Great Planes Extra 300S 40 Kit Electric conversion build
I searched and searched and could not find a Thread that covered this bird so I'm going to toss a few pics and comments up if anyone wants to read it.
I purchased the Kit from Tower http://www3.towerhobbies.com/cgi-bin...2034&search=Go
SPECS: Wingspan: 58"
Wing srea: 594 sq in
Wing loading: 24oz/sq ft
CG: 4" back from the leading edge
Currently I intend to put a Rimfire 60 in it but that may change after it's all done.
I chose this kit as my second build because it is inexpensive, and in the size range I was looking for.
I find it very difficult to find Kits that are designed for electric that I wanted to build.
Most of them were either too small, or priced higher than I wanted to spend yet as I am still learning it seems there is mid-range holdein the Kit market, but I understand Kit builders are a fading breed that that is most likely why.
comments so far:
Tower got the kit to me in very good time, packaged well, and everything so far is looking real good, the wood I have pulled out so far is consistent quality, no real bad warps and the instructions are very clear and concise.
It took me about 2 hours to get the Horizontal Stab finished, In my non-expert opinion the wood has been straight, and easy to work with not too heavy but good quality.
I cut the plan into three pieces as recommended and have the Stab drying overnight now.
I used medium CA for the frame work, but when it came to putting in the fillets and internal supports in I switched to a wood glue so that I had time to position it all in place before it dried.
Below is a pic during the build, easy and straight forward.
More as it progresses, if you have built this bird and have any comments or upgrades that you recommend along the way please feel free to toss them in.
Great to see someone building something.
I was looking at that motor, if you're running the 6s, you'll probably be around 300w/lb. That ought to fly alright! You might not even need the wings,,,,,:)
I have had to admit that I love building as much as flying, and since we get about 6-8 weeks of winter it gave me something to do that I love.
I built a GP Sportster 60 that I am most likely going to Maiden today if everything checks out right and I am comfortable doing it. It will be 70 today and the first flying day of the year so I'm going to toss around a few old faithfuls to be sure I'm ready :-)
It has slowed down my aircraft aquistion building them too!
my Stab got stuck to the "glue proof" plastic I was using so I have a little careful scraping to do before I move on, I should have just used wax paper......
but that is part of learning!
Till the next update, have fun!
Not a lot of progress, but here it is as it is.....
There was a big difference in some of the balsa strips so I selected th lightest ones for the rest of the tail.
I sanded the Horiz stab, and even used a Mic, to be sure it was the same thickness all the way through perhaps silly but it only take a second.....
Mental note :-) - apply the few drops of thin CA to the spots that need it AFTER you remove it from the plan!
Anyway, hope to have more to report next time.
** All up weight of the Horiz Stab is 1oz on the dot!
OK no real exciting stuff yet, but the tail feathers are close, I have learned, not to use the plastic film that is designed to lay over the plans, it's glue "resistant" my butt :-)
Wax paper works a lot better, got the elevators done but not joined, Vert-stab built and all hinge surfaces cut and test fitted with hinges.
Although this is only the 3rd or 4th time I've cut hinges and bevels in balsa, I must admit using the Great Planes Hinge slotter, guide and centering tool make quick work out of it. I was able to do it in minutes compared to about an hour to do a elevator on another plane the old fashioned way and I never got it straight. I used a razor plane to create the bevel and a touch of 220 grit paper on a block to smooth it out.
I got two of the hinges off center on the back side of the rudder so I need to pay better attention when using the slotter, but it is straight where it counts most, when assembled it moves more than will be needed without binding.
The Vert. Stab has some putty drying on it, not sure if I'll get more done this weekend, but that is as it stands, I add a few things that were not in the plan, but the weight should be minimal (I know every gram counts) but I'm learning!
I have ordered the electronics, I'm going to most likely go with the RimFire 55, it is still overkill but I like to be able to fly normal flight at 1/2 stick, Hitec HS-485HB servos all the way around and I will but using one servo in each wing.
a castle creations Ice 75 will regulate power.
OK each wing is built upside down on the apposing plan, IE Right wing built upside down on the Left wing plan, this allows the tabs on the Ribs to keep the wing straight for you, and pretty much makes it idiot proof, BUT as usual I was a better idiot...... The first wing half went so fast I only got one picture ;-)
It all went very fast and very well, the first wing took a few hours, the second less than an hour as I understood what needed to be done.
I got both done, trimmed the edges and started lining up to the plan to make the final adjustments before making it permanent..... Then it dawned on me that the wing does not have a tailing edge, so I flipped forward in the manual reading all the steps to see when that comes into play..... I couldn't find it.....
Soooo I start flipping Backwards and I'll be darned there it was many steps previous which made total sense but I missed it. The manual has cute little boxes that you can check off when you complete a step, I think I will start using those :-)
Because of my little mis-hap my training edge sheeting is a bit off on one side, but nothing that can't be fixed. everything is dead on straight where it matters and that is the important part.
The quality of this kit and the wood is much better than my GP Sportster that I built first, perhaps I got a bad one but the Sportster took me 2.5 months to build I can see being done with this one in a week or two.
The only issue I had so far is the sheer webs were not quite the correct size as stamped out but little sanding and all was well. they look sloppy but even in the manual they look sloppy so I don't feel so bad.
Each wing weights 4OZ on the dot as pictured. I'm done for the day, I'll work on joining the wings sometime this week. I want to take my time and be sure it's 100% correct.
Overall nothing too exciting, nothing difficult (except reading ALL the directions) very cut-and-dry build and moving very rapidly. The tabs on the ribs are very fragile and I have had to glue a few back on after bumping them the wrong way
I may order the 46 as the build progresses, I was less concerned with weight last build but this time I'm really trying to get it in line with specs or better if I can.
We shall see I have several motors here but I've learned to wait until the build is about done to order parts or you wind up with several parts on hand :-)
My experience with that model is that the lighter you can build it the better. It has a pretty thin airfoil and is easy to stall, which is why it snaps so well.
I flew one my brother had until he spun it in by doing an inside/outside spin too low, if it had a thicker wing or was lighter it would have survived.
I just was given one complete that had flown and is equipped with an OS 46 FX and Pitts muffler and my son is going to start flying it next week. We are retaining the glow engine for economy (I don't have to buy another motor, just a rx and batt!). It is box stock and has a 1/2 pound lead weight in the nose and the cg is right on. The servos, rx, and rx batt are all forward of the leading edge of the wing.
Sand every sheet of wood, use as little glue as possible when building the back of the fuselage, make the battery mount able to accept the batt right up into the motor mount (forward, or through the firewall) would by my thoughts if building an electric conversion from new. Also, engineer yourself a top battery hatch from the front of the canopy to the firewall or inclusive of the canopy, you'll thank yourself later (or hate yourself if you don't!).
P.S. I made big holes in the aft fuselage of one of my models, I cannot remember exactly the fuse layout on the Extra but it might by possible to open up the bulkheads and fuse sides to get rid of unnecessary material weight because the kit was for a pounding glow engine, you won't need a lot of that lumber. In fact, maybe some lite ply could be substituted with balsa?
GREAT info thank you very much, I will read that thread for sure.
I maidened my first Kit build today and it took two clicks up elevator and that was it. A moral booster. goes very well I am proud and happy with it.
With this build the goal will be light, light, light, hopefully it work out!
I did things slightly different then the plans, partially cause I goofed a little and partly because I am going to use dual servos so I did not place the servo in the center.
When I joined the wings I sanded a little too much off the ends of the spars, the instructions call for plywood sheeting front and back, and I read some very old posts with others that had some concern about it being weak so I put a 1/4 inch support on top and bottom of the spars when I joined them I used 30 min epoxy and I'm sure it is good to go, I also cut a bit too much off the trailing edge so I bridged that gap to keep it even until it was sheeted.
one complaint that was popular in other threads I saw, the tabs on the ribs are a very great idea, but too weak, they are perforated to snap off easy after the build but any lateral movement and they break. I think I wound up CA'ing all of them at one point or another.
Some of the mis-colored wood is older stock I had replaced the factory wood with because it was easier for me.
My loving wife made me some sandbags that worked great for weights, heavy ziplock bags with wet sand work great.
I have a little warp in the trailing edge it's bowed out toward the rear in the center, but it is straight otherwise so a good sanding should take care of that.
I think that is it I'll update if I think of anything else
I hit a stumbling point on the wing and moved on to the Fuse, The fuse is as complete as it can be until I get the wing finished up so I'm back to the wing now....
The fuse went together so quick I forgot to take but a few pictures. - Yeesh I guess I'm not that great at reviews sorry - Anyway I was less impressed with the Light Ply in the kit, the die cuts we ruff like the die was dull but it all worked out ok, this may be normal this is only my second kit......
Basically you glue together the firewall, glue on the Fuse side doublers and rubber band it all together as you add pieces. I wound up sanding the edges and corners of ever piece of light ply as the die didn't quite make it all the way though and the edges were not straight and did not "just fit" like I said no big and it all worked out.
after it's all assembled and you have it straight you apply thin CA to the areas as specified and it stiffens right up, pretty nice so far.
The Light ply sucked up a lot of CA in some spots I could see where it traveled the entire width of the ply as it wicked in, I assumed this was a good thing and let it go I figure it will make it stronger.... perhaps a tad heavier but I doubt it will be noticeable.
OK as mentioned I put the wing aside and got the fuse to the point I needed the wing done and here is how it all worked out.
I got sorta stuck on how to be sure the center of the wing would be centered properly, it's basically the Ailerons extended to the center of the wing but they are glued and fixed.
Had I followed the instructions, this is where the Single Servo control rods would go, and I an doing dual servos so I improvised. The tips have a groove in them that is fairly weak because the control rods go through them what I decided to do was fill the grooves 1/2 way with epoxy, let it dry and then followed up but filling the rest of the groove with Epoxy and sticking them to the wing. I mounted the aileron still uncut and unbeveled so I could be sure that I was putting the tips on straight. I used plastic clamps that happened to hit 1/2 the aileron and 1/2 the wing to be sure it was centered until the epoxy dried. Worked great!
Next I put the actual wing tips on, I measured the length of the Ailerons and cut about a one inch wide section off the end for the tips, I bought a Miter Sander and this made things very simple to be sure all the lines were perfect as there is a little of a taper on the tips. I used the same clamp method fitting the unbeveled Aileron in the be sure everything was great and let the glue set up So far it looks perfect.
Next step was to bevel the Ailerons, trim to fit, cut the CA hinge slots..... Last build I bought a Great Planes Hinge slotter and all the accessories, this makes a several hour project simple, accurate and fast. another awesome tool.
To cut the bevel, I used the Great planes center marking tool, them marked the distance on the top and bottom of the Aileron as to how far back to cut and I used a Razor plane to gently take the taper down, after doing the with a saw and a jury rigged setup last built this was a major blessing, again, the right tool for the job makes it pleasurable. the Razor plane made it simple accurate and a perfect looking bevel. I wound up making the bevel a little more than it needed to be and as seen in the pics, I could get the deflection to 90 degrees easily, I wont need that much but I could if I wanted. I'm very happy with it so far.
So with all this done, all that was left was mounting the Servos into the wings.
I am mounting them on a 1/16 piece of birch ply, laying on their side, so that only the arm sticks out of the ply, looks neater and because the wing is not super thick I felt the best way to go. I figure you can figure out how to cut the ply, if any one has questions ask, I glued some pieces of a left over spar..... its a harder Balsa wood but much lighter than hardwood.... at each corner of the "pocket" to screw the ply servo cover to, I'll post more pics once it is complete but I think you will get the idea.
Next time I will finish up mounting the servos, check lateral balnace and adjust as needed, then I can work on mouting the Wing to the fuse!
Not sure if anyone is reading this but is anyone has questions please ask!
Finished up the dual wing servo mounts, 1/16 of an inch thick brich ply, I used a very thin "diamond coated" cutter wheel from Harbor Freight to cut the slots.
Very good cutters for the price.
I CA'd the hard balsa in the wing, put the screws in took them back out and used thin CA to harden up the threads.
I decided to go with HS-225BB's in the wings as the standard HS-485's were really too big and really overkill for the purpose. The 225's specs are below.
Motor Type: 3 Pole
Bearing Type: Top Ball Bearing
Speed (4.8V/6.0V): 0.14 / 0.11 sec @ 60 deg.
Torque oz./in. (4.8V/6.0V): 54 / 67
Torque kg./cm. (4.8V/6.0V): 3.9 / 4.8
Size in Inches: 1.27 x 0.66 x 1.22
Size in Millimeters: 32.26 x 16.76 x 31.00
Weight ounces: 0.95
Weight grams: 26.93
More as it comes along
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