RE: Skybolt hangar and clubhouse
Interesting landing gear on that one... looks a lot stronger than the GP design. Wonder what the weight difference is.
Posted on: 2/27/2011 7:41 PM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10368672

RE: Skybolt hangar and clubhouse
All good ideas. You seem to have really thought it through. I'm interested to see how it comes out.
Posted on: 2/25/2011 9:09 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10362786

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Jaybird Hi Matt. I will make a ''sandwich'' using the inner struts similar to the plans. One side will have 2-56 blind nuts and the other side will ride against the bracket. I had thought about making pockets for the brackets inside the struts, but decided it would make assemlbly easier if they could just slide into place with both wings on. I may change my mind later, but I wanted to test my idea before I went much further. Jaybird [/quote] Fair enough, that's what I would have done too. Maybe you can find some small thumbscrews to use in them? You'll probably also want to harden the balsa where it presses against the brackets so it doesn't squish, either by soaking with thin CA or putting a small thin ply plate there. My only concern (a very minor one) is that the original I struts are fixed at 4 points, front & back of the top & bottom, whereas yours are only at 2 central points. If the struts are hard against the wings that'll probably be ok, but if there's any play it'll let the struts rock fore & aft, allowing the top wing to wiggle around. I guess that's why GP arranged their ARF struts so the bolts pulled the struts down/up so they stay hard against the wings. With your 90 degree brackets you might want to use 4 per strut, emulating the original mounting points. Other than that I can't see why it wouldn't be a really good idea. I think if I were doing it from scratch I would have left the landing gear straps straight and mounted them to the side of the ribs, rather than bending & mounting to the top. Hmm no reason I can't do that now really, it just means cutting out 4 panels of covering from the wings, adding the brackets, then recovering. Something to think about.
Posted on: 2/25/2011 9:00 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10362769

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Jaybird I decided to use the kit interplane strut die-cut parts as a starting point and mounted the ''L'' brackets to the underside of the top wing. I have installed basswod blocks under the spar to screw into and 1/16'' basswood strips for them to sit on rather than the soft balsa. I transfered the location of the spar relative to the struts from the plans and then drilled the front mounting hole. I'll add a basswood block an inch or so away from the spar along the side of the strut mounting rib for a second ''L'' bracket and screw. I did a rough assembly of the wings and braces and everything positions itself pretty close to the marks. It was an evening of measuring diagonals and checking incidences so not a lot of building got done, but I'm more comfortable that the parts will be aligned properly when it's finished. The ''L'' brackets are Du-Bro metal landing gear straps bend over in a drill press vice. Jaybird [/quote] That's a great idea and should work well, I wish I'd thought of it before I assembled my wings. I notice you're only using the plywood inner parts of the interplane struts, without the balsa outers... what are you going to do with the struts? Make new ones from thicker ply? Use the standard inner ply & outer sheeting, just without the wire fittings? The standard design of the struts will be thicker than the ply inner you're using as a template, will your finished struts be as thick as the standard ones? And if so will you be embedding the brackets into the strut somehow so they sit at the standard location, or have the brackets against the outer face of the strut and just move them inboard a little from standard? Hmm now how am I going to re-engineer that onto my plane without completely disassembling the wings? :)
Posted on: 2/24/2011 8:19 PM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10361909

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: drube Just picked up this unfinished GP SSB from a guy I met for $50. He bought it in 96 and never had time to finish it.  I'm looking to do the fuel tank hatch mod as well as the battery hatch on bottom like on mods thread. Anyone have a link to detailed instructions for these mods?  My plans are to run a ST G90 with a slimline style pitts.    Thanks<img alt='''' src=''http://www.rcuniverse.com/forum/js/fckeditor/editor/images/smiley/msn/biggrin.gif'' /> [/quote] I don't have any detailed destructions on the hatches but they're not hard. For the upper one sheet the nose end of the fuse as per the instructions, then cut out & remove a section from the very forward end, between the two beams for the cabane mounts, till about 2" before the "dashboard" (make sure the hatch finishes before the canopy begins). Make it as wide as will fit between the cabane mounts. Use some balsa scraps to create "ledges" for either side of the removed section to sit on, and fit a balsa "tab" on the underside of the cockpit end of the removed section. The tab slides under the sheeting at the cockpit end, the whole hatch sits on the ledges, and it's all held in place by the engine cowl. (This means you can't use the plane without the cowl in place, of course, unless you replace it with rubber bands etc.) It's probably not a bad idea to make yourself some small balsa "ribs" to glue to the underside of the hatch to help it keep it's shape and give it some rigidity... 3 of them should do. You could also cut it a little shorter at the forward end and use a pair of screws through the hatch and into the firewall if you chose. I didn't bother with the top hatch since I figured there was no way I was going to get my fat tank out through that skinny hatch. Let's hope it never springs a leak coz that tank's in there for good! For the lower battery hatch it's a similar affair, sheet as normal then cut a square section out below the tank, just big enough to install your battery pack. Glue some ply ledges in, and use 4 small screws on the corners of the hatch to keep it in place. You want ply ledges instead of balsa here because you're screwing into it. I found it useful to glue some thin triangular ply onto the corners of the hatch to prevent the balsa being compressed by the screws, and I used small bolts & captive nuts instead of screws. You could even hinge this hatch, use concealed hatch latches etc, but why make it any harder for something you'll rarely open? Make sure it's a nice tight fit (use a sharp blade to cut it out, cover the inside edges of the hole and the edges of the hatch etc) if you're using a glow engine to stop oil seeping into the tank area through the hatch edges. Use your plans to figure out the best spot for this hatch. I'm sure if you browse back through this thread you'll find pictures of the hatches to guide you.
Posted on: 1/27/2011 8:27 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10292606

RE: Seagull Spacewalker II 120 Arf
Some flood pics... and to make them slightly relevant I'd love to try flying a spacewalker with floats off this :)
Posted on: 1/12/2011 5:57 AM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10257491

RE: Seagull Spacewalker II 120 Arf
[quote]ORIGINAL: MercerAUST To Matt. I hope you are on higher ground. I was in Brisbane during the 1974 floods and it took ages for low lying areas to dry out. I was only a kid, but remeber being excited because we got an extra 2 weeks off school. [/quote] Thanks for that... yeah I'm up on a big hill in Gailes, out Ipswich way. I barely managed to make it home from work today and I won't be going in tomorrow. I just came back from taking a stroll around the floods at the foot of the hill I'm on - will post a couple of pics here (a bit of a thread hijack but I hope no-one will mind too much.) I remember the '74 floods too, I was about 9 at the time. Big floods are always more exciting when it's not your house under water. Hmm maybe I should change to RC boats instead of planes... or sea planes perhaps. :)
Posted on: 1/12/2011 2:07 AM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10257285

RE: Seagull Spacewalker II 120 Arf
[quote]ORIGINAL: vhal [quote]ORIGINAL: AA5BY I have a 28cc gasser that swings an 18'' prop... will there be adequate ground clearance? [/quote] <img src=''http://www.aeromodelling.gr/album/albums/userpics/DSC_8474.JPG'' alt='''' /> I believe that the attached photo of my Spacewalker (taken by the fellow modeller/photographer evan) clearly shows that there is plenty of clearance when using a 18x6 prop. The engine is a CRRC Pro GP26R (26cc), that overpowers considerably this charm lady. Certainly a 20cc gasser would be more than enough for any aerobatic manoeuvre, except maybe 3D stuff (which would be ridiculous for this plane anyway). Please note the apparent up-thrust needed to fly the plane straight (@5300 rpm), combined with the elevator up-trim (both shown in this photo). Any proposed solution would be welcome... Best regards, Vagelis The Owl Airclub Greece (photos form our club's activities here: <a class=''linkification-ext'' href=''http://www.aeromodelling.gr/album/thumbnails.php?album=417'' title=''Linkification: http://www.aeromodelling.gr/album/thumbnails.php?album=417''>http://www.aeromodelling.gr/album/thumbnails.php?album=417 ) [/quote] Mine runs an OS 160 Gemini twin (really a nice solution because you don't need the cheesey plastic engine heads, as you have real heads either side of the cowl). I've had to put some lead on the tail wheel to balance it and it flies ok without any added up-thrust or up trim, but when it's inverted in flies noticeable tail-down, needs no elevator to keep it level, and is very eager to fly upward with any added down (inverted down) elevator. It's all made me think maybe it's a bit tail heavy, (not helped by the fact that I balanced it with a heavy nylon MAS prop and have since switched to a much lighter cherry-wood one without rebalancing) so I'm going to start experimenting with losing some of the tail weights. I've also had to use double the recommended aileron throws and always fly on high rates, or it turns into a very lazy plane indeed. I had standard throws on the ailerons for it's maiden and struggled to turn it around & bring it back... thought it was going to go on it's own little adventure to find the horizon for a while. All up this is a beautiful plane but I'm starting to think the factory settings are a little conservative. I certainly don't expect to do 3D manoeuvres with it (even though I discovered a few days ago that it can hover) but I don't think some basic aerobatic abilities are too much to ask. Will have more info when the floods here recede, my airfield dries out, and I can get some air time.
Posted on: 1/11/2011 1:47 AM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10254659

RE: Seagull Spacewalker II 120 Arf
[quote]ORIGINAL: AA5BY Thanks Sandman for the pictures and response. I think I'm going to have to sleep on this one a bit more. I've a Seagull SpaceWalker II 120 in the box and a 28CC engine but our field is rough. [/quote] That shouldn't be a problem.. the landing gear's pretty robust and could easily be reinforced with some fishing trace wire between the gear legs... and even with the 18" prop there's probably about 3" ground clearance when it's sitting level. I fly mine off grass... with those huge wings it really takes off and lands a lot like a trainer (albeit a tail-dragging trainer), with easy lift-offs and set-downs being the order of the day. Of course if the grass is really long you might end up mowing the lawn a bit. :D
Posted on: 1/10/2011 4:36 AM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10252200

RE: Seagull Spacewalker II 120 Arf
[quote]ORIGINAL: AA5BY I have a 28cc gasser that swings an 18'' prop... will there be adequate ground clearance? [/quote] I got my 18" props today in the mail. They're Turnigy 18x6 cherry wood props. Thankfully I ordered two, because the hole in one was so off-centre there was no way it would balance without carving chunks off the hub. Anyway, here's a couple of pics of the big prop on the 120 size seagull spacewalker 2. The prop's too big for scale, but will take off & land just fine.
Posted on: 1/9/2011 11:15 PM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10252001

RE: Seagull Spacewalker II 120 Arf
[quote]ORIGINAL: AA5BY I have a 28cc gasser that swings an 18'' prop... will there be adequate ground clearance? [/quote] Yep. I've got a 16" on mine and am waiting for an 18" to turn up in the mail.
Posted on: 1/7/2011 8:17 PM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10247213

RE: DeHavilland Mosquito
The whole thing's 'glass, tail feathers and all. The horizontal stabs are mounted the way you expect wings to be, with an alum tube running through the fuse... only the stabs are glued on instead of being bolted on like wings. It's been a while since I assembled mine but if I remember correctly the vertical stab is part of the fuse, moulded in one piece. Not a lot of options to lighten them really. Oh, and the mechanics for the rudder/tailwheel are pretty fragile & complicated too, most likely to save weight and keep it all internal. Most folks throw it away and do something a little more rugged... I've opted to stay with the included bits but with a pull-pull system instead of the pushrod. I also arranged an internal control horn for the elevators on a single internal torque arm, instead of the twin pushrods sticking out through the fuse. Looks great from the outside... hopefully it'll all stand up to the rigours of flight/landing. The whole weight problem simply comes down to it being a very long tail, the wings being fairly far forward, and the engines being mounted on the wings instead of the nose... all goes to making a very tail heavy plane. Yay for old WW2 designs. Now, if we mounted all the guns and ammo that the real once had in the nose, maybe it'd balance... :D
Posted on: 12/21/2010 7:31 AM by Author "Sandmann_AU" in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10209522

RE: DeHavilland Mosquito
Heya Jimm I know there's been some cowls extended, but that's been more about installing longer engines and reducing prop - cowl gaps. I think the basic reason for not doing it this: too much effort for too little gain. Even when extending the cowls to close up the gaps you alter the plane away (or further away than it already is) from a scale profile and if you start moving the engine forward that starts to become a major (ie: noticable) change to the profile. Despite the fact that the engines are the heaviest part, moving them forward a bit doesn't make much change in a twin because the distance between the COG and the mass of the engine is MUCH less than the distance from the COG to the tail. Even in a single engine'd plane 3 ounce of weight on the nose is roughly equal to 1 ounces on the tail, so it's probably close to a 5:1 ratio at the firewalls on a twin. You do however cause yourself a whole bunch of work around engine mounts, cowl extensions and so on for little gain.
Posted on: 12/21/2010 6:50 AM by Author "Sandmann_AU" in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10209459

RE: Seagull's
I haven't used the Magnum 52's, but all my 4 strokes can have their carbs reversed to swap the throttle arm. Would that help your problem. Should fly nice with twin 52's, just be careful you have enough clearance for the props so they don't contact the fuse. Might have to use 3 blade props to reduce diameter.
Posted on: 12/11/2010 3:34 PM by Author "Sandmann_AU" in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10190948

RE: Skybolt hangar and clubhouse
Here's a couple of pics showing various stages of the build. I'll be copying your rear flying wires, but since I've never had any problems with the landing gear spreading I won't be modifying that. I also built in an extra spar running the width of the horizontal stab about half way between the leading & trailing edges. I tried a 15x7 3 blade prop on my Saito 125 but I got better results from the 2 blade 15x8 so I'll start with that, then swap it over and see if I like it better. I prefer the look of the 3 blade but you can't see the blades when you're flying so I'll go with performance. :) I've also moved the engine about 1/4" forward with a ply spacer behind the engine mount, which should mean a little bit less lead. It'll also have the battery pack and another battery for the on-board glow mounted below the tank. As you can see I've modified my 'bolt to be a twin seat, open cockpit. It'll have a pair of small windshields (cut from the original canopy). As of tonight I've done most of the covering - I still need to add the red trim to the leading edges of the wings & horizontal stab (similar to the vertical stab's LE). I also have to paint the cowl, interplane struts, and wheel pants (which still need to be finished assembling, they're glued together but that's all). I bought DuBro 3" wheels for it but I think they're too big, will swap them out for 2 1/2" wheels. It's using a pull-pull rudder control, and the elevators have a [link=http://www.centralhobbies.com/control_linkage/Bellcrnk.html]"Dual Elevator Ball Bearing Bell Crank"[/link] thingy. It took a bit of work to fit, and was very fiddly when sanding & covering but it seems like a neat solution and less "messy" than a Y pushrod (those things have a habit of coming apart in flight, and never have truly symmetrical movement of the elevators). The biggest problem with the bell crank so far has been the fact that you can't get your hand into the fuse, so you have to be careful when pulling arms etc off the side for sanding. If you only take one side off it's ok, but if you take off both side the shaft threatens to disappear into the bowels of the fuselage, never to be seen again. Time will tell if it was worth the trouble & expense. Otherwise the servos are Spektrum DS821's (except the throttle, which I think is a Hitec 311, some analogue cheapie), and the Rx is a Spektrum AR7000. Batteries are a home made pack of 2200mah NiMH cells. When It's finished I'll figure out the CG and weight the entire thing and post it in here.
Posted on: 11/11/2010 7:29 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10128403

RE: Skybolt hangar and clubhouse
What I know about gas engines you could write on a stamp, but I know a bit about 'bolts so here's some thoughts for you. The biggest prop you can swing on the GP 'Bolt is 15", with a 16" you run out of ground clearance when landing, and any bigger and you won't even be able to take off. Weight however is not so much of an issue - I built my first one with an ASP 120 4 stroke and had to put a bunch of lead on the front to balance it. If it's speed you're after with the gasser you're going to run into a bit of a wall when it comes to drag. The airframe simply won't go (happily) over a certain speed with the drag of it's dual wings, big blunt nose etc. I changed out the 120 for a 160 twin with a 15" 3 blade prop but ended up with about the same speed (more vertical though). I also ended up snapping the horizontal stab a few times due to the increased weight & power when pulling out of dives. Had to reinforce the stab with rectangular section carbon fibre tubes. It did look cool with the twin heads though, and sounded great. It'll fly nicely with your magnum and I don't see any real benefit to the gasser other than using less & cheaper fuel. My second 'bolt (which is close to finished) is built around a Saito 125.
Posted on: 11/10/2010 6:52 PM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10127443

RE: OS 300 Twin plane suggestions?
I had the same dilemma with an OS FT160 twin. I shoe-horned it into a 90-120 (4stroke) sized GP Skybolt kit, but it proved too much for the tail to handle. I ended up putting it into a 120-160 (4c) sized Spacewalker. It flies the plane ok, but the plane itself isn't terribly exciting in the air. I'd recommend that 1/3 scale Pitts for yours, you'll get more fun out of it than the 1/3 scale Spacewalker.
Posted on: 11/8/2010 9:01 AM by Author "Sandmann_AU" in the forum "Sport Flying"
http://www.rcuniverse.com/forum/fb.asp?m=10122330

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Cougar429 Those fiberglass cowls are also lighter. brenthampton79, if Sandmann and I are on the same page and referring to Fiberglass Specialties, their selection is huge, so should have a good chance of covering your needs. [/quote] Yep. That's the one I got. Good service. Get the 'glass wheel pants from them at the same time.
Posted on: 10/24/2010 12:20 PM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10090498

RE: Seagull Spacewalker II 120 Arf
Should be fine. I've got an ASP 1.20 4stroke (ASP is a clone of Magnum) which I've run in a few planes. It's a pretty strong motor which should fly the spacewalker nicely. It's not going to be a speed demon or a 3D plane, but it's not supposed to be.
Posted on: 10/24/2010 10:30 AM by Author "Sandmann_AU" in the forum "ARF or RTF"
http://www.rcuniverse.com/forum/fb.asp?m=10090281

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: brenthampton79 does anyone know if ithe gp skybolt arf cowl will fit on the gp skybolt kit, my cowl looks pretty rough and I need to increase some cooling on the engine as well [/quote] I asked the same question about 6 months ago, even rang great planes but noone could give me an answer. I ended up buying an aftermarket fibreglass cowl specifically for the kit version. they're well made and a lot stronger than the ABS plastic ones GP supplies.
Posted on: 10/13/2010 4:28 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10065554

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Cougar429 If you stay with the same diameter 3-blade, the pitch has to be reduced to allow the engine to compensate for the extra drag. I never had a lot of luck running 3-blades on my 2-strokes, but the Saito does not seem to mind. [/quote] Yah... the 2 blade's a 15x8 and the 3 blade's a 15x7. There's no 15" 3 blade with a lower pitch available. I did run a 3 blade on the OS1.60 twin cylinder with my previous Skybolt, but that was more about ground clearance than anything else. Think I have a 14xSomething 3 blade prop around the place, if I can find it I'll give that a go too. With the Saito I wanted to run a 3 blade for the scale look, but I'll happily sacrifice that for performance. :) I will try flying all these props of course... you can do all the math you like, but nothing will tell you which prop "feels right" better than "the seat of your pants". I am expecting the best results from the 2 blade 15x8 though.
Posted on: 10/11/2010 10:13 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10061350

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Zor No poblems starting the Saito 125 but the first three starts the engine was running backward. I wish to understand how a four stroke can run in the opposite direction. It did run for an apprreciable time in each case like 20 second to half a minute till I shut it down. That sure is a fascinating subject to try to figure out. [/quote] Only a guess here... I'm assuming there's a little overlap on the cam lobes... ie: the inlet valve and exhaust valves open slightly before Top Dead Centre (TDC), with the compression & power strokes swapping functions. With the engine spinning backwards that would let it suck a little fuel at the beginning of the reversed exhaust stroke, and exhaust slightly at the beginning of the reversed compression stroke, thus allowing it to idle (roughly) backwards but without enough fuel or exhaust to do anything more than an idle. It could also be explained if the camshaft timing were retarded (eg: the cam is on or more teeth "out" from where it should be). If that were the case it would also run backwards, and have less than optimum power when running forwards. It can't happen in a car's engine (unless it's already hot & has significant carbon build up) because the spark plugs wouldn't be firing at the appropriate time, but of course in a glow engine the the glow plug's always hot when starting so ignition isn't controlled. [quote]ORIGINAL: Zor On one of the fast run full power was reached and the plane took off and started a climb nosing up about30 degrees and at about the height of a single story bungalow (20 to 30 feet) the engine quit.. ... These pants are made of two halfs glued together and the original halfs were not the same length (3/16'' difference) and he rear part of that joint was weak. ... I have a strong suspicion why the engine quit and I will look into that. The high speed mixture needle was opend only 2 1/2 turns and  I think she leaned out. [/quote] I'd agree, that does sound like a lean condition, or possibly overheating (or both) - unlikely in your case since you have most of the cylinder poking out in the fresh air. You might also want to check fuel flow, pinched fuel lines etc, and make sure the tank's vent line to the muffler doesn't have a hole allowing tank pressure to escape. Get an assistant to hold the plane horizontal while you wind it up to full throttle, then have your assistant hold the plane vertical (still with wide open throttle) for a minute or more, to see what happens to the engine speed. IF the engine speed remains constant or even increases slightly you have plenty of fuel flow and your mixture's probably about right, if it falters and/or dies then you have either restricted fuel flow or a lean mixture. You also want to check the cam timing as I mentioned re: the engine running backwards. [quote]ORIGINAL: Zor I saw three fellows taking their model home as a basket case. I felt sad about that. [/quote] Yah, it's a tough model, even for a kit build (which are always stronger than ARF's). That's the positive side of it being a heavy model, it's fairly forgiving of abuse. My build is basically complete now, I just have things like the final sanding, trimming the angles on the control surface leading edges, hinging the ailerons etc still to do, then the covering of course. I've decided on I've cut the cowl to suit the engine & exhaust already - I ended up mounting it horizontally and used a 90 degree adapter to get the muffler mounted inside the cowl, with just the exhaust pipe sticking out the bottom of the cowl back toward the firewall. I'll have to get a small length of aluminium tube to extend the exhaust pipe, make it look like one of the "stingers" on a pitts muffler to keep the mess off the bottom of the fuselage. Not much of the engine sticks out the side of the cowl, only about 1/2 of the head at the front and the valve covers. I'll include a couple of pics. I tried a couple of props on my Saito 125, a 15x8 2 blade, and a 15x7 3 blade. I was getting about 8850RPM with the 2 blade but only about 8200RPM with the 3 blade. I put those figures into ThrustHP and it tells me that both speed AND thrust are better with the 2 blade... figures are as follows: 2 Blade: RPM: 8850 Speed 67.05 MPH Load: 405000 HP: 2.005 Static Thrust: 11.22lb 3 Blade: RPM: 8200 Speed: 54.36 MPH Load: 531562.5 HP: 2.09 Static Thrust: 9.63lb As you can see I'm (theoretically at least) better off with the 2 blade prop in this case. I checked out the 14x7 and 14x9 3 blade props also but got similar results. Anything smaller (eg: 13x8 3 blade) will let the engine over-spin and won't have enough diameter to direct airflow around the fuselage well. I was using the fuel I had mixed up for my other (ASP 1.20 and OS 1.60) 4 strokes, so I will have to mix some up specially for the Saito, see if bumping up the nitro and removing the castor oil will improve the running. Oh well, I'm going overseas for a 2 week holiday tomorrow, so all this will have to wait till I get back. Looking forward to seeing it airborne.
Posted on: 10/11/2010 2:27 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10060920

RE: Moving engine forward changes geom'ery?
[quote]ORIGINAL: beepee Did the reverse for the same reason. Shortened the nose 3'' on an EAA Bipe by Balsa USA in order to install a small gasser. Had flown it with a 120 4-stroke in standard config. Did not notice a difference. Go for it! Bedford PS: Darnit Sandman! I got smudges all over my expensive new monitor because of you! [/quote] hehehe sorry about that. You're the second person in a week to try to squish my avatar. It's even caught me once or twice when I first started using it. :) When you shortened your bipe, were you doing it to fit the engine into it (thereby leaving the prop in the standard position) or to reduce required tail weight (and moving the prop further back from standard in the process)? Oh.. for da Rock... the skybolt has its tank pressed up hard against the firewall, and I've actually echo'd a lot of the newer ARFs by cutting a hole in it for the tank neck to protrude through, so a little extra fuel line length shouldn't be a problem. For Gray Beard... yah I actually posited the same question in the Skybolt clubhouse thread but got no response. I figured I'd get more action from a new thread. It worked. :) Thanks to all for your responses. They seem to agree with my guess that it won't matter... the nose of the plane isn't a particularly aerodynamic part of the plane so it shouldn't notice being a little longer. Guess I'd better start shopping for some longer mounting bolts. :)
Posted on: 9/29/2010 6:46 AM by Author "Sandmann_AU" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=10034935

Moving engine forward changes geom'ery?
I'm currently building a GP Skybolt kit, the second one I've done since the first met an untimely end. The kit's an old design, pre-dating 3D and builds heavy, especially tail heavy, and there's not much you can do about making the tail lighter without compromising strength which leaves most of these planes carting useless lead around in the nose. Currently the fuse is 90% complete, and the engine (saito 1.25) is mounted. The cowl for these is a 2 part affair (front & rear halves) which needs to be cut down to size & glued together. I've done the cowl, but rather than cutting on the supplied "cut here" lines I just trimmed off the flashing from the rear half, leaving the cowl almost 1/2" longer than standard. I was measuring it all up last night, working out how much I needed to trim from the cowl when it occured to me that I could just put a thick ply block behind the engine mount, moving the engine forward about 1/2", and reducing the required lead. The kit actually omes with 3 such blocks, intended for use with smaller 2 stroke engines, so I can't see any mechanical problem with it My question is will moving the thrust (prop location) forward of it's standard position alter the geometry, dynamics, balance etc of the plane? My suspicion is that it will be fine but theres more that I don't know about aircraft design than there is that I do. :)
Posted on: 9/28/2010 7:14 PM by Author "Sandmann_AU" in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=10033908

RE: Skybolt hangar and clubhouse
Yeah but that either puts two minis in the rear, which is equal to 3 times as much weight at the front, or has you requiring two pushrods (extra weight), and two channels & mixing or a Y adapter. Added complexity either way really... both have advantages.
Posted on: 9/28/2010 8:38 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10032722

RE: Skybolt hangar and clubhouse
Hey guys... Just had a thought while admiring my latest handiwork. When I cut out the engine cowl I took the absolute least off the end so it's longer than normal. I also haven't sanded back the nose of the fuselage so the cowl fits on properly yet. I measure the engine & mount, and compared it to the firewall to end of cowl and I need to move the cowl back about an inch to get it over the engine. It then occurred to me that maybe I could put a couple of the blocks that're intended for mounting a 2 stroke under the engine mount and move the Saito forward an inch or so, thereby reducing the amount of nose weight I'll need. So what do you think? Will this substantially alter the geometry of the plane? Will it change things like the appropriate CG etc? Or can I do this and end up using less lead just by having a longer nose?
Posted on: 9/28/2010 5:25 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10032572

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Cougar429 Love the girlfriend idea. Would like some more info or pics on the CF rod idea. Sounds like an elegant solution, (and I love those) but I come up with some questions. From my own experience I found standard, linear-orientation CF rod is great for deflection loads, but torque is a different fish. The other question is if you run the servo linkage fully embedded in the fuse and, if so, how you access it? Same type of queston regarding installing the arms to the rod withoud damaging the fibers. [/quote] Yah, she looks happy up front... big grin on her face. Let's see how happy she looks covered in dead bugs with no goggles. [:D] OK, I'm not 100% sure this really is carbon fibre... maybe it's nylon etc. The horns themselves are definitely some sort of plastic. All I know is it's a man made material and it's light, strong, & black. I'll include a pic from a website of the device here. Easy question first... regarding the pushrod being encased. Yes it is, but I've done things a bit backwards to normal using a Z bend on the elevator coupling and a nylon clevis on the servo. I figure the Z bend's the bit least likely to need any attention, and I can adjust things at the servo end. The website I found this on (dedicated to pattern planes) recommends ball joints and CF pushrods all round but I think that's probably overkill. The two external pushrods will be steel 4-40 size, with adjustable clevises on one end and soldered ones on the other (same idea as the aileron linkages). However no, once it's built (at least in the skybolt) accessing the internal bits would require surgery. OK, I just wrote a huge paragraph trying to explain how it all works, then I realised it's easier with a diagram, so I'll attach one to here. The purple shows the main shaft that runs through the fuselage, and the central control horn that's fixed in position. The red is the wedge shaped balsa "packing" & supplied thin ply plates I had to use to give it parallel mounting surfaces. The green is the actual mounts that are held in place with two small machine screws and contain a ball bearing race, the blue are the two external control horns. What's not shown is a single bolt that goes through the entire thing from one external horn to the other to hold it together. Fitting is a matter of locating a suitable point (it has about 1/4" of adjustment in its length so that's not too critical), drilling a pair of 12mm holes (take care to get them exactly perpendicular to the centre line of the fuse), fitting the two external mounts with their tiny machine screws, fitting the main shaft (has to be done from inside the fuse, not easy once the plane's already built!), sliding the two external horns onto either end of the shaft (the shaft has a pair of "flats" on either end so there's no slop in the horns, and they can only be fitted in line with, or 180 degrees from, the central horn), then screwing the long bolt through the whole contraption to pinch it together. I've found that I can remove one external horn & mount and the whole thing will stay in place as long as I leave the other side fitted, allowing me to sand, cover etc the plane without the device disappearing into the bowels of the plane. The external horns are quite a tight fit onto the shaft and won't easily pull off - in fact I've been using a large screwdriver to lever them off rather than just tugging at them, for fear of snapping balsa etc in the removal attempt. Finally, the thing's made by a mob called MK, and you can see it [link=http://www.centralhobbies.com/control_linkage/bellcrnk.html]here[/link]. There's another one on this page by someone called CHS but it uses a sleeve rather than ball races and so would probably create more drag. **EDIT** Hmm I just looked more closely at the CHS ones, they appear to have ball races in them too, so scratch that. FYI I didn't order from that site, my local hobby shop managed to get it in. I have no idea what that site's service is like. [image]http://www.centralhobbies.com/miscellaneous/Images/bbellcrank.gif[/image]
Posted on: 9/26/2010 11:25 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10028032

RE: Skybolt hangar and clubhouse
Just a quick update on my build. Fuselage is basically complete (at least up till the point where the instructions say to go build the wings). I've gone with the idea of a twin seat, open cockpit style. I'm using the pilot from my first 'Bolt and I got him a girlfriend to sit up front. Turns out that with the twin seat design it becomes obvious that my original pilot's about the right scale but an inch too short, so I had to carve & paint a balsa torso for him so he could see over the dashboard. I'll chop up the standard canopy to make a pair of windshields. I've also used a dual elevator coupling made by MK. This is basically a carbon fibre rod that runs across the fuselage and pokes out either side just ahead of the horizontal stab, and has 3 control horns on it. This lets me use a single elevator servo & single pushrod without to make having a clumsy Y pushrod and having uneven elevator movement. I was going to use a carbon fibre pushrod too, but it weighed about the same as a steel one so I figured I wouldn't bother. I had to stick balsa "bumps" on either side of the fuselage where the rod exits so the mounts (with the tiny little bearing races) could be mounted parallel. If you try to force them to match the plane's taper it all seizes up and gets hard to move. The rudder's using a Dubro 2-56 size pull-pull system, as do all my planes. No particular reason other than that I like them. I've also got a dubro tail wheel mounted to the plane, but I'm not convinced that I'll use it yet. If I change my mind I can just remove it and go with the standard one. The engine's a Saito 1.25ci 4 stroke, mounted sideways. I'm using the standard muffler with a 90 degree adapter, which will let me hide the muffler inside the cowl with just the tip exiting through the bottom of the fuselage, plus a silicon exhaust extender to keep the filth off the bottom of the plane. Chances are I'll be using a MAS 3 blade 15x7 prop with it, unless it behaves poorly when spun up in the real world.
Posted on: 9/26/2010 6:34 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10027661

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Zor If you are using two servos for the ailerons; one in each wing _ _ _ are you using a Y connector ? or are you using a mixed transmitter channels ? [/quote] Two channels. Only reason for this is so I can use Aileron Differential, to reduce roll coupling. I also mix a bit of rudder into my ailerons too. If not for this I'd probably still use two channels, but only because a second servo extension is cheaper than a Y adapter and all my Rx's are 7 channel. Also, I use "lost model alarms" on all my birds, they connect to the aileron servo and they behave unpredictably when used with a Y adapter & two servos. [quote]ORIGINAL: Zor If you are mixing two channels, which ones are you using ? Which channel for the right servo and which one for the left servo ? [/quote] I'm using a Spektrum DX7, so my channels are "Aileron" for port and "Aux1" for starboard. [quote]ORIGINAL: Zor Has anyone used the ''flaperon'' set up ? [/quote] There's no way you'd need them on a 'bolt, or any other bipe really, as the twin wings provide lots of both lift and drag. I've used them on other (mono-wing) planes and I've always found them to be somewhere between useless and dangerous. The reasons for a plane to have proper flaps are taking off on short runways with a heavily loaded plane, or landing (or flying very slowly with) a plane with a high wing loading. Reason 1 is typically void with RC models as they don't carry loads and almost always have a much higher power:weight ratio than full size aircraft. Reason 2 applies to RC planes for models such as scale warbirds so they don't fall out of the sky/tip stall etc as you're landing them. Some people try to use flaps as air brakes to slow the aircraft but this only works at larger angles (greater than 45 degrees). At normal angles all they do is provide more lift. Using flaperons in this fashion reduces the functioning of the ailerons significantly, causing more problems than it fixes. I do have a 46 sized Harmon Rocket 3 that I've fitted a 60 2 stroke into. Because of the extra weight, stubby wings, and the difficulty in getting the engine to spin slowly enough to let the plane slow down it really needed real flaps but came without them. On a landing approach it didn't want to stop flying, and would descend to about 3' above the runway and then just float the entire length, but if I slowed down earlier so it would land properly it got very unstable and wanted to tip stall. I ended up modifying the wings to have genuine flaps which completely changed the way it lands; I now start my approach at a higher altitude, chop the engine completely as soon as the approach begins and drop the flaps at the same time. She descends now on a roughly 45 degree flight path, and I just tweak the throttle before she touches down to reduce the descent rate and induce a little flare. Landing this plane used to be a struggle, now it's a thing of beauty.
Posted on: 9/25/2010 10:21 PM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10027229

RE: Skybolt hangar and clubhouse
[quote]ORIGINAL: Zor The idea of my request is to help Skybolt fliers wih a mental picture of the possibilities with this model. [/quote] Well, in the spirit of sharing & caring... 1st one was a kit built GP Skybolt. In it's first iteration I used an ASP 1.20ci 4 stroke with a 15x6 MAS 2 blade prop. Flew nicely. I later upgraded it to a 1.60 ci twin cylinder 4 stroke. This started with a 16x10 MAS 2 blade prop but I had ground clearance problems when landing unless it was absolutely greased in. I changed this out for a 14x8 MAS 3 blade prop which made it fly like a rocket ship, but the horizontal stab kept folding up till I built one reinforced with carbon fibre tubing spars. It was heavy but flew well and sounded great. It met it's untimely demise through pilot error. I'm currently building a second one (same kit) but am using a Saito 1.25ci 4 stroke. It will run either a 15x8 2 blade MAS, or a 14x7 or 13x8 3 blade MAS prop. Not sure which yet. Ran the engine up today for the first time with the 15x8 2 blade and it peaked at 8880 rpm. Will see what the lower diameter 3 blade props yeild after it's had a few more tanks through it, then I'll run the numbers through ThrustHP and make a decision. Hey Zor, while I'm thinking about it could you do some close up pics of your flying wires? Also FYI, I decided to go with the Saito mounted sideways. I got hold of a 90 degree adapter for the exhaust and I can now hide all but the tip of the muffler inside the cowl. I'll have to arrange a support wire from the muffler to an engine mount bolt though as the adapter is meant for the flexible exhaust only and comes with a warning that it can snap if used with a standard muffler due to the unsupported weight. I'm still hoping to find someone using this engine in this plane with the slimline pitts muffler though.
Posted on: 9/23/2010 9:52 AM by Author "Sandmann_AU" in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=10021730