weight and balance

[Old Koreelah]

3 hours ago, RFguy said:

Not sure how that all happened at BRM. Seems a rookie mistake having a airplane get into production and then  to need to add that mass....

 

Perhaps they designed it for the heaviest, highest-spec engine available- constant speed prop, turbo, dual battery EFI, etc.

[facthunter]

That could be the reason. Every model aeroplane built is faced with the same problem and people get over it. Balance point 1/3rd back from the leading edge of the wing.   Nev

[skippydiesel]

1 hour ago, Old Koreelah said:

Perhaps they designed it for the heaviest, highest-spec engine available- constant speed prop, turbo, dual battery EFI, etc.

Yeh/But! If this be the reason (likely) it seem a cheap/nasty way of achieving balance. Why not move the engine forward? Would require an engine frame/bed redesign/modification and the same for the cowling but may have improved internal space/volume availability.

[Old Koreelah]

They might have decided that sticking with a single engine mount and cowl design is cheaper.

[facthunter]

What does the "weight" weigh?   Nev

[Blueadventures]

25 minutes ago, facthunter said:

What does the "weight" weigh?   Nev

That one was just over 7kg, less than 8kg.

[RFguy]

46 minutes ago, Old Koreelah said:

They might have decided that sticking with a single engine mount and cowl design is cheaper.

 

 

Edited September 2, 2023 by RFguy

[skippydiesel]

8 hours ago, Arron25 said:

When doing the design to fit a 2.2 Jab to my Sonerai, a consideration is to utilize a weighted firewall (notice I didn't call it ballast😊) to keep the prop in the original position to use the original cowls and maintain the traditional look, figuring it was designed for the weight of the VW so no loss or gain there just a 30% increase in power and a prop spinning the other way.

We all have our own philosophy/priorities - for me function comes first every time. Form is the poor relation. For an aircraft with the potential of a Sonerai (http://worldrecordplane.com/) "the traditional look"  is way down the list.

[facthunter]

The sloping fin is more a style thing than a function, as an example.  Nev

[skippydiesel]

1 hour ago, Arron25 said:

You Do realise that SGS and SRS are to a Sonerai ..what a TBucket is to a Model T...

Changing weight placement /wing design /build process etc.. all achieve what you may be aiming for , but all wander too far from that original designers concept and become a in essence New Design... why SGS is called Sera172 not Sonerai.

I happen to like the original design, I did 150hrs in it before cooking the VW motor, and if I can hide a more reliable 85hp motor where the original 45hp motor was, that is my 'Function' while still maintaining 'Form' in original look and handling characteristics

Are you sure? - I understood that SGS's airframe was essentially stock. Meticulous build and a lot of work on the cowling.

 

I agree SRS is a much modified/improved  Sonerai

[skippydiesel]

Not quite "stock" but not far from it.

 

Given this is a plans bult (not kit) aircraft and like most of its genera, has buildermodificatons to personalise the aircraft , I would consider SGS  to be a Sonerai II. While SRS is  part of the same stable, she is very much more developed aircraft. Pity that Sonex doesn't seem intersted in  incorporating any of Robin's ideas -  I, for one, would love to have such an aircraft.

 

"SGS was in no way built as a racer although I was fanatical about achieving highest standards in construction,  finish and aesthetic qualities. Solid countersunk AN rivets were used for high efficiency and to build a quality base for further development.  Many aerodynamic compromises were however accepted to improve the overall functionality, including a taller, wider and longer canopy and extra cockpit occupant space. Also, increased wing angle of incidence and reduced instrument panel height for better in-flight visibility, and larger massed-balanced, modern shaped tail surfaces and taller turtle deck for improved control authority and positive stability in all 3 axes. These compromises were offset by a complete re-engineering of the aircraft from the firewall forward including sleek, new, low-drag engine cowlings.

 

Minimising weight was a critical consideration, however there were compromises here too wherever increased functionality or safety benefits outweighed any weight disadvantages. These compromises included rollover protection, contoured leather seats, auxiliary wet wing tanks, fuel delivery and transfer pumps, redundant fuel bypass circuits, full-span flaperons, differential ailerons, upgraded spar carry-through structures, upholstery and sound deadening, baggage provision, thicker canopy for improved bird strike protection, a Rotax slipper gearbox clutch, full corrosion protection throughout and a crash activated ELT. Despite all these improvements (and many other minor ones) finished empty weight was kept at a respectable 277 Kg (611 lbs) wet."

Edited September 3, 2023 by skippydiesel

[GolfWhiskeyHotel]

Thank you everyone for the input. I don't like putting weight in the tail. But there was nothing to move. The aircraft weighs 6 kilos more than original and 2.5 of that is tail ballast.  I could use a much heavier battery (  12?  kilos ) and place it behind the seat next to the fuel tank, then run much  heavier cables next to the fuel tubing down the centre of the fuselage. That would be adding considerable lbs to the total weight..... If I did the job again I would put the engine and inch closer to the firewall and alter the cowling.  If anybody needs the measurements I am quite happy to supply, The aircraft flies straight and level with the tailplane horizontal.  It can also climb at a frightening angle. Not been solo yet, but I estimate  2000 ft per min to be a realistic number. it also runs a bit too cool, I could have used a smaller radiator, smaller air scoop and carried less water.   Next time I'll know. Thanks again. Geoff

[skippydiesel]

Hi Geoff,

 

"............ it also runs a bit too cool, I could have used a smaller radiator, smaller air scoop and carried less water. "

 

"Bit cool" is on the right side of engine temperature management . With over cooling, you can relativly easily restrict cowling air flow in/out or both or blank off a bit of the radiator to get the temperature where you want it.

Too hot, the problem is much more complex & costly & time consuming.

 

"...........carried less water."

What does this mean? - is it a motorglider?

[Blueadventures]

1 hour ago, GolfWhiskeyHotel said:

Thank you everyone for the input. I don't like putting weight in the tail. But there was nothing to move. The aircraft weighs 6 kilos more than original and 2.5 of that is tail ballast.  I could use a much heavier battery (  12?  kilos ) and place it behind the seat next to the fuel tank, then run much  heavier cables next to the fuel tubing down the centre of the fuselage. That would be adding considerable lbs to the total weight..... If I did the job again I would put the engine and inch closer to the firewall and alter the cowling.  If anybody needs the measurements I am quite happy to supply, The aircraft flies straight and level with the tailplane horizontal.  It can also climb at a frightening angle. Not been solo yet, but I estimate  2000 ft per min to be a realistic number. it also runs a bit too cool, I could have used a smaller radiator, smaller air scoop and carried less water.   Next time I'll know. Thanks again. Geoff

How does your load mass (empty aircraft, you, fuel, cargo etc) fit to the J160 specs being:- 

Forward Limit: 180-mm (7.09”, 18.2%MAC) aft of datum up to & including 440 kg (970lb) 233-mm (9.17”, 23.5%MAC) aft of datum at 540kg (1190lb) Linear variation between points.

Aft Limit 292-mm (11.50”, 29.5%) aft of datum at all weights Datum Wing Leading Edge

 

Cheers and look forward to your flight feed back.

Edited September 3, 2023 by Blueadventures