Planejaw

My Feedback: (53)

JD,

I built a spacewalker last year, put a new Saito 150GK in it. Flies very well, should also fly well with the G-26. I've got a number of gas airplanes and much prefer the cleanliness of the gas burners.

As for flying surface controls, I installed two elevator and one rudder servo in the tail section, to help offset the weight of the Saito 150. I originally had 2/56 rods on the surfaces and have converted them to 3/16" carbon fiber tubes and 4/40 titanium rod ends (from Abell Hobby). Same with the control rods on the ailerons, which are now all carbon fiber/titanium rod ends.

I've only got about 6 or so flights on mine since building it last summer. Very nice airplane, very light, so watch for vibration and be sure to balance your prop. Aircraft seems to like a much more forward center-of-gravity, but again, I need to get more flights on mine this summer.

MormonMike

My Feedback: (2)

Yup, same set-up as mine except I use 4-40 rods all around. Does'nt float in on final at 4500 feet ele though, kind sinks fast. Just luv it. MM

Sandmann_AU

Hey guys... Just bought myself a Spacewalker 120 to be the new home for my OS FT160 (after the last home decided to land upside-down at speed). Using Spektrum DS821 servos for everything except the throttle, MAS classic 16x8 prop (might switch out to a wooden prop later, the plane's style screams for wood here), and Dubro 4-40 size pull pull rudder, otherwise everything's staying as it came in the box. I'm usually a kit builder so I'm pretty picky about the hardware I use (since I normally choose it myself) but I have to say I was pleasantly surprised with the quality of hardware in this ARF, even the tank looks reasonable and for once I don't have to swap it out for a larger tank!

I was thinking about getting the Keleo exhausts to suit the FT160 Gemini engine and have them exit under the plane, but since the heads will stick out either side of the cowl I won't be using the (dodgy looking) dummy engines so I'll stick with the standard exhausts and just add some alum extensions to them to emulate the scale pipes from the Lycoming engine - it'll be nice to have "scale-ish" pipes that are actually functional!

One thing I'm scratching my head over right now is how to get the cowl over the twin horizontal cylinders without hacking it up too much. I'd considered removable/hinged panels on the sides of the cowl to give me "wiggle room" but I'm leaning more towards cutting the whole thing in half horizontally at the prop shaft and mounting the cowl as a two piece unit, using thin ply at the joint to reinforce it. Any better ideas on that before I take to the cowl with a dremel?

The plane seems really light for it's size (probably because I'm comparing to kit builds!) and with those enormous fat wings she should really float along. I'm looking forward to seeing it in the air.

I've taken some pics of the FT160 mounting and will also photograph the cowl solution (once I finally decide on it), so if anyone wants to see them let me know.

Planejaw

My Feedback: (53)

Matt, splitting the cowl makes good sense. Some cowls on full size aircraft are also split horizontally, through the prop-shaft. That way, when looking at the aircraft from the top, you won't see the seam or screws, but you're also dealing with a little more complication getting around the cylinder openings in the cowl. Either way, it should actually look a litle more scale with a split cowl. I'd like to see some photos when you're done. Didn't put any fake cylinders on the left side of the cowl on mine...looked just a little too fake.

John

MormonMike

My Feedback: (2)

Here's another way of installing engine with an RC Specialties type turbo muffler. MM

Sandmann_AU

hey again all... l'm close to finished building this plane - just got the cowl, CG, and a final check of all connections before a ground test. I'm setting up the throws on the control surfaces, rudder & elevators were pretty much as expected but when I got to the ailerons the manual calls for 3/8" for high rates and 3/16" for low! Is it just me being used to more aerobatic machines or does this seem way too small to you? What sort of throws did you use, and what sort of roll rates do you get?

Planejaw

My Feedback: (53)

Matt, I've got my control surfaces set up for quite a bit of throw on high rates and somewhat lower on low rates. Not sure of the exact numbers, but the manual's low-side is just too little throw. I pretty much set up for max throw based on the servo and linkages for high-rates, then back it down at least 50% for low rates. Fly most of my aircraft at high-rates and use a deft touch on the controls. You'll always have max if you need it for anything.

The Spacewalker is not a strong aerobatic performer, but it will hold it's own in basic aerobatic maneuvers, but remember, the original wasn't really designed for that. With that large rectangular wing, you'll want plenty of throw to roll it. Does it most scale like, though. But if you're looking for a real zippy performer, this ship won't do it. Converting all of my 2/56 rods to 3/16" carbon fiber and titanium ends, so I'll get a better feel for her this spring. Should be a little more responsive.

John

Sandmann_AU

Yeah... I'm not after an exciting (read nerve wracking) aerobat with this plane... more of a sunday afternoon relaxing flyer. I'll leave the aileron throws standard for now and use high rates if I want more roll for the first flight or two.

Well, I've finished the assembly, the only thing holding me from ground testing it is waiting on Tower Hobbies in the US to send me a replacement exhaust pipe - the last crash sort of bingled one of them and now it won't seal. I've got tomorrow off so I might just fire it up anyway and see how it goes.

As promised I took some pics of the twin cylinder engine mount and my cowl solution. I ended up removing a "chin" from the lower front of the cowl which worked out really well as you'll see.

Sandmann_AU

OK then... as promised some pics. In order of appearance...

1. The FT160's a lot easier to mount than regular single cylinder glow engines. The back plate has vertical & horizontal centres marked on it, so you just match it up to the firewall marks. Yeah, I know the horizontals look out of place in this pic, but that's just parallax error from the camera angle.

2. The stand-offs I used to get the engine where it needs to be. I can't remember where I found these... they were online someplace - might have been Desert Aircraft as they're intended for gas engines. Nicely made, very light, there's 3 different length "mains" available and they all come with 3 different sized spacers giving you a lot of "play". I ended up removing the thinnest ones for a perfect length firewall - prop drive.

3. The mounting plate fitted with standoffs. The thing I love about this engine is being able to easilly remove the engine with 4 screws and still have the whole mount undisturbed.

4. The engine in place on its mount.

5. Engine mounted, with all the plumbing, wiring, & throttle control in place. You can just see two copper pipes I put in that exit below the plane. These are an engine breather (very messy on the FT160, you really want it venting outside the plane) and the fuel tank breather (no mufflers, so no pressure fitting). This puts all the mess below the plane instead of inside the cowl, and the 5/16" copper pipes have a larger internal diameter than fuel line which avoids the "snorkle effect" of making a breather longer. The oil can run down the inside wall without blocking up airflow. (Well, we hope so. It worked on my last plane, but this time the breather's a bit longer. We'll see.) You can also see the cowl fitted, without it's "chin".

6. The cowl's "chin", with cut-outs for engine cylinders, exhaust etc. It's held in place by screws & thin ply "tabs" epoxy glued to the cut edges of the main cowl.

7. The complete cowl.

8. Balancing... gotta love Vanessa rigs.

9. We don' need need no steekin' fake cylinders. I'm thinking of getting some aluminium tubing & making up exhaust extensions to approximate the length & position of the real Lycoming exhausts - just got to try to figure a way of attaching the extensions securely and still have them removable, and have the mount deal with the heat and metal expansion.

I thought I'd have to cut a hole in the front of the cowl to let the carb breath, but there's at least an inch between the carb inlet and the cowl so it's probably not required. On the last plane this engine was in the cowl had an enormous hole in the bottom with the entire carb exposed, and every time it nosed over the carb would fill with dirt. [:@] I'm also debating putting a pair of small air inlets at the front and some larger outlets at the bottom rear of the cowl for cooling but again I don't really think it'll be required as the heads are external & exposed to the airflow. Sure the cylinders are internal but the vast majority of engine heat occurs in the head, so I figure having them in the prop blast should keep them more than cool enough.

After this build I'd pretty much swear that this plane was designed with the FT160 in mind - its power output's right in the plane's recommended range (more than a single cylinder 120, less than a single cylinder 160), there was no issue finding room on the firewall for the mounting bolts, there's ample room in the cowl for this engine (albeit with some surgery to allow the cowl to fit over the flat engine), it only took 70 grams (about 2.5 oz) of lead strapped to the tail wheel to balance, and it leaves the cylinders exposed in a very scale-ish manner. You've got functional scale exhausts? Big deal, I've got functional scale(ish) HEADS! Once I have the maiden under my belt and have the plane settled I'll spring for a nice wooden prop, just for the look of the thing.

Sandmann_AU

I maidened my Spacewalker a week or so ago, and figured I'd better post a post-maiden report here. I was going to write one up from scratch but since I've been exchanging emails with one of the readers of this thread I figured it would be easier just to paste them in here. Personal details obscured...

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The following was sent to you through RC Universe:
-
Hi
Enjoyed reading your article on fitting the OS FT160 into the plane. I have just purchased this motor and am considering buying the seagull spacewalker ARF
to put it in. Have you flown the plane yet? Any comments since your last post.

================================

The spacewalker had it's maiden flight 3 days ago. It was a sunny day with light to moderate winds blowing across the runway, and I was flying off a very well maintained grass runway. I was using a 16x10 Master Airscrew Classic prop. As for the plane itself, it flew very much as expected, a lazy sunday afternoon flyer with no bad habits, and very floaty (almost trainer-like) on landing approach. I found the aileron throws to be way too little with the plane sluggish to bank even on high rates. I've since doubled the recommended throws on the ailerons, and used about 25% exponential on all surfaces.

Specifically as regards the FT-160 I found the engine very well suited to the plane with the only drama being a tendency for the carb to drip fuel if the plane's left sitting with a full tank, due to the carb being lower than the tank's centre line. I found that when I ground tested the plane the engine started to get hot enough to affect its performance after about ten minutes, dropping about 500 rpm from max, however in flight this didn't occur most likely due to the increased airflow and the fact that I was usually running the engine about 1/2 throttle for flight, and wide open constantly for the ground test. I should state that I have cut NO holes for cooling in the cowl as the heads and exhausts are fully exposed, leaving only the cylinders and crankcase inside the cowl. Also I have not cut an air inlet hole for the carb as there is about 20-30mm clearance from carb mouth to the cowl. The engine did not appear to suffer for the lack of air. I do not have the "choke" on my engine (it came without one, I bought a new one for it, and the rubber pad fell off on the first flight) but the engine has never had problems starting without the choke - just a few turns of the prop will prime it. The long (about 150mm) copper tube I used to get the engine breather external seemed to work just fine, if the amount of slime on the underside of the fuselage is anything to go by! The tubing I used is 5/16" diameter. I chose copper as it's easier to bend than brass or aluminium and isn't affected by glow fuel.

I had to remove the cowl between flights to tighten the engine mounting bolts, and I found the method I'd chosen of cutting the "chin" out of the cowl to work very well, being both easy to remove for engine access and robust when fitted. As a bonus you can remove the "chin" without removing the prop which lets you access all the fuel-related areas of the engine. The prop must be removed to remove the main cowling, however there's nothing serviceable on the top of the engine (the glow plugs & valve rocker covers are exposed) so the only reason to remove the main cowl is to check engine mount bolts.

As I said I am using a 16x10 prop, simply because that was what I had at hand that suited the engine, however I feel that the engine would benefit from a larger diameter & smaller pitch as these engines have a lot of torque but not a lot of RPM. With the current prop the best RPM I've seen on the ground is 8200. With the current prop the engine's performance felt a bit sluggish and I intend to try an 18x6 prop with it shortly, though with this plane's ground clearance you could certainly go up to a 20" prop if you like. On the previous plane this engine used a 3 blade 14x7 prop.

The plane's ground handling has been mentioned in the forums, and I did notice that it likes to wander about a little while it's its wheels. It was not something I found particularly worrying, but you do have to keep your wits about you somewhat. My second landing was a little less than perfect with a few bounces, and the undercarriage held up very well with no tendency to give way or bend. The plane required 70g of lead on the tail-wheel mount to balance at the recommended CG. Make sure all your fasteners are well tightened and glued into place - as I said all four engine bolts were trying to spin out and I managed to lose one of the four bolts retaining the cockpit while in flight. The only real deviations I made from the manual were a pull-pull set-up for the rudder, and moving the rudder servo forward to sit next to the throttle servo (mainly to keep the pull-pull cables away from the two elevator servos). Moving that servo forward makes it a little fiddly to access the rear wing mounting bolts, but it's not impossible to do. I did have to cut/break parts off 2-3 fuselage formers where the tubes for the rudder pushrod & 36MHz antenna were fitted to clear a path for the cables, but I was able to do this without compromising those formers strength. The throttle pushrod has the straightest run from servo to carb that I've seen on any plane. The plane's manual recommends metal gear servos, but I used Spektrum DS821 servos with Carbonite gears without an issue. You do need a fair chunk of torque in your servos as it has big control surfaces, but it's not designed to be an aerobatic model so there won't be too much "yanking and banking".

Other planes I could recommend you to for your FT-160 would be Top Flite's Giant Scale Stinson Reliant, or from SIG the 1/4 scale Spacewalker, 1/4 scale Piper J-3, 1/4 scale Clipped Wing Cub. All of these are builders kits however, not ARFs. If it took your fancy you could run any of those other than the Spacewalker on floats very nicely too.

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So the OS 160 twin is not to powerful on the Spacewalker?
Whats it like at full throttle?
What prop are you using?

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Not at all, very suitable in fact. You'll find the FT-160's power to be a bit more than a 120 4 stroke, but less than a 160 4 stroke single cylinder due to the extra friction of the 5 sets of bearings and 2 pistons. It's also slower revving, but has more torque allowing it to spin a prop up tp 20 inches. I guess it would be comparable to a single cylinder 140 4 stroke, slower running, more torquey, and much smoother. I'm running an MAS 16x10 classic prop right now (left over from this engine's previous incarnation in a skybolt) but will be changing it out to an 18x6 soon, probably in wood for the old fashioned look. I get about 8000 rpm right now, the engine has a max rpm of 10500 from memory.

A couple of other things to know about this engine (that I had to go looking to find out)... it doesn't need mufflers as it's a very quiet engine with a pleasant note, and no mufflers means no tank pressure line. It doesn't need the pressure line because the carb's air inlet's very narrow which creates a strong vacuum on the fuel line. I can fly inverted with this engine without a problem. You will however still a tank vent - I use a 5/16" copper line that exits below the cowl. It also has a breather at the bottom of the engine, and this is where it dumps most of the oil out rather than out the exhausts like other engines. Again I use a copper line that exits next to the tank breather. Be careful not to make this too long and don't use fuel line for long runs, as it both blows and sucks air through the breather as well as venting oil, and too long/narrow a line can result in the engine sucking oil back in before it vents resulting in high back pressure in the crankcase. You'll find the sides of your plane stay fairly clean but the underside becomes an oil slick. You can use the breather to pump after-run oil in to lube the cam bearings, and use a short piece of fuel line from the breather to the tank vent to stop drips while it's in storage.

Planejaw

My Feedback: (53)

Matt, I must say that you did a fantastic job on the cowl. I really like your idea to split the cowl below to access carb and for tuning. Very clean and neat-looking job. Just like full-sized aircraft cowls!

I'm spinning a Master Airscrew 18X8 with a Saito 150, as seen in my previous photos. Plenty of power. I do have some new Xoar props of the same size, and I will see what they offer. Like you, I don't do a lot of aerobatics, I like to fly realistically and shoot plenty of touch-and-go's. Just finishing converting my control surface actuation to 3/16" carbon fiber tube and titanium ends. Ailerson are done, just need to do each elevator half and rudder. I mounted three servos in the tail to help compensate for the mass of the Saito.

Keep us posted on further flights.


John

rsad

Hi folks,

I just found this thread. I am planning on purchasing this airplane. Can anyone tell me if there is enough prop clearance for a 20 inch prop with the model sitting level. I'd buy it if I can coax 1 inch clearance from the ground. I have an existing electric system from one of my larger models that needs a home and I have always appreciated the beauty of the spacewalker II. Thank you all for the great thread!

Planejaw

My Feedback: (53)

Though I only have about 4 flights on my Spacewalker with the Saito 150 GK, I've ordered a new rear-carb DLE-30 for it. I've become so enamored with the simplicity and ease of flying giant scale gassers, I thought I'd take the plunge and convert the Spacewalker.

It's likely to have more power than the Saito 150, but I'm really not installing it for power. I wasn't comfortable with the reliability of some of the smaller gassers, like the CRRC 26's, and the Zenoah's were quite a bit more expensive than the DL. I'll take some photos of the retrofit after I break in the engine a bit.

Planejaw

My Feedback: (53)

Rsad,

I think the 20-inch prop should work quite well. I'm spinning an 18/8 on mine with the Saito 150 and there is definately more room for another inch of clearance.

Planejaw

My Feedback: (53)

Did you build one with the DA 30 for power? Going to switch my Saito 150 for a DA-30 with the new rear intake.

Planejaw

My Feedback: (53)

Here are some photos of my "Walker" with the Saito 150 removed and a new DL 30 installed. Pitts Muffler and 18X8 Xoar prop from Chief Aircraft. Balances perfectly (I've got my servos in the tail end). Also just replaced the stock "bolt-type" control horns with large-scale Dubros, along with all 3/16" carbon fiber tubes/4-40 titanium rod ends with large Dubro 4/40 ball links on all control surfaces. Plenty of power, but not grossly over-powered. The big thing for me is it's now a gas-burner, as are a number of my other ships. Love the gas, beginning to not like the messy and oily nitro!!

vhal

Hi John, and congratulations for your successful conversion.

I would like to ask you a couple of things that would help me to finish my plane:
Is it possible to show some photos with the cowl removed? (I'd like to see throttle arms and choke levers)
I think you have a pitts muffler - can you tell me which one?

Thanks in advance, and happy landings,
Vagelis

Planejaw

My Feedback: (53)

Vagelis,

The muffler is a J-Tech Pitts-style muffler. I purchased it through Chief Aircraft. Bisson also makes a Pitts style muffler, both will run around $75.00 US. That can be purchased through Tower Hobbies, along with the engine.

I'll get some photos the next time I pull the cowl off. I ran a flexible Nyrod through the fuselage and connected to the larger throttle arm that comes with the engine. The choke is actuated by a rod attached to the choke, which runs through a small hole (similar to an engine mounting lug) on the side of the crankcase. It may be hard to see in my photos, but I run the rod toward the front of the engine with an "L" bend downward. You reach into the airplanes left cowl opening and push the rod in to close the choke, then pull it out to open the choke. Works very well.

I highly recommend the Pitts style muffler for two reasons. First, the stock muffler is very loud. It is not large and the exhaust sound has a very sharp "bark" at almost any engine RPM's. Second, if you use the stock muffler that comes with the engine, you cannot get the cowl onto the Spacewalker without cutting an opening in the left side of the cowl to clear the actual muffler. With the Pitts style muffler, you only need cooling-air inlets in the front of the cowl, a small "teardrop" shaped opening for the spark-plug wire and boot, and a hole on the right side of the cowl to access the high/low speed needle valves. My two exhaust stacks come out of the bottom of the cowl where the cooling air exits.

I also had to remove the stock fuel tank (which is not gasoline safe) and built a shelf to hold a DuBro tank, which rests over the leading edge of the wing, just below the removeable top hatch (cockpits for the pilots). Having the fuel tank a little more rearward helps prevent the CG from being too far forward when the fuel tank is full.

I've included a photo close-up showing the choke rod that is visible through the left side of the air-intake, on the left side of the spinner. I'll get more photos with the cowl removed so you can see things more clearly.

vhal

I really appreciate your detailed description.

Thank you!!

Vagelis

Planejaw

My Feedback: (53)

Vagelis,

You are very welcome. Unfortunately, describing many facets of our hobby requires very detailed and sometimes very intricate/lengthy explanations. I too, like to see photos or drawings, as they seem to help explain more than just describing using words.

By the way, I wasn't too happy with the Pitts style muffler from J-Tech. It extended too far aft of the rear of the engine-mount standoffs. It could have been welded/cut so that it did not do this. I had to trim some of the bottom edge of the firewall to get it to fit. If I get another DL-30, and I will for my Hangar 9 Cub, I'm going to get the Bisson Pitts style muffler from Tower Hobbies.

BlackPhantomDragon

[size=3]Hi Planejaw.
Was just looking to see if a DLE30 would fit in when come across your post.
Looks great. Do you have any pics of the engine with the cowl off.
Just wondering also where did you put the CDI. Would also like to see that fuel tank repositioned as I thought this would be a good idea anyway.

Also would like to see where/how you installed the elevator servos in the rear.

Thanks enjoyed reading what you have done with this.

Regards Greg[/size]

Planejaw

My Feedback: (53)

Greg, Thanks for the note.

Unfortunately, I didn't take any photos with the cowl off. After a few flights, I removed the DLE-30 and put it in another airplane, so right now, I don't have an engine in the "Walker." I need to get another DLE-30 to put in the business end, then get her back in the air. I'll probably do that this winter. Winter is a long, cold affair here in Michigan.

the CDI was mounted on the underside of the engine-mount box, if I remember correctly. There was plenty of room there to mount it on a piece of 1/4" foam and with 4 holes drilled in the area it was mounted, I was able to use zip-ties to fasten it down. Worked just fine.

As for the fuel tank, I removed the original tank, as it's not all that great. I built a shelf and mounted a new Du-Bro tank...just ahead of the CG. Seemed to work out OK. I'll take some photos of that as well.

One reason I took the engine out of the Walker is that I wasn't all that happy about the airplane's flying characteristics. It seemed somewhat squirrely. particularly when on final approach, even with a fair amount of expo dialed into the transmitter, it felt like the approach wasn't as stable as it should have been. I really need to mount another DLE-30 in it and give it it a little more time. It's a real nice looking airplane and had plenty of power with the DLE-30 in the nose.

As for me, the jury is still out on Seagull models. This is the only one I have. I've been building and flying models for the past 45 years and you can't really go wrong with the established names in modeling, like Goldberg, Sig, (and for the ARFs): Hangar 9 (some of them) and Great Planes. Aeroworks also makes some very nice ARF airplanes...one of the few that actually makes their aircraft in the US! If I really wanted a nice Spacewalker, I'd build a Sig 1/4 or 1/3 scale kit. I'm finishing up a Sig Morrisey Bravo right now (86" span). Beautiful airplane, but the kit went out of production 20 years ago.

I'll take some photos of the elevator/rudder servos, as well as the fuel tank and where I mounted the CDI box tonight and post them.

dan4466

My Feedback: (68)

hey Planejaw- did you balance yours like the manual says? 11mm from leading edge. I've never seen anything like that. Less than half an inch.

Thanks

My bad: I see its cm, not mm.

BlackPhantomDragon

Thanks John for getting back.
The info is much appreciated. The tank and servo photos will be good as well.

I am in the process of learning at present on a Boomerang 60 and am in the process of getting a Phoenix Tiger 60 and putting an ASP90FS in. The Space walker was going to be my 3rd plane so I could practice some Aerobatics as I like the look of the older style planes. I have looked at the Sig kit but don't have a lot of room to build at present so thought I would leave kits till I get some more room. Have built Kits years ago and flown Control line but just getting back in to RC as I now have time and older children.

Living in Queensland we don't really have a winter like yourself as we are sub tropical on the coast so Winter is pretty good. Still gets cold to us but the days are usually around 15-25c which would be 59-77f in your temp. Nights can get down to below 8c (46f) but still pretty good so flying as normal all year round.

Thanks again Greg

vhal

The manual says 11 cm not 11 mm...
This is more than 4,25 in

Vagelis