Just an added note to below, The service manual that Rob attached shows the current configuration. I have asked Diamond if they had any documentation of the initial configuration and they havn’t.
Note the drawing of the aileron bell crank is made from flat steel From: [email protected] On Behalf Of Ian Williams Sent: Saturday, 27 June 2020 8:31 p.m. To: [email protected] Subject: RE: [DOG mailing list] Low RPMs Hi Gyozo, This is an interesting topic to discuss. Our flying Dimona is S/no 3537 and is was one of 10 purchased by the Royal Thai Air Force in the early 80’s. I also am in the long process of “restoring” S/no 3534 and also have obtained S/no 3507 which was wrecked and only any use for parts. Both also were ex Thai. During the work on S/no 3537, I did get a lot of support from Both Rob and Nigel from Australia (I am in New Zealand). The learning curve was very steep. The airfoil section is a Wortman FX63-137. It is/was quite commonly used for other gliders of that time … Libelle, Cirrus etc. If you look at the section. It has a very dominant “concave underside with downwards droop at the trailing edge. It is not a high speed wing but is very stable at slow speeds so is really good for gliders. You have probably noticed this .. ie comparing slow speed characteristics of the Dimona with a Grob 109A. The Dimona can thermal happily at 50 Kts or even less, while the 109 would be falling out of the sky. However, at the top end speed .. ie 100Kts, there is a significantly high “up”load at the trailing edge. When Wolf Hoffman built the first few H36’s (which did include some of the Thai ones) he (unfortunately) configured the aileron push rods such that when both ailerons were providing a significant “up”load, the aileron push rod inside the wing was in compression. Which really isn’t ideal of course. To try and overcome this, it seems that 5 linear bearings were installed in each wing because this compressive load would bend the push rod slightly. However, even with 5 bearing sets per wing, there is still enough bending to lift both ailerons at high speed. Ours is up to around 25mm. In practice I have no concern as a little positive movement of the ailerons does reduce drag a little. Later manufactured H36’s had a modified aileron circuit where the rods were reconfigured so when the “up”load was present, the push rod was in tension. This became the standard configuration. But to answer your question… I have set the ailerons level when on the ground and get about 25mm rise at 100 Kts I think that if your H36 flies straight with no tendency to roll , I would leave everything as is. As a further interesting issue, some of the Thai Dimona’s had the 10 linear bearing sets (5 per wing) consisting of 3 bearings around the aileron push rod mounted in a little wooden frame. The bearings were a typical ball bearing however the entire outer including the ball race was nylon.. Because presumably of the high humidity in Thailand, all the bearings of 3537 were seized ( 10 bearing sets 30 bearings total) I was able to purchase 10 sets from Diamond (they are the same as the DA40 elevator bearings). It was a mission to install them but all done and no problem. S/no 3534 and 3507 have Teflon rings mounted in a plywood holder as the aileron bearings rather than the ball bearing sets. There are 2 things that you can check what type of system you have 1. The aileron bellcranks out on the wing if the “old” type are made from steel tube while the “new” system has the bellcranks made from flat plate steel 2. There is no centering springs under the fuel tank if the “new” system included. 3. The later design uses only 3 linear bearings per wing. It is not a practical suggestion to modify an “old” system to the “new” configuration. I hope this is of interest to you. Best regards Ian Williams ZK-GCB New Zealand From: <mailto:[email protected]> [email protected] On Behalf Of Rob Thompson Sent: Saturday, 27 June 2020 10:39 a.m. To: <mailto:[email protected]> [email protected] Subject: Re: [DOG mailing list] Low RPMs Control defections are on pages 36 and 37 of the Service manual See attached regards Rob Rob Thompson 0429 493 828 On Fri, Jun 26, 2020 at 10:47 PM Győző Horváth <[email protected] <mailto:[email protected]> > wrote: Dear Ian, You mentioned that your Dimona is an early one with the original aileron push rod configuration so it has some aileron upward deflection at cruise. My Dimona was produced in 1983. The aileron deflection is quite there on the ground as well. Is it OK or should I set it zero on the ground and it should be visible only in air? With many thanks and best regards Győző Az iPademről küldve > 2020. jún. 1. dátummal, 17:14 időpontban Ian Williams <[email protected] > <mailto:[email protected]> > írta: > > Our Dimona is a early one with the original aileron push rod configuration so > we do get some aileron upward deflection at cruise. --------------------------------------------------------------------- You are subscribed to the Dimona Owners Group mailing list. To unsubscribe, send email to: [email protected] <mailto:[email protected]>
