Homepage of Theo Volkers

This homepage presents:


Analysis of the F3B Launch and Speed task

Software: F3B launch and speed task
This sottware is embedded in an excel file and written in a VBA macro. It is written almost 20 years ago. At that time the results matched the actual performance. At present it still gives insight in the effect of variations of the input parameters.

Analysis of the F3K Launch

Software: F3K simplified launch simulation

This software is a simplified launch simulation of a DLG model. It is embedded in an excel file and written in a VBA macro. It can be used to get insight in the effect of change of mass, minimum air drag and release speed on end height.

Article:  "Aerodynamics of a DLG unravelled"

PDF file with said article

Stream NXT

An article written for "Flug + modell-technik" Feb. 1980

with help from L. Boermans and interview with W. Thies (in German language)

 Windkanalvermessung der Eppler Profile E 385 und E 387

Copy of Memorandum M-276. 

Memorandum M-276

This is a preliminary report on wind tunnel measurements performed during my study on some airfoils that were popular around 1977.

The final report has never been finished, but the pictures in the report speak for themselves for all people who are interested in airfoil characteristics.

Eppler 387

Measured Eppler 387 airfoil characteristics from Memorandum M-276

XFOIL comparison

Comparison of XFOIL (default settings) computations with measurements from memorandum M-276

Laminar Separation Bubble Visualization; comparison WT results with XFOIL results

This is a pdf file which shows the results of an oil flow visualization of the laminar separation bubble on the Eppler 387 airfoil and the above comparison of XFOIL with Wind Tunnel test results.

Some interesting links related to RC models 

Homepage of Ornithos

Homepage of De Starthaak

BIGGS large sailplanes interest group

Photographs which highlight my hobby

Start of the F3b Cobra

Landing of the Cobra

Nico van de Burg and Theo Volkers launching the ZEFIER and three proud builders of their team design "Zefier", in memory of Gerrit Versteeg

Alsema Sagitta, 4m span


F3J NAN Explorer1, 3.5m, converted to F5J; the orange one far right on the groupsphoto 2014 F5Jcontest Deventer

Launch Explorer

Launch of my Explorer

Fokker DVII

Fokker DVII 

Tigerfleet Ornithos

Tiger fleet of Ornithos winterproject

Sink rate Analyses for Stream NXT and Nan Xplorer1

Sinkrate Stream NXT

Computed Sinkrate Stream NXT, based on XFOIL analysis on measured wing sections at 1, 34 and 65cm span and estimated parasitic drag.

Corrected version published on 17 June 2020

Sinkrate Xplorer1, 3.5m

Computed Sinkrate NAN Explorer1, based on XFOIL and analysis on measured Mid section and estimated parasitic drag.

My F5J (former F3J), 3.5m span Explorer from 2006 has a mass of 2.4kg. Current F5J Explorers weigh only half this value.

Email Theo Volkers for questions or comment

Last update January 21, 2021