One piece belly

[Shadrach]

58 minutes ago, FlyingDude said:

I thought that was due to the materials used, not the oneness. I haven't seen a one piece yet, so I don't know if the fasteners that run laterally are still there. 

I would do the labor (under supervision) so to me, it's like suffering for 2 days one time but then never worrying about spending hours on the bottom panels in the future.

it is due to the materials. 10K for a one piece belly has to be the pinnacle of ridiculous aviation investments. It's not like it's structural.  I personally think the belly panel aching is a bit silly. Yes its a lot of screws. Times are better now with brushless (no spark) power drivers with adjustable torque settings.  The mix of machine and sheet metal screws is a bit annoying but easily remedied by bagging the screws from each panel. It should take about half hour to get them all the panels off. Closer to an hour to put them back (I do a final hand torque). the ROI on a single piece belly does not work in my mind.

[aviatoreb]

So why hasn't somebody made a single belly panel that just screws in where my normal belly panels are - like just one of them - not a one piece - but made of something transparent for radio?  And heck why not carbon fiber or something light while they are at it?  For the purpose of hiding antenna and no other reason, and also to do so without needing to rework the airplane machining in any way to save the majority of the mod labor requirement?

[RobertGary1]

20 minutes ago, aviatoreb said:

So why hasn't somebody made a single belly panel that just screws in where my normal belly panels are - like just one of them - not a one piece - but made of something transparent for radio?  And heck why not carbon fiber or something light while they are at it?  For the purpose of hiding antenna and no other reason, and also to do so without needing to rework the airplane machining in any way to save the majority of the mod labor requirement?

I suspect no two mooneys have the screws in the exact same location. These were hand built planes and they’re all shaped ever slightly different 

[Shadrach]

43 minutes ago, aviatoreb said:

So why hasn't somebody made a single belly panel that just screws in where my normal belly panels are - like just one of them - not a one piece - but made of something transparent for radio?  And heck why not carbon fiber or something light while they are at it?  For the purpose of hiding antenna and no other reason, and also to do so without needing to rework the airplane machining in any way to save the majority of the mod labor requirement?

Juice not worth the squeeze unless they made a complete set that was considerably lighter. What's an extra .5kt and a 5lbs of useful worth?  I might spend a few AMUs on panels like that before a repaint but I would not go out of my way. Hard for a producer to get their investment back.

[FlyingDude]

3 hours ago, Shadrach said:

the ROI on a single piece belly does not work in my mind.

Ok, that's fine...

[aviatoreb]

7 hours ago, Shadrach said:

Juice not worth the squeeze unless they made a complete set that was considerably lighter. What's an extra .5kt and a 5lbs of useful worth?  I might spend a few AMUs on panels like that before a repaint but I would not go out of my way. Hard for a producer to get their investment back.

But people already spend a fortune on a one piece.

looking at a subdue panel I just don’t get it / it’s a flat piece of metal.  Why not a flat piece of carbon? Sane size drill your own holes?

[aviatoreb]

2 minutes ago, bluehighwayflyer said:

You could probably do that yourself, Erik, using your old panels as a pattern and without a STC.  Talk to your A&P/IA about it and see if he’d be comfortable signing it off as a minor alteration.  The only way I see it even remotely being worth it, though, is if you can bury a few antennas in the process.  It’s the kind of thing that might be worth it to someone like @jetdriven running races, but it wouldn’t be to most of us.  

That’s the point - burying antenna.  On the cheap.  Is that all it takes?  An ia sign off as minor mod?

I bet it’s a knot or two.  Not worth it?!!

[EricJ]

Those pieces aren't completely flat in either dimension, though, so making them out of anything non-flexible might take some additional effort.  The aluminum panels fit because they flex to fit the attachment contours, which include some cross members for shaping and stiffness.   

[47U]

Burying antennas and reducing the number of screws is secondary to me.  I want the access for inspection and maintenance.

Photo credit to @Sabremech

[hammdo]

David @Sabremech did that. I now have it ;o)

-Don

[A64Pilot]

On 8/11/2023 at 10:25 PM, aviatoreb said:

That’s the point - burying antenna.  On the cheap.  Is that all it takes?  An ia sign off as minor mod?

I bet it’s a knot or two.  Not worth it?!!

In truth I’d be surprised if all the antennas put together were a kt or two.

Most of the drag in an airplane is in its design, in particular I think in our aircraft the tail boom has more drag than you might think, but of course that’s a whole new airplane.

I did what I thought was a real significant drag reduction once, admittedly it was a Crop Duster, but draggy airplanes are easier to reduce drag on than clean ones.

I really expected to get 5 kts or so, now I did get that later, but it was a very modified aircraft with a 10” longer engine mount which removed 200 lbs of weight and a large reduction in frontal area, but that was a whole different airplane, a clean sheet re-certification with its own type data sheet.

Long story short I increased parts count, reduced serviceability and the difference was not much, hard to quantify, so of course 90% of what I did we dropped, some of it we kept based largely in truth because it looked better, more modern and clean, until the new aircraft.

Drag is in the darndest places, by a large margin I believe most of the drag we could significantly reduce is cooling drag for the motor, by we I mean the Industry, not we owners, because we really can’t replace the tail boom for example, I’ll even go so far as to say that properly designed I think we could eliminate the cowl flaps.

I don’t think carbon fiber is RF transparent, in truth neither is fiberglass, it attenuates signals somewhat, not as much as metal of course but an antenna buried say in the wing tips will lose some performance. Mooney wasn’t stupid if they could have put the towel bars in the wingtips without any loss, why didn’t they?

Be careful with carbon fiber, don’t let it come into contact with metal, it forms a battery and will cause corrosion, so be sure you keep a barrier between the two.

I guess what I’m saying is that particularly in the Modern Mooney’s there really isn’t much low hanging fruit, you could remove the step, but I doubt you could measure the difference, or why did Mooney stop retracting it?

We are I suspect to the point that a kt or two costs at min several thousands of dollars or more per kt, and that’s for the first one or two, after that I’d suspect the price goes WAY up.

I bet though if Hartzell REALLY was motivated I bet they could get several kts. All it takes is to show Joe Brown that another companies prop outperforms a Hartzell.

I’d be real surprised if you could get anything from the belly, I’d have to tuft one to see, but I think the airflow just might not be what we think it is, but it could be you don’t know until you test.

Tufting is REAL easy, just a bunch of yarn, tape and a go pro. It goes faster if you run the yarn full length, then apply the tape and after all the tape is applied, cut the yarn.

[A64Pilot]

On 8/11/2023 at 10:25 PM, aviatoreb said:

That’s the point - burying antenna.  On the cheap.  Is that all it takes?  An ia sign off as minor mod?

I bet it’s a knot or two.  Not worth it?!!

An IA only has to get involved if it’s a major, minors an A&P can sign off.

In my opinion, which means nothing of course, but the belly panels aren’t structural, they are just fairings, so long as you don’t change airflow replacing them with non metal is a minor. AC 43.13 is your guide.

Before I did anything I’d talk to my FSDO inspector, they may or may not go for it, toughest question I think is why do it as in explaining to the inspector. Most of the time you could just do it, record the work in the log book and that’s the end of it, but asking I guess is just CYA.

You can get cured fiberglass in rolls about .020ish thick I think. I had several rolls of it at the plant left from the Ayres days, it’s used in cargo aircraft on the insides of the fuselage, Ayres had it I believe because they built the cargo doors for Fedex’s 727’s back in the day. That could be used to replace belly panels, you might need to glass in reinforcements just like the existing panels, but all your accomplishing is replacing metal for glass.

I thought most one piece belly’s came from gear ups? Just like at least in other aircraft, most three blade props came from prop strikes. Mine did anyway.

[aviatoreb]

37 minutes ago, A64Pilot said:

An IA only has to get involved if it’s a major, minors an A&P can sign off.

In my opinion, which means nothing of course, but the belly panels aren’t structural, they are just fairings, so long as you don’t change airflow replacing them with non metal is a minor. AC 43.13 is your guide.

Before I did anything I’d talk to my FSDO inspector, they may or may not go for it, toughest question I think is why do it as in explaining to the inspector. Most of the time you could just do it, record the work in the log book and that’s the end of it, but asking I guess is just CYA.

You can get cured fiberglass in rolls about .020ish thick I think. I had several rolls of it at the plant left from the Ayres days, it’s used in cargo aircraft on the insides of the fuselage, Ayres had it I believe because they built the cargo doors for Fedex’s 727’s back in the day. That could be used to replace belly panels, you might need to glass in reinforcements just like the existing panels, but all your accomplishing is replacing metal for glass.

I thought most one piece belly’s came from gear ups? Just like at least in other aircraft, most three blade props came from prop strikes. Mine did anyway.

Im not about to do this one.

I was just curious - why anyone would spend 10k plus to go one piece if they are thinking its a speed mod...instead of as I suggested which should do at least the same speed stuff.  Which you say is 1knot or less.  I have no way of judging.  Lasar claims its 6 but that seems like a lot to be likely not true.

[M20F]

I recently learned that the human six pack is a fallacy.  Due to genetics you may only have a four pack or be a rarity and have a ten pack.  No amount of exercise can fix this, we are all born with the belly we have. 

[EricJ]

45 minutes ago, M20F said:

I recently learned that the human six pack is a fallacy.  Due to genetics you may only have a four pack or be a rarity and have a ten pack.  No amount of exercise can fix this, we are all born with the belly we have. 

[A64Pilot]

10 hours ago, aviatoreb said:

Im not about to do this one.

I was just curious - why anyone would spend 10k plus to go one piece if they are thinking its a speed mod...instead of as I suggested which should do at least the same speed stuff.  Which you say is 1knot or less.  I have no way of judging.  Lasar claims its 6 but that seems like a lot to be likely not true.

In my opinion it’s marketing, and well it’s human nature to be proud of their possessions and the desire to fix them up. Same reason I guess some spend thousands on chrome wheels for their cars, fancy paint jobs for their airplanes, nice interiors etc. none of those things increase the utility of the vehicle but if your a normal person you like your possessions to be above average, you get enjoyment when you turn around and look at it when you walk away. I think that attitude is why we get up in the morning, go to work and often work harder than necessary, to have nice stuff. It’s pretty hard to justify an airplane from a logic standpoint though, we have them because we want them, not need them. Most anyway.

Only way to know if there is any speed increase is to instrument an aircraft and fly it before and after, anything else is speculation and even then sometimes you get mixed results. I can bore you with an example if your curious.

If you take most anyones speed mods claims and add the numbers together it’s easy to get more than 10 kts from an airplane, but that’s not usually the case.

I guess I’m playing devils advocate, throwing out the opposite of marketing claims, the truth is probably somewhere in the middle, I’m pessimistic by nature. I find that way I’m not often disappointed.

I’m the guy that thinks if I put xxxxx money into the airplane how much does it increase resale value? Or said another way how much labor saved is this $10,000 mod?

By the way does it cost $10K or is it $10K all in, installed and painted? 

I look at the belly of my airplane and just get the belief that there just isn’t that much drag there.

It’s real easy to see where lower wheel pants would significantly reduce drag, but take them off and fly it and see. I did out of curiosity or actually left them off when I changed tires and at the speeds I fly just didn’t notice really any difference, but I put them back on anyway, maybe should have left them off because I do think they are harder on the landing gear mechanism, but that’s another unsubstantiated belief.

[1980Mooney]

10 hours ago, aviatoreb said:

Im not about to do this one.

I was just curious - why anyone would spend 10k plus to go one piece if they are thinking its a speed mod...instead of as I suggested which should do at least the same speed stuff.  Which you say is 1knot or less.  I have no way of judging.  Lasar claims its 6 but that seems like a lot to be likely not true.

I think a lot of the claimed speed gain comes from relocating antennas inside the  belly so that the exterior is completely smooth. Lasar historically was a credible source- not a “BS” marketing promoter. 

[Shadrach]

1 hour ago, 1980Mooney said:

I think a lot of the claimed speed gain comes from relocating antennas inside the  belly so that the exterior is completely smooth. Lasar historically was a credible source- not a “BS” marketing promoter. 

All of the claimed speed comes from the relocation of antennas.
 

LASAR is pretty optimistic with their speed claims. Adding all of the claimed gains from all mods available for my F works out to 26.5kts. That would make it a Mooney 207…

[A64Pilot]

I’m not saying they are BS, but 6 kts is a lot and well to some extent it depends on how you test.

I think Mooney was a credible source and not a BS marketing promoter, I think they likely did get 201 MPH out of a J, but mine doesn’t come close, I doubt many do.

Every bit of these guys claims are true, the pressure cowl does everything they claim, they aren’t lying

https://www.cacaircraft.com/pressure-cowls

I flight tested an aircraft before and after their pressure cowl installation and confirmed their claims.

But here’s the thing, that big air scoop produces drag, and therefore slows the airplane down, so if you increase engine torque to recover lost airspeed, your fuel consumption increases, your torque increases, same for temps to about the same as before installation. But it takes more torque to fly the same speed and since at crop duster altitudes your torque limited not Ng speed or ITT, in the flight levels your Ng limited or possibly ITT so you need the pressure recovery inlet, but Crop Dusters don’t often fly in the Flight Levels. So in the real world your slower because you can’t overtorque.

See they set torque the same for their test and got good numbers, if they had instead have used airspeed as their test point their advantages go away.

If you take an unmodded aircraft and fly at the same airspeed as one with the pressure cowl, guess what? Tq, Ng, ITT and fuel flow are about the same because the decrease in drag results in lower torque required.

So their numbers are real if you use torque as the test point, but not if you use speed.

However back to my Mooney, I doubt every antenna put together could be 6 kts, and which ones can you put in the belly anyway? Transponder surely, but what else, maybe Comm? Towel bar ones could go in the wing tips I guess, glide slope is inside the cockpit now, you could replace a fuselage skin with fiberglass and put the GPS under it, or maybe on the glareshield?

But antennas in the belly are in sort of an open ended metal box, so there would be significant shadowing, they wouldn’t work as well as if the were out in the open. The towel bar ones in the wingtip I suspect would though, how much attenuation from the fiberglass? I don’t know but there is some.

[1980Mooney]

On 8/11/2023 at 9:04 AM, FlyingDude said:

I thought that was due to the materials used, not the oneness. I haven't seen a one piece yet, so I don't know if the fasteners that run laterally are still there. 

I would do the labor (under supervision) so to me, it's like suffering for 2 days one time but then never worrying about spending hours on the bottom panels in the future.

 

On 8/11/2023 at 10:13 AM, Shadrach said:

it is due to the materials. 10K for a one piece belly has to be the pinnacle of ridiculous aviation investments. It's not like it's structural.  I personally think the belly panel aching is a bit silly. Yes its a lot of screws. Times are better now with brushless (no spark) power drivers with adjustable torque settings.  The mix of machine and sheet metal screws is a bit annoying but easily remedied by bagging the screws from each panel. It should take about half hour to get them all the panels off. Closer to an hour to put them back (I do a final hand torque). the ROI on a single piece belly does not work in my mind.

Here is another excellent article from KNR with more detail regarding how the mod is actually done.
 

 “you need to plan for one full week on your back under the airplane to complete this job; even more time if this is your first conversion. The retrofit of a one-piece belly on your pre-1984 Mooney is no easy task and it covers all types of work from welding to fabrication to avionics and electrical work.”

”A bit of a warning here: if you are not a sheet-metal-savvy mechanic, do not attempt this job without qualified help, including an experienced gas welder. All bare aluminum surfaces should be zinc chromate primered before riveting.”

https://www.knr-inc.com/shop-talk-articles.html?view=article&id=27&catid=25

[Shadrach]

7 minutes ago, 1980Mooney said:

 

Here is another excellent article from KNR with more detail regarding how the mod is actually done.
 

 “you need to plan for one full week on your back under the airplane to complete this job; even more time if this is your first conversion…

After reading the article I can see why Mooney never offered this as a kit…

 

[Pinecone]

49 minutes ago, Shadrach said:

LASAR is pretty optimistic with their speed claims. Adding all of the claimed gains from all mods available for my F works out to 26.5kts. That would make it a Mooney 207…

In the car world, that is called Ricer HorsePower.  Mainly smaller Japanese cars, with mods.  They add up the claimed HP for each mod and come up with hundreds of extra HP.

[Pinecone]

Drag reduction can be real and come for all sorts of areas.

The Grumman Tiger is as fast or faster than many 200 HP retractables (not Mooneys), using only 180 HP and fixed gear.  The American General version is almost 10 knots faster with a prop change and burying the beacon in the fin tip.

[A64Pilot]

Just now, Pinecone said:

Drag reduction can be real and come for all sorts of areas.

The Grumman Tiger is as fast or faster than many 200 HP retractables (not Mooneys), using only 180 HP and fixed gear.  The American General version is almost 10 knots faster with a prop change and burying the beacon in the fin tip.

My money is on the prop.

That’s why I said that I bet Hartzell could find several kts if they were properly motivated.

Before I did a lot of prop testing I would have told you that the difference in constant speed props couldn’t be much because the governor will adjust pitch until the prop absorbs all available power and the difference in one blade design and another just wouldn’t be much.

I couldn’t have been more wrong.

Almost always props are a compromise, a one size fits all type of thing. It makes sense for a prop manufacturer to sell as few different models as possible and not build different props optimized for each different aircraft, but from experience I’ve seen if they want to, most often they can

[aviatoreb]

On 8/11/2023 at 1:33 PM, Shadrach said:

Juice not worth the squeeze unless they made a complete set that was considerably lighter. What's an extra .5kt and a 5lbs of useful worth?  I might spend a few AMUs on panels like that before a repaint but I would not go out of my way. Hard for a producer to get their investment back.

I was imagining what if there was one panel you could get for like 500 bucks - and then install is easy if it is just a direct replacement for a current panel, and then you could separately hide your antenna underneath it. Then it might be interesting.  I agree otherwise, juice is not worth the squeeze.