Ok chaps need help on what engine to fit to a seagull spacewalker 40, this will be my second model. Its a large 40 size (more of a 50) at 61 inch wingspan.

I wanted a four stroke for it and after reading and looking about I thought the sc 90fs I have already for a future sig hog bipe would be to heavy for it.
With this in mind I bought aasp 61 four stroke as it weighs about the same as a 46 size two sroke and a 52 four stroke.
I looked at the sc 70 fs but did not buy it as itweighsmuch the sameas thesc90fs that I have (prob would have been the perfect choice).

Anyway turns out when balanced upside down at 7.5 to 8 cm from leading edge the plane will balance perfectly with no weight added with the 91fs.

To balance with the 61 fs I will need to add weight to the nose even if I move the battery to the firewall, this plane seems to be very tail heavy and able to take a large engine.

Im worried that the plane may be underpowered with the 61 fs and overpowered with the 91 fs, another engine is prob the real answer but if you had to choose one of the two engines I have what would you do.

The plane would fly fine with a 61 fs. However, if you have to add weight to the nose you might as well add weight that makes power

Put a Magnum 70Fs in the nose. I have heard they are a perfect match. The Spaecwalker is not a high speed plane, it will fly with a 61Fs in the nose very well. The magnums are on sale right now too.


Dru.

Thats what I was thinking stang but I welcome any advise as to what problems I may/may not have with each choice.

I thought a 52 fswould besimilar in power to a 46 two stroke and a 61 fs would then be even better but now I believe this is not the case and I dont want a guttless model (i know the spacewalker is not designed to be a fast plane) as she is quite a big bird that looks like it will have a lot of drag.

The magnum 70 weighs almost the same as the sc 90 fs I havei think thats why im thinking the 91 fs would not be a issue to fit

not sure why my font is bold now im not shouting

thanks for the quick replys so far

If it where my plane a .70-.82 four stroke would be ideal. The 91 would hover it (with the right prop). The engine does not make the model fly too fast! the throttle stick and the elevator stick do.

I'm running a Satio .72 in mine.
Flies nice and sounds good.

Tim

dont make this mistake, i bought a yak54 and it called for a 46 2 stroke or 70 4 stroke. i used the same line of thinking you just used...well its only 3 oz more... but that isnt counting the much larger prop and the larger spinner (you should use an aluminum one for 4 strokes)
get the 70 and you will be fine, my yak flew horrible even though the balance was spot on, just to much wing loading and not enough speed w/ the 4 stroke. it may work if this is a really floaty plane but i still wouldnt do it
the 70 will be plenty of power, the 61 may be enough.

I'm flying a seagull spacewalke 2 with a OS 46 AX and it flys great.Has plenty of power and can fly around at half throttle no problem.
You'll like the plane!

a wee update. The spacewalker maidened today with the sc 91fs, no lead on theplane it balanced perfectly!. 7 lbs all in.
Nobad issues on take off and minor trim required.Slowed to a crawl with out stalling badly and burst into life with the throttle (sounds great).
The plane came in to land and floated in at idle no problem this plane seems really happy with the big motor onit.
Maybe I will rip the firewall off with a heavy landing due to the weight on thenose, time will tell, saying that I would have had to put the battery and 3/4 oz of lead on thefirewall to balance withthe asp 61fsso whats the difference.
Think I will have fun with this as my second plane.