Jim, The service bul # 57 goes on to say " Removal of aelrion balance weights is not mandatory, but is recommended for all Ercoupes Model 415C,415D,415CD,E,andG. The weight of the parts removed totals 3.55 pounds and their CG is 55.5" behind the Datum line." See #56 for proceedure on checking play. ( Note that the service bulletin suggest that if there is excessive play, then one might induce aelrion flutter. Flutter develops very quickly, and often destroys the control surface, causing loss of control of the airplane)
As to metal props/wood props, be careful when changing . The metal prop weighs considerable more than the wood prop, and for the coupe to stay in Balance, a weight must be added to the tail cone (just under the cover) to offset this additional weight. (My coupe has a3.5# weight installed. It is molded to fit exactly along the mounting bolts of the rear former.) As to the nose wheel shimmy. If the nose wheel is in balance, and the wheel bearings are not worn, then the shimmy is probably due to loose linkage in the sissors assy. The bolts holding the assy are often left loose to allow the sissors to move freely. The proper proceedure is to tighten these bolts properly so that the bushing in which the bolts pass, move as bearing. The bolts and special washers lock the bushing in place, making the bushing turn, not the bolts. This should correct the shimmy, unless the bolts have been left loose enough so that they no longer can eliminate the play. In this case, additional repairs must be made to the sissors assy to regain the proper bolt hole size, etc...... I have often read that the conversion to metal covering on the wings adds about 40# weight. I don't have a reference to show that, but the STC from SkyCraft Design; Met Co Air, and all the other STCs should state the added weight. I, too think that the weight of fabric and dope probably equal the weight of 0.020 " alunimum sheeting, but I really don't know. Certainly a Weight & Balance calculation should be done for any change in the airplane. WHILE THE COUPE IS A VERY FORGIVING AIRPLANE, IF ONE EXCEEDS THE FORE AND AFT WEIGHT LIMITS IN WEIGHT AND BALANCE, THEN ONE IS FLYING AN EXPERIMNENTAL AIRCRAFT AND YOU ARE THE TEST PILOT. This is illegal, unless you are licensed to do so, and probably cancels all insurance, etc, etc... Nuff said? Fly Safe - Have Fun Regards, Harry Francis 93530 Blacksburg, Va.
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