Experimental 12 Build

[skywagon8a]

Trying to do as much research/math as possible to figure out if a short engine mount will allow for a full 2200 pound plane without falling out the back of the cg envelope. opinions here?

Set up a weight and balance program on a spread sheet in your computer. Try different loading scenarios with both the long and short mount engine location. You have some mandatory ballast which you will be carrying at all times..... A battery! Move it's location around from the original stock location to the engine side of the firewall. You will easily be able to answer your question without making any parts.

 

[stewartb]

The benefit of the short mount is centralizing mass. Greater arms fore and aft make a less responsive airplane. For 2200# you’ll be better off adding the heavy stuff in a belly pod. Shove the lighter stuff in baggage. Same as Cub guys do.

 

[DENNY]

Just because it is not my money, I would consider a 0360 over with stock pistons over a 0320 with high compression pistons. If you don't already have a motor do a cost comparison. You can run Mogas with 8.5 -1 and the 0360 performance is noticeable once you break ground. I fully agree with Stewart the belly pod changed everything for flying heavy!!!! DENNY

 

[NWCruiser]

Just because it is not my money, I would consider a 0360 over with stock pistons over a 0320 with high compression pistons. If you don't already have a motor do a cost comparison. You can run Mogas with 8.5 -1 and the 0360 performance is noticeable once you break ground. I fully agree with Stewart the belly pod changed everything for flying heavy!!!! DENNY

We do already have a motor, but are strongly considering the 360 option. Wanna buy a 320 with stock cylinders?

 

[stewartb]

There’s no replacement for displacement. Especially at heavier weights. My nephew built a hotrod 0-320 and lamented that the 0-360s kicked his butt. If you really plan to fly at 2200# you’ll want the bigger motor. Or a 390.

 

[KevinJ]

We do already have a motor, but are strongly considering the 360 option. Wanna buy a 320 with stock cylinders?

Sure, what do you have?;-)

 

[Scooter7779h]

Sold mine 10 years ago. That owner is a member here and he flies the heck out of it. He’d be a good resource to talk to. Not many guys have as much -12 time as Scooter7779H. And look up MikeMCSRepairs’ photo album of the -12 he built for member PA12drvr after he helped finish mine. That’s another very nice -12.

Yes, it has flaps and VGs, Cub tail, Cub gear, etc. Good performing -12.

That’s me. Owned and Been flying -12s since 1978. Stewart’s 53M build I have now is a superb plane and fits my mission perfectly.

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[stewartb]

That’s a very special airplane!

 

[DENNY]

That is not a good flying airplane, it is a GREAT flying airplane!! I won this year at Skwentna because he did not make it in to spank me!! That picture is of a 24/7 365 day of the year Alaska plane/pilot.
DENNY

 

[pa12drvr]

Couple of thoughts / anecdotal stuff without the knowledge or experience of the other posters:

- FWIW, unless you really anticipate a need for the left-side door / access, I wouldn't put it in. Nothing particularly wrong with it, but I've used mine more to do stuff like replace battery, sweep out the floor, etc than any real substantive purpose.
- The flat floor concept is great
- AOSS on 18-Gear is a great setup and helps with the pilot-induced rough-ish landings. I'm unfortunately more familiar with those than I want to be.
- The upped GW is great; would go along with the others and recommend the -360 for a variety of reasons, including that there is no substitute for displacement.
- Make sure the tailcone cluster (is that the right term?) is exposed after covering...helps that area to dry out.
- If you're in a hot area, and if you go with a lot of "glass" on the "cabin" planning, you'll need ventilation.
- 18 tailfeathers are a necessity and a very positive difference
- Since you have the weight, upper and lower extended baggage are very nice to have.
- If you can go with some sort of adjustable / constant speed prop, there's some significant benefit to that.
- VG's / Flaps are a game-changer.

The old saying that the best mod is burning more av-gas is very true; I think the challenge is always for the pilot to fly to the limits of the aircraft. In my case, I can't routinely fly to the plane's limits....and building a rip-snorter of an experimental -12 may lead to an identifiable variance between pilot and plane ability, but it would be great fun to work on closing that gap.

 

[skywagon8a]

- FWIW, unless you really anticipate a need for the left-side door / access, I wouldn't put it in. Nothing particularly wrong with it, but I've used mine more to do stuff like replace battery, sweep out the floor, etc than any real substantive purpose.

if you were a seaplane pilot you would find the two door version very useful. On wheels alone, I'll agree with you.

 

[pa12drvr]

if you were a seaplane pilot you would find the two door version very useful. On wheels alone, I'll agree with you.

Absolutely, no disagreement whatsoever. I should have made that clear.

 

[NWCruiser]

Thank you for all this input! As far as the gap between aircraft and pilot ability, someone told me that a -12 will do 90% of what an-18 will do, and you really shouldn't be doing that last 10% anyway.

 

[NWCruiser]

We will be on floats for half the year, big tires for the other half.

 

[Scooter7779h]

if you were a seaplane pilot you would find the two door version very useful. On wheels alone, I'll agree with you.

Having had a -12 for 34 years with a single fold up right side door and now 10 years with current -12 I completely disagree. I LOVE having two doors, and I fly exclusively on wheels and skis although Stewart flew it a lot on floats.

Reasons are access and ability to load unique size and shaped cargo. I leave hydraulic wheel ski pump in year round (on wheels with handle removed) and it’s on the floor on right side. I’d either have to remove and reinstall each season as its a bit in the way. I can be in and out of the left door in two seconds as flap handle is moved forward and out of the way. Loading to passengers in rear seat? Easy with 2 doors they don’t have to play “Twister” trying to get seated and buckled in. Weird loads, no problem as you can load with both doors open and finagle things in. I can load and carry a complete Honda 90 3-wheeler in one load. No way that’s going in with a single door. I’ve carried shower stalls, long shaft outboards and other big/bulky weird stuff. All which is strapped down to cargo rings that are very easy to access with both doors open. I challenge you to find anyone that has really worked both a single door and double PA-12 or PA-14 who would say it’s not worth it on wheels or skis. YMMV.

Thank you Stewart and Mike MCS (Skup) for doing all the mods of doors, removable cross-bars, seats, cargo rings and interior to make it such a versatile and capable -12.


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[stewartb]

My favorite part of the full double door is the view it provides from the back seat. With the shape of the -12 airframe the plex on both sides allows the rear seater to see forward, down, and sideways. My new Cub mimics that detail without the left side door. Plex is heavier than fabric but the open feel and great visibility is worth every ounce.

 

[skywagon8a]

- FWIW, unless you really anticipate a need for the left-side door / access, I wouldn't put it in. Nothing particularly wrong with it, but I've used mine more to do stuff like replace battery, sweep out the floor, etc than any real substantive purpose.

if you were a seaplane pilot you would find the two door version very useful. On wheels alone, I'll agree with you.

Having had a -12 for 34 years with a single fold up right side door and now 10 years with current -12 I completely disagree. I LOVE having two doors, and I fly exclusively on wheels and skis although Stewart flew it a lot on floats.

Like pa12drvr said, "Nothing particularly wrong with it" which is what I am agreeing with. My Cub has two doors by choice.

 

[stewartb]

If you do two doors in a -12 you need to think about how to introduce ventilation air. It wouldn’t be hard to make an opening window in a seaplane door but I’ve never seen one done. The choice for high quality vents is very limited. Something similar to a Cessna fresh air door could be handy. Pressurize the heat ducts with cool air. That could pay dividends for winter heat, too, like in a Cessna. Hmm, that could work.

Another “should be” simple vent solution would be to add Cessna-style vent tubes in the wing roots fed by a small intake hole in the leading edge. I need to look into doing that myself.

 

[pa12drvr]

I think the (2nd) Original Poster has got all the information needed on the left door :smile:....but FWIW, I guess that my thought as a non-seaplane user is that the utility needs to be compared to the weight penalty. I don't know what the weight comparison is for door vs. fabric and, certainly in my case, the easiest place to reduce weight is in the pilot's seat rather than anywhere else.

With the 2nd OP's higher GW, the weight savings / penalty of the left hand door are probably more than offset by the utility, but, like everything else, best to do that evaluation before the build is 75% or more complete.