DB Models 80" SE5a

[David Holland 2]

I bought the above at our club auction a couple of years ago, built and covered but without the plan and unflown. I have completed it and attempted to fly it, not very successfully but without damage. The rigging and incidences were all over the place and I have now sorted as far as I can but I have no idea what the difference, if any, between the upper and lower wing incidences should be. A quick google did not come up with anything specific but the consensus seems to be that upper wing should be the same as the lower or a degree or so less. If anyone has built one and can give me chapter and verse my gratitude would be undying.

 

Thanks, guys.

[Jon H]

I would email Db themselves, they have all the details. 

[David Holland 2]

Thank, Jon, that was my first action but patience is not my greatest virtue........

[John Rickett 102]

3 hours ago, David Holland 2 said:

Thank, Jon, that was my first action but patience is not my greatest virtue........

Not sure what you mean by the incidence being all over the place, the lower wing incidence is set by the pre-cut wing seat and the upper by the pre-formed wire cabane, so unlikely to be far out. Apart from adopting a slightly nose high or low attitude, the only effect you're likely to see is at the stall, a less positive incidence on the upper wing means that upper wing will stall later, which is a good thing. Warps however are something else, the wings are quite flexible until restrained by the rigging.

I'd suggest you check the CG is correct first, a rule of thumb would be 25% from the mid point of the leading edges.

This example from a very early kit, and built to the plan, flies a treat. Don't be afraid to add weight to the nose, the wing area can carry it!

I should also mention that rudder is required in the turns, attempting to fly by banking with ailerons and hauling round with elevator won't look pretty, the adverse yaw is quite evident, so coordinated turns every time for balanced flight.

 

  

Edited June 19, 2023 by John Rickett 102

[J D 8]

   What John says is spot on for most aircraft of this era, even semi scale ones like my DB Major Mannock

[David Holland 2]

John, the original rigging was setting the tip incidences of the individual wing panels and it was this that introduced the anomalies. As I said in my original post, I bought the model built and with no plan so was unaware of how the cabane was constructed and, if you are correct, then I can assume that all is as DB intended. I am now waiting for day with benign weather to try again.

[John Rickett 102]

David, you could check that the struts are not pushing the wings out of true as the model is being assembled. Each strut had to be made the correct length, there is no post assembly adjustment. Also the wire cross rigging between the struts is probably soldered to hold each pair of struts in the correct position. If the strut lengths or cross rigging are not correct it will cause a wing panel to adopt a wash in/out twist.

All easily corrected so worth a check that the wings are not being warped by the struts before the flying and landing wires rigging are connected.     

[David Holland 2]

John, everything is now true to within 0.1 of a degree (the limit of accuracy  of the inclinometer on my phone). I set the dihedral and incident of the lower wing, adding 1 degree of washout for good measure, using the rigging wires from lower ends of the struts to the upper mountings on the cabane and, with the struts in place, checked that the upper wing incidence was the same. I made a tensioned gadget that located on the leading and trailing edges with a platform for the phone to ensure consistency. I then arranged the rigging reacting the flying loads from the upper end of the struts down to the lower centre section using those clever tensioners, that I assume were supplies with the kit , to tension the rigging but without introducing any unwanted twists. As I said, all is now true to within 0.1 of a degree so I am hoping for a successful second "maiden" flight as soon as the weather gods cooperate