plan enlargement
02-15-2009, 12:18 AM
#6
RE: plan enlargement
For example the Goldberg Tiger 40 = 61" and the Tiger 60 is 70" then divide 70 by 61 and you get 1.15 or 115%
Super Sportster 40 = 55" and the Super Sportster 60 = 61" then divide 61 by 55 and you get 1.11 or 111%
Four Star 40 = 59.75" and the Four Star 60 = 71" then divide 71 by 59.75 and you get 1.19 or 119%
Super Sportster 40 = 55" and the Super Sportster 60 = 61" then divide 61 by 55 and you get 1.11 or 111%
Four Star 40 = 59.75" and the Four Star 60 = 71" then divide 71 by 59.75 and you get 1.19 or 119%
02-15-2009, 12:50 PM
#8
RE: plan enlargement
I have a friend the built a World Models Robinhood 99 some yrs ago
He scaled down the plans at the blue print store
He has made a Robinhood 80, 70, & 50 and enjoyed them all
I have another friend that scaled up a 110% Slow Poke at Office Max. Installed a Saito 72 was a great flyer
He scaled down the plans at the blue print store
He has made a Robinhood 80, 70, & 50 and enjoyed them all
I have another friend that scaled up a 110% Slow Poke at Office Max. Installed a Saito 72 was a great flyer
02-15-2009, 05:52 PM
#9
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RE: plan enlargement
the above examples using commercial kits are a good basis for scaling up, but if you cannot find such an example to suit your requirments, then following might help.
when you scale up a model, the wing area goes up by the square of the scale up - eg scaling up by 20% gives a wing area increase of ( 1 + 0.2 ) x (1 + 0.2 ) which gives 1.44 or 44% increase in area.
the volume of the plane or more specifically, the material and its weight used in construction , increases by the cube of the scale up , ie 1.2 x 1.2 x 1.2 = 1.73 or an increase in weight of 73%.
this estimate will be affected by any major changes in material or construction particularly if scaling up to very large models, but for modest scale up it is a good estimate.
I keep the power weight ratio the same and in this example the power increase needed would be about 70%.
Working backwards from the requirement to scale up from a 40 to a 60 engine, simply take the cube root of the ratio of the power change , ie 60/40 = 1.5 and the cube root of 1.5 is 1.15 - that is a scale up of 15% which is similar to the recommendations above.
I have scaled up Goldbergs 42"cessna skylane to 84" and also Vic Smeeds Mamselle from 38" free flight to 72" and then to 108" for R/C and power came in just under the estimates from above, but I built them very light.
hope you find this useful
John
when you scale up a model, the wing area goes up by the square of the scale up - eg scaling up by 20% gives a wing area increase of ( 1 + 0.2 ) x (1 + 0.2 ) which gives 1.44 or 44% increase in area.
the volume of the plane or more specifically, the material and its weight used in construction , increases by the cube of the scale up , ie 1.2 x 1.2 x 1.2 = 1.73 or an increase in weight of 73%.
this estimate will be affected by any major changes in material or construction particularly if scaling up to very large models, but for modest scale up it is a good estimate.
I keep the power weight ratio the same and in this example the power increase needed would be about 70%.
Working backwards from the requirement to scale up from a 40 to a 60 engine, simply take the cube root of the ratio of the power change , ie 60/40 = 1.5 and the cube root of 1.5 is 1.15 - that is a scale up of 15% which is similar to the recommendations above.
I have scaled up Goldbergs 42"cessna skylane to 84" and also Vic Smeeds Mamselle from 38" free flight to 72" and then to 108" for R/C and power came in just under the estimates from above, but I built them very light.
hope you find this useful
John
04-12-2010, 09:37 PM
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RE: plan enlargement
All the above is for the wing and engine increase. What about the fuse enlargement? Do I simply add 44% to the 40 sized dimensions on the plans, the same as the the wing? The plane I want to scale up is a RCM plan "Northrop Eagle II" that has a relatively short tail moment (distance between TE of wing to LE of tail feathers). I have been told that due to this, I have to be sure to keep the proportion the same. The 40 size flies so well, straight and true with no bad flying characteristics. I want to get into large planes, so I am eager to get a larger version of this plane flying. Thanks in advance, Bryan
04-13-2010, 04:55 AM
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RE: plan enlargement
Bryan,
the example I gave was for a 20% scale up which applies to all linear dimensions of the complete model - ie the fuselage length, breadth and height are all increased by 20%.
A 20% scale up leads to a 44% increase in wing area and an approximate 73% increase in weight.
I then use these figures as a guide to establish power and wing loading.
Hope this clarifies it for you
John
the example I gave was for a 20% scale up which applies to all linear dimensions of the complete model - ie the fuselage length, breadth and height are all increased by 20%.
A 20% scale up leads to a 44% increase in wing area and an approximate 73% increase in weight.
I then use these figures as a guide to establish power and wing loading.
Hope this clarifies it for you
John
04-13-2010, 08:47 AM
#13
RE: plan enlargement
ORIGINAL: John 38
the above examples using commercial kits are a good basis for scaling up, but if you cannot find such an example to suit your requirments, then following might help.
when you scale up a model, the wing area goes up by the square of the scale up - eg scaling up by 20% gives a wing area increase of ( 1 + 0.2 ) x (1 + 0.2 ) which gives 1.44 or 44% increase in area.
the volume of the plane or more specifically, the material and its weight used in construction , increases by the cube of the scale up , ie 1.2 x 1.2 x 1.2 = 1.73 or an increase in weight of 73%.
this estimate will be affected by any major changes in material or construction particularly if scaling up to very large models, but for modest scale up it is a good estimate.
I keep the power weight ratio the same and in this example the power increase needed would be about 70%.
Working backwards from the requirement to scale up from a 40 to a 60 engine, simply take the cube root of the ratio of the power change , ie 60/40 = 1.5 and the cube root of 1.5 is 1.15 - that is a scale up of 15% which is similar to the recommendations above.
I have scaled up Goldbergs 42''cessna skylane to 84'' and also Vic Smeeds Mamselle from 38'' free flight to 72'' and then to 108'' for R/C and power came in just under the estimates from above, but I built them very light.
hope you find this useful
John
the above examples using commercial kits are a good basis for scaling up, but if you cannot find such an example to suit your requirments, then following might help.
when you scale up a model, the wing area goes up by the square of the scale up - eg scaling up by 20% gives a wing area increase of ( 1 + 0.2 ) x (1 + 0.2 ) which gives 1.44 or 44% increase in area.
the volume of the plane or more specifically, the material and its weight used in construction , increases by the cube of the scale up , ie 1.2 x 1.2 x 1.2 = 1.73 or an increase in weight of 73%.
this estimate will be affected by any major changes in material or construction particularly if scaling up to very large models, but for modest scale up it is a good estimate.
I keep the power weight ratio the same and in this example the power increase needed would be about 70%.
Working backwards from the requirement to scale up from a 40 to a 60 engine, simply take the cube root of the ratio of the power change , ie 60/40 = 1.5 and the cube root of 1.5 is 1.15 - that is a scale up of 15% which is similar to the recommendations above.
I have scaled up Goldbergs 42''cessna skylane to 84'' and also Vic Smeeds Mamselle from 38'' free flight to 72'' and then to 108'' for R/C and power came in just under the estimates from above, but I built them very light.
hope you find this useful
John
Here it is in graphic form
04-13-2010, 12:17 PM
#15
RE: plan enlargement
ORIGINAL: John 38
(B)limeybob,
sorry - coudn't resist the pun.
is this a commercial program or all your own work ??
john
(B)limeybob,
sorry - coudn't resist the pun.
is this a commercial program or all your own work ??
john
Yes, on both accounts, its on my web site, I wrote this in Visual Basic 5 about 5-6 years ago, so its a bit ancient but it does work, even with Vista, I use it all the time as I do a lot of CAD design work for RC.
Bob
04-13-2010, 12:23 PM
#16
RE: plan enlargement
ORIGINAL: John 38
(B)limeybob,
sorry - coudn't resist the pun.
is this a commercial program or all your own work ??
john
(B)limeybob,
sorry - coudn't resist the pun.
is this a commercial program or all your own work ??
john
The intent was to be able to design a scale flying airplane for scale competition.
The software has lots of other stuff too.
Bob
04-15-2010, 11:06 PM
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RE: plan enlargement
Thanks John, W8ye, and limeybob! I'll take that into consideration. I have a new workshop being built / powered now (12' x 24') and want to find a project to "break it in". I'll keep you updated when i start the project.
Bryan
Bryan
