Scratch build a 35cc sport plane
#1
Thread Starter
Scratch build a 35cc sport plane
I picked up a set of balsa covered tapered foam cored wings a few years ago for $5 NIB. They needed a fuselage and I needed a winter project. A sketch and then drawing was produced of what I wanted, a fairly simple mid wing, open cockpit with top hatch.
A few pics of the beginning effort.
Sorry, no good image of the plans.
A few pics of the beginning effort.
Sorry, no good image of the plans.
#4
Thread Starter
RE: Scratch build a 35cc sport plane
The gluing of the firewall and gear mounts marks a progress milestone as the fuselage can be removed from the building board allowing the board to be used to work on stabs.
The fuselage has a good bit of work remaining however such as fore/aft turtle decks, nose ring for round cowl and stringers to fair it all.
I've greatly enjoyed this build so far. After several arfs, the pleasure that comes with building had faded. Wishing however, that I could build as light as arfs, but that is not in my DNA... I join the rest of the over builders.
The fuselage has a good bit of work remaining however such as fore/aft turtle decks, nose ring for round cowl and stringers to fair it all.
I've greatly enjoyed this build so far. After several arfs, the pleasure that comes with building had faded. Wishing however, that I could build as light as arfs, but that is not in my DNA... I join the rest of the over builders.
#5
Thread Starter
RE: Scratch build a 35cc sport plane
With the fuselage off the board, the nose ring could be set. Shown is how to cut a large circle (at least in light ply) on the band saw. Simply provide an axle nail adjacent to the blade the radius of the desired diameter. Might need to clamp some plywood to the table top to receive the nail.
The second pic is shows the value of the courtesy drilling mount pattern supplied by MLD, a great time saver.
There were no surprises and the diagonal distance across the longerons came out perfect for the diameter of the nose ring as planned. The bottom of the ring will have a 3" wide wind tunnel for cowl exit air and the top will form the turtle deck with the sides being faired back to the fuselage taper.
One advantage of the setup is that the motor and cowl can be adjusted fore and aft 1.5" simply by changing the length of the engine standoffs to help in balancing. The trade off for the adjustment is a slight gap (perhaps 1/4") around the cowl, which isn't much issue on a sport plane.
These steps were to confirm that the nose ring will center on the engine.... it was very close.
The second pic is shows the value of the courtesy drilling mount pattern supplied by MLD, a great time saver.
There were no surprises and the diagonal distance across the longerons came out perfect for the diameter of the nose ring as planned. The bottom of the ring will have a 3" wide wind tunnel for cowl exit air and the top will form the turtle deck with the sides being faired back to the fuselage taper.
One advantage of the setup is that the motor and cowl can be adjusted fore and aft 1.5" simply by changing the length of the engine standoffs to help in balancing. The trade off for the adjustment is a slight gap (perhaps 1/4") around the cowl, which isn't much issue on a sport plane.
These steps were to confirm that the nose ring will center on the engine.... it was very close.
#6
Thread Starter
RE: Scratch build a 35cc sport plane
The nose ring was glued in along with the forward turdle deck former at the hatch line as well as the last of the fuselage box structure. Ready now for forward turtle deck stringers.
#9
Thread Starter
RE: Scratch build a 35cc sport plane
Forward turtle deck is framed. The aft deck is more complicated than normal because I didn't want to start it at the rear point of the wing cavity because an open cockpit just looks too far aft there. So, the aft turtle deck has to come forward several inches onto the top hatch.
#10
Thread Starter
RE: Scratch build a 35cc sport plane
Spent a day so far on the aft turtle deck and hatch and work yet remains on them. Having no templates requires a good bit of tedious effort to produce the needed formers.
#12
Thread Starter
RE: Scratch build a 35cc sport plane
The aft turtle deck fairings are best carved and sanded prior to sheeting the turtle deck. As the stabs will be bolted on, a mock up of their thickness provides the means of doing that. In the past, I've glued the fairings to a piece of 1/64" plywood that will sandwich between the vertical and horizontal stab so that the faring will be a separate entity that gets bolted on when the stab is bolted on.
I don't have the soft balsa block needed for the farings yet but when they are shaped, pics will be provided that should explain how this is done.
For those who might be curious about weight... the current weight is 37oz, less the turtle deck sheeting and remaining fairings and the stabs. The wings weigh 53oz including a heavy aluminum tube @ 9oz.
I don't have the soft balsa block needed for the farings yet but when they are shaped, pics will be provided that should explain how this is done.
For those who might be curious about weight... the current weight is 37oz, less the turtle deck sheeting and remaining fairings and the stabs. The wings weigh 53oz including a heavy aluminum tube @ 9oz.
#14
Thread Starter
RE: Scratch build a 35cc sport plane
When first contemplating what to do with the wings my thought was a sport stick... a simple square fuselage with tapered mid wings. However the original sketch expanded on that and included an open cockpit with fore and aft turtle decks.
Self design and scratch build of course aren't restricted by the parts in a kit... the project can go wherever the builder is led. As can be noted, this project is certainly no longer a sport stick.
Self design and scratch build of course aren't restricted by the parts in a kit... the project can go wherever the builder is led. As can be noted, this project is certainly no longer a sport stick.
#17
Thread Starter
RE: Scratch build a 35cc sport plane
Thanks.... and the hope is it's not the field ugly duckling and that it flies well.
Not much new to post a pic of. The forward and aft farings are complete. Two formers were added to the aft turtle deck following the decision to not sheet it as wanted is fabric over frame work look. Scallops were added to the aft side of its forward former to soften the former edge.
A little work is left adding fillers and stringers on the mid fuselage side sections and then two bottom stringers to get the covering clear of the lite ply on the center box. Last of course, sheet the forward turtle deck and cockpit.
Not much new to post a pic of. The forward and aft farings are complete. Two formers were added to the aft turtle deck following the decision to not sheet it as wanted is fabric over frame work look. Scallops were added to the aft side of its forward former to soften the former edge.
A little work is left adding fillers and stringers on the mid fuselage side sections and then two bottom stringers to get the covering clear of the lite ply on the center box. Last of course, sheet the forward turtle deck and cockpit.
#18
Thread Starter
RE: Scratch build a 35cc sport plane
The last of the fuselage framing... the open cockpit on the top hatch. Making the last preparation before sheeting.
All farings and stringers are completed. Next step will be the stabilizers and they are typical stuff so there will be no pictures or updates until they are finished and then I'll provide some completed pics prior to covering.
There is some work to do on the wing with the addition of some round tips and cutting in flaps. They will be detailed when they happen. So, the thread will rest for a few days until the stabilizers are build and fitted. And... probably will need to order some wood to complete those.
Also needed is a dummy engine for the cowl.
All farings and stringers are completed. Next step will be the stabilizers and they are typical stuff so there will be no pictures or updates until they are finished and then I'll provide some completed pics prior to covering.
There is some work to do on the wing with the addition of some round tips and cutting in flaps. They will be detailed when they happen. So, the thread will rest for a few days until the stabilizers are build and fitted. And... probably will need to order some wood to complete those.
Also needed is a dummy engine for the cowl.
#19
Thread Starter
RE: Scratch build a 35cc sport plane
Only a small amount of progress this week as work kept me busy. The mains and tail wheel are fitted and construction of stabilizers has started with the horizontal stab framing done (less the elevators).
A dummy engine was found for the Seagull AT-6 cowl. The Great Planes Super Stearman dummy engine fits perfectly.
A dummy engine was found for the Seagull AT-6 cowl. The Great Planes Super Stearman dummy engine fits perfectly.
#22
Thread Starter
RE: Scratch build a 35cc sport plane
The wing tips required a jig....err two jigs so as not to waste too much time. I had more pics but had a camera glitch and lost the beginning pics. At any rate, these pics show the process I chose to build the tips. 3-4 more layers of 1/16 x 1/4 balsa are needed to make up the laminate edge. Then lots of sanding. Fortunately the tips can be components and then attached when finished.
#23
Thread Starter
RE: Scratch build a 35cc sport plane
Tips are finished. The process was easy and went well. Planing and sanding took about a half hour each tip but it was an easy half hour.
#24
Thread Starter
RE: Scratch build a 35cc sport plane
Ok... construction is 99% finished. Hinge slots yet, secure the antenna tube, and a chase tube for the carb mixture screws... then a final fill and sand dents and it is ready for covering.