KROnline

NEWSLETTER 3435 OCEAN PARK BOULEVARD, SUITE 206

SANTA MONICA, CALIFORNIA 90405-3311

TELEPHONE: (310) 390-8000

FACSIMILE: (310) 397-0028

EMAIL: BSHADR@AOL.COM


Volume I Issue V December 1996


The KROnline Newsletter is intended to serve as a conduit for information and building ideas about the KR family of experimental aircraft. It is meant to share the knowledge that has been hard won by those who have gone before us. Education is the cornerstone to a quality built KR.

The article submissions each month are from KR builders and suppliers. Opinions express are solely those of the individual authors and not of KROnline. Any ideas or techniques discussed are to be duplicated and used at the sole risk of the experimental aircraft builder. KROnline does not endorse or warrant any certain outcomes.

Rand Robinson Engineering is in no way affiliated with KROnline and as such, does not formally endorse any information published in KROnline.

 


 

 

 

 

 

 

 

 

Bobby Muse Jrís tri gear KR2

 

 

Roy Marshís KR2S

 

 

\


BUILDERíS BASE

By Ken Davy



 

(EDITORíS NOTE: I discovered this program recently. It is an easy way to track your project progress. Being shareware, there is no cost to download and use it. However, if you do actually utilize it, we suggest you send a nominal donation to Ken. Almost any computer program has a purchase price, so a $10 or $15 donation would not be out of order for an application specific program we as homebuilders derive benefit from.)

I've written a database program to help track my time and expenses while building my Kitfox. It is a free standing program called "BUILDER'S BASE" and needs no other application software to run. It will run in either DOS or Windows. You can track as many projects as you like and even keep track of both direct and related expenses. You can set the value of your time and keep track of it as an expense. It also allows you to keep a photo logbook of your progress. It includes a separate contacts database for fellow builders and suppliers. The browse windows for the records you enter have selectable keys so you can sort by different fields right in the browse window. The reports have a query utility to let you pick and choose what is included.

This version of the zip file already contains a database of contacts. These contacts are members of the Internet Kitfox builders user group. While they are not all building a Kitfox, they have all been willing to share information about their projects through postings on this user group. If you do not wish to have the hundred or so members of this user group as part of your contact database, you can start with a fresh contact database by renaming or deleting the file CONTACT.DBF.BUILDER'S BASE will create a new contact file the next time you run it.

I hope you find this program to be a useful tool as you complete your experimental aircraft.

(EDITORíS NOTE: The program is included in ZIP form with this issue. If you do not wish to view or use this program, just delete it.)

 

 

 

 

 

 


Nose Gear

from the past



 

Jim Murphy and Val Barnhardt systems are better than the original Bede system. The Bede system actually works quite well. The only drawback is that the nose wheel is a Scott 3200 and is a little small in diameter. The weight on the nose wheel should be carefully limited as some builders have had main castings crack. The nosegear should be carefully checked on each pre-flight as it is very important to the longevity of your airplane. Check the nose wheel by taking the weight off of it (have someone push down on the aft fuselage), and then attempting to swivel the wheel by hand. It should be quite difficult to swivel.

Most tail wheel shimmy quite easily if the design geometry is wrong (most are) or if the friction device (Scott #3234, thrust plate) is

mis-adjusted or gets grease on it. The Scott 3200 friction cannot be increased by tightening the main pivot bolt. The assembly must be disassembled, degreased carefully, and the condition of the 'thrust plate' checked. The 'thrust plate' is held under pressure (against Scott #3207, washer) by several small springs (Scott #3233, spring compression). If there is not enough friction, either install a new thrust plate, install stronger springs, or the existing springs can be raised by putting something under them.

Nose Gear, Murphy:

The Murphy brothers started building BD-4s right when Jim Bede first sold plans. They did a lot of work on improving the airplane but some of the improvements were of a type that most homebuilders could not accomplish in their home shops. This gear was sold by Jim Murphy to many builders. Jim is now totally out of the business but the drawings below show the technique used in the 'Murphy Nose gear'.

The following is quoted directly from the Murphy plans:

The nose gear replacement kit is designed to give the builder that has his or her BD-4 finished or nearly finished an easy way to replace the small nose wheel and/or thin wall strut with a 0.125 wall strut without great difficulty. Many of the parts are interchangeable and fit right in the fuselage without modifying it. The main difference in the two systems is that the replacement strut is in a more horizontal plane and is rigidly mounted to the fuselage with a 500 x 4' Goodyear wheel mounted in a castering fork.

When you hit a large bump at high speed the strut will flex up and the pudgy tire will help absorb some of the shock. When you hit a large bump with the stock system with strut mounted more vertical toward the center line of the little 10' diameter tire, the shock goes up the center line of the tube right to the bushings, distorting them. The wheel does not have time to accelerate over the bump, working something like a karate chop. Notice the axis center line (pivot point) of the stock system and you can see that the wheel has to accelerate over the bump (or jump forward). A tail wheel or a trailing suspension when the wheel hits a bump the wheel will actually pause and lift over the bump. The pivot point housing only being 10' wide and the strut is 34' long from the pivot point to wheel so any play in the bushings will be compounded by a ratio 3.4 : 1. When the nose wheel starts to flutter it is encouraged by the play in the strut. The fixed system does not have bushings and is supported as far out as where the shock was.

The nose fork is tilted forward 7° and has a large 1.5 i.d. bushing on the full tube diameter plus a simple drag clutch making the flutter possibility very low.

Disadvantages:

1. The larger nose wheel will cause more drag.

2. It is difficult to push the airplane backwards.

3. It is expensive to replace something that you have already paid for.

4. Takes all the excitement out of your landings - you do not have to worry about breaking off the nose strut or having shimmy!

5. Lets you have confidence in making short field landings in fields that you may not get out of.

 

 

 

 

 

 

 

 

 

The following are building tips for the Murphy Nose gear:

1. Make now gear as shown except heat treat.

2. Make nose wheel fork as shown above.

3. Assemble nose wheel and tire on nose gear. A friction washer must be placed above the spring loaded steel ring that fits on top of the fork and also below the fork. These can be make of micarta or of heavy rubber belting or tire material. The inside of the bronze bushing is lightly greased but no oil or grease should be on the friction washers. It should be difficult to swivel the fork on the strut by hand

4. Install nose gear and wheel on airplane with airplane blocked up so as to insure proper attitude and propeller clearance.

5. Make the structure that replaces the Delco shock using LGN-10 to hold top of structure.

6. Remove welded assemblies and have them heat treated and magnetically inspected.

7. Paint assemblies except where nose wheel fork fits and install in airframe permanently.

8. Make shackles - drill only the holes in the end that bolts to LGN-14.

9. Make a three inch long transfer punch out of some 3/8 steel rod.

10. Put one shackle on LGN-14 and align with nose gear assembly. Slip punch through hole in nose gear and punch location of hole into one shackle. Remove shackle and repeat operation on the second shackle. Drill holes out of airframe.

11. Install shackles.

 

 

 

 

 

 

 

Nose gear modifications (Val Bernhardt): Early BD-4 builder Val Bernhardt decided that the Scott tailwheel 'nose wheel'

was too small so he designed the following modifications. Val's design is nice as it takes very little machining and yields a very robust nose wheel.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The 5/8', 4130 steel rod is sometimes replaced with a thick strap of steel (1/4' thick? by 1' wide?). The 'strap might be easier to weld to the vertical spindle and the axle hole can be drilled right in this piece.

If you notice the 'backward angle' of the axis of swivel, it should be noted that this is the zero weight position of the nose gear strut. When moderate loading occurs the 'axis of swivel' should be vertical.

 

 

 

 

 

 

 

 

 

 

 

 



Does your KR need a diet?

By Ross Youngblood rossy@teleport.com


A Quick Look at KR Weights

One question that continued to interest me was the weight of a completed KR-2. A couple of years ago, I went through all my back issues and jotted down the weights. I thought I would turn this into a KROnline article by putting the data into EXCEL, and plotting an excel chart. Someone suggested going over old newsletters, and summarizing the information, so here is an example of what I found, my back issues go to 1988 so if you have more to add, get the spreadsheet from me and add away!!

The end of this article contains an EXCEL spreadsheet of the data used. Most of the data

was gathered from KR newsletter back issues, but a couple of data points came from the

KR Quarterly.. N numbers weights and names were those gathered from the newsletter.

 

The Stock KR1, KR2 and KR2-S weights were thrown into the data as well,

it is assumed that at least one each of these exist at the specified weights.

Model

Weight

KR-1 Specification Aircraft

310#

KR-2 Specification Aircraft

480#

KR-2S Specification Aircraft

520#

Min KR2 Weight

524#

Max KR2 Weight

910#

Average of Published Figures

626#

From this chart you can tell where your project fits in the scheme of things with respect to

weight.

Two of the three KR-2ís weighing in at > 700 pounds later were reported destroyed in newsletter and/or Kitplanes articles. The 910# KR was forced onto a mountain road due to engine failure, with no fatalities. A 700+# KR crashed with two fatalities, it is suspected that a loss of the canopy contributed to this incident. Weight does not appear to be a primary factor in these incidents.

If your KR is not on this list, send me an email to rossy@teleport.com, and eventually

I may update this table. Copies of the EXCEL spreadsheet are also available via email

just drop me a line.

Attached is the raw data I gathered for this summary:

KR2 Weight Statistics

Registration

Weight

Newsletter

Owner

Range

Quantity

N55DS

609

Quarterly #10

Dave Shirey

300

0

N4924R

608

Quarterly #10

Ken McCormick

350

1

N81RV

644

Quarterly #10

Stan Vanderboss

400

0

N147S

625

Quarterly #10

Jerry Robinson

450

0

N44DD

607

Quarterly #10

Dan Diehl

500

2

N2AK

704

Quarterly #10

Max Calkin

550

5

N335KC

553

Quarterly #10

Ken Cottle

600

7

N651AC

712

KR #162

Al Campbell

650

12

N86CT

670

KR #160

Jerry F. Johns

700

8

N3LL

635

KR #159

James Takomoto

750

2

N200RH

910

KR #158

Roger Hanson

800

0

N39426

640

KR #154

Dave Feiger

850

0

C-FAFY

530

KR #153

Adrian Carter

900

0

N707V

540

KR #152

Steve Howlett

950

1

N42VK

524

KR #147

Elwood Harding

N151TG

562

KR #147

Todd Goudeau

N7786GL

575

KR #147

Louie Brochetti

N282B

650

KR #147

Mike Smith

N74DL

604

KR #147

Don Lott

N4207Z

588

KR #147

Roger Bulla

N53645

550

KR #145

James Caldwell

N161TD

562

KR #145

Todd Goodeau

N395DS

575

KR #145

Dave Steeves

N28AK

700

KR #142

Max Calkin

N90JC

628

KR #206

David Caroll

N4288C

670

KR #203

John Savelli

N991TM

699

KR #190

Terry Maxwell

N32V

667

KR #187

Ralph Sawyer

N13UG

600

KR #181

Larry Buck

N85JV

680

KR #172

Jerry Vanatta

N20FN

655

KR #172

Francis Neff

N8575C

688

KR #171

Richard Lind

N31097

482

KR #167

Martin Robert

N191MR

630

KR #167

Average

626

KR1 Spec

310

KR2 Spec

480

KR2-S Spec

520

 

 

 

 



Foiled Antennas

By Tim Hughes thughes@voyager.co.nz

 


The foil antenna can be made to perform brilliantly in a plastic 'plane like the DF. We used a foil system which came as a kit of parts with a Q200 project we once owned. It is placed about 12-16" aft of the wing drag spar. The "vertical" part runs from the corner of the fuse side/bottom on the starboard side up and somewhat around the curved top of the rear fuselage. It is connected to the center conductor of the coax. The other leg runs almost at right angles to the coax across the floor of the fuselage, as near as possible to right angles to the center line. Three ferrite beads are placed over the coax about 1/2" from the antenna, and spaced at 1/4" intervals.

The antenna performance is not greatly affected by the hot (vertical) wire being less than straight. The big trick with the antennas is in it's placement relative to metal fittings in the a/c and mostly in the tuning. To tune the antenna, first make it too long (about 23"). Then get an "SWR meter" from some radio ham you know. The idea is to gradually shorten both antenna legs, keeping the ground leg about 10% longer than the hot leg, and taking about 1/4 inch off each leg at each try. The aim is to get a very low SWR ratio across the entire aviation band. Hold the transmit button on, and tune the radio across a range of (unused locally) frequencies from 118 to 135Mhz. You will see the SWR is lower at lower frequencies. Shorten the antenna foils and watch the frequency at which there is minimum SWR. Keep shortening the antenna until the minimum SWR frequency is about 125MHz. You should end up with very low SWR across the entire band.

When you have done this, what you actually did is match your antenna to the radio conducting properties of the air, i.e. you have made the maximum amount of radio energy enter your antenna on receive, or leave it on transmit. Our results were outstanding 1.1:1 or better across the whole band and a very sensitive radio installation. E-mail me for more details.

Key points:

* Keep the whole antenna at least 18" from other metal, further if possible

* keep it at right angles to the nearest metal,

* keep the hot wire, cold wire and coax mutually at right angles to each other,

* Strive for low SWR using test equipment

* When painting the aircraft with anti-static paint, leave the region around the hot wire clear for at least 18", except for around the coax and cold (ground) leg.

* Keep the antenna and coax well clear of any transponder or gps installation, and at least 30" from the ELT antenna.

Best of luck with your internally mounted drag free high performance antenna!

Best Regards

Tim Hughes

thughes@voyager.co.nz

 

 

 

Related post on KRNET:

Check out Jim Weir's RST Catalog at http://www.rst-engr.com. Good company to

work with; I bought one of their intercoms and put it together two years ago.

Works exactly as advertised (how often does that happen?). Jim sells the

copper foil antenna information and kits.


 

 

Oil Impregnated Sintered Bronze Tail Surface Hinge Bearings

By Mark Langford langford@hiwaay.net

Oilite bearings are normally constructed of sintered bronze. Oilite is a commonly used brand name, but there are many sources. They are manufactured in a manner which leaves tiny voids throughout the structure, somewhat like a sponge. They are then thoroughly impregnated with oil, so that during use, oil is constantly released to keep the rotating parts lubricated. This continuous lubrication makes them ideally suited for KR tail surface hinges.

Oil impregnated sintered bronze flange bearings are available in many different shapes and sizes, but the selections are slim down in the .1875" ID range. The bearings shown are actually made by slicing a longer bearing in half (Boston Gear #FB35-3). The flanged part has a 3/64" flange, and is cut so that the bearing extends 1/8" (full depth) into the larger of the two hinge channels. The remaining part of the bearing is then machined down to 1/8" length and is used on the inner 1" channel. Because there is no flange on the inner hinge, an aluminum or nylon spacer must be installed around the bolt as a positive means of preventing the spacer from slipping out of the hinge. Of course, you could also put another flanged bearing on the inner hinge, and cut the excess bearing away, or just buy a 1/8" long sleeve bearing for this location (Boston Gear #B25-1).

Installation instructions vary, but the bearings are usually installed as an interference press of about .001" for this size. The press fit will compress the inner diameter somewhat, so the bore will then require reaming to the proper bolt diameter to provide a .001" running fit. Use a sharp reamer, as a dull one may smear the pores of the surface, effectively closing off the oil supply. Follow instructions provided by the bearing manufacturer. Of course, the instructions say to countersink the flange 3/64" so that it is flush with the surface. That would almost certainly require a machine shop, so they were simply left on the outside. Longer hinge bolts will be required. Iíve also heard that after assembly, you can soak the bearings in a 130-150 degree oil bath to replenish some of the oil lost during the machining process, but have never seen this as part of the installation instructions from a manufacturer.

For the do-it-yourselfer, you could just drill the required 5/16" hole slightly large for a slip fit, and use green Loctite to hold the bearing in place. Green Loctite is used when joining oily materials, and is well suited for this job. Also, the flange will hold the outside, and the spacer will ensure that the inner bearings stay put. Also, note that tolerances on these bearings are not extremely tight, so treat each one as if it were different. It probably is. After a press fit installation, an AN3 bolt will probably not even fit in the hole, so expect to buy a 3/16" reamer for sure.

Any local bearing emporium will have (or can order) oil impregnated sintered bronze bearings. I bought mine at an Invetech bearing store for about 50 cents each, with two required for each hinge (mine were cut in half, remember?) But if there are no local sources, one is Boston Gear at 14 Hayward Street, Quincy, MA 02171. They can be reached at (617)328-3300.

KR TIDBITS

 

Drain ALL the H2O!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Get Bent the right way

By Corky Scott

 

As to the bending part of this posting, what that refers to is the problem of how to bend pieces of metal that are too thick for the normal or even abnormal bending break. Some bracketts have bends on either side of the brackett for strengthening the piece which is 8" long. Normally, with a smallish piece of metal, you can chuck it in a vise and hammer it over the proper bending radius and get an acceptible brackett, but not if it's 8" long. And definately not if the material is .062" thick. My solution was to build a V-block press after seeing one in Kitplanes magazing several years back. It's a simple press, utilising a common floor jack for pressure which pushes an arbor into the material which is layed over a piece of 90 degree angle iron. I had great fun wandering around a local metal scrapyard looking for pieces of metal I could scrounge to do the job. I had the thing pictured in my mind and tried to find pieces that would work. The scrap metal cost $5. and I had to buy some pieces of non scrap hot rolled round stock for the guides that the arbor would slide up and down on. That cost $10. When I had cleaned everything and shaped the base and top the way I wanted, I loaded everything in my car and dashed to a friends place who has a monster MIG welder. Half an hour later the thing was welded up and I raced home to try it out. I needed to go back and reweld a couple of the rods, but basically it works. I even welded bits of the rod to the arbor platform and to the top so that I could wrap some bungee cords around the arbor to make it automatically retract from the down stroke after releasing the valve of the jack. So how well does it work? Well enough to bend 12 aileron brackets made from .125" 4130 steel 90 degrees. It was a lot quicker and more accurate than my first attempt to bend this bracket up using the vise and a 12 lb. sledge. My wife objected to that effort because the house was shaking :-). Next I'm going to try to bend up that 8" piece I mentioned earlier.

Work has been pretty slow lately because winter is coming soon and the plow has to be made ready, storm

windows installed, kids homework to help with etc etc, most of you know what I'm talking about. :-) Till next time.

Corky Scott

 

For Sale

I saw your Homepage while netsurfing and thought that you may know of someone looking for a project. Last year my father-in-law left a KR-2 in our garage which is +/- 75% complete. wings have 1st coat of glass,

turtle deck and cowling have not been secured to body. Engine is rebuilt Porche. While visiting the rest of family he became ill and is unable to finish the project.

If you know of anyone looking for something like this we are negotiable. The builder of the engine can be reached for specs,etc. Also do you have the telephone number to the KR Newsletter? We would like to put in in there as well. I can be reached at 281-360-8476 h or 713-669-7906 w for questions or photos.. or vjluszc@charon.ppco.com

 

 

 

 

 

 

Cowlings and Separation

By Jon Finley and Rich Goldman

Question; Any suggestions on construction techniques, release agents, cowl layup schedules, etc would be greatly appreciated.

 

I sure don't envy you right now and wish all that work your doing would fit my Q2!! I have built more cowls than any person should have to. With that said I suggest:

2 ply of 10oz BID over the entire cowl. In large flat areas 2 ply is relatively flexible(you can push on it and it will bow in and then bounce back) but has always been plenty strong for air loads.

1 - 2 ply 10 BID or UNI(whichever is appropriate) in the areas that provide a natural "structure". This is usually an inside or outside radius of some sort.

1 ply Kevlar BID and 1-2 ply 10 oz BID along all edges. The kevlar makes an unbelievably tough edge and doesn't allow holes(screws) to elongate. It can be a pain in the butt to work with though.

 

Those are my hints of the cowl! My Q2 cowl(kit) is heavy as sin and is quite thick all over. This really isn't necessary and weighs a ton.

Jon Finley

amc-msp@minn.net

N54JF 1835cc VW Quickie

N90MG 2100cc Revmaster Q2

Bloomington, Minnesota

 

I found that the best way for separation is to use urethane varnish, 3 coats on the plug. Let it dry completely (overnight at least) and then coat it liberally with that green alcohol mold release sold by wicks or spruce. When that is dry, glass up. Separation is a little scary at first, but as soon as you get the first separation, the fiberglass comes smoothly off. I did not find waxing to be of any great value. I assume that you are building the plug out of foam.. Fill the foam with fast dry lite pre-mixed spackle. Do NOT do what Bingalis says and spray primer or paint over that.. It will eat the foam away and you will have to almost start over. let each coat of

varnish dry before the next one goes on. This is important as it fills in the pores and seals the plaster from the glass. Good luck. Soon your cowl will jump over the moon(ey)

Rich Goldman

ARGOLDMAN@aol.com

 

Well folks thatís it for now, I will try and get the next issue out by March 30th. Whatís coming up in the Jan issue?

How about some money saving tips for those of you building on a tight budget!