AVRO Mk IV Triplane Project
12-11-2003, 06:46 AM
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RE: First Weight Calculation
You are correct. The real one did indeed have torsional problems that made turns difficult. This was also evident in the replicas made in the early 60's and the 1/2 scale R/C model made in 1992. In all cases, the issue was greatly reduced if not solved by lacing the open structure with fabric from the end of the solid fuselage back to the horizontal stab. (If you see the movie "Those Magnificent Men...", the flying scenes have the fabric.) I intend to do the same along with some additional rigging.
I picked up one of those plastic models recently but haven't built it yet. I also have a 1/12 scale model from a RN kit that I built 25 years ago for reference.
IN ADDITIONAL NEWS...
It looks like an AXI 2820 electric will do the trick. I may even be able to reduce the cells from 12 to 10! But if I don't go electric, I have found a way to get an 9 oz fuel tank into the fuselage. It will have to be a custom triangular tank but it will fit.
I picked up one of those plastic models recently but haven't built it yet. I also have a 1/12 scale model from a RN kit that I built 25 years ago for reference.
IN ADDITIONAL NEWS...
It looks like an AXI 2820 electric will do the trick. I may even be able to reduce the cells from 12 to 10! But if I don't go electric, I have found a way to get an 9 oz fuel tank into the fuselage. It will have to be a custom triangular tank but it will fit.
12-11-2003, 08:41 PM
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Uh Oh. Weight Problem!
It's not even built yet and I may have a weight problem!
The bare bones plane will weigh in at 4.00 lbs.
The plane with four Proctor 4" wheels adds a pound, making it 5.03 lbs!
Adding the radio adds just 8 or so ounces, bringing it to 5.64 lbs.
If I go with four stroke glow power, it would top out at 6.32 lbs.
Electric with 12 cells and an AXI2820 comes in at 7.50 lbs.
The wheels are certainly a problem. Since four are necessary, every savings (or increase) is magnified by 4 times! The Proctor wheels are very attractive but pricey. I'm not looking forward to spending $216 for just the wheels! I hope there is an alternative.
The electric option is a 1-1/4 lbs heavier than the glow option. If anyone can see where I have made a mistake, please let me know.
Your comments are always welcome.
The bare bones plane will weigh in at 4.00 lbs.
The plane with four Proctor 4" wheels adds a pound, making it 5.03 lbs!
Adding the radio adds just 8 or so ounces, bringing it to 5.64 lbs.
If I go with four stroke glow power, it would top out at 6.32 lbs.
Electric with 12 cells and an AXI2820 comes in at 7.50 lbs.
The wheels are certainly a problem. Since four are necessary, every savings (or increase) is magnified by 4 times! The Proctor wheels are very attractive but pricey. I'm not looking forward to spending $216 for just the wheels! I hope there is an alternative.
The electric option is a 1-1/4 lbs heavier than the glow option. If anyone can see where I have made a mistake, please let me know.
Your comments are always welcome.
12-13-2003, 05:22 PM
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RE: Uh Oh. Weight Problem!
You want comments, here they are.
I have a 1/6th scale VK Fokker Dr.I electric powered.
It has an all up flying weight of 100 oz with 14 SCR cells (2 oz each).
It has two HS 81s, one for elevator and one for rudder. It has two HS 85s, one on each aileron (overkill but what I had on hand). The radio system weighs about 9 oz (600 mAh Rx pack, 1 oz Rx and assorted wires, switch, etc.
Subtract the weight of the speed control and motor and the airframe (covered and painted), two 4.5†Williams’s wheels, bass covered wire landing gear, and pilot bust (Williams) weighs about 3.5 lbs.
I don’t know your wing area, but the Fokker is around 800 sq in (200 scale feet converted).
In my opinion you need to revisit your materials and construction methods. The Dr.I is very strong but light. Its construction is as follows.
The wings are mostly 1/16 balsa ribs with 3/16 sq spars. There is a LITTLE 1/16 A/C ply where the cabanes attach and some 1/16 sheeting on the leading edges. The fuselage is 3/16 sq bass (substitute spruce for same weight) with a very small amount of 1/64 ply gusseting and doubler from the firewall to the wings. There is a little 1/16 balsa sheeting here and there. These are the kind of wood selection that will give good weights.
I don’t know your design but as per my earlier suggestions here is my run down.
Longerons should be 1/8 sq spruce. If you have to have ply in the nose limit it to strengthening critical areas and carrying flight and landing loads and make it 1/64 or 1/32 at most. If the original had a ply covered forward fuselage then 1/16 balsa stained should be used. If you must have ply then use 1/64. As to the rear fuselage get some spyder wire (fishing supply stores) and string it between joints and CA it in place. If you use 1/64 ply gussets (triangles) at each joint then drill holes and string up the line as per the original and CA where it passes through the gussets. The pilot can be carved from foam and given GI Joe clothes (check eBay, maybe something there!).
The ribs should be 1/16 except where they connect to the cabanes or other structural sections where the balsa should be doubled with 1/32 ply or replaced with 1/16 ply. Make the spars from 1/8 or 3/16 sq spruce. Covering should be something like Oracover light or one of the new light coverings from (I think) Coverite. Choose an antique or beige color (unless the AVRO was something else).
Before getting off materials think light. Use contest balsa for everything and assume a weight of 8 lbs/cu ft. Spruce and basswood is 24 lbs/cu ft. I don’t have the numbers on ply in front of me but do have them somewhere. As an aside 1/64 ply is 2/3 the weight of 1/32, not half! You list brass hinges, fittings, etc. What for? Use 1/2A nylon hinges, or CA hinges. Anywhere the full size had a fitting try aluminum litho plate (.008) or a little thin plastic (.020) sheet.
As for radio gear use HS 81s for rudder and elevator. For the wing warping an HS 225 should be the most you will need. If you go for ailerons then HS-55s will do fine. You are talking minimal flight loads here. Top speed should be under 50 mph. A micro RX (HiTec 555 or similar) is well under 1 oz and a 270 mAh RX pack will do fine (or use a similar weight NiMH one) and weigh about 2 oz. If you go for electric a simple light weight motor mount can be made by extending the fuselage sides similar to the original.
There have been a lot of articles on building your own wire wheels. Most are aimed at park fliers but construction should be similar for your plane. In fact park fliers and sailplanes should be your inspiration here, not typical glow plane construction. You have to build to fly not build to crash.
One more thing for construction materials, for wing tips, tail outlines, etc. a laminated outline of 1/32 basswood or better still cane (rattan rounds) is ideal. I picked up lots from a rattan furniture manufacturer nearby for well under $20 in three different diameters. Just soak in bleach(?) solution and hold to a form until dry.
Stephen
I have a 1/6th scale VK Fokker Dr.I electric powered.
It has an all up flying weight of 100 oz with 14 SCR cells (2 oz each).
It has two HS 81s, one for elevator and one for rudder. It has two HS 85s, one on each aileron (overkill but what I had on hand). The radio system weighs about 9 oz (600 mAh Rx pack, 1 oz Rx and assorted wires, switch, etc.
Subtract the weight of the speed control and motor and the airframe (covered and painted), two 4.5†Williams’s wheels, bass covered wire landing gear, and pilot bust (Williams) weighs about 3.5 lbs.
I don’t know your wing area, but the Fokker is around 800 sq in (200 scale feet converted).
In my opinion you need to revisit your materials and construction methods. The Dr.I is very strong but light. Its construction is as follows.
The wings are mostly 1/16 balsa ribs with 3/16 sq spars. There is a LITTLE 1/16 A/C ply where the cabanes attach and some 1/16 sheeting on the leading edges. The fuselage is 3/16 sq bass (substitute spruce for same weight) with a very small amount of 1/64 ply gusseting and doubler from the firewall to the wings. There is a little 1/16 balsa sheeting here and there. These are the kind of wood selection that will give good weights.
I don’t know your design but as per my earlier suggestions here is my run down.
Longerons should be 1/8 sq spruce. If you have to have ply in the nose limit it to strengthening critical areas and carrying flight and landing loads and make it 1/64 or 1/32 at most. If the original had a ply covered forward fuselage then 1/16 balsa stained should be used. If you must have ply then use 1/64. As to the rear fuselage get some spyder wire (fishing supply stores) and string it between joints and CA it in place. If you use 1/64 ply gussets (triangles) at each joint then drill holes and string up the line as per the original and CA where it passes through the gussets. The pilot can be carved from foam and given GI Joe clothes (check eBay, maybe something there!).
The ribs should be 1/16 except where they connect to the cabanes or other structural sections where the balsa should be doubled with 1/32 ply or replaced with 1/16 ply. Make the spars from 1/8 or 3/16 sq spruce. Covering should be something like Oracover light or one of the new light coverings from (I think) Coverite. Choose an antique or beige color (unless the AVRO was something else).
Before getting off materials think light. Use contest balsa for everything and assume a weight of 8 lbs/cu ft. Spruce and basswood is 24 lbs/cu ft. I don’t have the numbers on ply in front of me but do have them somewhere. As an aside 1/64 ply is 2/3 the weight of 1/32, not half! You list brass hinges, fittings, etc. What for? Use 1/2A nylon hinges, or CA hinges. Anywhere the full size had a fitting try aluminum litho plate (.008) or a little thin plastic (.020) sheet.
As for radio gear use HS 81s for rudder and elevator. For the wing warping an HS 225 should be the most you will need. If you go for ailerons then HS-55s will do fine. You are talking minimal flight loads here. Top speed should be under 50 mph. A micro RX (HiTec 555 or similar) is well under 1 oz and a 270 mAh RX pack will do fine (or use a similar weight NiMH one) and weigh about 2 oz. If you go for electric a simple light weight motor mount can be made by extending the fuselage sides similar to the original.
There have been a lot of articles on building your own wire wheels. Most are aimed at park fliers but construction should be similar for your plane. In fact park fliers and sailplanes should be your inspiration here, not typical glow plane construction. You have to build to fly not build to crash.
One more thing for construction materials, for wing tips, tail outlines, etc. a laminated outline of 1/32 basswood or better still cane (rattan rounds) is ideal. I picked up lots from a rattan furniture manufacturer nearby for well under $20 in three different diameters. Just soak in bleach(?) solution and hold to a form until dry.
Stephen
12-14-2003, 12:38 AM
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RE: Uh Oh. Weight Problem!
What a great reply. There is a lot there and I will study it more thoroughly but I can reply to some of it.
First, I found a bug in SolidWorks. It incorrectly processed the arrayed parts in the parts list. The parts list (and therefore the weight calculations) had 650 ribs instead of the proper 90!!! After fixing that, I changed some minor parts from thicker spruce sticks to thinner rod stock. It's actually more like the real thing and surprisingly, it did save some weight.
I chose birch plywood sheeting for the fuselage for one main reason. There is so little interior room for radio stuff and other non-period items that I didn't want it taken up with support members that would be necessary for structural integrity to be then sheeted with balsa. I am assuming that the ply fuselage need far less underlying structure and would be the roughly the same weight than a beefier internal structure with balsa sheeting.
I went with 1/4" longerons. Because of the triangular fuselage, the full scale had torsional twist problems. The thicker material should help lessen this and it doesn't represent much weight but I'll check it out.
Just the wood and wire bits calculate in a 3.5 lbs (no wheels and uncovered)
The wheels are definitely an issue because four are required. The ones that I've found will add from about 1/4 to 1/2 lb total for the four. Not much that I can do about that.
The final electric powered plane will weigh in at 6.7 lbs (uncovered). About 1-1/2 of that is for the 12 battery cells. If I can get away with ten, then I'll save over a quarter of a pound. A gas powered version would weight 5-1/2 lbs.
I'll look into the servos that you recommended. They may save me some weight. I may also be able to use one servo for the ailerons instead of two.
Thanks again.
First, I found a bug in SolidWorks. It incorrectly processed the arrayed parts in the parts list. The parts list (and therefore the weight calculations) had 650 ribs instead of the proper 90!!! After fixing that, I changed some minor parts from thicker spruce sticks to thinner rod stock. It's actually more like the real thing and surprisingly, it did save some weight.
I chose birch plywood sheeting for the fuselage for one main reason. There is so little interior room for radio stuff and other non-period items that I didn't want it taken up with support members that would be necessary for structural integrity to be then sheeted with balsa. I am assuming that the ply fuselage need far less underlying structure and would be the roughly the same weight than a beefier internal structure with balsa sheeting.
I went with 1/4" longerons. Because of the triangular fuselage, the full scale had torsional twist problems. The thicker material should help lessen this and it doesn't represent much weight but I'll check it out.
Just the wood and wire bits calculate in a 3.5 lbs (no wheels and uncovered)
The wheels are definitely an issue because four are required. The ones that I've found will add from about 1/4 to 1/2 lb total for the four. Not much that I can do about that.
The final electric powered plane will weigh in at 6.7 lbs (uncovered). About 1-1/2 of that is for the 12 battery cells. If I can get away with ten, then I'll save over a quarter of a pound. A gas powered version would weight 5-1/2 lbs.
I'll look into the servos that you recommended. They may save me some weight. I may also be able to use one servo for the ailerons instead of two.
Thanks again.
12-14-2003, 10:39 AM
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RE: Uh Oh. Weight Problem!
>After fixing that, I changed some minor parts from thicker spruce sticks to thinner rod stock.
Are you changing from square spruce to dowel? I think the spruce will give better strength, especially if the wood is chosen well.
>I chose birch plywood sheeting for the fuselage for one main reason. There is so little interior room for radio stuff and other non-period items that I didn't want it taken up with support members that would be necessary for structural integrity to be then sheeted with balsa. I am assuming that the ply fuselage need far less underlying structure and would be the roughly the same weight than a beefier internal structure with balsa sheeting.
Balsa IS a structual material. Did you know it is classified as a hardwood because of its strength? Again we are building to fly not strain the plane through the trees. You have not answered as to ply thickness. If you use the longerons as motor mounts you do not need a firewall so all your formers can be hollow (just use the uprights). You can use 1/16 ply cross members (across the top longerons) to attach all the radio gear to. The battery pack can use a similar arrangement with 1/8 ply. What you want is to firmly anchor the pack so it cannot move during 'normal' flight. Very little structure is required to restrian a pack of this size but it must be rigid within the space provided.
>I went with 1/4" longerons. Because of the triangular fuselage, the full scale had torsional twist problems. The thicker material should help lessen this and it doesn't represent much weight but I'll check it out.
Increasing the size of the longerons, or the formers, does little to increase the torsional strength. What does is the 'structure' on the outside of the fuselage which connects the longers. Think shell. In the front the sheeting provides this strength. In the back you need something else. That is why I strongly suggest bracing wires. You could use covering (as per the movie). One option is clear covering. If you go with glow it would make it easier to clean. If you gusset each joint in the rear with triangles of 1/64 ply the rigidity goes way up. Add the flying wires and you get another major increase for very little weight, but some work.
As an example of this this is the main reason for a 'D' tube wing leading edges on built up wings. With this plane you will probably not go that route and you will have to have either use a much more massive spar system or the flying wires between the wings will have to be functional and carry a lot of the load. This is not hard to do but can increase set up time at the field. I have a few ideas on this as well.
You have to remember how you will be flying this plane. If you get over a 30 degree bank from level it is probably because some disaster is happening. This is not going to be doing knife edge flight and may never see even a loop or roll! The originals barely managed turns and take offs and landings are DIRECTLY into the wind (trust me on that one). You will be nursing this thing around the sky, not 'beating the air into submission'! The originals suffered from torsional issues because the scale wood size would probably equate to 1/16 sq longerons and somebody's life is on the line each time they went up.
>The wheels are definitely an issue because four are required. The ones that I've found will add from about 1/4 to 1/2 lb total for the four. Not much that I can do about that.
I noticed your other thread on the wheels and the suggested ones look great! At this size 4 to 8 oz is not bad at all. I have a pair of Williams 6.5" dia golden age for a 1/5th scale between the wars fighter I hope to build in the next few years and they weigh 20 oz for the pair. Typical WWI langing gear (before wheels) in this size is expected to add about a pound to the plane. There are ways to build lighter but you must allow for reduced strength or increased build complexity.
>The final electric powered plane will weigh in at 6.7 lbs (uncovered). About 1-1/2 of that is for the 12 battery cells. If I can get away with ten, then I'll save over a quarter of a pound. A gas powered version would weight 5-1/2 lbs.
The reduced structural requirements for vibration free electric flight can usually offset half the weight differences. Further approaching the plane on the basis of getting 'scale' flight characteristics allows reducing the weight further. Remember, we can use very large slow turning props to give great thrust but limited top speeds, an ideal solution in these applications. The cells I recomended are what I know. The recent increases in lithium technology can totally eliminate the weight and duration penalties.
>I'll look into the servos that you recommended. They may save me some weight. I may also be able to use one servo for the ailerons instead of two.
I think the two servo approach makes more sense than the added complexity of connecting two ailerson on a plane like this. Is is possible to get a drawing of what you are doing? I use AutoCad 2000, but am only 2D competent. Even a scan of a print out would be great. Please be kind though as I have dial up. You can email me direct at [email protected]
Stephen
Are you changing from square spruce to dowel? I think the spruce will give better strength, especially if the wood is chosen well.
>I chose birch plywood sheeting for the fuselage for one main reason. There is so little interior room for radio stuff and other non-period items that I didn't want it taken up with support members that would be necessary for structural integrity to be then sheeted with balsa. I am assuming that the ply fuselage need far less underlying structure and would be the roughly the same weight than a beefier internal structure with balsa sheeting.
Balsa IS a structual material. Did you know it is classified as a hardwood because of its strength? Again we are building to fly not strain the plane through the trees. You have not answered as to ply thickness. If you use the longerons as motor mounts you do not need a firewall so all your formers can be hollow (just use the uprights). You can use 1/16 ply cross members (across the top longerons) to attach all the radio gear to. The battery pack can use a similar arrangement with 1/8 ply. What you want is to firmly anchor the pack so it cannot move during 'normal' flight. Very little structure is required to restrian a pack of this size but it must be rigid within the space provided.
>I went with 1/4" longerons. Because of the triangular fuselage, the full scale had torsional twist problems. The thicker material should help lessen this and it doesn't represent much weight but I'll check it out.
Increasing the size of the longerons, or the formers, does little to increase the torsional strength. What does is the 'structure' on the outside of the fuselage which connects the longers. Think shell. In the front the sheeting provides this strength. In the back you need something else. That is why I strongly suggest bracing wires. You could use covering (as per the movie). One option is clear covering. If you go with glow it would make it easier to clean. If you gusset each joint in the rear with triangles of 1/64 ply the rigidity goes way up. Add the flying wires and you get another major increase for very little weight, but some work.
As an example of this this is the main reason for a 'D' tube wing leading edges on built up wings. With this plane you will probably not go that route and you will have to have either use a much more massive spar system or the flying wires between the wings will have to be functional and carry a lot of the load. This is not hard to do but can increase set up time at the field. I have a few ideas on this as well.
You have to remember how you will be flying this plane. If you get over a 30 degree bank from level it is probably because some disaster is happening. This is not going to be doing knife edge flight and may never see even a loop or roll! The originals barely managed turns and take offs and landings are DIRECTLY into the wind (trust me on that one). You will be nursing this thing around the sky, not 'beating the air into submission'! The originals suffered from torsional issues because the scale wood size would probably equate to 1/16 sq longerons and somebody's life is on the line each time they went up.
>The wheels are definitely an issue because four are required. The ones that I've found will add from about 1/4 to 1/2 lb total for the four. Not much that I can do about that.
I noticed your other thread on the wheels and the suggested ones look great! At this size 4 to 8 oz is not bad at all. I have a pair of Williams 6.5" dia golden age for a 1/5th scale between the wars fighter I hope to build in the next few years and they weigh 20 oz for the pair. Typical WWI langing gear (before wheels) in this size is expected to add about a pound to the plane. There are ways to build lighter but you must allow for reduced strength or increased build complexity.
>The final electric powered plane will weigh in at 6.7 lbs (uncovered). About 1-1/2 of that is for the 12 battery cells. If I can get away with ten, then I'll save over a quarter of a pound. A gas powered version would weight 5-1/2 lbs.
The reduced structural requirements for vibration free electric flight can usually offset half the weight differences. Further approaching the plane on the basis of getting 'scale' flight characteristics allows reducing the weight further. Remember, we can use very large slow turning props to give great thrust but limited top speeds, an ideal solution in these applications. The cells I recomended are what I know. The recent increases in lithium technology can totally eliminate the weight and duration penalties.
>I'll look into the servos that you recommended. They may save me some weight. I may also be able to use one servo for the ailerons instead of two.
I think the two servo approach makes more sense than the added complexity of connecting two ailerson on a plane like this. Is is possible to get a drawing of what you are doing? I use AutoCad 2000, but am only 2D competent. Even a scan of a print out would be great. Please be kind though as I have dial up. You can email me direct at [email protected]
Stephen
12-14-2003, 07:27 PM
#31
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RE: Uh Oh. Weight Problem!
The R/N kit I have used wood for all the members of the undercarriage and that is what I started with in the design. Looking closer at the one made for the movie, there are several metal braces in addition to the wood skids and other wood members. I just moved to metal braces where appropriate and made them thinner. (I think the wood versions were too thick anyway.)
Your point is well taken regarding the merits of balsa but I think ply is the best choice for the fuselage skin. There are a number of items that need to be attached to the fuselage side and ply would be the better material. I have designed it with 1/8 thick ply but 3/32 can do the trick just as well.
I do intend to use internal wire bracing for the open portion of the fuselage just like the full scale. I will either gusset the areas where the members meet or if I can manage it, I'll fabricate brass brackets. Since the original and the movie version still exhibited torsional problems, I'll lace fabric over the structure. As you say, no loops or rolls are in the offing. I just need it to make a turn when necessary.
I don't mind being realistically powered given the weight. This plane will probably just do a few circuits around the field (hopefully to the ooo's and ahhh's of the onlookers) and that's about it. I just want to make sure that the damned thing will get off the ground and back down again. Wind? What wind?
I never intended to connect one servo directly to the ailerons but I do think I can now use one servo to move one control arm that connect to each aileron. That saves some room and some weight.
I can provide lots of stuff for you to get a real good feeling for the design, including AutoCAD compatible drawings. Let me get through this next series of changes (moving to HiTec servo etc.) and I'll put up a link where you can download it at your convenience.
Salute!
Your point is well taken regarding the merits of balsa but I think ply is the best choice for the fuselage skin. There are a number of items that need to be attached to the fuselage side and ply would be the better material. I have designed it with 1/8 thick ply but 3/32 can do the trick just as well.
I do intend to use internal wire bracing for the open portion of the fuselage just like the full scale. I will either gusset the areas where the members meet or if I can manage it, I'll fabricate brass brackets. Since the original and the movie version still exhibited torsional problems, I'll lace fabric over the structure. As you say, no loops or rolls are in the offing. I just need it to make a turn when necessary.
I don't mind being realistically powered given the weight. This plane will probably just do a few circuits around the field (hopefully to the ooo's and ahhh's of the onlookers) and that's about it. I just want to make sure that the damned thing will get off the ground and back down again. Wind? What wind?
I never intended to connect one servo directly to the ailerons but I do think I can now use one servo to move one control arm that connect to each aileron. That saves some room and some weight.
I can provide lots of stuff for you to get a real good feeling for the design, including AutoCAD compatible drawings. Let me get through this next series of changes (moving to HiTec servo etc.) and I'll put up a link where you can download it at your convenience.
Salute!
02-07-2004, 09:20 AM
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Update Feb 6, 2004
Well a lot has taken place since my last update. The plane is now 1/4 scale. Calculated weight without the electric power system is 8.3 lbs. Pretty good for a 94 in wingspan triplane. Up to another pound maybe saved with a change to the wheels. CG looks very good and should require very little additional weight if any. It is also now a wing warper and much more to scale thanks to the donation of some very detailed pictures of the Shuttleworth version.
But there is a problem that I would like some help with. I have decided that it would just be too cumbersome to break the plane down by separating the fuselage and the wings. Too much rigging and control lingage would have to be undone and redone. That is just asking for mistakes and trouble. So I think it is far better to break the fuselage in two pieces. No servo linkages would have to be touched. A minimal amount of rigging would be affected and just the rudder and elevator cables would have to disconnected.
To do this, I designed two almost identical bulkheads at the split point. The forward one stays with the forward section and the rear one stays with the rear section. The rear bulkhead gives something for the rear fuselage members to attach to and stay aligned. When joined, the rear bulkhead tucks in under the top and sides. A 1/4-20 bolt holds the lower portion of the bulkheads together. Four #4 screws through the rear fuselage members into blind nuts in the front fuselage members hold the upper portions together.
The problem is the amount of wood available in the forward fuselage members for the #4 screws to attach to. Since the fuselage is triangular, the wood tapers in. It looks like there isn't enough room for the blind nuts. If I make the upper fuselage members larger, that encroaches on the cockpit cutout and takes things further from scale. I am uneasy about taping the wood directly as an alternative.
Any suggestions to this concept or an entirely different approach would be appreciated.
But there is a problem that I would like some help with. I have decided that it would just be too cumbersome to break the plane down by separating the fuselage and the wings. Too much rigging and control lingage would have to be undone and redone. That is just asking for mistakes and trouble. So I think it is far better to break the fuselage in two pieces. No servo linkages would have to be touched. A minimal amount of rigging would be affected and just the rudder and elevator cables would have to disconnected.
To do this, I designed two almost identical bulkheads at the split point. The forward one stays with the forward section and the rear one stays with the rear section. The rear bulkhead gives something for the rear fuselage members to attach to and stay aligned. When joined, the rear bulkhead tucks in under the top and sides. A 1/4-20 bolt holds the lower portion of the bulkheads together. Four #4 screws through the rear fuselage members into blind nuts in the front fuselage members hold the upper portions together.
The problem is the amount of wood available in the forward fuselage members for the #4 screws to attach to. Since the fuselage is triangular, the wood tapers in. It looks like there isn't enough room for the blind nuts. If I make the upper fuselage members larger, that encroaches on the cockpit cutout and takes things further from scale. I am uneasy about taping the wood directly as an alternative.
Any suggestions to this concept or an entirely different approach would be appreciated.
02-07-2004, 02:55 PM
#33
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RE: Uh Oh. Weight Problem!
hi there new member here, big fan of pioneer aircraft thought you would like these pics taken at Old Warden,s twilight air display Sept 2002
chris
chris
02-07-2004, 03:13 PM
#34
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RE: Uh Oh. Weight Problem!
hi again i missed one, first one was Avro on solo pass, second was Avro in formation with another of the Magnificent men aircraft the Bristol Boxkite, third on this page is the Blackburn monoplane, the Old Warden site has a model aircraft club that flys from the same strip on non flying days, i have the privelige of being a member and enjoy flying my models and being able to see the full size in museum also, this year we have a unique oportunity to share some special days, the museum has evening displays of there aircraft and during the day before the main display we are to display some of our models for the public, cant wait.
02-08-2004, 02:39 PM
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RE: Uh Oh. Weight Problem!
OOPS! I know Iknow Ian the last one is a Depardusin (cant spell either) sincerimost apologisings!!!!! im no very good with these computery things seem to have deleted some of my pic files hmmmm!!
06-05-2009, 08:07 AM
#37
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RE: First Weight Calculation
WOW, is this thread old! And a lot has transpired since Istarted it literally years ago. The Triplane was put on hold while Igot involved in the Hudson Flier project. Now that the the full scale and my R/C model are under construction, Ihave turned my designing attentions back to the AVRO.
The HF project was a great learning experience and the AVROwill benefit from it. I have gone over the entire design of my full scale model which Idid from pictures and measurements that I took personally from the plane at Old Warden in the UK. I am creating a new version of the 1/4 scale model and it is coming along quite well. Lots of bracing and brackets to do but the main bits are all there.
I am striving for scale accuracy all the way. No flat bottomed wing when the original was undercambered. No ailerons when the original was a wing warper. This is the real deal. On the other hand, I want it to be buildable with reasonable building skills. (Why make it hard on myself!
) So far, so good. So much so that Iam considering making this into a kit. (Yeah, Iknow I'm nuts.) A lot has to happen before Iget that far but Iam considering it.
Stay tuned...
The HF project was a great learning experience and the AVROwill benefit from it. I have gone over the entire design of my full scale model which Idid from pictures and measurements that I took personally from the plane at Old Warden in the UK. I am creating a new version of the 1/4 scale model and it is coming along quite well. Lots of bracing and brackets to do but the main bits are all there.
I am striving for scale accuracy all the way. No flat bottomed wing when the original was undercambered. No ailerons when the original was a wing warper. This is the real deal. On the other hand, I want it to be buildable with reasonable building skills. (Why make it hard on myself!
) So far, so good. So much so that Iam considering making this into a kit. (Yeah, Iknow I'm nuts.) A lot has to happen before Iget that far but Iam considering it.Stay tuned...
06-05-2009, 04:01 PM
#39
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RE: First Weight Calculation
Thanks LD. Are you sure you have the right plane in mind. The triplane in the Shuttleworth is most definitely a wing warper. It got goose bumps turning that wheel myself and seeing them move.
06-05-2009, 04:15 PM
#40
RE: First Weight Calculation
Oh heck, you're right. I was thinking of the Bristol Boxkite. Sorry.
Saw them in person in Sept. 2007. Unfortunately, it was too windy and they never made it out of the hangar. would have loved to see the Edwardians fly, love that era ofaviation.I have a hankering to do a 1/4 scale Blackburn Monoplane D myself.
Saw them in person in Sept. 2007. Unfortunately, it was too windy and they never made it out of the hangar. would have loved to see the Edwardians fly, love that era ofaviation.I have a hankering to do a 1/4 scale Blackburn Monoplane D myself.
09-24-2010, 09:18 PM
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RE: AVRO Mk IV Triplane Project
Well once again this project has been restarted. The Hudson Flier project has finished and what a learning experience that was! On to the triplane now. This isn't a build thread yet but more like a design thread at this point. Because of the HF project, I have made some decisions that apply here. One is that because of the great performance of the anti-vibration mount on a plane more delicate that this one, I have decided not to make it electric. For now a Saito 72 sits in the nose but that may change when the weight calc finally come in. I can see this being a good candidate for one of the new small gassers too.
Anyway, to whet your appetites, here are some of the CAD images. If nothing else, the manual should look pretty good
Anyway, to whet your appetites, here are some of the CAD images. If nothing else, the manual should look pretty good
09-24-2010, 09:43 PM
#42
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RE: AVRO Mk IV Triplane Project
Hi Chevelle- I know the wing warp cables wrap around pulleys from the wheel and the same cables enter then exit the pivot tube that the elevator bellcranks are attached. When I built my Boxkite I let the servo operate the ailerons (and elevator) remotely and had cables to the control stick 'slave' off the ailerons. You could do something like that if you haven't thought of it already and feel it a worthy idea! The wings don't need much warp to be effective. My Bleriot only moves 1/2" each way and it is plenty.
09-24-2010, 10:13 PM
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RE: AVRO Mk IV Triplane Project
We are of like mind. Take a look at the illustration. The warping/aileron cabling is in green, the elevator in red.
The warping cables wrap around a servo mounted double pulley. This keeps the lengths the same no matter what angle of the servo. The cables go to pulleys (not shown) back near the controls. They go up into guide tubes that route the cables out through the control shaft just like the original. The control shaft is actually two pieces, one sleeved over the other. The outer sleeve doesn't move but holds the bent cable guides. The inner tube rotates within the sleeve and around the cable guide. (There is a gap in the inner tube to allow it to move around the cable guide.) That rotation controls the elevator movement.
This is the approach so far in CAD anyway. When Iget there, I will mock this up to see if it works. Let me know if you have any thoughts.
The warping cables wrap around a servo mounted double pulley. This keeps the lengths the same no matter what angle of the servo. The cables go to pulleys (not shown) back near the controls. They go up into guide tubes that route the cables out through the control shaft just like the original. The control shaft is actually two pieces, one sleeved over the other. The outer sleeve doesn't move but holds the bent cable guides. The inner tube rotates within the sleeve and around the cable guide. (There is a gap in the inner tube to allow it to move around the cable guide.) That rotation controls the elevator movement.
This is the approach so far in CAD anyway. When Iget there, I will mock this up to see if it works. Let me know if you have any thoughts.
09-25-2010, 08:24 AM
#44
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RE: AVRO Mk IV Triplane Project
Hi Chevelle- How about letting the warp servo hide in the scale fuel tank under upper wing? The servo wires could then be hidden inside a tube to replicate the fuel line. It would simplify the 'closed loop' for warping the wings and make it easier to 'slave' the yoke and make the control wheel turn.
09-25-2010, 08:53 AM
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RE: AVRO Mk IV Triplane Project
Hmmm. Isuppose that would work. The servo does seem to fit. Issues to be worked out though. It would probably be best that the servo actually mount to a piece of ply in the upper wing and just engage a hole in the tank. That would be the best for rigidity. More would show with this approach. That wing is awful thin. I have to carefully consider running stuff through those ribs. Something to consider though.
