Brodaks Vector .40, design by Randy Smit

LAST EDITED ON Apr-27-03 AT 07:34 PM (CDT)
 
Brodak Vector .40
Kit Instructions: (1-5 - 5 is best) 4.5

As per Brodaks usual instruction booklets. Pretty complete, very minor last minute variations not covered, but for all intents and purposes excellent. Plans are complete, and the attempt has been made to show all the parts. There was a problem with a missing few pages in the instruction book, but a call to Brodak and a new book was soon at my house.

Materials & Packaging: (1-5) 4.5

Shrink wrapped box, colorful art work, and the wood quality is about as good as I might have hand picked, at least in the example I have. There was a missing plywood sheet, but again a call to Brodak and a replacement was in my hands.

Ease of Build & Finish: (1-5) 5.0

Just started build, Seems straight forward. I will be commenting on the build as it progresses.

Design & Appearance: (1-5) 4.5

The design is straight forward, attractive. It comes from a long line of successful designs, and already has several major competition wins to it's credit. The wing is a bit smaller than many of the 40 size designs I've seen in the past, but built light, and with care, it should be fine.

General Flight Characteristics: (1-5) 5.0

Those I've seen fly have been very good. I'll comment more about it when I get to that part.

Performance Capabilities1-5) 5.0

This design is able to slug it out with the best. Pilot skill is the determining factor here.

Maintenance & Repair1-5) 4.5

As per most full fuselage designs, no surprizes.

Comments:

I saw this design first, at the '95 Nat's, being flown by young Derek Barry. He won his age class, and finished high in Advanced as well. The plane has sleek lines and functions well for it's purpose, that to get you moving up the ladder without the plane holding you back.

Build Tips: See comments as build progresses

Setup Tips: Same as above.

Power Tips:

I would consider the smallest acceptable engine and power to be equal to a modern .32. This plane is designed to work with the most popular sized engines for most of us, a modern .40 sized power plant. The OS LA .46 should be fine, but I wouldn't think going larger would really be of much benifit. Many fine engines are available, both standard and piped for this airframe, but the plane isn't really designed for a pipe, though it could be easily adapted to one. I would recommend a rear exhaust with a muffler for that clean look in the front.

In the beginning.......

Upon opening the box, once again, I'm impressed with the care taken to supply good value for the cost, as practised by the manufacturer.

Small parts, and sub-assemblies, are packaged seperately. I like this practise as it keeps small parts organised and together until I need them. Some items I expect to change will be to redesign the flap horn for "corrected geometry", upgrade the rest of the control system to ball links. I also plan on changing the rib spacing slightly to increase the span 1 inch on each side. I expect that this will give me about 18 additional sq. inches, which for my altitude won't hurt.

Brodaks normal, excellent, quality with the die cutting, and wood selection. The parts seperated cleanly, with, once again, some exacto knife work required on the plywood sheets. Same reason as before. As mentioned, one plywood sheet was missing, but quickly replaced after a phone call. Once again, the thicker balsa pieces had some die crushing, but for the right reasons. lighter softer wood, rather than harder wood that will cut cleanly.

A liesurely hour was spent removing and marking the parts. Be sure to check, compare, and mark the parts. The second plans sheet shows them all, and can be used to scratch build or cut needed parts should repairs ever be needed.

Spend some time to carefully read the instruction book so you can get a good idea of how the build should proceed.

The disclaimer;

I purchased this kit direct from Brodak. I had nothing to do with the design or the drawings, they were skillfully drawn by Curt Contrata.

I'm wondering why everything is spinning around?

LAST EDITED ON Apr-28-03 AT 08:10 AM (CDT)
 
Building the wing, part one:

Yesterday, I framed up the wing. Brodak's manual uses the simple levelling bar system of rigging or jigging. I've used it on previous builds, such as when building my Cardinal profile. It works pretty good, but requires that you have an absolutly flat surface to begin with. Should you desire to use this system, follow the instructions in the manual.

I opted to use my Combo jig utilizing Aero 95th. squadron jig fixtures. I've built several wings with this jig, including the Legacy wing. The jig uses a similar system as Tom Morris's Lincoln Log or Mellenium wing jig with more ease and versatility.

I jigged it up about the same way that I did with the Legacy wing.

Since I have made the decision to add 1 inch to each wing half, the first thing I found out was that the supplied leading edge, spar, and sheeting material, was not going to be long enough. No problem, I took some appropriate sized stock out of my scratch building supply, and added the too short pieces to the stash. I used a piece of 9X16" X 3/16" balsa stripped from a nice sheet, for the traiing edge piece. This is another departure from the manual, but needed to use my jig.

I cut pieces of scrap balsa to the correct rib spacing, one to set the center spacing (3") one for the inboard wing, and another for the outboard. All the ribs were set, spaced, and glued to the leading edge pieces, and by using a scrap piece of 1/8" balsa to guage, the ribs were glued to the trailing edge.

Now, it's time to instal the spars. The Vector uses a 1/4" sq. spar on top, and a 1/8" X about 1" spar on the bottom. Here's where I ran into a problem.

The spar slots were not quite wide enough. I wish I'd have checked them before glueing the ribs in place. I could have rigged up a fixture to make the slots wider, but decided to strip out new top spars, just wide enough to fit. I figure that stregnth will be more than adequate with the very slightly narrower top spars.

The slot for the bottom spars was also not wide enough for 1/8" balsa, so I checked and 3/32" sheet fit perfectly. OK, I took the easy way out and made the lower spars out of 3/32" X ~1" balsa. I will extend the 3/32" spar to the upper spar as in shear webbing out to the 4th or 5th bay for additional stregnth, so I believe that it will be plenty strong enough, and likely no more weight than stock, especially once the leading edge sheeting is in place.

At this time, the wing is sitting in the jig awaiting installation of the bellcrank and mounts. I intend to deviate from the kit in this area, and go with my favorite method as I used with the Legacy. I'll make them from 1/4" basswood, in one piece and mount them in a similar manner as the plans show. I also intend to mount the Bellcrank reversed as I prefer having the forward line as the up line.

Part two soon.

I'm wondering why everything is spinning around?

Part 2 designng the flaphorn.

I've decided that I'm at the point where I should design a "Corrected Geometry" flap horn. I've gotten to where I won't fit anything else to my stunt ships. I decided to first check and see how much error was coming from using the stock setup.

Using the CAD program to lay out the control geometry, I found that the stock system as shown on the plans show some errors when the controls are activated.
It isn't too bad, but they are there and could cause some trim problems down the road.

By swinging the bellcrank through 50 degrees each direction, the following errors appear. At full down command, there will be 24 degrees of down elevator, while the flaps will be deflected up at 24 degrees.
With full deflection in the other direction, there will be 26 degrees of up elevator, and the flaps will be deflected down at 26 degrees.
This rotation is realized using the middle bellcrank hole on a 4 inch Brodak unit.

I prefer slightly more than 30 degrees pf flap, so I decided to see what would happen if I used the outer hole on the Bellcrank throw with the stock setup.

Using the same 50 degree throw in each direction, I found the error has increased. Giving full down control, the flaps deflect up at 33 degrees, while the elevator will deflect down the same 33 degrees.
By giving full up control, the flaps now deflect down at 37 degrees, and agian, the elevators will deflect up at 37 degrees.

For many pilots, this is something they might be able to get used to, but for competition, more linear tracking will make the plane easier to precisly manuever. If your mainly a sportflyer who enters none or few competitions, the stock setup should serve you as it is.

On the other hand, if you plan on competing and want the best in the way of control and feel, it would be worth your time to correct the geometry of the control system. Easier trimming, a better groove, and equal turning rates will be the benifit.

I have taken the time to draw up a new flap horn that corrects the errors. It's attached to this post. Take the time, should you decide to use it, and make it as accurate as possible. Notice that the lower hole for the flap to elevator pushrod is not at 90 degrees relative to the pivot point. In checking the corrected system out, without this lower hole being moved, I found that by using the middle hole on the bellcrank throw, the controls are 1 to 1 almost. the flaps will rotate equally at 24 degrees up and down, while the elevator still has the 3 degree error favoring up elevator.

By moving the middle hole, on the flaphorn, back, so it is at the shown position, the controls are now equal in throws at both the flaps and elevator. 24 degrees and 1 to 1.

I still prefer a bit more throw, so I next checked out what would happen if I used the last, or outer hole on the bellcrank throw. I wound up with 1 to 1 controls with ~35 degrees in each direction. This is the setup I intend to use.

The dimensions are important should you decide to build a similar flap horn for your Vector. I also should say that this horn is designed for the Vector and may not work the same on other designs. I also intend to order a slider horn from Tom Morris for the elevator as most of my planes wind up with about 32 degrees of flap and ~37 degrees of elevator. This is what works for me, and the slider horn allows me to dial in more elevator should I want to.

A good material for horn construction is .060 brass sheeting from K&S. Better would be .060 mild steel if you can find it.

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I hope I made the link right.

I'm wondering why everything is spinning around?