Tri-Mower Design

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blane.c

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blane.c

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Anyway I like the MicroMaster concept, always have. It is better than many other plans/ideas I have seen. I hope it comes to fruition. I would like to actually build my Tri-Mower too, then we can compete for the longest glide ratio two engine out.
 

blane.c

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So I am thinking that based on your 1st post in Micromaster that it makes sense, I am thinking 550lbs for empty weight Tri-Mower, and "look" I did not completely rip off your Tri-Mow-tor name. Tri-Mower 24 foot wingspan 54" chord so 108 square feet. You were building at 7.3lbs per cubic inch this seems rational as for engine loss it would double to 14.6lbs per cubic inch. That would be like a 1430lb gross weight VP-2 on 98 cubic inches (1600cc) {Micromaster 717lbs on 49 cubic inches with one engine out} not what you normally want to do but it is do-able, that is I bet the VP-2 thing has been done though not comfortably. I am looking normally around 1100lbs or 1150lbs so losing one engine would put me at say 1150lbs on 98 cubic inches, losing two isn't a good idea as 1150lbs on 49 cubic inches direct drive you are looking for best glide.

MICROMASTER.png MICROMASTER 2.png
 

Vigilant1

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Like I said, I think the triple can be a fine idea, if the numbers work out.
I would like to actually build my Tri-Mower too, then we can compete for the longest glide ratio two engine out.
:)And/or, we can see who has the first real in-flight engine failure. All else being equal, a plane with 3 engines is 33% more likely to have an engine failure than a twin is. If the expected time between failure for each engine is 1000 hours, the triple can expect to have its first, on average, at 333 hours. The twin should expect one, on average, at/around 500 hours.

Build a Tri-Mower 2-seater and work through the FAA mechanics of using that plane to get a MEL rating on the cheap. I'll fly the single seat MicroMaster while you do that. Then, I can build a two-seat Beetlemaster and use what you found out to get my MEL certificate and then take my lucky (and long suffering) bride on a tour of the US in the Beetlemaster.
 
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Vigilant1

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So I am thinking that based on your 1st post in Micromaster that it makes sense, I am thinking 550lbs for empty weight Tri-Mower, and "look" I did not completely rip off your Tri-Mow-tor name. Tri-Mower 24 foot wingspan 54" chord so 108 square feet. You were building at 7.3lbs per cubic inch this seems rational as for engine loss it would double to 14.6lbs per cubic inch. That would be like a 1430lb gross weight VP-2 on 98 cubic inches (1600cc) {Micromaster 717lbs on 49 cubic inches with one engine out} not what you normally want to do but it is do-able, that is I bet the VP-2 thing has been done though not comfortably. I am looking normally around 1100lbs or 1150lbs so losing one engine would put me at say 1150lbs on 98 cubic inches, losing two isn't a good idea as 1150lbs on 49 cubic inches direct drive you are looking for best glide.

View attachment 92878 View attachment 92879
For a recap (not to go too far afield from your TriMower idea)
After a couple hundred posts and doing some refining, the most recent configuration of the Micromaster was (MicroMaster thread, Post 240 ):
Span: 26'
Wing Area: 70 sq ft
Empty Weight: 450 lb
MTOW: 770 lb (450 EW + 250 lb pilot and baggage + 70 lb fuel). I'd include a bigger tank to take more gas if less cargo was aboard.
Engines: 2 x B&S 810cc (28 HP at SL, 22.5 HP at 6000'), 46" diameter props (34.6" pitch, optimized for 110 MPH).

Projected performance:

.......Condition.............................No-lift drag........Drag due......Reqd Total Thrust..........Total thrust.............Climb
..................................................................................to lift..........for level flight...............Available............Available

2-engines, level flight, 60 KT, SL ........... 28 lb..............16 lb.................44 lb........................168 lb..............1160 FPM
2-engines, level flight, 60 KT, 6000' MSL ...23 lb..............14 lb.................37 lb........................134 lb...............900 FPM
1 engine level flight, 60 KT SL .............37 (stopped prop). 16 lb............... 52 lb........................ 84 lb.............. 300 FPM
1 engine level flight, 60 KT, 6000' MSL... 31 (stopped prop)...14 lb.............. 45 lb.........................67 lb............... 200 FPM
2 engine cruise: 100 KT, 6000' MSL ......... 63 lb...............13 lb ............... 76 lb...................... 114 lb............... 350 FPM
---110 KT, 6000' MSL............................... 77 lb...............10 lb.................87 lb....................... 98 lb............... 100 FPM
---100 KT, sea level................................ 76 lb...............15 lb................ 91 lb.......................142 lb............... 470 FPM
---110 KT, sea level ............................... 92 lb................13 lb.............. 105 lb.......................122 lb............... 160 FPM

So, at MTOW the MicroMaster would have a wing loading of 7.7 lbs/sft.
2 engine (SL) power loading of 13.75 lbs/HP, single-engine (SL) power loading of 27.5 lbs/HP.
If the TriMower has an MTOW of 1150 lbs, then with one engine out you'd be at a power loading of 1150/56HP = 20.5 HP/lb, which is better than the situation with the MicroMaster when flying singe engine. With all engines operating the MicroMaster and the TriMower would have the same power loading = 13.7 lb/HP.

FWIW, TiPi believes pretty strongly that these engines are good for more than 28 HP in aircraft use. The MicroSport folks advertise the same engine modified to their SE33 standard as producing 33 HP. That could be handy in a pinch.

How did you estimate an 1150 lb MTOW? My back-of-the-envelope WAG:
MicroMaster EW: 450 lb (nothing scientific, just a rough guestimate based on a plussed up SD-1 (270 lb EW) with more structure/wing (90 lbs) and another engine/prop/mount (90 lbs)
+ Another engine, mount, and prop: 90 lbs
+ additional structure, landing gear, wing area, another seat, etc for the for the 33% larger MTOW: 100 lbs
Total TriMower empty weight: 640 (Sanity check: A light Sonex weighs 650 lbs, and has just 170 lbs of engine. A VP-2 is about the same. The TriMower will be carrying more engine weight. A 640 lb EW might require more a more "weight-conscious" design than we associate with the VP-2 )
2x 190 lb occupants: 380 lbs (more for baggage?)
Fuel: 100 lbs
TriMower MTOW(?): 1120 (?)

FWIW, when I was noodling around with numbers to see if the MicroMaster SE climb would work out, drag was more important than I'd first considered and weight was a little less important than I'd thought it would be. Just 3-4 more pounds of drag had a greater impact on SE climb than 50 lbs more weight. The TriMower will have a few more ponies at work in case of an engine failure, but drag might still be an issue for you, especially if this plane looks more like a VP-2 than a motorglider. You may want to consider a bit more wingspan to reduce induced drag at climb speed if this becomes an issue. Or, give the passenger a parachute and a quick course in how to use it--there, you just reduced your engine-out climb weight considerably!
 
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blane.c

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810CC TAPERED SHAFT.png
I personally want to find out if this tapered end 1 1/8" crankshaft that is fitted on the 810 propane models is a forged crankshaft. If it is a forged crankshaft why would you mess with any of the other crankshafts?
 

blane.c

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The VP-1 empty weight is 440lbs per Evans. A VW engine firewall forward is 141lbs from "Pops" cowling call it 9lbs for 150lbs firewall forward. So VP-1 290lbs aft of firewall. If the 810cc firewall forward package for the SD-1 is 70lbs that is 210lbs for three and the other 50lbs will evaporate quickly. Then 600lbs people and fuel. =1150lbs
 

Vigilant1

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The VP-1 empty weight is 440lbs per Evans. A VW engine firewall forward is 141lbs from "Pops" cowling call it 9lbs for 150lbs firewall forward. So VP-1 290lbs aft of firewall. If the 810cc firewall forward package for the SD-1 is 70lbs that is 210lbs for three and the other 50lbs will evaporate quickly. Then 600lbs people and fuel. =1150lbs
IMO, verrrrry unlikely on that empty weight. But, heck, it's the rare aircraft that meets the original weight estimates, so you (and I) would be in good company.
 

Vigilant1

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View attachment 92884
I personally want to find out if this tapered end 1 1/8" crankshaft that is fitted on the 810 propane models is a forged crankshaft. If it is a forged crankshaft why would you mess with any of the other crankshafts?
I thought you were hankering for B&S stock EFI systems? You can't get an engine with that crankshaft and the EFI or it would at least be a special order (and they'd have probing questions for you . .), so you'd need to buy a loose crankshaft and fit it to an EFI engine or buy an EFI (and suitable throttle body, etc) to fit to the stock propane engine. None of that is impossible, but it does add hassle.
The aviation installations that attach the prop to the flywheel side are working well, no reported broken cranks, no bearing failures, no need to find a way to remove weight on the non-prop end of the shaft, etc. Proven in flight is good.
 

jedi

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Like I said, I think the triple can be a fine idea, if the numbers work out.

:)And/or, we can see who has the first real in-flight engine failure. All else being equal, a plane with 3 engines is 33% more likely to have an engine failure than a twin is. If the expected time between failure for each engine is 1000 hours, the triple can expect to have its first, on average, at 333 hours. The twin should expect one, on average, at/around 500 hours.

Build a Tri-Mower 2-seater and work through the FAA mechanics of using that plane to get a MEL rating on the cheap. I'll fly the single seat MicroMaster while you do that. Then, I can build a two-seat Beetlemaster and use what you found out to get my MEL certificate and then take my lucky (and long suffering) bride on a tour of the US in the Beetlemaster.
The indicated trend is to use fewer engines and get more flight time between engine failures. That works but in the tri motor you will have more practice with engine out performance. The chance of engine failure can be reduced to zero by flying gliders.
 

Vigilant1

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. That works but in the tri motor you will have more practice with engine out performance.
I'm hoping that most of that engine-out experience will be from >simulated< engine failures.;)
 

cluttonfred

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I think we need to file this...

"The chance of engine failure can be reduced to zero by flying gliders."
--jedi

with this...

"If its not there, it cost nothing, weighs nothing, and is 100% reliable."
--Pops

;-)
 

blane.c

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Ok … I like the idea of gliders, well motor gliders I would want the independence to self launch.

But my heart is in the triple. I am virtually alone and a cast-away on the triple island. It seems absolutely no one else likes the idea. That is ok. I am fine with that. I still like it, and I know it isn't the most efficient in the manner most people look at things but I have always looked at things differently than others. It is efficient in one of the things I feel is important. I like landing at airports well with this kind of airplane I do. Off airport is a whole different plane altogether. I have plenty of time landing in the boonies and on skis but the triple has a different mission.

Isn't trend another word for fad? Fads come and go. One thing I have noticed however is that many concept aircraft that are electric have multiple motors. The first electric float plane the Lazair had two motors. So it isn't such a foreign idea these days to have more than one motor or the idea of it. But it is almost sacrilegious to have the idea of more than one engine and we all know the sky is falling if for some reason someone would suggest more than two engines. It is as if there are ICE police. Thou shall not go against the train of thought instilled in all of us for the last sixty something years … thou shalt not.

Anyway I proceed but I thank you very much for reminding me of the glider thing, it is something Topaz mentioned several years ago but I couldn't figure out the rules (or lack of them) at the time. It is still muddy water but I think I see the creek bottom.
 

jedi

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Ok … I like the idea of gliders, well motor gliders I would want the independence to self launch.

But my heart is in the triple. I am virtually alone and a cast-away on the triple island. It seems absolutely no one else likes the idea. That is ok. I am fine with that. I still like it, and I know it isn't the most efficient in the manner most people look at things but I have always looked at things differently than others. It is efficient in one of the things I feel is important. I like landing at airports well with this kind of airplane I do. Off airport is a whole different plane altogether. I have plenty of time landing in the boonies and on skis but the triple has a different mission.

Isn't trend another word for fad? Fads come and go. One thing I have noticed however is that many concept aircraft that are electric have multiple motors. The first electric float plane the Lazair had two motors. So it isn't such a foreign idea these days to have more than one motor or the idea of it. But it is almost sacrilegious to have the idea of more than one engine and we all know the sky is falling if for some reason someone would suggest more than two engines. It is as if there are ICE police. Thou shall not go against the train of thought instilled in all of us for the last sixty something years … thou shalt not.

Anyway I proceed but I thank you very much for reminding me of the glider thing, it is something Topaz mentioned several years ago but I couldn't figure out the rules (or lack of them) at the time. It is still muddy water but I think I see the creek bottom.
Don't give up so easy blane.c we are just having a good time here. I am on your side. I have had many good hours in a trimotor and some of my most memorable engine failures have been in trimotor aircraft (DC-10s). My second son is currently designing a trimotor UL type aircraft and has purchased the engine and propeller for thrust/weight/performance/durability testing.

Your concept is sound and if you are onboard you will continue in spite of the negative comments and jibes. That's the way the world works and progress is made. What more can I say to help you succeed?


I think we need to file this...

"The chance of engine failure can be reduced to zero by flying gliders."
--jedi

with this...

"If its not there, it cost nothing, weighs nothing, and is 100% reliable."
--Pops

;-)
And if we are still talking about the number of engines I will add "You will never run out of fuel and it does not use any gas."

I still like the trimotor motor glider concept, but that negates the above referenced glider advantages.
 

blane.c

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I was thinking that a glider is in one respect a engine in it's own right. So a proper glider just two engines plus the glider. Got to make the engines virtually disappear when not in use so finding a way to store two, would look like a Stemme 12 on the front and one of those engine hanger thingy's in the rear.
 

jedi

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I was thinking that a glider is in one respect a engine in it's own right.
........
That is a little different way of looking at things. Normally I look at an engine failure as an irregularity. The engine is supposed to run when needed. I look at the glider as though it is an airplane. Like any airplane it has a limited fuel supply. The goal is to land before you run out of fuel (altitude). The neat thing about gliding is that there are aerial tankers all over the place on a good soaring day and they give away the gas for free (not even taxed).

Did I convert any airplane drivers? It is like the difference between sailboats and stinkboats in the nautical world.

PS: Nothing against stinkboats if you can afford the gas. Donations accepted.
 

blane.c

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We let a Lufthansa MD11 pilot fly in my co-pilot seat of the DC-4 on a part 91 leg, I thought he was going to break his face the way he smiled.

You ever see this guy's stuff (from another thread) http://basia38.tripod.com/jozefborzecki/id34.html

Interested in the propeller.PADDLE PROP PICTURE 1.jpg PADDLE PROP PICTURE 2.jpg

Also interested in popular and unusual folding propeller mechanism's.

Don't give up so easy blane.c we are just having a good time here. I am on your side. I have had many good hours in a trimotor and some of my most memorable engine failures have been in trimotor aircraft (DC-10s). My second son is currently designing a trimotor UL type aircraft and has purchased the engine and propeller for thrust/weight/performance/durability testing.

Your concept is sound and if you are onboard you will continue in spite of the negative comments and jibes. That's the way the world works and progress is made. What more can I say to help you succeed?

And if we are still talking about the number of engines I will add "You will never run out of fuel and it does not use any gas."

I still like the trimotor motor glider concept, but that negates the above referenced glider advantages.
Cool about your son and the tri-motor. Take pictures eh?
 

lr27

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I think the tri-mower idea will work, as long as you don't need it to be a sailplane too.
 
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