John R Posted September 27, 2020 Share Posted September 27, 2020 Whilst building the Pro Resin 707A I thought that the airflow splitter on the intake looked a little thick so I looked up a picture I had taken of the 707C to see what the real thing looked like and discovered that the intake/fuselage junction on the model was completely wrong (surprise!). However the photo of the 707C revealed something interesting. Behind the splitter plate it appears as if there might be a recess (it could be just the shadow) for another form of intake. Might it be an offtake for the boundary layer? Does anyone have any ideas, knowledge or pictures of that area? I belive that it is the same for the 707A and C. I have looked at the pictures of the a/c in the Manchester Museum and they are maddeningly inconclusive. The drawing in Barrie Hygate's book was no help and I suspect may be in error in that region. John Link to comment Share on other sites More sharing options...
zebra Posted September 27, 2020 Share Posted September 27, 2020 I think it looks like a boundary layer offtake. Here's my photo from MOSI: If you click on the photo it should take you to Flickr where you can zoom in for a closer look. hope this helps Julian 1 Link to comment Share on other sites More sharing options...
John R Posted September 27, 2020 Author Share Posted September 27, 2020 A really nice picture but the point of the splitter plate obscured the bit I wanted to see however on your Flickr site I found the following which shows that there is no opening. something that, to me, looks most unaerodynamic as it looks as if the airflow meets a blank wall. Anyway thank you many times over. You have been a great help. John 2 Link to comment Share on other sites More sharing options...
The Tomohawk Kid Posted September 27, 2020 Share Posted September 27, 2020 (edited) I have the Olimp Pro Resin's 707 /A/B/C and the BAC 221 getting very close to the top of the build pile - I will therefore keep a close eye on this thread. I believe the 707s were manufactured at Avro Bracebridge Heath (very close to where I grew up) and were towed down and across the A15 to RAF Waddington for their first flight. Tommo. Edited September 27, 2020 by The Tomohawk Kid Link to comment Share on other sites More sharing options...
alt-92 Posted October 10, 2020 Share Posted October 10, 2020 On 9/27/2020 at 3:12 PM, John R said: [...] there is no opening. something that, to me, looks most unaerodynamic as it looks as if the airflow meets a blank wall. Boundary layer splitter plate function is to provide clean airflow into the engine intake by separating the flow over the fuselage surface. Where would you say it is unaerodynamic when the airflow is directed over/under the wing roots? Link to comment Share on other sites More sharing options...
wellsprop Posted October 10, 2020 Share Posted October 10, 2020 On 27/09/2020 at 14:12, John R said: something that, to me, looks most unaerodynamic as it looks as if the airflow meets a blank wall. It doesn't really matter at the leading edge of the wing root as the airflow is stagnated at the leading edge and the boundary layer will be fully developed. The boundary layer development is approximated by the 99% thickness and displacement thickness equations. https://en.m.wikipedia.org/wiki/Boundary_layer_thickness Link to comment Share on other sites More sharing options...
John R Posted October 11, 2020 Author Share Posted October 11, 2020 Thank you for that explanation. My first thought was that it's 60 years since I had any dealings with the mathematics of boundary layer flow and knowledge has moved on since then but then I realised that the 707A was designed about another 10 years before that so how did its designers know that much about the boundary layer? Regardless of the logic I still think that it does not look right! Link to comment Share on other sites More sharing options...
Graham Boak Posted October 11, 2020 Share Posted October 11, 2020 Boundary layer grows from the leading edge, regardless of the stagnation point. This is entirely a point in the mathematical sense in that it marks the split of the airflow into under and over the wing, but has no physical existence where air can gather to grow a boundary layer. Knowledge of boundary layer flow clearly existed long before the Avro 707, being based on Reynolds numbers which have been in use before aircraft, (It is also useful in pipe flow.) What strikes me as odd is the apparently bluff nature of the root inside the strake, and the almost right angle change to the upper surface. This is asking a lot for the air to stay attached, although the apparent increasing width of the gap spanwise (ie towards the top) may be intended to compensate for this. Maybe. Link to comment Share on other sites More sharing options...
71chally Posted October 11, 2020 Share Posted October 11, 2020 22 minutes ago, Graham Boak said: What strikes me as odd is the apparently bluff nature of the root inside the strake, and the almost right angle change to the upper surface. This is asking a lot for the air to stay attached, although the apparent increasing width of the gap spanwise (ie towards the top) may be intended to compensate for this. Maybe. It's an optical illusion from that angle of viewpoint, ie when you are stood level with it. Really difficult to explain, and easier when you are looking over the real 707, but the wing root due to it's thickness 'cuts' in to the fuselage at an angle, that and the combination of the fuselage curvature if you happen to be viewing at that angle straight on it appears bluff like that. The 3/4s overhead view illustrates things a bit better. http://plane-crazy.k-hosting.co.uk/Aircraft/Jets/707/avro_707.htm Link to comment Share on other sites More sharing options...
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