FLPHG Technical Information

Details and links to technical information relating to power harnesses.

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General Interest

Bar Position - Many newcomers to flphg are confused by the apparent change in control bar position. Even with power off, the control bar will be almost a foot further back than you are used to when free flying Nothing about the glider or how it flies has changed. What has happened is that, with the weight of the engine below your feet, the CG (center of gravity) of the pilot and harness are lower on your body than without the engine. With no pressure on the bar, the CG will be directly beneath the hang point. Thus, it is your body position that has moved forward relative to the hang strap. This is graphically illustrated in this CG Comparison CGComparisonS.jpg. Note that vertical lines are drawn through the hang strap and at the shoulder, and the relative distance between these lines. This situation is generally the same whether or not power is applied (although there can briefly be large changes in relative position when suddenly applying or reducing power - see section below).

Bar Position Changes With Power - The above applies to the engine being off. Now, what happens when the engine is turned on? What happens to the control bar position when you add power? Think about if first, before reading the explanation: Control Bar Position Changes With Power Added

Engine Torque and Gyroscopic Forces - Many pilots talk of engine torque causing the "right wing to dip on takeoff", but this explanation does not stand up under close examination. A discussion of what rotational forces and moments are caused by the addition of power, and a possible explanation of the 'right wing dip" phenomenom: PowerForces.php

Download FLPHG Archive - Now you can download and search the entire Yahoo FLPHG Discussion List. Very useful information in over 32,000 posts over 13 years - EASILY SEARCHABLE in the downloaded form: Archive Download

Modifications and Maintenance

Glider Rack - When I got a newer vehicle, I discovered that the front end was all plastic, nothing to attach a glider rack to. Here was the solution I finally came up with: Glider Rack.

Video Camera Mount - I have played with mounting cameras on the wing-tip now and then, but never found a suitable arrangement until recently, when I used one of my earlier Video Cam Mounts with a New HD Helmet Cam

Red Head Conversion - The Red Head is a cylinder head modification developed by Hidden Mountain and offers a significant increase in performance. There was some impressive data to prove it posted on the former Hidden Mountain site, but that data is no longer available. In 2008 Distribution of the Red Head was taken over by Stephen Wolf ( ) of Tailwind Technologies. I took delivery of one of Stephan's first units - here are the details of the Red Head Installation

NOTE: In the years since this was first posted a number of pilots reported engine failures (piston seizing) using the Red Head modification. I don't know how common this was, but it appears to be out of production now. Mine is still working OK, but I am careful to monitor the head temperature and not run too long at full throttle. Even if you are not interested in this modification, the link above shows some useful disassembly illustrations.

Electric Start Conversion - Photos and text about converting the Mosquito NRG to Electric Start. Many units now come with electric start, and there is also a dual (manual and electric) start option. Even if you are not doing a conversion, this link provides useful disassembly information.

Clutch Disassembly - A photo series showing the parts and dis-assembly of the Radne centrifugal clutch.

Electric Starter Disassembly - a photo series showing the parts and disassembly of the Radne electric starter.

Walbro WG Carb Disassembly - a photo series with diagrams and explanations, showing disassembly of the Walbro WG Carb. See section below for more Walbro information and resources.

Gerry Farell - Explorer Modifications - Gerry was active in trying many modifications on his Explorer harness. Most of them involved the Radne engine, so they should apply to most flphg units. Gerry is not currently active, and the links below are archival copies of his pages - I have not been able to find them currently posted anywhere else. I've put the last know working URL's below for reference.
These are some good detail photos showing carb setup and fuel-line modifications: Explorer Modification Archive Page
And this is a throttle plate modification to improve idling of the Radne. I have done this modification and it works well: Idle Adaptation Archive Page

Here is a pdf version of Gerry's info, with added notes: http://www.elpasoparagliding.com/ppgtechinfo/top80/hrservicenotes/walbrowg8/GerryFarellmods.pdf

These are the last known links for the archived pages above:

Large (225) Falcon Glider Modification - Marked up Wills Wing Falcon drawing showing modification notes: Falcon 225 details drawing

Dual Tank Setup - A second fuel tank is a Mosquito option (presumably the same general method could be used for other makes too). The vented gas cap on the single tank is replaced with a different cap that has a hose attached, with the same sort of quick disconnect used on the harness. This attaches to the fitting on the second tank. As fuel is drawn out of the first tank, the resulting vacuum pulls fuel out of the second tank, until it is empty. This shows the setup, as well as a mistake to avoid - forgetting to open the vent on the second tank: Flat Tanks. The red arrow points to the plugged vent line. Over half the fuel from each tank had been burned, and the engine was still running.

Platform Launching - Here's another way of launching if you have bad knees or only rough fields available. It's a modification of the ATOL type platform tow launch, except you don't need a long field or winch, or winch operator: Platform Launching

Wind Drifter Testing Laboratory - It's not fancy, but it was easy to rig up. I plan on using it for comparing different props and gearing. A 7 foot long piece of PVC pipe transfers the thrust from the bottom of the harness boot to the Thrust Measurement Device (the fact that it looks just like a bathroom scale is purely coincidental :) WD Testing Lab

Keel Attachment Piece - Most people just use a tubing sleeve, (either inside or outside) of the keel to make the keel end removable. But if you have just gotten a new metal lathe/mill set, like I had, then you might get carried away with something fancier: KeelAttach.jpg This started out as a solid bar of aluminum, machined to a tube. The pop-up button started life as a brass pipe plug. The slot machined in one end is to allow the bracket to be inserted into the keel past a bolt that attaches cables. A pop-rivet attached the bracket to the keel extension.

Technical Tips - This document contains a collection of useful tips and information compiled by Ben Rembalski and posted in the Yahoo Groups FLPHG List Files section: TechnicalTips.pdf (160 kB) Ben updates it from time to time, so you may wish to check the URL at the beginning of the document to see if there are newer versions available.

Technical Tips2 - This site contains a collection of useful technical tips (former non-working link) for the Mosquito harness and Radne engine. NOTE: this site appears to have been taken down. The URL I have is http://www.woodleydowns.demon.co.uk/TechnicalIssues.htm -
Viktor Placek was kind enough to locate an archived version in http://web.archive.org/ and combined it into a single page: Technical Tips 2-from Archive

FLPHG Manuals

These are what I have so far. If you have a manual you would care to contribute, please contact me (see bottom of page)

Mosquito A10 (Older Model) - Thanks to Garry Lee for this manual scan. MosquitoA10Manual.pdf (1.1 MB)

Mosquito NRG Manual - this came with my NRG in 2001. It says there would be a new manual in a short time, but I have not seen it if a new one exists: NRGManual.pdf (3.5 MB)

DoodleBug Owner's Manual - DBManual.pdf (10 MB)

Explorer Manual - thanks to Gerry for this one: ExplorerManual.pdf (6.0 MB)

Raven Owner's Manual - RavenOwnersManual.pdf (100 KB)

NRG Spare Parts List - This is also available directly from the Swedish Aerosport website: NRGSparePartList.pdf (3.3 MB)

Radne Engine Resources

Radne Engine Manual - A complete scan of the Radne Manual in Adobe pdf format. It is approximately 2 MB in size. If you do not already have it installed you will need the Adobe Acrobat Reader to view the file. The engine diagram in this manual is for the pull-start model. Here is the Electric Start Engine Diagram

Radne Factory - Radne produces lightweight 2-cycle engines. The 120cc model is currently used by all of the power harness manufacturers. They have a nice online store and catalog:

Spark Plug Cross Reference - Check out this chart to find a local replacement for your Radne spark plug: http://www.nology.com/chart.html The NRG uses the Nippon-Denso #W22MP-U

2-Cycle Engine Animation - This is an excellent animation and description of how a 2-cycle engine works, including the role of the expansion chamber in the exhaust. Note that the animation shows a Reed Valve between the carb and crankcase. The design of the Radne is slightly different in that it uses a "piston ported" design which does not incorporate a Reed Valve.

Radne Power Curve - These KW vs RPM power curves were supplied by Radne for the 120 Aero engine. You have a choice of either the original Microsoft Excel Spreadsheet or printed in an Adobe pdf format file. (Note: 1 KW=1.341 HP; 10.21 KW=13.7 HP) Here is another version of the plot which shows Power and Torque in both metric and English units.

Fuel Information - The EAA (Experimental Aircraft Association) has extensive information regarding the differences between automotive and aviation fuel, and considerations for their use in aircraft: http://www.eaa.org/education/fuel/index.html

Walbro Carburetors

This is a collection of Walbro carb information from a variety of sources. The Walbro WG6/8 (Radne part # 32048) is standard on the Radne 120 Aero engine used by the majority of flphg units.

Walbro WG Disassembly - a photo series with diagrams and explanations, showing disassembly of the Walbro WG Carb

Walbro Metering Lever Height Gage - The official Walbro gage for setting metering lever height. You can print it an cut it out, or simply use the dimensions shown. To print it, be sure "page scaling" is turned off in Adobe Acrobat reader WalbroGage.pdf

Walbro Service Manual - Disphragm Carburetors
- Thanks to Gerry Farell for this contribution. This large download (5.8 MB) is also the most comprehensive, with 33 pages of useful information: WalbroServiceManual.pdf

Walbro WG Carburetor - Here are diagrams and parts lists of the Walbro WG carb obtained from different sources:
This image from Greg Dewenter:
Exploded view and parts list
1. WalbroWGListFig1.zip received from Riaan Olivier of Sperwill ( http://sperwill.com ) - these are scanned from a Walbro manual
2. WalbroWGListFig2.zip which were originally copied from a Spare Parts pdf document found on a UK Power Tool website: ( http://www.partner-uk.com/ - the link to the Spare parts document no longer works, but is provided for reference. The figures are in the zip file, however. The Power Tool Website link still works) The numbers in the list and figure are different from the Walbro numbers, but can apparently be used to order parts from this dealer. The schematic and list figures are only useful when used in the proper pairing, which is why they've been separated into two separate Zip files.

Wallbro Troubleshooting Chart - walbro_chart.jpg

Walbro WB Carburetor - Thanks to Riann Olivier ( riaano@sperwill.com ) of http://www.sperwill.com for providing this copy of the WBmanual.pdf (800kb) Riann also provided this photo for identifying the difference between the older and newer WB/WG diaphrams: WB_MeteringDiaphram.jpg The older style diaphragm has a button which allows easy bleeding of air from the fuel lines, the new one apparently does not.


Here are a variety of useful calculators and conversions:

Units Conversion - a very handy (and free!) utility to convert between almost any sets of units. It sits on my desktop and is used quite often: http://www.joshmadison.com/software/convert/

Density Altitude - "Density Altitude" is a single number which effectively combines the effects of true altitude, temperature, humidity and barometric pressure. As density altitude increases stall speed becomes higher, engine power is reduced, and more power is required to maintain flight. Below are a calculator for determining Density Altitude and a "Koch Chart" for estimating the resulting decrease in performance.
Density Altitude Calculator:
This calculator is referenced to "standard" sea level conditions which means it will show 100% stall speed at 0 MSL altitude, 59 degrees F, 29.921 in HG Baro Pressure and 0% Relative Humidity. http://wahiduddin.net/calc/calc_da_rh.htm This site also discusses the equations used for these and other calculations.

Koch Chart:
This chart uses the location temperature and "pressure altitude" (which does not include the affects of humidity but does include barometric pressure). By drawing a line between these two values the resulting decrease in climb rate (as compared to "Standard" conditions) can be found: Koch Chart

Prop Calculators and Information: Prop Performance Calculator: http://www.gylesaero.com/_frames/f_propcalc.shtml ; How to measure pitch on your prop: http://www.mh-aerotools.de/airfoils/propgeo5.htm ; Powered paraglider site with information about repairing wooden and composite props. It is up to you to decide whether you consider this a safe thing to do: http://www.olympicppg.com/

More Calculators: More useful calculators can be found here: http://www.csgnetwork.com/relhumhpcalc.html

Flying Basics and Wing Performance

See How It Flies - An excellent on-line book about all aspects of flight physics and techniques. http://www.av8n.com/how/

Ground Effect: Here is some good technical info on what "ground effect" is and how it works: http://www.se-technology.com/wig/html/main.php?open=aero

Animated Polar Plots -
This page has some outstanding illustrations and explanations of the aircraft "polar plot". It is geared towards light aircraft, but the principles are the same. Very good animations actually showing the differences of flying at different speeds in different conditions: http://www.5c1.net/Glider%20Performance%20Airspeeds.htm

Weather Stuff - Weather is a very basic part of soaring flight, and even when it is not a flying day, learning about soaring conditions has given me an appreciation for all sorts of weather. This is a collection of observations I have found interesting: Weather Stuff

Flight and Engine Instrumentation and Accessories

Tiny Tach - A tachometer is very useful, especially before take off, when you can't decide whether or not the engine is delivering full power. A very popular model in the flphg community is the Tiny Tach: http://www.tinytach.com/tinytach/index.php Note that the "original" only updates every 2 seconds, while the new "commercial" model is every 1/2 second. If the commercial model had been available when I bought mine I would have gotten it instead. The standard 6 foot cable is a bit short, be sure to add a couple of extra feet when you order.

Flight Computers
Quest - flight logging, engine info and more: http://www.activeflightsystems.com/
Brauniger IQ Motor - flight logging, engine info: http://www.brauniger.com/info/english/products/iqseries/motor.html
Jooser Flight Data Measurement - also a solar battery charger: http://www.aerodat.co.uk/

Fuel Gage
An electronic fuel gage for checking the level in your tank. Particularly useful for those setups where you cannot see the tank, as with the Doodlebug and others that have the tank inside of the harness: http://www.microfuelgauge.co.uk

Air Band Radios
- Airband radios are useful if you are flying from or near an airport. There are a number of small hand-held air band radios available now. ICOM's IC-A4 Sport model can be had for under $200 USD. Be warned however, that standard Ham radio type microphones will not work with the air band radios. It took me several months of frustration to finally learn the solution to this. Aerial Pursuits (Australia) was able to describe the problem as being one of a different standard (based on old carbon microphones). All that is needed is to fix the problem is a small pre-amplifier which they also sell: http://members.ozemail.com.au/~aerial/comms/pttccts.htm Once you have the microphone wired, there is still the antenna to consider. Air band radios are AM band, which means they don't have the normal noise suppression of FM (ham radio) bands. That is, the unshielded Radne ignition is very audible. Here is a useful article about antenna connection and placement: BMAA Article on Radio Antennas

Battery Information
- With the electric start, radios, etc., it is likely you will have battery issues to work out at some point. Here is a handy resource: http://www.powerstream.com/BatteryFAQ.html

(updated June 16, 2015)
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