Shovel-Head

My Feedback: (1)

I have searched and searched but still can't decide on the engine for my Goldberg Ultimate ARF. I bought the plane with a ST 90 and slimeline pitts. The plane has never been flown but the engine is mounted and the cowl has not been cut yet.
I'v read that this engine is a good choice but other seem to be going with the 120ax or hot four strokes. I can't seem to make up my mind and would like to do it right the first time instead of changing engines down the road. I know this is not a 3D bird but I like to have good power on my planes for a little extra fun. Any thoughts on this from someone that has flown the bipe with diffrent engines?
Thanks!

daveopam

My Feedback: (9)

The ST 90 is a good engine for the GB. I have had two kit built ones with ST 90's on them. Both turned a 14x6 with authority. The ARF I have now has a OS 1.20AX on it. This is over kill in every sense of the word. I mounted two small servos in the tail to get the CG where I wanted it and it flys great. I just never sees full throttle unless it's going straight up. I am also a fan of 4 cycle power. If you go that route a Saito 1.25 would be my choice with the new Saito 1.15 a close second.
One more consideration might be fuel. If you keep the Tigre on there it does not like a lot of nitro. Since I run Saitos on a lot of my other stuff I wound up having a sepperate fuel can for the Tigre with 10% in it. My flight box had 15% in it so when I took the Ult out I had to carry the extra can. It's not that the Saito's wont run off of 10% or the Tigre off of 15%. It's just not ideal. So keep in mind what else are you going to fly?


David

Shovel-Head

My Feedback: (1)

I was thinking about the 120ax or Saito 125 myself. I also want to put to Hitec 225's in the tail just because I hate the Y-pushrode. How did yours balance with the 120? Any bad habbits or anything?

turbo.gst

My Feedback: (8)

I plan on using either a ST 90 or K&B 1.00 in mine.
turbo

daveopam

My Feedback: (9)

With the 120AX and stock muffler with 90degree adapter, and two mini servos in the tail. I got the CG at 3-1/8" with a 6V battery(5 AA cells) just behind the canopy. I made a little tray in the turtle deck and strapped it right there. This is a little tail heavy, but it flat spins really nice. If it has any bad habits, it's from the amount of elev I have put in it. My last GB Ult used the split push rod. I could not get all the elev throw I wanted from it. So the two servos in the tail helped with the CG and gave me a bunch of throw. Turns out this extra throw is not needed. I cant use all the throw for flat spins without it flopping out, and if I pull a little hard in a tight climb or loop, it will snap out of it. It's not a terrible snap, it goes from wings level to knife edge. I thought this extra throw would make it 3D better. It's just not a 3D bird. It still wont harrier worth a darn. It's great at the things an Ult is great it, I just expected to much out of it. Lomceveks and blenders are a blur BTW. :-)


David

daveopam

My Feedback: (9)

A few pics of the servos in the tail.

David

DustBen

My Feedback: (3)

I'd strongly recomend that keeping the model light will pay off in the performance capabilities. The model flies fast without overpowering it anyhow. Any good .60 2-stroke or a Saito .80 4-stroke (light weight engine built on the .65 case) might be best. Bear in mind that the wings are fairly thin... it'll move out well but loading the plane down will, like any airplane, greatly reduce it's mid and low speed handling.

The Ultimate isn't a model for sheer speed so much as what you'll findit'll dojust above the stall speed!

daveopam

My Feedback: (9)

I agree with Ben to a point. I ran 90 two strokes in the other two i had cause it's the same size and weight as a 60 but has greatly improved vertical. To each his own and I am not saying Ben is wrong. it's just a different approach.

David

prop wash

Try a saito 180.I've flown mine for about ten years now and replaced the fire wall two years ago with 1/4 " ply.This is one great combo.Unlimited vertical and I do most flying at half throttle.Pic 1 shows that I recovered it also,new sceme.
Tom

fallingleaf

My Feedback: (1)

Second David on the 120ax - perfect. Sato 1.80 would be good too and more authentic in terms of sound.

I'd dull down the pitch on any prop though as you don't need insane top end speed more thrust (will help slow you down on landing too). Get the CG right and you can get some pretty mad scale aerobatics going on

juanjulian

My Feedback: (9)

dle 20 gas engine.

It seems it is th equivalent.

The engine will pay itself

Twin_Flyer

My Feedback: (4)

I have a YS 120 on mine.

I'll snap a few pics this weekend and post them.

Have not flown it yet.

Bill