europapete Posted February 24, 2023 Share Posted February 24, 2023 (edited) Hi Gang, just been looking at Reini78's really nice model over on RFI. A thought popped up (HEY! Quiet at the back!) that on the vast majority of Swordfish models one see's, it looks like the lower wings have anhedral. I don't have many ref's for this. Should they have anhedral or be neutral? Btw, to my eyes the Hanriot fighter from WW1 always seems to have the same look also. Edited February 25, 2023 by europapete added text Link to comment Share on other sites More sharing options...
dogsbody Posted February 25, 2023 Share Posted February 25, 2023 I've got these two drawings. Doesn't look like there was very much hedral in either direction. Chris 3 2 Link to comment Share on other sites More sharing options...
LDSModeller Posted February 25, 2023 Share Posted February 25, 2023 4 hours ago, europapete said: it looks like the lower wings have anhedral. I don't have many ref's for this. Should they have anhedral or be neutral? If you check out this video, it has some excellent frontal shots showing the lower wings. Have to agree with Chris above, 0 Anhedral. Fairey Swordfish "why Pilots loved this Mistake of an aircraft" Regards Alan 1 1 Link to comment Share on other sites More sharing options...
Work In Progress Posted February 25, 2023 Share Posted February 25, 2023 (edited) Put a ruler across it. The visual impression of lower wing anhedral is seductive, but is an illusion brought about by multiple factors. The lower wing had slight dihedral, but the false impression of anhedral is given by: a) the lower wing dihedral being less than the upper wing dihedral, which is contrary to the more usual pattern, and therefore goes against cultural expectation so "looks weird". (On the Hanriot, the bottom wing is dead flat and the upper wing has dihedral. Again, put a ruler across it) b) the considerable tapering in thickness of the lower wing root sections, all of which is done on the underside, so that when the eye is drawn to the fuselage / wing root interface, a real focal point, the apparent anhedral there is what captures the attention. Look at the top surface though, and put a ruler across the lower wingtips, and you will see that the lower wing does have slight dihedral Edited February 25, 2023 by Work In Progress 4 1 Link to comment Share on other sites More sharing options...
gingerbob Posted February 25, 2023 Share Posted February 25, 2023 Although I haven't done a rigorous test, my impression has been that Tamiya's 48th kit tends to look that way. I don't know whether there's something about it that leads a builder to end up with a wrong angle; it seems too consistent or common to just be carelessness. I also don't think that it is an optical illusion, but I suppose it is possible. 1 Link to comment Share on other sites More sharing options...
tango98 Posted February 25, 2023 Share Posted February 25, 2023 Just had a look at the official rigging instructions for the Swordfish which gives the dihedral of the lower main wing as 1 degree +/- 15 minutes with the upper main wing dihedral at 3 degrees +/- 15 minutes. HTH Cheers Dave 4 3 Link to comment Share on other sites More sharing options...
Seawinder Posted February 26, 2023 Share Posted February 26, 2023 The diagrams show a slight gull-wing effect on the inner bottom wings. Could that add to the impression of anhedral? 1 Link to comment Share on other sites More sharing options...
Work In Progress Posted February 26, 2023 Share Posted February 26, 2023 That's what I said 1 Link to comment Share on other sites More sharing options...
europapete Posted February 27, 2023 Author Share Posted February 27, 2023 errr....I'm still trying to figure out how you land the one in Dogbody's top plan. Do you land parralell to the quayside with one wheel on the harbor wall and hope the tide is in? 2 Link to comment Share on other sites More sharing options...
Work In Progress Posted February 27, 2023 Share Posted February 27, 2023 You need to learn to limp 1 Link to comment Share on other sites More sharing options...
Seawinder Posted February 27, 2023 Share Posted February 27, 2023 17 hours ago, Work In Progress said: That's what I said Well, not exactly as I read your post. If you put a ruler across the tops of the inner wing segments (inboard of the inner struts), the tops of the wings do slant down slightly. Link to comment Share on other sites More sharing options...
Graham Boak Posted February 27, 2023 Share Posted February 27, 2023 If the dihedral is in the rigging instructions, but not in the drawing, then the drawing is wrong, however you put your ruler. I think that we can ignore variation in wing thickness over most of the span. The rigging is checked with dihedral boards placed on top of the wing. PS This is ignoring any changes between static and flying - because it is measured static. However in-flight loads will only increase the dihedral. PPS This is ignoring bunts or inverted flying. PPPS Real aircraft are complicated. 2 2 Link to comment Share on other sites More sharing options...
Ed Russell Posted February 27, 2023 Share Posted February 27, 2023 PPPPS - Many drawings are incorrect in some aspect or another PPPPPS - Unless a photograph is at exactly the right angle, what you are measuring is not quite right. Link to comment Share on other sites More sharing options...
wellsprop Posted February 28, 2023 Share Posted February 28, 2023 From a design/aerodynamics point of view it would make absolutely no sense to have anhedral on the lower wing (as this would counter the positive stability effect from the upper wing). Generally, biplanes have either; dihedral on both wings or, dihedral on one wing I would guess the Swordfish lower wing has either no dihedral, or 1 or 2 degrees of dihedral. It may be in the leading particulars of the pilots notes. 1 1 Link to comment Share on other sites More sharing options...
Ed Russell Posted February 28, 2023 Share Posted February 28, 2023 5 hours ago, wellsprop said: I would guess the Swordfish lower wing has either no dihedral, or 1 or 2 degrees of dihedral. No need to guess - the rigging instructions are quoted above. 2 Link to comment Share on other sites More sharing options...
Graham Boak Posted March 7, 2023 Share Posted March 7, 2023 On 2/27/2023 at 11:29 PM, Ed Russell said: PPPPS - Many drawings are incorrect in some aspect or another PPPPPS - Unless a photograph is at exactly the right angle, what you are measuring is not quite right. Even if at the right angle, you cannot accurately measure lengths and angles because of the parallax effect. For example, in a photo taken centrally head on, the wingtips are further away from the camera than the wingroots, and this will cause distortion. 1 Link to comment Share on other sites More sharing options...
Tailspin Turtle Posted March 7, 2023 Share Posted March 7, 2023 (edited) On 2/28/2023 at 3:16 PM, Ed Russell said: No need to guess - the rigging instructions are quoted above. Unfortunately, the rigging instructions quoted don't include how the dihedral is measured, although my guess is that it's the upper surface of the wing, probably along a spar. Aerodynamicists prefer it to be defined with respect to the chord line, which is somewhere in between the upper and lower surface of the wing: that's what it generally is when given in specifications. For those who might want to know more about that (you need to scroll down to the A4D dihedral example) or see some deceptive appearance of non-existent dihedral/anhedral in photos and drawings, see https://tailspintopics.blogspot.com/2014/03/anhedraldihedral-and-wing-sweep.html Edited March 7, 2023 by Tailspin Turtle 2 1 Link to comment Share on other sites More sharing options...
Tailspin Turtle Posted March 7, 2023 Share Posted March 7, 2023 Here's an interesting video of setting dihedral on a Piper Super Cub, with one method being to measure the dihedral with respect to the lower surface of the wing: https://youtu.be/uUayKl7dhug 1 Link to comment Share on other sites More sharing options...
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