A Collection of R/C Modelling Tips - RC World

Now that is dune you must have a Backing plate or Flange that comes out about an inch directly behind the surfaceyou just molded into place. This will be used for the Mold that we are just about to make. This will become the rimof the mold. It gives it strength and also a great place to have splash over of the resin.Now we have a Fuselage with a fake cowl on the front of it. NOW is the time we start to make a Mold forthe real fiberglass cowl. This also has steps you must follow.1. You must get a Releasing agent. this comes in two types a wax and a type of paint on film. Theyboth act as a separating film between the Hardened surface and the Resin you are about to apply.( A type of condom if you wish to see it that way :-) No surface should not be with out this filmbecause if there is no film the resin will stick to it like :-) Glue. To get the releasing agent go to yourfiberglass supplier and ask there. As for the wax, do not leave big lumps of wax on the surface.... itis a thin film....2. it is best to have apposing reasons when designing a mold. You have to make a decision. Do youwant the cowl to be made of Epoxy or Polyester fiberglass ? if you want an Epoxy Cowl you makethe mold of Polyester and Visa-Versa.3. Make the first batch of resin to cover the howl surface ( Don’t be bashful use a lot ) and wait till itjust gets that stage before it is take to touch( If you wish use a heat gun to spread it up a bit ). Nowmix the reason ( Same type ) to layer on with the fiberglass.4. Leave to set .... There you are you have a Mold.... Just take it of and remove the back Cowl fromwithin it.Now we have a mold what about the Cowl that we want to make ? it is exactly the same...5. Coat the mold with the releasing agent just like above.6. Cut the fiberglass to a pattern so it will lay in the mold nicely.7. If you made the mold out of Polyester reason the cowl will be of Epoxy. and just like above.8. Make the first batch of resin to cover the howl surface ( Don’t be bashful use a lot ) and wait till itjust gets that stage before it is take to touch( If you wish use a heat gun to spread it up a bit ). Nowmix the reason ( Same type ) to layer on with the fiberglass.9. and now put the fiberglass and reason around the sides.10. Once it is dry and has hardened simply take the cowl out of the mold. it might be hard at first but itwill separate.Why Down Thrust ?Lift is proportional to velocity square. For airplane with non-symmetricalairfoil, say, the Clark Y, will going up too much with power up (evenwith zero angle-of-attack) if no down thrust, so you need some downthrust to compensate this. Not only Eagle2, many other trainers also needdown thrust. Hope this helps.The reason:Since it is a flat bottom airfoil with a lot of positive incidence, thefaster it goes, the more (LOT more) lift it generates. The down thrusttries to compensate for this by pulling the nose back down as throttle(and speed) increase. It would be a lot better to design trainers with alot less positive incidence in the wings and make it fly more neutral.If the down thrust was lessened on the Eaglet, the plane could do loopsjust by application of throttle.Or rather, the difference in incidence angle between the wing and tailon this type of airplane is high. True incidence should be measuredbased on the zero lift datum line (i.e. the datum line that defineszero lift when it is parallel with the direction of flight). Flatbottom airfoils have to point significantly nose down to generate no