u2builder
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Serafin Electric Build Notes
I recently built a Serafin with a motor. The Blejyzk planes have caught my eye because I love the look of natural wood, but I have never built one .... until a few weeks ago. I like the looks of Serafin. It looks a bit like an oversize DLG with its pretty "ellipticalish" wing. The Serafin is very similar to the Mefisto and there are several comprehensive build threads on that, but I couldn't find much information on building either the Serafin or the Mefisto with a motor so I figured I would post my experience here in case others are interested. Unfortunately I didn't take any photos during the build but I have attached a few of the finished glider.
I have built lots of balsa ply models, including several older and newer 2 m gliders, mostly from kits and a few from plans since getting into this hobby after I retired. The Blejyzk planes are pretty much already "built" but there are still quite a few critical steps left for the builder.
I found the E-Serafin build "challenging" in several respects, partly because this was a completely new type of assembly, partly because I could find no info on the electric version and mostly because I realized there was little room for error and it would be a lot more difficult to "cover up" mistakes than on a balsa ply film covered glider.
I knew from reading previous threads that a two bolt one piece wing would probably be stronger and easier to build than the four bolt two piece wing. Nevertheless, I decided to build the 2 piece wing mostly because I really didn't want to apply fiberglass in the center section. I didn't want to risk making a mess in the middle of this beautiful wing and my previous attempts at fiber glassing have been less than perfect. Also, while I don't need to remove the wing to fit in my vehicle, I can see that it could be desirable if I get a small vehicle in the future.
The two wing panels don't precisely line up as has been mentioned by others and I wanted the little spar to be removable so I put a tube to accept the spar in both wings. It took a lot of filing and fiddling and checking to get the wings lined up and with the proper dihedral. Locating and exactly drilling and countersinking the holes for the wing bolts was the next task that left no room for mistakes. I drilled pilot holes and progressively enlarged them but but there was a tendency for the bits to run a little off center and I had to use a tiny round file to center a couple holes. There was not much room to spare in the fuselage for the blind nut attachment either and of course the wing had to wind up perpendicular to the centerline of the fuselage. I was glad to see Wayne's Mefisto 10 year old build thread with the removeable wing on RC Groups. I took my time, and really did measure several times before drilling holes. Luckily it came out good, but I could and can see how it would be easy to screw this up. As a final note, I replaced the supplied slot head 4 mm nylon bolts with Phillips head type which are much easier to use and better for the wing skin.
Installing the Corona DS-843MG digital metal gear servos in the wings was the next challenge. I used the marked the openings which were almost perfect for these servos, and cut them out with multiple passes with a hobby knife. Removing the foam was easy by cutting around the perimeter and then plucking out the foam and scraping the bits off the veneer with a small chisel. I did not use a hot soldering tip because I didn't want to have to scrape off globs of melted plastic. I thought about reinforcing the veneer with fiberglass as others have done but decided instead to epoxy the veneer I had cutout to make the openings to reinforce the "bottom" of the opening. Pulling the servo wires went well. I made the tunnel between the flap servo and the wing root a little larger. The next step was to try to figure out how to position the servo arms and what holes to use, challenging because once the servos are glued in changing these things is difficult. I had to use z-bends on the arms to get full movement of the arms without cutting away more wood. I tried to hold a servo in place while using a servo tester to see how much movement of the control surfaces I was getting. It was surprisingly difficult to hold the servo in place! I wanted to use the closest to center hole in the servo arm for good resolution and still get enough surface movement. I wound up using the second hole out from the center of the arm for the ailerons and the third hole out for the flaps and offset the flap servo arm on the servo output shaft to get the maximum down flap as well as enough up flap so flaps could be used as ailerons. Because the servos were so hard to hold in place I decided to glue small pieces of basswood onto the reinforced skin. I attached little "wing" adapters that came with the servos and screwed the servos to these blocks in addition to wrapping the servos with masking taping and epoxying them to the skin. For extra measure I glued a strip of CF to the servo across the top as others recommended in the Mefisto threads. When I did the final setup on using Mike Shellim's excellent E-Soar Plus for ETHOS the flaps and ailerons all the surfaces moved to the recommended limits with very linear curves that went through or close to the origin. The top hinging limits the flap servo deflection to maybe 50 - 60 degrees. I am not sure if they will be effective for braking, but pretty sure I won't need flap braking anyway.
I decided to make the cross tail removeable, which should have been very easy except that I didn't know the blind nut for the stab was already installed since it wasn't visible or mentioned in the instructions. The hardware kit that came with my cross tail version was for the V tail and came with 3mm blind nuts and screws for the tail and when I drilled a 3mm hole in what I thought was a guide hole I hit the preinstalled hidden (very blind!) 2mm blind nut which then had nothing to hold it. I didn't have a 2mm bolt anyway and the kit didn't come with one so I removed the 2mm nut and drilled a larger hole for a 3mm blind nut and set that in epoxy to keep it in place. I used double stick tape under the stab in addition to the screw. The removeable cross tail is a great design. With the removeable wings the Serafin will almost fit in the tiny box it came in. It is very portable.
I recently built a Serafin with a motor. The Blejyzk planes have caught my eye because I love the look of natural wood, but I have never built one .... until a few weeks ago. I like the looks of Serafin. It looks a bit like an oversize DLG with its pretty "ellipticalish" wing. The Serafin is very similar to the Mefisto and there are several comprehensive build threads on that, but I couldn't find much information on building either the Serafin or the Mefisto with a motor so I figured I would post my experience here in case others are interested. Unfortunately I didn't take any photos during the build but I have attached a few of the finished glider.
I have built lots of balsa ply models, including several older and newer 2 m gliders, mostly from kits and a few from plans since getting into this hobby after I retired. The Blejyzk planes are pretty much already "built" but there are still quite a few critical steps left for the builder.
I found the E-Serafin build "challenging" in several respects, partly because this was a completely new type of assembly, partly because I could find no info on the electric version and mostly because I realized there was little room for error and it would be a lot more difficult to "cover up" mistakes than on a balsa ply film covered glider.
I knew from reading previous threads that a two bolt one piece wing would probably be stronger and easier to build than the four bolt two piece wing. Nevertheless, I decided to build the 2 piece wing mostly because I really didn't want to apply fiberglass in the center section. I didn't want to risk making a mess in the middle of this beautiful wing and my previous attempts at fiber glassing have been less than perfect. Also, while I don't need to remove the wing to fit in my vehicle, I can see that it could be desirable if I get a small vehicle in the future.
The two wing panels don't precisely line up as has been mentioned by others and I wanted the little spar to be removable so I put a tube to accept the spar in both wings. It took a lot of filing and fiddling and checking to get the wings lined up and with the proper dihedral. Locating and exactly drilling and countersinking the holes for the wing bolts was the next task that left no room for mistakes. I drilled pilot holes and progressively enlarged them but but there was a tendency for the bits to run a little off center and I had to use a tiny round file to center a couple holes. There was not much room to spare in the fuselage for the blind nut attachment either and of course the wing had to wind up perpendicular to the centerline of the fuselage. I was glad to see Wayne's Mefisto 10 year old build thread with the removeable wing on RC Groups. I took my time, and really did measure several times before drilling holes. Luckily it came out good, but I could and can see how it would be easy to screw this up. As a final note, I replaced the supplied slot head 4 mm nylon bolts with Phillips head type which are much easier to use and better for the wing skin.
Installing the Corona DS-843MG digital metal gear servos in the wings was the next challenge. I used the marked the openings which were almost perfect for these servos, and cut them out with multiple passes with a hobby knife. Removing the foam was easy by cutting around the perimeter and then plucking out the foam and scraping the bits off the veneer with a small chisel. I did not use a hot soldering tip because I didn't want to have to scrape off globs of melted plastic. I thought about reinforcing the veneer with fiberglass as others have done but decided instead to epoxy the veneer I had cutout to make the openings to reinforce the "bottom" of the opening. Pulling the servo wires went well. I made the tunnel between the flap servo and the wing root a little larger. The next step was to try to figure out how to position the servo arms and what holes to use, challenging because once the servos are glued in changing these things is difficult. I had to use z-bends on the arms to get full movement of the arms without cutting away more wood. I tried to hold a servo in place while using a servo tester to see how much movement of the control surfaces I was getting. It was surprisingly difficult to hold the servo in place! I wanted to use the closest to center hole in the servo arm for good resolution and still get enough surface movement. I wound up using the second hole out from the center of the arm for the ailerons and the third hole out for the flaps and offset the flap servo arm on the servo output shaft to get the maximum down flap as well as enough up flap so flaps could be used as ailerons. Because the servos were so hard to hold in place I decided to glue small pieces of basswood onto the reinforced skin. I attached little "wing" adapters that came with the servos and screwed the servos to these blocks in addition to wrapping the servos with masking taping and epoxying them to the skin. For extra measure I glued a strip of CF to the servo across the top as others recommended in the Mefisto threads. When I did the final setup on using Mike Shellim's excellent E-Soar Plus for ETHOS the flaps and ailerons all the surfaces moved to the recommended limits with very linear curves that went through or close to the origin. The top hinging limits the flap servo deflection to maybe 50 - 60 degrees. I am not sure if they will be effective for braking, but pretty sure I won't need flap braking anyway.
I decided to make the cross tail removeable, which should have been very easy except that I didn't know the blind nut for the stab was already installed since it wasn't visible or mentioned in the instructions. The hardware kit that came with my cross tail version was for the V tail and came with 3mm blind nuts and screws for the tail and when I drilled a 3mm hole in what I thought was a guide hole I hit the preinstalled hidden (very blind!) 2mm blind nut which then had nothing to hold it. I didn't have a 2mm bolt anyway and the kit didn't come with one so I removed the 2mm nut and drilled a larger hole for a 3mm blind nut and set that in epoxy to keep it in place. I used double stick tape under the stab in addition to the screw. The removeable cross tail is a great design. With the removeable wings the Serafin will almost fit in the tiny box it came in. It is very portable.
