Stringers and other bits

 Acroduster  Comments Off on Stringers and other bits
Sep 162019

This is where loads of fun can be had. To the naked eye, adding a few stringers should be a 10 min job. Yes, sure, but if I can stretch it for a few days? First I added the round formers from firewall aft. They all have the same radius as the firewall, so that makes life a bit easier.

Anyway, a good day was had, and I think I have the process worked out now. As always, let the pictures tell the story.

The bending contraption, borrowed from Thomas 😉
Difficult to see, I try to show the false formers here.
try gluing a tiny bit of metal to a 4 mm tube, when you only have 2 hands.
the end result, stringer #1 done.
cockpit side
tail side
Even Paolo’s brazing look a mess until cleaned up, so I don’t feel too bad.
one side done..
nice job, even if I have to say so myself
 Posted by at 6:19 pm

when in doubt..

 Acroduster  Comments Off on when in doubt..
Sep 052019

…check There are a surprising amount of active builds going on, and luckily the Acroduster is alive and well. Just an example: here’s a pic of an ”original” compared to mine. Isn’t that fun!

I will have to ask the original posters if I can use their pics here, so right now I’ll leave it at this one pic.

This is a repair job, but there are so many interesting details here.
Mine follows the drawings, other then that, not bad!!

Looking at the full size one and the original drawings there are a number of small differences, but as each person decided how to tackle a problem differently, each solution is as good as another.

For me the pic answers these questions:

When the landing gear moves past a certain point, the bungees have to go through the bottom of the fuse. Guess what, you see little doors, which are not in the original drawings. Great idea! You might notice that the skin covering the landing gear is a narrow strip, so when you bump her down too hard, all you need to replace is the 5″ section that covers said LG.

The drawings are not very clear about how to attach the skins to the frame, all you can see is a number of crosses where bolts go. Here you see the answer: a strip is welded to the frame. This is where all the bolts go!

There is a bow for the bottom skin, but not clear how to attach it, other then to the side longerons. Here you see them connected to the heavy cross section. Simple and logical.

This is what you see everywhere, the plans were/are just a general description of the big important stuff. Everything else is left up to you, for your entertainment and pleasure 😉

 Posted by at 6:16 pm

Every engine needs a firewall.

 Acroduster  Comments Off on Every engine needs a firewall.
Sep 032019

Slow day today, ran out of silver again. Never mind, Ralph from is sending another load!

Anyway, stumbled across a bit of aluminum that just looked like it wanted to be a firewall. I made it the high tech way, from dxf to cnc. Of course I keep saying to myself that in order to cut alu you need the right bits and proper cooling. Never mind, it worked sort of. No damage was done to man or machine.

Blue dot is carb intake. Not planned, just sort of happened to end up there.
..and it’s a good time to check prop clearance. Looks ok, it’s about 8+ cm when on wheels.

No workies today? I officially have now joined the ever growing army of AOP’s. Not full time mind you, for starters just 2 days a week, the other 3 are needed to fund the hobby! But it is nice to have a 4 day weekend 😉

Tail wheel support.

 Acroduster  Comments Off on Tail wheel support.
Sep 022019

Wanted to keep this reasonably light, not perfect scale, but looks close enough when done. I can always change it! Mounting is with 2 M4 screws.

always looks horrible before cleaning.
A bit of a departure from ‘real’, but this part does get a beating.
2 M4 nuts welded in place. Top part is also U-shaped to fit between longerons, bottom U-shaped to fit carbon part.

The seat is built from 6 alu strips going front to back and 7 crosswise. Sort of like in this test. I need to think about this a bit, the center one going to the rear will have to be somewhat special.

Seat for the all important driver.

How to build your own plane

 Website  Comments Off on How to build your own plane
Aug 282019

Lots of inspiration comes from: Achim Engels, build your own Fokker plane. 

And another one: Kerry Ann’s Piper.

Again on close inspection you recognize so many of the tricks that are used in the SA-750. If some construction detail is not clear, check here!

Another great source is . To view everything it wants a donation, but it is worth it when you are building.

 Posted by at 8:30 am

One legged plane

 Acroduster  Comments Off on One legged plane
Aug 242019

The first leg is the easiest, the second has to match, which is far more work. However, I’m quite pleased with the weekends work. Total weight of the leg is 118 gram. I also added all the pilot seat tubing, giving a total fuse-weight of 1148 gram. (still hoping for a less then 2 kilo RTF fuse.)

I started with the main pipe, angled forward 8 degrees. Followed by the cross-way pipe to which the bungy-cord attaches. Next the support for that, so that the triangle is complete. Next the rear support to lower main leg. Then the bit between front and rear support, and finally the cross between rear and bungy-cord pipe.

Note to self: Need to make a 4+ mm bushing to fit snugly into the 5 mm fuse attachment tube. With a 4+ mm bushing and 3 mm bolt to secure the bushing, all will be perfect!

right leg done, wheel axle is for later.
this juncture was a bit of a challenge, initially forgot the add magic goo to the cross brace. That does not work well!
front vieuw
a bit of discoloring from brazing on the main support.
 Posted by at 2:00 pm  Tagged with:

After brazing

 Acroduster  Comments Off on After brazing
Aug 212019

Closeups of my handywork. After sandblasting I ‘ll reheat the joints to make them flow a bit more and fill any voids leftover. This will be for cosmetical reasons only.

front u/c support
rear u/c support – front wing support

bottom parts 2mm steel, top 3 mm steel.

Looking good!

Wing & u/c attachment hardware

 Acroduster  Comments Off on Wing & u/c attachment hardware
Aug 182019

The plans call for square tubing for mounting the wings, but you guessed it, not available in the size I want, not even close. Here I have to deviate from the plans and make something that will look the same, but is something I can make. At stations 31 and 51 I added the normal tubing cross bracing. Then I made some solid steel supports that look like the original. I use short pieces of steel. Later I will put a false ‘square’ cover over the visible bits in the cockpit area.

I’ve always been reluctant to start milling steel, but actually, if you take it slow, it goes quite well! (surprising myself here.) This stuff is plain cheap ironbar, I will have to try stainless steel as well, but that is probably a different game. Time will tell. (Note to self: This was done with a 2 mm bit, @300 mm/min, 0,1mm layers. Probably can go larger on the layers, but I need to do something about cooling, since WD40 is not that great as cooling liquid.) Looking at the parts you see that the toolbit vibrates, it creates an uneven surface. However, using a 2 mm bit is really pushing things. I will need to study this subject a bit more!

bottom right made by human, rest by machine.
lower wing attachment point

While I was at it, I also made the support for the LG-front attachment point. By using 2 mm parts I get enough strength, and I can easily cover the gap between the supports with a 0.2mm strip. The rears support consists of triangular gussets. Again a milled part will be the real support, gussets will/ might be added to make it look nice.

main LG tube will attach here.
5mm tube is for alignment, center to be removed once it is all fixed.

Rudder finished as well.

 Acroduster  Comments Off on Rudder finished as well.
Aug 172019

As you can see, the new shipment of tubes has arrived. Visible progress is made again today. Overall I’m happy with the result, there are always little things that do not quite turn out as intended, but since this is all about learn as you build, it’s not a disaster. (So far I have not had to scrap anything)

1040 grams so far

The outline of the rudder is not 100% accurate, I went more along the route of TLAR. I might have a couple of square inches more rudder area, which never hurts. Most of the rudder was build freehand. I pre-bend the outline of the TE as much as I could, then stuck the front of the tube in the top rudder tube, soldered the main post, and added the ribs as I went, keeping a nice smooth shape as I progressed.

after a bit of blasting

Again, 2 bottles of sand were blasted into the atmosphere. At 8 bar air pressure, the ribs do deform, better use 5-6 bar and take longer. Nothing drastic, but keep it in mind.

I found out that stress was present in the construction (surprise) which causes a slight bow in the rudder post. The balancing part of the rudder is now to close to the rudder part. Nothing that can’t be fixed, but it goes to show how much tension develops in the parts after cooling down. I could of course stick everything in an oven @600C for 24 hrs. Only problem is I don’t have one.

stress in the rudder caused this uneven distance.

 Posted by at 3:07 pm  Tagged with: