Posts: 1635
Joined: 7/29/2002 From: Fairfax,
VA, USA Status: offline
tubig, The Platt Zero muffler is on the way so its almost ready for the maiden flight. I have the canopy on rails with enough friction to hold it closed. I will try magnets to hold the rear of the canopy down on a HE-162 I'm currently building. I am going to try scale main door closing as the kit design is complex and heavy. Scale is just a rod from strut to door. When to ball mounts the attachment points I believe I can get it to work.
pic 1-2: BT uses four 1/4-20 (nylon) bolts to secure the wing to the fuselage. the first thing to do was to find and drill the holes through the wing. i cut out a small portion of the sheeting and made a wooden jig block to help drill straight holes perpendicular through the wing holddown ply plate.
pic 3: after that i needed to install the fuselage blocks. i waited until now to do this to make sure the wing and fuse was in alignment. i made up some practice balsa blocks first to test the position for the bolt holes. it was a good thing i did because you can see in the photo i was a little off with the forward holes.
pic 4: after making my corrections i installed the real maple blocks, put the wing on, made sure the wing to fuselage alignment was correct and drilled through the wing hold down into the fuselage blocks.
pic 5: the last thing to do was to enlarge the holes for the bolts by simply rolling up some sandpaper, putting into the smaller hole and allowing it to "expand" as i twisted the sandpaper in the hole to gradually make the hole larger.
p.s. i found out that the ply gussets i used on the aft fuselage blocks did not give enough support when tightening the bolts. the balsa slab side on one side ended up splitting due to the force (really, i wasn't screwing down all that tight). anyway, i had to remove the aft blocks by using a heat gun to soften the epoxy, add a 1/8" ply plate and reinstalling. btw, BT shows this ply plate on the plans but he uses some other device for capturing the bolt so that's why i didn't follow it initially. now i see why the ply plate is there. i still need to add some ply gussets for the maple block.
began work on the dreaded wing to fuselage fairings. actually, on the 109 they're not so bad as they are relatively small. pic 1: for these i used scrap balsa wedges as the main filler and then filled in the holes with balloons/epoxy.
pic 2: after the initial sanding i found that somehow one of the upstands had angled slightly (probably due to the balsa wedges) which required more balloons to fill out the space that is adjacent to the fuselage body (the large brown area in the photo). the rest of the fairing is finished out with balloons, hobbylite filler and lightweight spackling.
after looking over some of the photos i have i noticed the wing/fuselage fairing at the wing leading edge is almost at 90 deg. so i have to go back and do some more shaping.
pic 3: meanwhile, i also noticed when i put the fuse on the wing that something at the junction of the wing and cowl didn't look right. i couldn't find anything on the plans and after looking at some more photos i realized there is small fairing on the wing bottom that blends into the cowl. so i drummed that up as well.
rich, yeah, that's the way BT does it. there is an inner balsa slab side that protrudes from the fuselage and is what the wing actually rests on (pic 1). then the upstand comes up from the wing to mate with fuse at the scale joint on the real version (pic 2). it all works pretty slick once you've figured out how BT designed it.
Posts: 2245
Joined: 12/6/2003 From: Northridge,
CA, USA Status: offline
I like the design. Looks like it will be easy to get a nice tight and virtually invisible fit. A kit or two down the line, I think I'll look into a BT design.
yes, it would be except i won't need to do that. there is a 1/32" ply piece that actually covers the joint for the entire length of the joint except at the front where it kind of makes it's z-bend. that part will be covered with some lithoplate (or equivalent).
made the aileron counterbalances today. pic 1: i used the polyester glazing putty in the photo below for the actual mass balance and some 1/16" ply as the arm.
pic 2: i put the soft putty into some plastic spoons to give me a general shape and as the putty started to harden i placed the ply arms in up to a marked line (to get the correct angle of the mass balance when installed in the aileron.)
pic 3: sanded to shape. the arms are just friction fit for now. they'll be removed for finishing.
i'm wrapping up the wing now in preparation for glassing. one of the things i needed to do was to close the gaps between the ailerons and flaps and between the flaps and fuselage fairing. i used a technique i first read about in RCSI awhile back. i believe it was written by Pat McCurry. anyway, it uses some sort of putty and 2 layers of masking tape on one side of the control surface. the putty is troweled into the gap and sanded when dry.
pic 1: this was the putty i used first time around.
pic 2-3: i decided to apply the putty to the flap on both ends. here is two layers of masking tape applied to the aileron and a layer to flap just to keep the excess off of the flap (less sanding). i came to find out that the putty caused the adhesive in the tape to stay behind on the wood which was a real pain to clean off. next time i'll just go with standard balloons/epoxy.
pic 4: here's the same joint after sanding. a nice, even, close fitting gap.
pic 5: i did have some problems with the putty flaking off in a couple of spots so as i mentioned above i went back with the trusty balloons/epoxy mix. i wanted to show just how small a gap you can make this way. this is the flap-to-fuselage fairing gap.
< Message edited by tubig -- 3/14/2006 12:33:54 PM >
while i waiting for the putty to dry i made the pitot tube. pretty simple, just a 1/8" aluminum tube that had a flat spot sanded on it and a 1/16" ply arm epoxied on. for the end cap i used some leftover balloon/epoxy mix, glued it on and shaped it. as with the mass balances, this is just friction fit in place now.
Posts: 1097
Joined: 3/31/2002 From: chicago,
IL, USA Status: offline
Tubig, Should we all take some bets as to how long it'll take to snap that beautiful pitot tube off with a bout of hangar rash ! I usually drill out a little 1/8" hole and CA some inner nyrod in there to make them removable.....even then I snap 'em off . The German planes all seem to have some sort of really vulnerable item on the bottom there. My lucky items are like yours and the machine gun tubes in the wing as well as the radio loop at the bottom on the FW's.
I usually drill out a little 1/8" hole and CA some inner nyrod in there to make them removable.....
i've done something similar before with antenna masts made from balsa. i thought the pitot tube arm made from ply would be a little more sturdy but i'm sure it won't take long for me to knock it off anyway.
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All Forums >> RC Airplanes >> RC Warbirds and Warplanes >> RE: BT Bf109E-4 
RE: BT Bf109E-4 - 
! I usually drill out a little 1/8" hole and CA some inner nyrod in there to make them removable.....even then I snap 'em off 
. The German planes all seem to have some sort of really vulnerable item on the bottom there. My lucky items are like yours and the machine gun tubes in the wing as well as the radio loop at the bottom on the FW's.