Porterfield Airplane Club

Keep the Skinny Birds Flying Safely

Hi All,

Our CP50/65 G-AFZL is ready to fly following rebuild, trouble is we have a weight problem! It looks like we've gained over 100lbs in empty weight over the factory figure, which will mean that we might only be able to get her certificated as a single seater or have severe restrictions on payload (a good excuse to lose some personal weight maybe).

I find it difficult to see how we could be 100lbs overweight, although I do realise aircraft do gain weight over the years, but not that much, especially as the fabric covering is now lighter.

We will weigh her again to see if any errors have crept in, in the meantime I would be grateful for any of your empty weight figures so I can get my head around a solution - this will probably include removing the wheel spats (pants), the generator and paring down the interior even more than it is already.

Also it would help if we could get the airframe re-classified as a CP65 as the MAUW is about 25lbs higher. My observations over the years are that there is no structural difference between the CP types, can anybody put me right on this? I don't believe that Porterfield would have bothered to beef up the airframe to take the extra 15hp of the A65 engine.

Any help appreciated, otherwise it's going to be a bit lonely in the air in future.

Cheers everybody

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Comment by Andy Gelston on November 5, 2014 at 1:23pm

My "skinny bird" is one of the more corpulent Collegiates at ~820 pounds empty, as she has a Franklin 90 up front, though no generator, battery and electrical system, nor spats.  She has, however, had all the seaplane mods made to her, per TCDS 720, giving her a gross weight of 1320 pounds.  I realize it's a bit late for you to be adding tubing to your landing gear vee and 3/32" plywood to your rear spar, etc., so you'll probably have to perform some triage on your accessories, or resign yourself to being a lone eagle.

Joe Rankin wrote me a letter stating that there is no difference in airframes between the CP, FP, and LP series of aircraft, when some knothead at the FAA voiced his mistaken interpretation of TCDS 720 that only a CP-65 could be modified for the seaplane configuration.  Perhaps, for a modest fee, Joe would write you a similar letter about the dearth of structural differences between the CP-50 and the CP-65.

Soft landings,  Andy

Comment by Olivier Duque on October 19, 2014 at 3:05pm

Hello,

Sorry, I do not have answer regarding maximum mass of a CP50 Vs CP65.

It's  strange because I understand that engine weigh is the same.

1940 CP65 Collegiate original s/n 720 weight was 732 lbs (332kg). In addition to this weight, "optional equipment" were approved for 38,8lbs (17,6Kg). Aircraft is now equipped with these options (brakes, compass, carpet, heater, primer, wheel pants…).
1940 weight amount would have been  771 lbs (349kg) for  maximum mass at 1200 lbs (544kg).

Please see original M&B

A very accurate weighing just completed this month with French standards (no gasoline and full of oil) at 815.71 lbs (370 kg )

Plane took 44 lbs more with years and I can not find where and why...

Regards

Olivier

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