|
|
|
|
|
|
|
|
|
|
|
- althought there is a rumor, that "depron" isn´t commercial standard under this name, and therefore any sustitutes such as strange wallpapers or an equivalent are recommended, it is relatively easy to find.
at least in vienna/austria this is the situation. i presume, that it is pretty easy to find it in any relatively large city. everywhere, where architects and archictectural students live, a lightweightmaterial that is easy to manipulate but non the less stiff is needed for assemblimg architectural models. thus at least in all university cities there is a source for teaching materials where these persons have their depron supply. in shops like this you can get it in plates with thicknesses of 2mm and 4mm (sometimes in 6mm too). it´s cheap and readily available!
|
|    |
|
- throw away every cutting device, you may have bought from modellers-stores or do-it-yourself markets. none of them cut cleanly, nor do they last long. pay a visit to yor nearest medical-supply-shop. buy a surgical scalpel (best from swann morton) and a box of dispensible blades, which meets your approval. in my opinion the blades marked "20" are best suited to our purposes, but there is no harm done in trying out a few others as well.
you will be amazed, how good the jobs of cutting, scratching, separating, model any surface, portioning and so on will be done!
|
| |
|
- paul from graz wrote on 29.02.2002:
if you fail in finding depron use under-wallpapers sold by OBI (greatest D.I.Y. shop in middle-europe) in big plates (~80x125cm), 3 and 6mm thickness. the material is rather stiff and has a preferred direction.
the best to glue is fermacell, a screed-glue! VERY light, indeed. it is yellow, foams gentle while setting and has a high liquidity. small gaps are vanishing. it hardens in 4 to 6 hours.
comment by wolfgang: a similar glue is made by henkel and sold under the trade name: ponal pu-leim.
or spray-glue for wider things, such as covering of wing-cores. let it dry well, avoid accumulations (especially if using styro). i use tesa; if anybody knows of a product not using acetone or gas as solvents, please email :-)
or hot glue: fast and well glueing. you have to watch the temperature, if too hot it will melt depron and styro! it is bonding also on tape, well suitable for glueing servos. its best if you want to build only this afternoon! drawback: quite heavy.
or 5-min epoxi: emergency-repairs, mounting of motors. if you are not in that hurry, use screed-glue (lighter also!).
for covering of whole models package tape (tesa transparent) is best. it increases stiffness considerably and is the best choice for rudder-hinges, to stiffen depron-rudders, to act as a spar on depron-wings (which are fairly indestructible if built with a core of styro), for repairs, as a fixation while building is under way, and so on, and so on..
´till now i´ve built 6 planes as described. they are prooven in low-altitude-flight and aircombat - very stiff, indeed. after an A-10 (2xspeed 400, 8Z 1800, 1.2m) i´m building an OV-10 Bronco(2xPro 480, 8Z, 1.15m).
this year i will start a new project, a Canadair CL-415 (2x480, 2.14:1, 8Z 1800, 1.5m) equipped for inflight filling and emptying of an onboard water-tank.
i almost loose all of the formerly available place, because the things can nearly not been destroyed beyond repair!
|
| |
|
- i found some interesting facts dealing with range problems based on measurements on the homepage of Flugsportverein Siewisch e.V.. i recommend to all, which have a deeper interest into this topic, to study the article with data-logging-printouts there.
the greater the transmitting power, the greater the range (double range however unfortunately means increasing sixteen times the transmitting power).
the larger the antenna efficiency of the transmitting- and the receiving antenna, the larger the range. (short corkscrew aerials with security have a smaller antenna-efficiency then normal lambda/4-blade-antennas).
the highter the location of the transmitter, the smaller is the influence of reflections at the soil and therefore the greater is the range (conclusion: hopefully disturbances can sometimes eleminated through high-hold of the transmitter).
the higher the receiver location the better the range (conclusion: particularly in large distances do not fly deep).
the smaller the minimum-field-strength of the receiver, the better the range (double range via quadrupling minimum-field-strength of the receiver).
the influence of the receiver on the range is thus about four times as large as the influence of the transmitter.
by a certain directional characteristic of the antennas the range becomes smaller or increases.
in search for eleminating of range problems before all examine the receiver and particularly its antenna!
conclusions:
| increase range | decrease range |
| lambda/4 transmitter antenna | corkscrew aerials |
| antenna of model relatively at 90° to antenna of transmitter | transmitter-antenna aims on model or model is flying directly to the transmitter or away from it |
| antenna as far as possible away from conductive parts | rudder-linkage or similar parts parallel and near to antenna (even worser if the linkage is grounded) |
| free mounting of antenna | antenna is within shielding construction units (alu, CFK,..) |
additional improvements
the installation of the receiving antenna along to the rear is not the most favorable installation position, since particularly in the approach flight (where height is additionally low) the antenna shows directly away from the transmitter.
first improvement:- a good alternative which can be realized simply is to install the antenna in a L-shape (e.g. to the rear and at the vertical stabilizer up or along the horizontal tail unit). during the approach directly in the line to the transmitter the bent piece of antenna receives still sufficient. this is however not the wisdoms last conclusion, since there are likewise certain angles with which the signal of the bent piece of antenna will interact with the signal of the remaining antenna and may lead to no output. for more range within the approach flight the method is however completely well suitable.
second improvement:- still more favorable is it to build the antenna lengthwise into the wings, however when circling the antenna points possibly to the transmitter (this happens generally however in larger heights).
third improvement:- it is best to insert the antenna in the model showing perpendicularly up- or downwards (e.g. trailing antenna in slowly flying models, or a sturdy blade antenna).
|
| |
- measure high currents
05.11.2002
|
- particularly in the field of electric flight it is necessary or desirably again and again to measure high currents. relatively expensive devices for this are offered by industry. it is more favorable by far, to do this with house-average devices. and it can easily be done, which is more important perhaps.
theory first:
as the well-known equation U=I*R, known as ohm's law says, with a given resistance [R] the measured voltage loss [U] is direct proportional the current [I].
practice:
thus the only remaining difficulty is, to manufacture an accordingly small measurement-resistance (so the result of measurement is not falsified by itself, e.g. with 0.001 ohms) with sufficient accuracy. for this task you need an approx. 20cm long piece completely normal insulated flexible installation-wire (1.5 to 2.5mm² cu), two of the current plugs you are using in your models, two measuring braids including plugs for your multimeter in the desired length, some heat shrink hoses as well as a soldering iron, tin and two multimeters (one borrowed from a friend. indeed!). during the adjusting-procedure the first device measures the voltage drop, the second the current.
adjustment measurement setup: | 1 cable to measure
2 voltage supply
3 load resistance (blocked motor)
4 measurement of the voltage drop
5 current measurement
|
measure both units at the same time! make sure that by a current of e.g. 4A the indicated voltage loss is e.g. 4,0mV. shorten and resolder the resistance line again again and again till you are satisfied with the achieved accuracy! (my precision resistance line has a resulting length of 8.3cm). after that procedure the measured voltage drop in mV times the factor (in this example 1000) gives the result of the measurement as the current in A.
hp: naturally also "bent" proportionality factors, (e.g. 1,83mV correspond to 5A) are possible. however you would always have to have your pocket calculator to hand or to rescribe a new scale on your analogue multimeter!
seal with heat shrink hoses afterwards and have a universal laboratory resistor, by using it currents of up to the melting point of the flexible cable (briefly far over 100A!!) can be measured accurately, safely, comfortably and nearly free of charge.
|
| |
- cyanoacrylates
19.10.2003
|
- never again clogged caps of cyano-bottles:
lightly grease the neck of the bottle and the thread of the cap before first use! if cap and tip is already covered with cured glue remove it by soaking the parts in a jar with acetone (nail polish remover). after approx. ½ hour the glue will be gelified and is wipeable.
|
| |
- mixing epoxies
19.10.2003
|
|
| |
|
- notice: epp is heavier than depron, epp is more flexible than depron!
- preliminary note
baking paper: virtually no glue adheres to the surface of ordinary household brown baking-paper. therefore it can be used as a separation layer. advantage: dimensionally stable.
plastic clingfilm is also of good use for the same purpose. advantage: self-adhering and flexible.
- machining epp:
- machining with heat
cut with a heating wire, smaller receptacles can be melted using a soldering iron or the like.
- machining without heat:
- cutting:
with a sharp hobby-cutter (preferably a scalpel with a new blade). the cutting edge have to be very plain. otherwise there is a certain danger of telescoping the material (as it occurs when styrofoam is cut).
- sawing:
with metal-sawing blades or jagged knives. it sounds corny, but it really works. the reason is, that the notches separate the fibres within the see-sawing motion. as a result of this, a clean cut over-all is achieved.
- sanding:
use a permagrit-sander or rough abrasive paper.
- millcut:
astonishingly, the material can be millcut by using a dremel or proxxon set at the highest speed.
- glueing:
any pu-glue like "pu-leim" by ponal or "fermacell" screed-cement may be used. pu-glue is easily identificable through during the process of curing (by reacting with the moisture of the air) the glue froths up. curing-time >2 hours, therefore fixation may be necessary (tip: cover the surface with plastic cling film. the pu-foam doesn´t stick onto this material, therefore less subsequent reworking is necessary). curing may be accelerated by adding small amounts of water. thus the glue sets extremely hard and doesn´t stay as flexible as without using additional water. use baking-paper!
pva-glue: i haven´t tested it yet!
rubberlike curing household-glues: (usa: marine-goop, england: shoe-goo, middle europe: fendermender (obtainable in RC-car shops, there it is used for reinforcement and repairs on lexan-car-bodies), bison kraftkleber?). if you know of another usable brand, please inform me!
unsuitable: cyanoacrylates, because they cure to hard and brittle. therefore the joint breaks on bumpy earth-kisses (rumors say, that this, seldomly of course, may occur).
epoxies, because depending on settle-time they either don´t soak up enough and therefore form a weak joint, or they soak up much too much and penetrate the whole material, which causes a break on this (hard and unflexible) area. if you are using epoxy anyway, use baking-paper or plastic cling film.
- smooth out:
if a smoother surface is wanted, smooth the (rather rough and scarred) surface by using a spatula and a suitable filler. i have had good experience with the filler "nie mehr risse" by methylan (a wall-filler material; translates as "no more cracks"). this sets to a flexible rubberlike compound, which is however sandable using my permagrit-sander. useful too for filling missing individual globules of epp.
- fitting of servos in epp-wings:
cut, route or burn a proper receptacle (tight around servo). produce a thick epoxy using microballons. to prevent any leakage cover the surrounding area and the opposite side of the wing with sticky tape. generously apply the epoxy to the bottom and the walls of the receptacle. insert the plastic cling-filmed servo (with as less wrinkles as possible). remove any epoxy, which is pouring out. pin down the servo with a proper weight till final hardness of epoxy is achieved. remove servo. remove plastic cling film. the servo will snuggle tightly into its bed. the same principle applies also to other elements like rudders.
- applying strapping tape:
- pretreatments:
at least the high-stress-areas must be sprayed with 3M universal glue 77 . let it set for half an hour, minimum. the sprayed areas have to have a sticky but dry feel. don´t produce clogs of adhesive. this means, keep the spray-beam movin´. better too little rather than too much!
- covering:
use solely the 51mm strapping tape from 3M. it is recognisable by the bearing-ring, which shows the mark "3M ruban adhesiv scotch® nastro adhesivo scotch® pressure sensitive tape scotch® klebeband" on yellow background. if smaller strips are needed the tape can be cut using (sharp!) scissors. make absolutely shure that no part of the tape is sticking to one of the scissor-blades. invariably the tape makes self-sticking foldings with itself. if this occurs, you have to waste this part.
the tape behaviour slightly differently in the cross- versus the spanwise direction. therefore follow the taping-proposals given by the producer of the kit. if applying the tape crosswise to flight-direction, due to the orientation of the joint-edge begin aft.
stick with 5mm overlap minimum. if this is not allowed, you will encounter bursting of the interlocked compound at exactly this place in case of a harder soil-contact. make shure you apply the tape crinkle- and wrinkle-free and make as few cuts as possible.
it pays to give some tought to the way the fibres are running before doing the glueing.
don´t build up overlaps with more than three layers.
because of the relative weight of the tape, use less rather than more.
during application don´t pull too much, you will catch a warp! rub the tape, and use a cloth to do so. skin produces too much friction on the plastic!
if any warping occurs, redo the strapping; any hope for subsequent ironing out remains a hope!
cover the upper- and underside of the wings alternately.
after finishing applying the tape, iron it on (temperature <=150°C, ~ 300°F). the tape will shrink slightly, tighten, lay itself (relatively) uncreased around curvatures and stick considerably better afterwards.
on difficult places rub the iron for a longer time. make shure you keep the movements towards the edges of the tape, otherwise you may accidentally slide the last piece onto itself.
avoid prolonged contact of the iron with one particular place, it may burn the tape.
during ironing-on think about the fact, that both the tape and the epp underneath are softened by applying heat. so the danger of causing warping is immanent.
should this type of ironing not settle your claims (especially on complex curvatures as on the extreme tip of fuse) increase slowly (in steps of 5°) the temperature to the max. of 170°C ~ 340°F! have in mind, that this temperature is capable of easily melting all of the used materials, including possibly used balsa :-). a dent emerging out of this is virtually not repairarable. hence, it is better a to leave a spot on the plane that does not look so perfect than a ruined model! using higher pressure and ironing longer is better than using higher temperature, as has been prooved. use cotton socks on the iron. rubbing the tape with a cloth immediately behind the iron whilst the materials are still warm has the advantage that the softened glue sticks even to lower patches of the epp.
final result: a more rigid airplane.
don´t be surprised that after cooling down the previously absolutely smooth tape assumes a gentle ripple structue along the interwoven glass-filaments. this just happens and cant be prevented!
at this stage it could look like this:
never try to obtain a perfect surface. epp is definitely the wrong material for winning the beauty-contest. | 
|
because the strapping tape isn´t as UV-resistant as it should be for our hobby (which we do in open air in most cases, anyway), you have to cover it!
|
| |
- reverse servo rotating direction
18.04.2005
|
- 2 servos are connected to one outlet of the receiver via an Y-cable and one of them rotates in the wrong direction???
possibility 1: accquire a servoreverser. drawback: increase of used space, of weight, of costs...
possibility 2: invert the position of the servo. drawback: often not possible
possibility 3: change the direction of movement directly on servo! drawback: warranty is over&out!
|
unscrew servo, change both supplies to the motor and both outer connections of the potentiometer. thats it! |
|
|
|
|
|
| ......ban billy, the guy who is responsible for all of our crashes......
.....if linux is making it into private computers, if linux is selfinstalling, let´s give it a try....  |
|
|
