Originally Posted by
lamarkeiko
David, you mentioned that you use a Sullivan round 10 oz. tank. The tank that came with this DB is flat on bottom and a very tight fit. Do you think the Sullivan tank will be an easier fit? The bottom of the body cavity (top really) is very thick balsa, and I'm sure it could be scraped down a little without weakening the structure.
Lamar,
Bridi designed some nice planes but they weren't especially light or "conceptually clever". One such example is how the front top curvature in the tank bay area was dealt with. Basically in order to achieve top roundness, the tank bay was spanned with a slab of 3/8" balsa followed by the 1/4" (or was it 3/8" in the original - can't recall) top sheet. This results in the center portion in the tank bay being 5/8" or perhaps 3/5" thick! So yes, you can hollow out this area which will also allow you raise the tank level putting it more inline with the carb height in an upright engine installation. In my redesign, I kept much of the original structure the same in the interest of honouring Bridi but I took the liberty to drop fuse side thickness (1/8" down from 3/16") as well as doubler weight and remove unneeded wood. The front tank block is an example where I cut out much of the middle leaving only the front and sides present where wood is needed. The Sullivan 10 oz tank fits with no problems as I suspect most other shallow draft 10 oz tanks would. With a little effort, one could probably get a Hayes 12 oz low profile in as well but they are unfortunately discontinued. Whatever you do, I strongly recommend you use new accessories. Not worth the hassle to do all the work and have 20-40 year old parts fail on you - especially the tank.
The Hobbico 3 pack set of mechanical retracts is not that expensive. I think I'll order that set, then I'll be able to see if room is available to fit the base mount nose retract.
The Great Planes DB 60 ARF instruction manual has a section on installing Hobbico mechanical retracts that looks very informative.
Sounds wise!
I have extra standard analog servos. Will these be ok to use for my main retracts and nose gear retracts?
Yes. Provided you can get proper throw out of them with the arms. 60 deg might require a large servo wheel on the mains. With analog servos you can use an electronic gadget called a "servo stretcher" to increase throw and reduce output arm size. A retract servo on the mains might be an easier and cheaper solution.
I don't think this original old DB was built very light. Does this plane benefit by keeping it as light as possible during my restoration. It seems that most planes do, but the reason I ask is because I read the Ultra Sport 60 build thread by the late Minnflyer, and he stated that the Ultra Sport flies better with more weight.
This is a ballistic era model so a little mass helped in windy conditions when performing "one pass" pattern manoeuvres. That said, model airplanes typically benefit from light weight for better performance. A light DB40 does well on a 46 size engine but for excellent performance, a 55 is great. The extra power can carry a slightly heavier bird too.
After looking at the photos of this DB that I've posted, do you have any idea how old it may be? Possibly 70's vintage?
Lamar
Probably late 70's to mid 80's. I'm not sure exactly what year the smaller 40 size version was kitted by BHE. I think the DB60 article was published in 1976 with Joe having built his models in '75. Perhaps the DB40 kit came out in '78.
David
PS I wouldn't install the NG servo back where you drew it on the photo. Use that area for tail servos and receiver. Install the NG and throttle servos further up just aft of where the battery is needed for balance - probably behind the fuel tank with the 55AX.