. It reminds me a lot of a 4-stroke (the way it pulls and runs) on my OMP Yak.

Ernie

I have the same setup as Ernie and am very impressed with the 55ax. Pulls hard, throttles up quick and very very reliable. I found it on ebay NIB for $100 - so I had to try it, and very happy I did. Using Xoar 13x4 and OS F plug

<span style="font-size: small">I'm currently running an OS55AX with a 13x4 APC, it flies rather well with this engine. Iwould however like a little more power to pull out a little quicker from low altitudes, as I've been flying helis, parkflyers, and foamies and have gotten accustomed to flying in small areas and low altitudes.

Iwas thinking of trying an OS91FX or one of those ASP4 strokes as they seem to have decent reviews. Not too mention they are fairly cheap and if Idecide 4 strokes or nitro altogether is not for me I'm not out too much $$. Ican just convert this UCDto electric.

Thanks for the replies guys, keep em coming.

Aloha,
Les</span>

The 91FX is not a great 3D engine unless you can find a 3 needle carb like the 7L (rare).
Cheap 4-strokes get you less power/weight. Go with Saito or YS and you won't regret spending the money.
Os was in the low power to weight category until the alpha series came out. They are way too spendy though.

Electric is a better option as every day passes. The motors are getting better but the real advances are in battery and ESC's.

How much does the UCD weight ready to fly?

For faster throttle response you might try:
Try a wood prop - Lighter so faster spool up
Also a good, fast throttle servo - HS 85mg

You can also comb the classifieds and ebay for a used saito. You can find deals out there if you know what to look for.

<span style="font-size: small">Iam new when it comes to Nitro planes, so let me see if Iunderstand correctly.

Is this because this engines power is mostlyin the higher end of the throttle range( 3/4 and above) and many 3D planes utilizethe lower throttle range (0- 3/4), and with only a 2 needle carb its harder to tune the midrange where most 3Dpilots use?
Is 4 stroke preferred because of their ability to make power at a lower rpm with more torque swinging a bigger prop moving more air, instead of moving air faster?

Forgive my limitedknowledge when it comes to2 stroke vs. 4stroke, but this is the reason Ihave come to you who have the knowlegde soIcan educate myself.

Aloha,
Les</span>

I've had 3 of the 46 Do's and the engine set up that I've found to be best on them is the Saito 82 with a 14x4W APC.[8D]

In a nutshell, it has poor mid-range performance and swings a small prop.

It's partly that and the 4-stroke will change the speed of the plane quicker because of the bigger prop.

<span style="font-size: small">Thanks for the info TSkull. Iam just trying to grasp the how's and why's of Nitro 3D.
Now Ijust need to find a great deal on a Saito 82 and I'm set. Unless of course Idecide to convert this UCDto electric.

Once again thanks for the info.

Aloha,
Les</span>

Les,
See if you can find a used Saito 72. This engine will also work well in an UCD.

I fly both 2 and 4 strokes in my 40 size slabs. It's just a matter of personal preference and flying styles.

<span style="font-size: small">Has anyone tried a Saito FG14 gas engine? If so, how is it working out for you. Nitro isn't getting any cheaper here in Hawaii, and if Ican save some $$ by using gas instead of Nitro Iwill. If anyone has tried this let me know your results.

Aloha,
Les</span>

Gas under 30CC and 3D don't work. The power is not enough to overcome the extra weight.

<span style="font-size: small">Well Iwas going with this advice, however the LHSdidn't have any wodden 13x4's. Ifound a 13x4 K series MasterAirscrew. At first Icouldn't get it to run too good. Fiddled with the needles, still not happy. Changed from an OS8 to an OS 7 medium hot plug and she ran better. Wow what a difference, my engine was really screaming now, richened her up till she was 4 turns out on the hi needle. Ihad it so rich but the rpms were still up there and the engine was still cool 150*F. This sucker climbed vertical with lots of power, Ididn't get a chance to tach it. Ithink I'll try a Kseries 14x4 or 15x4, maybe then Ican still get alot of power and lean her out a little. It just seems like with this lighter prop Imay be able to go with a bigger diameter while keeping the pitch, without straining my engine.

Istill need to fine tune the lo end to get the midrange running cleaner and more reliably. Imay not even need a bigger motor to get this UCDto perform the way Iwant it to. Just a little more fine tuning and throttle management.

Thanks for the help guys. I'll keep you posted on my progress.

Aloha,
Les</span>

Re-read post #2 where I covered the prop you should use on that engine.

[<span style="font-size: small">quote]1. OS 55AX 13x4 Xoar or APC sport. Would be just enough power. 2. Saito 82 14x6 Xoar or MAS S2. What I would recommend as a first four stroke for this plane.[/quote]

Icouldn't find a 13x4 APC sport or Xoar at my LHS. And Ididn't know if you meant the 14x6 MAS S2 could be used on my 55AXas well as your recommended Saito. At any rate mt LHShad a lot of wooden props too so Ifigured I'd look that way like someone else had mentioned. Since there wasn't a wooden one Itried a 13x4MASK Series.

Iam still looking locally if any of my club members have a Saito like you were suggesting. Iam still leaning towards running a 4 stroke in my UCD, but if Ican get decent performance from my 55AX Imay just stick with that. And use my money to get one of AJ's or ExtremeFlight electric planes.

Thanks TSkull. Guys here are great so much info for those who need it.

Aloha,
Les
</span>

14x6 is too much for the 55AX.
The 55AX best prop is 13x4 Xoar wood or APC sport (not W).
The 55AX should be enough with the right prop.

If you switch over to a Saito 82, the prop for the 82 is a 14x6 Xoar or Master Airscrew S2 (MAS S2).

Hi what size 4 stroke would be best for a 40" profile 3D plane? The air frame weighs 1 lb and I have not added electronics or servos yet. I am guessing the total weight to be around 2.5-3 lbs. I was thinking a saito 52 or 65? not quite sure yet.

Good choices or the older Saito 56 which might be found cheaply.

Ernie

If you really do come out at 3lbs all up weight, the 56 would rock it. If you are at or closer to 4lbs, the Saito 72 or YS63 would be better.

In answer to the original question on this thread, my vote goes for 4 stroke hands down. In my opinion there's no 2 stroke that can deliver the instant power like a 4 stroke and I've flown plenty of both.

I've flown both 2 strokes and 4 strokes in "40 size" 3D profiles. Despite the general consensus of a 4 stroke being superior, I still prefer a good 2 stroke, such as the 55AX over a Saito 72 or 82.

TTTTwo-stroke for me on 40 size. Above that I like the overcomplicated 4-stroke.

I think what it boils down to for me is that I think the right size prop for a 40 size is 13"
Bigger than that and the tail is more sluggish.

The AX series all seem to have gobs of grunt!

Ernie