BUSA 1/4 DR-1 Build Along
11-27-2012, 03:47 AM
#151
RE: BUSA 1/4 DR-1 Build Along
I see on my dr1 plans that busa has tailbrace flying wires going from the bottom of the stab outer corners to the bottom of the fusalage tail. I can see that this would aid in strength BUT does the full size utilize a brace on the stab?
If not, It would be very easy to mod the stab with a carbon fiber tube to get the strength without the wires...
If not, It would be very easy to mod the stab with a carbon fiber tube to get the strength without the wires...
11-27-2012, 05:38 AM
#152
RE: BUSA 1/4 DR-1 Build Along
All the drawings I could find show the tail brace, and this picture of a crashed one in WWI shows it.
The biggest problem with the tail on the BUSA model is that it's too flimsy- anything that large built out of only 1/4 sq balsa is very delicate. After mine was built and I realized what a disaster it was, I replaced all the fore aft sticks and the spars with 1/4"spruce, and "lined" the insides of the TE and LE with 1/4" spruce.
The fuse is also very flexible aft of the lower wing saddle- it can be twisted very easily. I put triangular balsa gussets at every junction of the various balsa sticks and that made it nice and solid.
The biggest problem with the tail on the BUSA model is that it's too flimsy- anything that large built out of only 1/4 sq balsa is very delicate. After mine was built and I realized what a disaster it was, I replaced all the fore aft sticks and the spars with 1/4"spruce, and "lined" the insides of the TE and LE with 1/4" spruce.
The fuse is also very flexible aft of the lower wing saddle- it can be twisted very easily. I put triangular balsa gussets at every junction of the various balsa sticks and that made it nice and solid.
11-27-2012, 10:10 AM
#154
RE: BUSA 1/4 DR-1 Build Along
The only modification I made to the rudder hinge was to wrap a couple layers of glass cloth around the tubing and onto both sides of the tail ahead of it. I tacked the cloth in place with CA, and then saturated it with epoxy. My tail is kinda lumpy back there because of all this, but the hinge is quite strong. The bird's been flying for two years without any problems in that area.
11-27-2012, 11:22 PM
#155
RE: BUSA 1/4 DR-1 Build Along
Mustang Fever,can you explain your method for constructing this elevator joiner wire and control arm. What is the arm made of and how is it attached to the elevator wire?
I reposted your pic. I hope this is ok..?
I reposted your pic. I hope this is ok..?
11-28-2012, 07:27 AM
#156
RE: BUSA 1/4 DR-1 Build Along
Tom: No worries, it's pretty simple.
I formed 0.125" music wire into a "U". The horn is K&S 1/4"x0.064 brass strip. There is one long piece of brass strip that goes onto the wire and has the hole for the clevis at the other end. There's also a short piece that doubles onto it at the wire end. (To get more surface area and rigidity.) It's all silver soldered together using a butane torch.
I formed 0.125" music wire into a "U". The horn is K&S 1/4"x0.064 brass strip. There is one long piece of brass strip that goes onto the wire and has the hole for the clevis at the other end. There's also a short piece that doubles onto it at the wire end. (To get more surface area and rigidity.) It's all silver soldered together using a butane torch.
11-28-2012, 08:02 AM
#157
RE: BUSA 1/4 DR-1 Build Along
ORIGINAL: Mustang Fever
Tom: No worries, it's pretty simple.
I formed 0.125'' music wire into a ''U''. The horn is K&S 1/4''x0.064 brass strip. There is one long piece of brass strip that goes onto the wire and has the hole for the clevis at the other end. There's also a short piece that doubles onto it at the wire end. (To get more surface area and rigidity.) It's all silver soldered together using a butane torch.
Tom: No worries, it's pretty simple.
I formed 0.125'' music wire into a ''U''. The horn is K&S 1/4''x0.064 brass strip. There is one long piece of brass strip that goes onto the wire and has the hole for the clevis at the other end. There's also a short piece that doubles onto it at the wire end. (To get more surface area and rigidity.) It's all silver soldered together using a butane torch.
Im startin the lower wing today yippie!! I grabbed some expensive hq spruce, got the pick of the whole box. every 36" piece is between 13 grams at 16 grams. I got 12 @ 15-16 grams for the wings and 5 @ 13grams for the stab!!
11-28-2012, 12:02 PM
#158
RE: BUSA 1/4 DR-1 Build Along
Tom:
The GP 4-40 size metal PRs are plenty strong enough for this bird. (Not much force on the surfaces as I've limited it to 30-35mph) I tried CF PRs one time, and scrapped them after I noticed they change length a lot with changes in humidity.
With the metal PRs, all the beefing up to the tail and aft fuse, etc., I had no problem balancing it at the recommended point with a total of 47 oz in the nose (OS 120AX engine, muffler, 4200 NiMh pack, throttle servo, and 2 oz of lead)
Your engine, muffler, and ignition come to 39.9 oz. If you can find room for a 4200 NiMH pack up there, you'll have 49.9 oz, so you should be OK. With your heavier engine, you might even be able to put the Rx and Ignition packs behind the firewall and still not have to add much lead. Don't be afraid to, though, as this thing has so much wing area that a few oz more doesn't make any difference.
The GP 4-40 size metal PRs are plenty strong enough for this bird. (Not much force on the surfaces as I've limited it to 30-35mph) I tried CF PRs one time, and scrapped them after I noticed they change length a lot with changes in humidity.
With the metal PRs, all the beefing up to the tail and aft fuse, etc., I had no problem balancing it at the recommended point with a total of 47 oz in the nose (OS 120AX engine, muffler, 4200 NiMh pack, throttle servo, and 2 oz of lead)
Your engine, muffler, and ignition come to 39.9 oz. If you can find room for a 4200 NiMH pack up there, you'll have 49.9 oz, so you should be OK. With your heavier engine, you might even be able to put the Rx and Ignition packs behind the firewall and still not have to add much lead. Don't be afraid to, though, as this thing has so much wing area that a few oz more doesn't make any difference.
11-29-2012, 03:59 PM
#161
RE: BUSA 1/4 DR-1 Build Along
That's kinda what I did- filled in between the ribs on the TE with 1/8 balsa, if I remember correctly. It stiffened the TE a lot, and allowed the covering to sit nice and straight along the TEs, rather than sagging down between the ribs.
11-29-2012, 05:09 PM
#162
RE: BUSA 1/4 DR-1 Build Along
ORIGINAL: jeffo
twn,do your self a favor and put a top trailing edge on.(same as bottom)-jeffo
twn,do your self a favor and put a top trailing edge on.(same as bottom)-jeffo
ORIGINAL: Mustang Fever
That's kinda what I did- filled in between the ribs on the TE with 1/8 balsa, if I remember correctly. It stiffened the TE a lot, and allowed the covering to sit nice and straight along the TEs, rather than sagging down between the ribs.
That's kinda what I did- filled in between the ribs on the TE with 1/8 balsa, if I remember correctly. It stiffened the TE a lot, and allowed the covering to sit nice and straight along the TEs, rather than sagging down between the ribs.
Not entirely sure what you guys mean?
11-29-2012, 07:26 PM
#164
RE: BUSA 1/4 DR-1 Build Along
Tom: The full size DR1s did not have a trailing edge per se. There was just a cable strung between the TE's of the ribs, and when the fabric covering was doped, it shrunk enough to scallop the cables along the TEs. That's what BUSA has done with the scalloped, balsa trailing edges, trying to get the scale effect. You can go ahead and leave it that way, but the trailing edges come out pretty delicate. If you look back along the thread, near the beginning, I think, you'll find a picture of how I doubled the trailing edge with balsa, between each pair of ribs, so it would be stronger and easier to cover. If I can find that picture I'll post it here.
12-01-2012, 05:42 AM
#165
RE: BUSA 1/4 DR-1 Build Along
Has any one who is following this thread added wingtip skids to the lower wing? If so what was your method?
I was thinking brass straps soldered to brass square tubing mounted to the outer most rib and then making the skid out of 2 layers 1/4 by 1/8 hard wood with a carbon rod sandwiched between the lamination to strengthen and the machine one end of it to a round point to look real...
I just wonder if the brass strapping and solder joint will be strong enough to withstand tip strikes...?
I was thinking brass straps soldered to brass square tubing mounted to the outer most rib and then making the skid out of 2 layers 1/4 by 1/8 hard wood with a carbon rod sandwiched between the lamination to strengthen and the machine one end of it to a round point to look real...
I just wonder if the brass strapping and solder joint will be strong enough to withstand tip strikes...?
12-01-2012, 06:29 AM
#166
RE: BUSA 1/4 DR-1 Build Along
I was going to go the ax handle route, but settled on making the lower wing a lot stronger than the plans called for. I took that decision after a few years with a Great Planes DR-1 ARF. I found that if I blew a landing or takeoff, a wing tip strike was inevitable. The lower wing tip has a lot of leverage over the wing where it joins the fuse, and the wing would crack in two at that point. (I think I went through 3 lower wings on that bird.)
On my BUSA DR-1, I used 1/4 square spruce for the upper and lower spars on the lower wing, and 1/16 lite ply shear webs full span. Near the center, the webs are on both sides of the spars. I had a couple nasty wingtip strikes early on, without so much as a dent in the upper surface of the wing at the fuse line.
There are three secrets to flying this bird that a lot of pilots resist: (A total of 7 years DR-1 experience talking here.)
1. DO NOT attempt crosswind takeoffs and landings. NEVERNEVERNEVERNEVER They did not do that in WWI. That's why they used "fields", so they could head off in any direction. Even at that they had two guys hanging onto the wingtips while they accelerated on to TO.
2. Takeoff: head into the wind, and quickly come up to about 1/2 throttle. This gets the tail up right away so the bird will go straight. With the tail on the ground, the rudder and aft fuse are blanketed, there's no weather vane effect, and she'll squirl all over the place, with a violent ground loop resulting. If the field is short into the wind, no worries. The rate of climb on this bird is fantastic. Even with my wimpy 1.20 two stroke, as long as I'm into the wind I can climb at a 45 degree angle and clear the tallest of trees, as there is almost no ground speed under those conditions and the bird goes up more or less vertically.
3. Landing: into the wind, and play with the throttle so that touchdown is made in a level attitude, being careful to maintain airspeed. This bird has beaucoup drag, so idle power approaches can only be made with the nose way down, or it will bleed off speed and fall out of the sky. It's better to come in only slightly nose down carrying some power to keep the speed up. After touchdown, go to idle and let it roll out, preferably with no control inputs. Any rudder on rollout usually results in a wintip strike on the opposite side, as the bird will lean over in rudder turns on the ground. Again, the trick is to have the tail high at touchdown so there's some yaw stability. Attempted three points can result in a violent ground loop as the tail is blanketed by the wings and there is no directional stability at all.
On my BUSA DR-1, I used 1/4 square spruce for the upper and lower spars on the lower wing, and 1/16 lite ply shear webs full span. Near the center, the webs are on both sides of the spars. I had a couple nasty wingtip strikes early on, without so much as a dent in the upper surface of the wing at the fuse line.
There are three secrets to flying this bird that a lot of pilots resist: (A total of 7 years DR-1 experience talking here.)
1. DO NOT attempt crosswind takeoffs and landings. NEVERNEVERNEVERNEVER They did not do that in WWI. That's why they used "fields", so they could head off in any direction. Even at that they had two guys hanging onto the wingtips while they accelerated on to TO.
2. Takeoff: head into the wind, and quickly come up to about 1/2 throttle. This gets the tail up right away so the bird will go straight. With the tail on the ground, the rudder and aft fuse are blanketed, there's no weather vane effect, and she'll squirl all over the place, with a violent ground loop resulting. If the field is short into the wind, no worries. The rate of climb on this bird is fantastic. Even with my wimpy 1.20 two stroke, as long as I'm into the wind I can climb at a 45 degree angle and clear the tallest of trees, as there is almost no ground speed under those conditions and the bird goes up more or less vertically.
3. Landing: into the wind, and play with the throttle so that touchdown is made in a level attitude, being careful to maintain airspeed. This bird has beaucoup drag, so idle power approaches can only be made with the nose way down, or it will bleed off speed and fall out of the sky. It's better to come in only slightly nose down carrying some power to keep the speed up. After touchdown, go to idle and let it roll out, preferably with no control inputs. Any rudder on rollout usually results in a wintip strike on the opposite side, as the bird will lean over in rudder turns on the ground. Again, the trick is to have the tail high at touchdown so there's some yaw stability. Attempted three points can result in a violent ground loop as the tail is blanketed by the wings and there is no directional stability at all.
11-30-2015, 12:48 PM
#167
Wow. December of 2012 was my last post on this bird. She's been one of my favorite flyers for the last five seasons. A real crowd pleaser at air shows.
I was at the scale show at the Pontiac Miniature Aircraft club, and on my third flight, the clunk came off the pick up tube. Didn't have near enough altitude for a dead stick, so she hit kinda hard. Broke the center wing in half, and damaged all three wings, mostly at the interplane strut mounting points. Very minor fuse damage: the plastic cowl was pulverized and the landing gear cleaned off without damage to it or the fuse. The repairs used up almost a whole roll of true red monokote.
Big news is that she's converted to a Turnigy SK3 6374-192 brushless motor on 8S LiPos. 22x12 prop, which is much closer to scale than my old 17 incher. Faster and more thrust. Weighs about 2 lbs more, (16.5) but the better performance more than compensates.
I was at the scale show at the Pontiac Miniature Aircraft club, and on my third flight, the clunk came off the pick up tube. Didn't have near enough altitude for a dead stick, so she hit kinda hard. Broke the center wing in half, and damaged all three wings, mostly at the interplane strut mounting points. Very minor fuse damage: the plastic cowl was pulverized and the landing gear cleaned off without damage to it or the fuse. The repairs used up almost a whole roll of true red monokote.
Big news is that she's converted to a Turnigy SK3 6374-192 brushless motor on 8S LiPos. 22x12 prop, which is much closer to scale than my old 17 incher. Faster and more thrust. Weighs about 2 lbs more, (16.5) but the better performance more than compensates.
