Individually Asked Questions

This is a record of some of the questions Bob [bw], Steve [sc], and I [hs] have received through the webmaster@bd-4.org account. Neither of us is a aeronautical engineer so please consider what we are saying just as an opinion of another fellow builder. It is generally better to ask the mailing list. There are knowledgeable people responding with excellent advice.

The general FAQ is here.

Q:	I know it is possible to extend the fuselage length. But can you tell me if there is a modification for widening the fuselage by about 2 to 4 inches?
A:	I don't know of a BD-4 that has been made wider. I make mine longer and higher but not wider. However, it is certainly possible to widen the fuselage. I would not expect two to four inches to be enough of a change to alter the basic static and dynamic characteristics of the BD-4. You will have to think about ways to beef up the center spar and/or wing spars. The center spar will probably have to be longer, for adequate overlap with the wing spars and better load distribution in the wing spars. Also, you are extending the effective wing span which, in combination with a heavier fuselage, calls for stronger spars. There are other structural elements that may need to be stronger, i.e. the landing gear box. But if you found a spar set equally strong as the super tube that was offered by Dream Aircraft I think you could extend the width without much worrying about the spars. It all depends on what gross weight you want, of course. Are you sure you need a wider fuselage? It is pretty wide as it is, in comparison to other planes in this class. Note this is a major alteration from the plans that impacts the structural integrity of the design. Be sure to consult competent advice! [March 2005, hs]
Q:	In the FAQ you mention that the BD-4 "has a rather high stall speed if the original (short) wings are used. You can improve the stall speed by having longer wings, extending the chord length of the flaps by about 2" and enable a 40% flap setting." What wing length is recommended?
A:	If you are a seasoned pilot and expect to fly mostly out airports with adequate strips it may be best to leave the wings unchanged. That way you don't have to look for stronger wing spars or reduce the gross weight to stay in the utility category (with the wing spars being your limiting factor). You may also see a better cruise speed at altitudes below, say 8000 ft. However, if you fly out of small strips, at high density altitude locations, or getting the stall speed down is a high priority for you then adding 2 ft each side has proved to be a good alternative. You will also get better climb. Roger Mellema used to sell 2 ft extensions. You'll find a bunch of pictures I took of this extension on the web site. After the extremely successful tests with vortex generators by Richard Martin and Steve Craigle it is now clear VGs offer a very effective way to reduce the landing speed. [hs]
Q:	Im curious to know how much more efficient the BD 4 taildragger is compared to the tricycle configuration option. Im a former Army helicopter pilot that is in the market for a reliable 4 seater airplane that has good cross country capabilities. I've seriously considered the Cessna 182 RG but when comparing purchase costs, the BD 4 appears to make more sense.
A:	There's no doubt the BD-4 is a lot more efficient than the 182. Getting the nose wheel off will reduce drag somewhat, but most BD-4 pilots seem to be quite happy with their performance either way. Some of the nose wheels were a little flimsy also. I'm a low time taildragger pilot, so I'm a little nervous about the whole thing. Give me a year in the air to fix that I hope. You will pay a price for the efficiency however. The 182 is going to be a much roomier 4 place. The BD-4 gets it's efficiency from small frontal area. The front seats aren't too bad. Maybe similar to the older Mooneys. (I haven't been in any newer ones.) The back seat is going to be real crowded for two medium sized or larger people. [bw]
Q:	Could a BD-4 be built with a longer wing, basic instruments, no electrical system, a 85 to 100 hp engine and possibly qualify for a Sport Pilot aircraft?
A:	The tough rule is the 1320lbs max weight. According to the specs the stock BD-4 with a 104PS engine weighs empty 960lbs. That leaves around 400lbs for useful and fuel. I don't know if I would extend the wings on such a light plane. That adds weight and you should be able to get the landing speed below the required 45kts with minor modifications to the flaps. Consider contacting Paul Kauffman. He had a water landing with his BD-4 last year and is now reusing the wings to build a Light-Sport compliant bird. His email address is: kauf [at] chartermi.net. [February, 2005, hs]
Q:	I want to build from plans. Where can I get the fuselage angles?
A:	There are several sources: Get them done at a local sheet metal shop. That's how I do it. I also built a little 4ft bending brake and can do a lot with this one in my garage, including the entire gear box. There are not that many parts that are longer than 4ft. Note you don't need dies to bend the angles at a local sheet metal shop. Just pick up a strip of aluminum or steel from the scrap pile and wrap it around the edge of the existing die of their press brake. If that's not enough use more than one strips. It works beautifully. Tardiff in CA. Craig Evans had his set made there. Bobby Murty. He does various parts for BD-4 builders. TVAP or Bede or Dream Aircraft. I don't know if that's possible, but would appreciate if you could tell me what you found out. Check the classifieds ads for an unfinished project. The contacts are listed on the supplier's page. Please let me know how you got your set together. [March, 2005, hs]
Q:	Are the plans for metal wings still available?
A:	Yes, those plans are still available. In fact, there are several: Currently, the most widely used are made and sold by John Raffensparger. John sends out large format plans and I have the CAD version from these plans and hand them out to those that have purchased from John. John's wings have the longer span, 30ft. Then there are plans for metal wings in Jim Bede's "How To Build..." book. These are the short wings. Jim Bede now offers a new metal wing and that also comes with plans. I believe you can buy the plans separately, too. There are Murphy wing plans. I have them here. But they are old, a bit small scale and not in the best shape. [April, 2005, hs]
Q:	How far forward did you move the gear box for the tailwheel conversion and how much change in CG location did the removal of the nosewheel and replacement with the the tailwheel produce?
A:	I put the gear box so the center of it is 23.75" aft of the firewall as shown on plans sheet BD-4-2-04. That would be Fuselage Station 73.75, since the firewall is defined as Sta. 50.00. This location gets the main gear where it needs to be relative to the wing for good ground handling. I ran some rough calculations on the cg movement due to changing from nosewheel to tailwheel configuration and it appears the movement aft is about 8 inches. This considers a 30 lb reduction in weight from removing the nosewheel strut and support structure (a number I measured on mine), estimated 7 lb nosewheel assembly moving from about sta 25 to 200, and the effect of moving an estimated 60 lb main gear assembly forward 23.5" per the plans. Refining the estimates would give a closer answer, but overall it's not a big issue as quite a large number of tailwheel BD-4s have been built without having to add ballast weight to cover the different gear configurations. [April, 2005, sc]