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Pattern Biplane

Old 07-23-2017, 06:13 AM
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speedracerntrixie
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Default Pattern Biplane

Just out of curiosity, as biplanes are gaining in popularity I am wondering what the wing area increase is over a monoplane. Not only that but what the actual reduction in size is of each individual wing. I am hoping that someone can explain if there is a percentage reduction, if that is influenced by the spacing between the two wings. Maybe even guys who are flying current bipes could post some measurements of root/tip cords and wing area so I can make some comparisons. There seem to be some large variances here by just looking at pictures but all seem to fly well. I'm at this point just trying to see what they all may have in common. Thanks to all who will participate in my little curiosity.
Old 07-24-2017, 03:39 PM
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Data for
Arbalest Evolution monoplane - Span 1810 mm, root 485 mm, tip 210 mm Area 65.3 dm2 (1012 sq ins) based on convention of projecting wing area to fuse centreline. weight 4250 gms
Mangonel biplane - Span 1730 mm, root 365 mm, tip 162 mm. Total wing area 89.3 dm2 (1384 sq ins) weight 4800 gms
Biplane used the monoplane fuse mold with canopy and top wing cabane and access hatch in place of the monoplane canopy. Can't seem to post pics but will try again later.
Bill
Old 07-24-2017, 06:00 PM
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Arbalest Evolution and Mangonel pictures attached I hope!
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Old 07-24-2017, 07:36 PM
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Thank you for the information, very useful as it seems I need to add a little wing area to a design I am working on. Over the past year I have done at least a dozen sketches of ideas for a very modern pattern Biplane. So far that has been the easy part, now figuring out wing area, wing outline, airfoils, tail moment, thrust line, stab locations etc. while still maintaining the look I want is making things more complicated. Of course that is what makes it fun. Thanks again.
Old 07-24-2017, 08:48 PM
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The goal is to keep the same amount of drag as a wide body, but have more lift. Trading fuselage drag for wing drag.
Old 07-25-2017, 04:19 AM
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Makes perfect sense. I see designs going away from cabine struts, I assume for that reason on part. Then again this brings the wings closer together which as I understand slightly reduces the effect of more wing area.
Old 08-02-2017, 10:01 AM
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CW - What is the area of the canalyzer? Some feel they provide significant lift and should be counted in the wing area.
Old 08-02-2017, 03:21 PM
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Anthony I agree. This one is fairly small 5.9 dm2 ( 91 sq ins) projected to the fuse centre line
Bill
Old 08-02-2017, 04:29 PM
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The reason I started this thread is that I am contemplating a scratch build for next season. I am leaning towards a biplane with a composite fuselage and foam surfaces. The plan at this point is to start the plug construction this weekend. Some features I am considering is a one peice bottom wing and plug in wings for the top. The top wing and stabs will have adjusters and the bottom wing will be set to .5 degree. Battery access will be a hatch just in front of the top wing. Still refining the outline.
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Old 08-02-2017, 04:41 PM
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Originally Posted by speedracerntrixie View Post
Makes perfect sense. I see designs going away from cabine struts, I assume for that reason on part. Then again this brings the wings closer together which as I understand slightly reduces the effect of more wing area.
I haven't seen any evidence of this being the case? If anything, the absence of struts would make it easier to keep the wings apart. The amount of wing separation would mainly depend on fuselage depth and design.
Old 08-02-2017, 04:57 PM
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It sure doesn't seem to be an issue with Chip's Finals Touch. My target wing area at this point is 1,300 sq. in. There will be interplane wing struts as I think they will add to directional stability, add side area and I for some reason really want to mount the aileron servos in them. Not certain about that through as it would require dealing with linkages and servo connections for assembly/disassembly.
Old 08-02-2017, 05:14 PM
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Originally Posted by speedracerntrixie View Post
It sure doesn't seem to be an issue with Chip's Finals Touch. My target wing area at this point is 1,300 sq. in. There will be interplane wing struts as I think they will add to directional stability, add side area and I for some reason really want to mount the aileron servos in them. Not certain about that through as it would require dealing with linkages and servo connections for assembly/disassembly.
Chip copped a bit of flak over how close the wings are together when he first designed the Finals Touch. But it hasn't proved to be as disastrous as some said it would be.

My Xareltoo is 1380 sq. in and has no struts. Knife edge is amazing. Not sure how much help struts would be for creating lift, unless they are big. Then the weight issue comes into it. A deep fuse really helps here.

Interesting thoughts on putting servos in the struts. Assembly would be a PITA, but as long as the struts are solid, no reason why it wouldn't work OK.

I've drawn up a bipe design with the thoughts of 2 piece wings and no struts. Getting around to building it is another matter. I've never had anything to do with molds, so a bit daunting to go that way. Full built up, then has it's own issues with weight.

It will be interesting to follow your progress.
Old 08-03-2017, 12:17 AM
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Hello
Originally Posted by speedracerntrixie View Post
The reason I started this thread is that I am contemplating a scratch build for next season. I am leaning towards a biplane with a composite fuselage and foam surfaces. The plan at this point is to start the plug construction this weekend. Some features I am considering is a one peice bottom wing and plug in wings for the top. The top wing and stabs will have adjusters and the bottom wing will be set to .5 degree. Battery access will be a hatch just in front of the top wing. Still refining the outline.
May be plug in wing for bottom wing would be preferable.
You have not to return plane on a stand to fix bottom wing !
Claude
Old 08-03-2017, 03:34 AM
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Claude, I did consider that but did not want the added complexity of making two hatches. The canopy would have to be a separate peice that would rest halfway on the top wing. The additional weight associated with its mounting is not desired as well. I have seen some of your scratch builds with your Harmone design and has given me inspiration.

Shawn
Old 08-03-2017, 05:27 PM
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Hey Shawn,
The bipe looks good on paper. Are you planning on kitting it or at least building a few? Going the composite fuselage route is a pretty serious commitment and a lot of work. There have been a few other threads here showing scratch built composite fuselages pulled from a plug. It would be nice to do the design in CAD then through a hunk of wood on a CNC lathe and watch the chips fly.
I think your idea of putting the aileron servos in the interplane struts has merit. Biplane wings are typically so thin the aileron servos have to be mounted on the side. Will you be using 4 aileron servos? You might consider making the servo mounts part of the wing and have the interplane struts attach to the servo mount. Then you don't have to deal with linkage detachment every time you take the plane apart. Plus you could make the servo mount/interplane strut mount removable from the wing, too; so a three piece interplane strut. The strut would be the only part that was regularly removed for transportation.
Good luck! I am looking forward to following the build!
-Will
Old 08-03-2017, 06:11 PM
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Will, thanks for the encouragement, this is where I am now with servo mounts and struts. The outside of each wing will have fences that will insert into each wing panel and protrude through to the other side of the wing. The tab that protrudes will serve as both the servo mount and strut mount. From a front view the strut will have an hourglass shape to fully cover the servos. The plug has started, I just finished gluing some 1/8" balsa sheets together and will start cutting tomorrow.
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Old 08-03-2017, 10:29 PM
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Hello Shawn

Design is beautiful. Idea to put servo in strust is excellent
Few years ago, only one servo was use to activate the 2 ailerons as shown on CPLR's plane. That went well.
Claude
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Old 08-04-2017, 03:01 PM
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Claude, I have done the same in the past, it seemed to work well but I was much less experienced back then. I notice in the pictures that Christophe originally had the linkage wrong? I did go with 4 servos on my Reed Falcon biplane and am very happy with the results. It was quite easy to get the travels all equal and then after a few flights getting the differential correct as well.

Now onto more decisions. I am leaning towards a full flying stab using Pull Pull. Any thoughts here?
Old 08-04-2017, 04:30 PM
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Shawn, The Arbalest & Mangonel pics I posted above both have full flying stabs. In my view that is the way to go. Main benefits are easier to build, lighter, easier to set up and easier to trim than conventional stabs with elevators. I have gone away from pull- pull on rudder and stab to avoid trim variations from cable stretch and temperature changes. All feels pretty locked in. I have made an integrated stab/ rudder servo mount that uses pushrods for both stab and rudder. This makes the all flying stab is easy to remove with one set screw without disturbing the linkage set up. If you wish, feel free to PM me with your e mail address and I will send you some sketches/ pics. that will show you how it works.
Cheers Bill
Old 08-04-2017, 05:05 PM
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Originally Posted by CW View Post
Shawn, The Arbalest & Mangonel pics I posted above both have full flying stabs. In my view that is the way to go. Main benefits are easier to build, lighter, easier to set up and easier to trim than conventional stabs with elevators. I have gone away from pull- pull on rudder and stab to avoid trim variations from cable stretch and temperature changes. All feels pretty locked in. I have made an integrated stab/ rudder servo mount that uses pushrods for both stab and rudder. This makes the all flying stab is easy to remove with one set screw without disturbing the linkage set up. If you wish, feel free to PM me with your e mail address and I will send you some sketches/ pics. that will show you how it works.
Cheers Bill
Temperature changes won't affect trim with pull/pull as both cables will expand or contract the same amount. Pushrods will affect trim as the expansion or contraction is only on one side.
I use pull/pull on ruddet and elevator and never have to adjust trims regardless of the temperature. That's one of the benefits for pull/pull.
I haven't had any trim issues with cable stretch. As long as the cables are good quality and not too light for the job, they don't stretch too much. Even then I adjust each side the same amount as I've found they sttetch evenly anyway.
I use nylon coated stainless steel fishing trace.

I prefer pull/pull, but ultimately depends on weight distribution for CG.

Cheers
Scott
Old 08-04-2017, 06:35 PM
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Bill, thanks for the email. There is some good info there and I am going to borrow at least one thing there. In regards to Pull Pull, I have used Pull Pull on the elevator of 3 different airplanes one of them being a 1/3 scale Laser. I did not experience any trim issues with any of them. I do however use nylon coated Kevlar and go to great lengths to get the geometry correct. I suppose at the end of the day this will be influenced mainly by CG as I feel either method works well.

Construction of the plug has started. I am about halfway through fabricating the fuselage sides. The construction method is very old school. Think of the old Bridi or MK kits where there is a bunch of wood and lots of sanding to get the final shape. The main reason for going this direction is that I find building a box more of less is much easier to keep straight and I have lots of material to adjust the shape/radius of parts as I go. Since this is a plug obviously weight is not an issue.
Old 08-14-2017, 09:20 PM
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The plug construction is well under way. It should be ready to glass in a couple weeks. Still working out some details with the shape but I think it will just require some patience and fine tuning my sculpting skills. Soon I will have to cut some wing and stab cores. These will be the actual parts used for the flyable prototype. The idea is to have them mounted onto the plug so I can get everything measured out and exactly right prior to pulling a mold. Unless there are any reasons to do otherwise, I plan to set thrust to zero degrees down, 3 degrees right, top wing at zero, bottom wing at +.7 and stab at zero but being full flying makes it not really matter. May even make the airplane more difficult to trim. It's been a fun project so far .
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Old 08-15-2017, 05:53 PM
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What is the material (wood) you are using for the plug?

ken
Old 08-15-2017, 06:10 PM
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Ken, it is all balsa except for the turtle deck and fin leading edge. Those are wrapped in 1/32 ply. The canopy was laid up using my Symphony canopy as a male mold and lastly the cowl started out as a Vanquish part that will be hacked up and drastically changed but gave me a good starting point. The hatch will be carved out of pink foam. When I am happy with it,I will move onto the wings and tail. Prior to glassing and finishing the plug I will be able to do a complete mock up. Lots of work ahead but I am very excited about the project.
Old 08-16-2017, 11:10 AM
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Hi Shawn

I love your work.
Very important for flight qualities is the name.
So what is the name of this biplane ?
Claude

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