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clrprop

Joined: 16 Sep 2008
Posts: 44
Location: SC

Posted: Wed Feb 18, 2009 7:05 pm Post subject: weight question

Could someone please give me a ballpark number on what the useful load should be on a Mark III C  with a 582 and standard configuration?



Thanks!



Keath T

rowedenny

Joined: 09 Mar 2008
Posts: 338
Location: Western PA

Posted: Thu Feb 19, 2009 4:02 am Post subject: weight question

 	  Quote: 	
		   Could someone please give me a ballpark number on what the useful load 

 should be on a Mark III C  with a 582 and standard configuration?



 Thanks!



 Keath T

 Keath,


	


Depending on the empty weight of the particular bird and if the established 

gross weight is 1000 pounds, the usefull load with ten gallons of fuel will 

be around 400 to 500 pounds.



Denny Rowe, Mk-3, 690L-70, empty weight 470lbs, useful load approx 470lbs.

PS, some people set their gross weight as high as 1200lbs when they register 

their Mk-3s, adding a lot to their legal useful load.

NeilsenRM(at)comcast.net
Guest

Posted: Thu Feb 19, 2009 6:10 am Post subject: weight question

Keath



Useful load really depends on how it is built. Most Kolbs are built heavy 

reducing their useful load. My MKIIIC with a VW weighs 598lbs. empty. The 

582 will weigh less but there really isn't a standard MKIII empty weight. 

They are after all experimental so the weight varies all over the place.



Also Kolb recommends a maximum gross weight of 1000 lbs. It is NOT good to 

recommend a higher gross weight. Some people have made modifications (me 

included) that they think increases the strength and have registered their 

planes heaver but? Kolb is conservative but they have to be because the 

builders might not build the plane correctly.  My plane is registered with a 

1050 lbs. maximum gross weight and it is beefed up to my satisfaction. There 

is only one person that I'm aware of that has a gross weight at 1200 lbs. 

and he did some major modification to do this.



Rick Neilsen

Redrive VW powered MKIIIC



---

aslsa.rng(at)gmail.com
Guest

Posted: Thu Feb 19, 2009 7:39 am Post subject: weight question

The other part of declaring a heavier weight is that you must test the aircraft at that weight and record such things as stall speed at that weight in order to legally come out of phase 1 testing. If you declare 1200 lb. and only test to 1050, or whatever, you have never truly completed your phase 1 testing. Check to see what your operating limitations say, too. 



Rick



On Thu, Feb 19, 2009 at 8:10 AM, Richard & Martha Neilsen <NeilsenRM(at)comcast.net (NeilsenRM(at)comcast.net)> wrote:

[quote] --> Kolb-List message posted by: "Richard & Martha Neilsen" <NeilsenRM(at)comcast.net (NeilsenRM(at)comcast.net)>

 

 Keath

 

 Useful load really depends on how it is built. Most Kolbs are built heavy reducing their useful load. My MKIIIC with a VW weighs 598lbs. empty. The 582 will weigh less but there really isn't a standard MKIII empty weight. They are after all experimental so the weight varies all over the place.

  

 Also Kolb recommends a maximum gross weight of 1000 lbs. It is NOT good to recommend a higher gross weight. Some people have made modifications (me included) that they think increases the strength and have registered their planes heaver but? Kolb is conservative but they have to be because the builders might not build the plane correctly.  My plane is registered with a 1050 lbs. maximum gross weight and it is beefed up to my satisfaction. There is only one person that I'm aware of that has a gross weight at 1200 lbs. and he did some major modification to do this.

  

 Rick Neilsen

 Redrive VW powered MKIIIC

 

 ---

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Fri Feb 20, 2009 8:55 pm Post subject: Re: weight question

Hello Rick and all....

I finally got my M3X home and getting it finished up for this spring.My airplane has a Jab 2200 on it and is fairly loaded up and when I did the weight and balance for the plane ,the empty weight came out to 596.2 lbs. I called Brian and he said to set the gross weight for my airplane at 1150 lbs and that would be no problem. I was glad to here ,Rick , that yours with the VW came in at 598.I was also told they figure the empty weight plus full fuel,and 2 passengers for the gross weight.(for a 2 place airplane that is).



chris ambrose

ces308(at)ldaco.com

aslsa.rng(at)gmail.com
Guest

Posted: Sat Feb 21, 2009 6:57 am Post subject: weight question

Chris, et al, I'm not trying to be critical here, but if ever there was an illustration of backward thinking, this idea of figuring up the total load for a finished aircraft by adding up the weights and then calling this the maximum gross is it. Any aircraft should be designed from the start with a structure to accommodate a given maximum gross weight. By doing this the designer sets the safety margin of the aircraft structure FOR THAT LOAD. The wing is sized for the maximum lift coefficient required to lift that load, as well the size of the horizontal stabilizer required to counter the pitching moment of the airfoil selected. And on and on. This is an iterative process by which all things required to accomodate the design maximum gross weight are adjusted until they meet this requirement.

 When you go about this in the backward manner suggested you are decreasing that safety margin of the aircraft's structure. You're increasing the required lift to get it into the air and keep it there and since you can't change this without changing the size of the wing your only option is to increase the speed of takeoff, cruise, and stall. Once again, and on and on.

 What your job, as builder, is to keep that maximum gross weight in mind at all times when you decide to make a change or add an accessory to the aircraft. As Burt Rutan always told his builders who asked about adding things to their aircraft, "Throw it up in the air, if it comes back down it's too heavy".

 What you shouldn't do is arbitrarily increase the maximum gross weight to accommodate the bloated aircraft you've built, unless you know and accept how much you have DECREASED the structural safety margin, controllability, and efficiency of your aircraft.

 You have, however, given me a great topic for our EAA chapter newsletter.

Rick

do not archive



On Fri, Feb 20, 2009 at 10:55 PM, ces308 <ces308(at)ldaco.com (ces308(at)ldaco.com)> wrote:

 [quote]--> Kolb-List message posted by: "ces308" <ces308(at)ldaco.com (ces308(at)ldaco.com)>

  

 Hello Rick and all....

 I finally got my M3X home and getting it finished up for this spring.My airplane has a Jab 2200 on it and is fairly loaded up and when I did the weight and balance for the plane ,the empty weight came out to 596.2 lbs. I called Brian and he said to set the gross weight for my airplane at 1150 lbs and that would be no problem. I was glad to here ,Rick , that yours with the VW came in at 598.I was also told they figure the empty weight plus full fuel,and 2 passengers for the gross weight.(for a 2 place airplane that is).

  

 chris ambrose

 ces308(at)ldaco.com (ces308(at)ldaco.com)

 

 

 

 

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 [b]

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Sat Feb 21, 2009 12:46 pm Post subject: weight question

At 09:56 AM 2/21/2009, Richard Girard wrote:

 	  Quote: 	
		  Chris, et al, I'm not trying to be critical here, but if ever there was an 

illustration of backward thinking, this idea of figuring up the total load 

for a finished aircraft by adding up the weights and then calling this the 

maximum gross is it.

Any aircraft should be designed from the start with a structure to 

accommodate a given maximum gross weight. By doing this the designer sets 

the safety margin of the aircraft structure FOR THAT LOAD...


	


While I agree with you, in general, there are a few caveats that may make 

it reasonable for an aircraft builder to specify a higher gross weight on 

the paperwork.



First, the gross weight is, as you say, set by structural and/or 

performance considerations.  Both of these take into account all possible 

flight conditions... for example, performance at max density altitude, 

structural strength in turbulence, etc.  What is a safe loading in one set 

of conditions may be unsafe in other conditions, etc.  If an aircraft is 

structurally safe to fly 3G turns at max gross on a bumpy day, then it's 

likely just as safe to fly, say, 10% over gross on a calm day with the 

pilot flying gently.  Similarly, an airplane with barely adequate climb at 

(or even under) gross on a hot humid day may well perform much better, even 

over gross, on a cold clear day (in fact, IIRC it's legal in Alaska to fly 

a certain amount over gross under certain conditions).  Also consider all 

the aircraft that are utility category at one gross weight, and normal 

category (with lower G limits) at a higher weight.



In such conditions, having the higher weight limit specified on the 

airworthiness certificate (which is purely a legal document, after all) may 

well prevent problems in the event of an incident where the FAA decides to 

investigate.



Does this mean that a builder should arbitrarily set the gross weight at 

whatever he wishes?  Of course not.  But it does mean that an informed 

builder should consider all the facts, including the type of flying he'll 

be doing, before putting down any number on that piece of paper.



-Dana





--

  Bill of Rights: Void where Prohibited by Law

NeilsenRM(at)comcast.net
Guest

Posted: Sat Feb 21, 2009 2:00 pm Post subject: weight question

Chris



First and foremost is my concern is for everyone's safety. I had a 

discussion years ago with the owner of Kolb at the time who had worked for 

Homer Kolb doing some of the design work for the MKIII, was their test 

pilot, and engineer. My question was how firm is the gross weight of a 

MKIII. If I remember the response correctly he said that the MKIII is the 

most conservatively rated Kolb in regards to gross weight. The weight can be 

increased a bit if it is flown in smooth air. His biggest concern seemed to 

be how well the plane is built. He would not budge on the 1000 lb. maximum 

gross weight recommendation.



I have great admiration for Brian's work on Kolb airplanes. If the gross 

weight can be increased then it would be one of Brian's that this could be 

done. I really question if Brian would make a blanket statement that a 

MKIIIX can safely have a 1150 lb. gross weight. If he beefed up the airframe 

of a particular airplane to handle the increased gross weight that might be 

different. I'm just very concerned that without a structural engineering 

study and follow on testing to confirm survivability at a 1150 gross weight 

that this might be very dangerous.



If I'm not clear enough then I would like to restate that the maximum gross 

weight of a Kolb MKIII is 1000 lbs.



If you choose to fly at the 1150 weight please don't subject innocent 

passengers to these dangers. Also PLEASE do not encourage others to do the 

same.



Rick Neilsen

Redrive VW powered MKIIIC



---

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sat Feb 21, 2009 2:41 pm Post subject: Re: weight question

Hi Rick,

Thank you for your input on the gross weight of a Mark 3 Xtra.I will be discussing this further with the factory monday morning and for anyone else with a M3X it's 1000 lbs max gross.



chris

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Feb 21, 2009 3:18 pm Post subject: weight question

> Thank you for your input on the gross weight of a Mark 3 Xtra.I will be 

discussing this further with the factory monday morning and for anyone else 

with a M3X it's 1000 lbs max gross.

 	  Quote: 	
		  

 chris


	




I have a mkIII that was designed and built long before TNK came up with the 

idea of a mkIIIx.



My mkIII has been flying for 17 years (next month), 2,873.5 hours on the 

airframe, and has a maximum gross take off weight of 1,200 lbs.



I'd say my mkIII has been thoroughly tested, and has performed impecably 

throughout her long life.  She has sported a 582, a 912UL, and two 912ULS 

engiens.  Performance was great with all engines, just got better as hp was 

increased.  I think the ideal engine for a mkIII would be a 912UL, 80 hp, 

based on fuel burn, spark plug life, and the fact that it is happy with 87 

oct auto gas.  Performance with an 80 hp Rotax is great.  100 hp kinda puts 

the icing on the cake, but it does cost more to operate.



I certainly don't encourage anyone to increase the gross weight of any Kolb 

they build.



I don't encourage anyone to do anything.  



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

NeilsenRM(at)comcast.net
Guest

Posted: Sat Feb 21, 2009 3:42 pm Post subject: weight question

John



Gosh darn it (I got my airplane fix so I'm more easy going). Your plane 

certainly isn't stock. You really need to make that clear when you talk 

about your gross weight.



Rick Neilsen

Redrive VW powered MKIIIC

---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Feb 21, 2009 4:10 pm Post subject: weight question

> Gosh darn it (I got my airplane fix so I'm more easy going). Your plane

 	  Quote: 	
		   certainly isn't stock. You really need to make that clear when you talk 

 about your gross weight.



 Rick Neilsen


	




Rick:



I'd fly a Kolb mkIII at 1200 lbs, built strictly by the plans Dennis Souder 

drew up in 1990, if I built it.



The kit manufacturer recommended my airplane be limited to 1,000 lbs.  I 

believe the max gross on new mkIII's is still 1,000 lbs.



The only thing I did to increase strength of the wings was put some aluminum 

angle on the all main rib noses, plus some stronger lateral bracing from the 

main spar to the leading edge, and beefed up bracing on the bow tip at 90 

and 45 degrees forward.  A copy of Dennis Sounder's plans sheet is attached. 

I also added aluminum angle to the tails of the first four outboard main 

ribs.



That's all I did.  Changing the main gear did not change max gross weight 

capacity.



I increased the up elevator cable to 1/8".  It is the one that works the 

hardest.  Down elevator cable is still 3/32.  It doesn't do much work.



Any other changes, as far as I know, did nothing to increase strength of my 

mkIII



Again, I am not encouraging anyone else to increase the max gross weight 

capacity of a Kolb they build.



I did.  It serves my purpose, and has more than proven it is capable of 

1,200 lbs max gross under any conditions I can subject it to.



I emphasize, I only speak of my airplane.  No one elses's.



Your mkIII may not be capable of 1,200 lbs.



john h

mkIII

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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

NeilsenRM(at)comcast.net
Guest

Posted: Sat Feb 21, 2009 5:38 pm Post subject: weight question

John



The plans from Dennis recommended that this be done to the outboard rib 

only. Which I did but you did all full ribs and four of the outer tails. I 

also added a jury strut which you did and it seems like you told me you also 

beefed up the lift strut.



My POINT IS...... Your plane has been beefed up to handle the 1200 lbs. 

gross weight. I never said you advised people to to increase the gross 

weight. The problem is you have put your plane thru the ultimate test and it 

did hold up with the higher gross weight. That says more than I or anyone 

else can say. That is why if you say 1200 lbs you have to tell us everything 

you did. John you are a friend so I really don't want to beat you up over 

this but lives are at stake here. Want it or not we hang on every word you 

say and I remember.



Does Brian do all this? I don't think a standard build would handle the 

treatment at 1200lbs.



Rick Neilsen

Redrive VW powered MKIIIC



---

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Feb 21, 2009 6:05 pm Post subject: weight question

> The plans from Dennis recommended that this be done to the outboard rib

 	  Quote: 	
		   only. Which I did but you did all full ribs and four of the outer tails. I 

 also added a jury strut which you did and it seems like you told me you 

 also beefed up the lift strut.

 >
	


 	  Quote: 	
		   Rick Neilsen


	




Rick:



Yep!  Made sense to me.  If it worked to beef up the outboard wing from 

abuse, mishandling, drops, ground strikes, etc., then it ought to work to 

beef up the other 4 main ribs on each wing panel.  That has to be one of the 

cheapest, easiest, simplest improvements one can make to vastly increase the 

strength of the rib.  I was primarily concerned with increasing strength of 

the rib noses.  Oh yea, and it adds negligible weight.



As far as handling, flying, hauling extra weight with Homer's wings, it'll 

do it.  I always said if I could stuff it in the mkIII, it would fly off 

with it.



Only reason I stiffened the tails of the four outboard ribs was the load the 

ailerons placed on them.  Made me feel better.



I used 1/2" od aluminum tubing to brace the leading edge to the main spar 

inboard and outboard.  Keeping the main rib noses in column is critical if 

they are going to do their job.



I ended up using 4130 tubing for lift struts inside the extruded streamlined 

aluminum struts.  Seems I had a difficult time getting the bolt holes 

drilled straight, ruined two sets of struts, then opted for the 4130 tubing 

(with fittings welded on) inside the aluminum strut.  Aluminum strut is 

nothing more than a fairing for the steel strut.  Had nice 4130 streamlined 

struts for the first flight, but one got destroyed during testing.  Couldn't 

afford to buy material for a replacement when I rebuilt.



If built correctly, the mkIII wing is tremendously strong in my humble 

opinion.



I tore up a lot of parts and airplanes during my growing pains in civilian 

aviation.  Homer used to refer to me as his best test bed.  If it could be 

broken, I'd breake it.  



Hope I have outgrown being his test bed.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sat Feb 21, 2009 6:11 pm Post subject: Re: weight question

Rick and John,

Looks like I opened a real can of worms here....I will call Brian and Dennis again monday  and let you know what they say .Please email me off the list and let me tell you how this all started.I certainly understand both of your urgencies on this matter and it was also my concern too,which is why I  called them last week.



later,chris

ces308(at)ldaco.com

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Feb 21, 2009 6:38 pm Post subject: weight question

> Looks like I opened a real can of worms here....I will call Brian and 

Dennis again monday  and let you know what they say .Please email me off the 

list and let me tell you how this all started.I certainly understand both of 

your urgencies on this matter and it was also my concern too,which is why I 

called them last week.

 	  Quote: 	
		  

 later,chris


	




Chris:



No worms.  No urgency.



Simply sharing a few things I have learned building and flying Kolbs for the 

past 25 years.  Forgot to add, and breaking them too.



I have my mkIII built and configured to perform so I can be relatively 

comfortable and accomplish the type flying I am accustomed to.  Get me there 

and get me home.



What I haul is not passenger weight though.  It is fuel, 150 lbs, and my 

gear, about 125 lbs, and me, about 200 lbs.  From my experience with the 

mkIII, they don't like heavy pilots and heavy passengers.  I believe this is 

primarily because of the high thrust line in the pusher configuration. 

Takes a lot of nose up trim to haul heavy passengers and pilot.  Looks like 

one could get in a pitch problem by trying to fly with 500 lbs of passengers 

in front of the cg and only 60 lbs of fuel behind the cg.  The weight in my 

mkIII is much more evenly distributed.



Even when I fly with a heavy passenger, 250 lbs, plus me, 200 lbs, and 150 

lbs of fuel, and an empty weight of 650 lbs, I am already up to 1,250 lbs. 

However, 150 lbs of that is in the back.  I won't fly with a lot of weight 

forward and very little weight in the rear.  Don't fly with 250 passengers, 

although have done some nice cross country flights with a 220 lbs passenger. 

A lot depends on how you configure your airplane.



I'm not trying to defend my mkIII.  Only sharing what I have done with it.



We used to fly a lot of passengers at Sun and Fun and Oshkosh back in the 

old days.  I can assure I got a lot of experience with different weight and 

size passengers.  My favorites were the kids.  You could hardly tell they 

were in the airplane.



Take care,



john h

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

zeprep251(at)aol.com
Guest

Posted: Sat Feb 21, 2009 6:49 pm Post subject: weight question

Chris,

     Let me know how you like the Jabiru.

                G.Aman MK-3C Jabiru 2200 410 hrs

 

   

 

   

 

 --

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sat Feb 21, 2009 7:31 pm Post subject: Re: weight question

So far it seems to have tons of power! I do not believe it will have a problem flying this airplane!



chris

zeprep251(at)aol.com
Guest

Posted: Sat Feb 21, 2009 7:34 pm Post subject: weight question

Quick question for the list.My MK 3 struts are .125 wall tube with 4130 end fittings with a short shim tube over the  fittings for fit.My friend Gary Jindra.bought an older, partially  done MK-C kit with poorly built extruded struts.On our recommendation he bought new stock and started over with the strut building.He was supplied with .250 wall tubing from Travis.Are all the new kits using this thickness strut tubing?

 

                                      G.Aman

 

   

 

 --

ces308

Joined: 03 Nov 2008
Posts: 317
Location: houghton lake ,mi

Posted: Sat Feb 21, 2009 7:53 pm Post subject: Re: weight question

My struts are 1 1/2 x .125 with the same ends you have.



chris

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