Harer Gross Weight

[Pearson]

I was having a conversation with Chuck Avon and the subject of the various options associated with the Harer STC came up. I was under the impression that the only way to be able increase the gross weight to 1500 lbs is to use the long mount to move the engine forward. Is this true, or is there a way to keep the short mount and increase the gross weight to 1500 lbs?

[T.Taylor]

Re: Harer Gross Weight

I was having a conversation with Chuck Avon and the subject of the various options associated with the Harer STC came up. I was under the impression that the only way to be able increase the gross weight to 1500 lbs is to use the long mount to move the engine forward. Is this true, or is there a way to keep the short mount and increase the gross weight to 1500 lbs?

Looking at the TCDS, the BC12D-85 shows a GW of 1280 for the land plane, and a short mount, noticable by the oil is at -21, while the BC12D-4-85 is the same GW, but the oil is at -30, so I think it is showing a long mount starting with the BC12D-4-85 and the Model 19 has the long mount with the 1500 lb. GW, hope this helps, Tom

[Robert Lees]

Re: Harer Gross Weight

...is there a way to keep the short mount and increase the gross weight to 1500 lbs?

In short, no.

[barnstmr]

Re: Harer Gross Weight

The STC is approved with the 1500 lb max. wt ONLY with the model 19 equivalent configuration which includes the extended engine mount and the extended baggage. HOWEVER. That is not to say it cannot be done. I am aware of at least one airplane approved at 1500 lb max. wt. with the short mount and C85-8. But the approval was done as a deviation from the STC and approved under a separate "field" approval.

[Pearson]

Re: Harer Gross Weight

OK, that is good to know. Thank you for those above who responded. I spent a good while on the phone with Chuck Avon talking about his conversion from the A65 to the C85. He was kind enough to share his entire album of photos taken during the change over. It is good to get ideas from others who have gone before you. His plane is what I am hoping for on my project bird, with one exceptiion. I am going to have to use the long mount to get the 1500lb gross weight. I know it affect the handling in a negative way, but I have flown an F19 and found it to still be a good flying airplane. It isn't quite as good of flying plane as an original BC12D with the A65 engine. But the slight degredation of handling characteristics is well worth it to be able to legally go up to 1500 lbs gross weight.

[Robert Lees]

Re: Harer Gross Weight

The STC is approved with the 1500 lb max. wt ONLY with the model 19 equivalent configuration which includes the extended engine mount and the extended baggage. HOWEVER. That is not to say it cannot be done. I am aware of at least one airplane approved at 1500 lb max. wt. with the short mount and C85-8. But the approval was done as a deviation from the STC and approved under a separate "field" approval.

I'm just a raggedy pilot looking after my cg, and I assume the person approving that field mod did not know what he was letting himself in for.

The basis upon the 1500lb approval was little to do with structural differences, rather the volume of space available to fit the additional load into the airframe (i.e. extended baggage). At (say) 800lb empty weight, I'd struggle to fit 700lb in, unless I were smuggling gold bullion!

The problem with an extended baggage compartment is the effect upon the already rearward-prone cg tendency of our beloved craft, so Jack wisely put the existing C85 engine on a 4" longer mount to counter this.

It's your STC now, Terry, so you of course call the shots, but I would not like it to be done.

I have actually flown one with an A65 to 75 conversion, short mount, with the extended baggage compartment (empty) and it was VERY tail heavy even then (it caught me out) and that was without any load therein (it's now in for rebuild, so that situation will not recur with this particular airframe).

Do you have any photos of Fred flying in TRex with his (large) dog in the back?

[barnstmr]

Re: Harer Gross Weight

Robert,
I did not say that C.A.P. supports or condones anyone who may have the 1500 lb. gross weight on an airplane with the short engine mount. I am acknowledging that some have done so via a SEPARATE approval, NOT part of STC # SA1-210. C.A.P. does not and will not support such a deviation from the STC.

[Robert Lees]

Re: Harer Gross Weight

That's what I was trying to say, Terry...I am sure anyone who studies the STC will understand that the 1500lb gross weight is only applicable with the long mount. I'm sure we're in agreement!

[Carrieve]

Re: Harer Gross Weight

I have a long mount on my '46 with the 85 -12. I have never flown an 85 with the short mount but mine seems to fly just fine. I can load a 100lbs behind the seat, two people and 24 gal of fuel and it still flies great. A little bit longer take off run other than that great travel plane.

[flyguy]

Re: Harer Gross Weight

Why would a 12D with an 85 on a short mount (without any baggage on board) be tail heavy? Engine is forward of CG and weighs a little more. Is the empty baggage compartment that heavy?
DC

[Acroeric]

Re: Harer Gross Weight

My old BC12-D N96035 had the C-85 on a short mount and it had the large baggage area. I have to admit to flying it with a little too much weight back there just once. It flew fine, cruised faster but the elevator was extremely sensitive. I recognized it immediately and flew a very conservative flight, wheel landing it at my destination. I was well within gross but a good bit aft of the limits.
My Clipwing is set up so the CG is AT (not past) the aft limit most of the time and it does great. I can tell a big difference in the way it snaps the farther aft it is. Past the aft limit is a bad idea and with the short mount and large baggage it is VERY easy to get it there.
The extended baggage in itself adds a little weight depending on how it is done but should not result in an aft CG without putting too much stuff back there even with a short mount.
Stick with what Terry is saying- he knows the STC better than anyone.

[Pearson]

Re: Harer Gross Weight

I am going to stick with the STC. The question only came up because I was admiring Chuck Avon's C85 installation and he mentioned he had a short mount. I want to build my project plane as sort of a poor mans bush plane with large tires, more powerful engine, and large baggage capacity. There are fishing holes here in the Pacific NW you can't get to very easily unless you have a "fishing plane". Anyway, that is the idea. I did as the drawings said and have whittled down 1/4" thick boards for each side to glue fabric to. I will have 3/16" plywood with aluminum glued to it for the floor, front and back of the baggage area. I have a piece of corrugated plastic for the top. I just haven't quite figured out how I am going to wrap it up the front end of the top of the baggage area into the wood crosspiece.

[Robert Lees]

Re: Harer Gross Weight

I am going to stick with the STC. ..."fishing plane"....

Richard, I've seen our sort of aeroplanes with a tube all the way down the back for fishing equipment (I reckon a 4" diameter plastic drain pipe or similar). (I've also seen certified aeroplanes with ski racks like that; Beech Bonanza springs to mind).

I suppose if you have a 15 metre carbon rod (pole) for fly fishing you could stick the end of the rod out of the aft end of the fuselage; it'ld make a good lightning conductor!

[flyguy]

Re: Harer Gross Weight

Thanks for the comment on the 85/short mount Eric. My 12D is that way and I couldn't quite understand the one comment here that putting a 85 on a short mount would make for a tail heavy condition, without any baggage. I was thinking that perhaps I was missing something that might be significant considering that the last 2 father/son IA/previous owners, for sure, faked the weight and balance on mine.
DC

[barnstmr]

Re: Harer Gross Weight

Battery placement is also critical. I noticed Chuck Avon installed a battery box on the firewall. With the short mount, this is likely just fine. But if you did that plus add a C85-12 on the long mount, a metal prop, starter, alternator... your engine installation can get pretty heavy. And if you use the old Delco generator and prestolite starter, you have a nose heavy situation. Think about it.... when Gilberti established the STC, none of the lightweight starters and alternators were available. Therefore, the STC configuration B (with long mount and -12 engine and large baggage compt.) calls for the battery at the aft most part of the baggage area. I always recommend that STC customers save the battery mounting location for last when installing the STC with electrical system. Install everything else first and then weigh the airplane, compute the Empty CG. And then I recommend running the numbers to see which is the most adverse loading configuration. Finally, place the battery as needed to offset any adverse CG circumstances. You should be able to nail the CG wherever you want to by doing it this way.