Author Topic: correct way to scale down a .60 size plane to a .46 size (Max Bee) (Read 5513 times)

Guy Markham · « **on:** August 11, 2016, 03:42:45 PM »

what is the formula to scale down a .60 size plane to a .46 size ie: (Max Bee) it is 660 sq in and WS is 60"

Brett Buck · « **Reply #1 on:** August 11, 2016, 04:02:35 PM »

Quote from: guy markham on August 11, 2016, 03:42:45 PM

what is the formula to scale down a .60 size plane to a .46 size ie: (Max Bee) it is 660 sq in and WS is 60"

There is no formula to do that without knowing what your target wing area might be. To know that you have to know what kind of 46 you want to use. If it's a 46VF with a pipe, no scaling is necessary. If it's a G21/46, I would suggest more like 600 square inches. If you want to scale 660 down to 600, you scale the linear dimensions by the square root of 600/660, or about 95% of the original dimensions.

Brett

Tim Wescott · « **Reply #2 on:** August 11, 2016, 04:44:15 PM »

Weight matters, too. If you can complete it with a dry weight less than 65 ounces you can probably fly it on a 46LA, even at 660 squares. Again for the 46LA, scaling it down to around 600-630 square inches may work out better.

Guy Markham · « **Reply #3 on:** August 11, 2016, 05:03:05 PM »

What would the electric motor specs be if it was 600 sq in and 57' WS ?

Air Ministry . · « **Reply #4 on:** August 11, 2016, 08:58:41 PM »

Build a DQ Special ! the plan downloads free on kaz's site .

Scaling wing area for the %age reductions ballpark , all other things being equal .

Malcluscos Crusaders closer than I think He Realised . Scale down the big one to .35 size
and its so close to the original its not funny , where he just used SV 11 with Crusader Lines , one thinks .

pmackenzie · « **Reply #5 on:** August 12, 2016, 04:51:51 AM »

FWIW, Max Bee is the same size as the Max II, which flew on a piped LA46

Pat MacKenzie

Avaiojet · « **Reply #6 on:** August 12, 2016, 05:56:28 AM »

Quote from: Tim Wescott on August 11, 2016, 04:44:15 PM

Weight matters, too. If you can complete it with a dry weight less than 65 ounces you can probably fly it on a 46LA, even at 660 squares. Again for the 46LA, scaling it down to around 600-630 square inches may work out better.

Tim,

I had no idea an LA .46 could handle that size model and weight. I'm impressed!

Thanks for that information.

Tim Wescott · « **Reply #7 on:** August 12, 2016, 11:14:07 AM »

Quote from: guy markham on August 11, 2016, 05:03:05 PM

What would the electric motor specs be if it was 600 sq in and 57' WS ?

It goes more by model weight and what timer you're using (the Burger, and presumably the Fioretti, timers use more juice than the Hubin and the Renacle timers).

A good place to look is the "List Your Setup" thread that's pinned to the top of the "All Amp'd Up" section. Shop around for similar-sized planes, and look at what people are using.

Howard Rush · « **Reply #8 on:** August 12, 2016, 06:35:27 PM »

Why would you want to scale it down?

Tim Wescott · « **Reply #9 on:** August 12, 2016, 06:58:47 PM »

Quote from: Howard Rush on August 12, 2016, 06:35:27 PM

Why would you want to scale it down?

I suspect he has an engine that he wants to fit it to. He hasn't told us yet what 46 he has, so no one knows what advise to give him about just how big it should be.

Howard Rush · « **Reply #10 on:** August 12, 2016, 07:55:55 PM »

Quote from: Tim Wescott on August 12, 2016, 06:58:47 PM

I suspect he has an engine that he wants to fit it to. He hasn't told us yet what 46 he has, so no one knows what advise to give him about just how big it should be.

He also axed about electric.

It's an interesting question. If one were scaling down an airplane into which little real design effort had gone and for which little competition reputation exists, the scaled down airplane might work as well or better than the big one. Scaling down a name-brand airplane like the Max Bee and matching the aerodynamic and inertial properties of the original would be more difficult.

I'm assuming that you want the smaller airplane to be as good a stunt plane as the big one. If you like the Max Bee just because it looks cool and don't care about winning stunt contests with it, it doesn't matter as much if the copy flies well, although it would be more pleasant if it did.

Supposing one has a .46 around, wants to make a Max Bee the optimal size for the .46, and wants to compete with it, here are the elements he'd want to trade:

Certainty of having a good-flying airplane
Cost of materials and sanding
Powerplant and fuel cost
Competition cost: entry fees, vacation time, lodging

Competition cost is my biggest expense by far. Having a .46 on hand will save you the cost of one night in a cheap motel. Competition cost would be the same for either size airplane, unless you need to fit your plane into a Miata (which I've considered).

Getting the copy scaled right and flying well could be a lot of work. It may take a few prototypes. Copying the original Max Bee and its propulsion system is a pretty sure bet.

Brett Buck · « **Reply #11 on:** August 12, 2016, 09:33:04 PM »

Quote from: Howard Rush on August 12, 2016, 07:55:55 PM

He also axed about electric.

It's an interesting question. If one were scaling down an airplane into which little real design effort had gone and for which little competition reputation exists, the scaled down airplane might work as well or better than the big one. Scaling down a name-brand airplane like the Max Bee and matching the aerodynamic and inertial properties of the original would be more difficult.

I was going to find a slightly more gentle way to say the same thing, but yes, scaling all the dimensions down to 95% size might not yield a model that flies the same. Some things scale and some things don't, and certainly the mass properties will not be comparable.

Brett

Guy Markham · « **Reply #12 on:** August 13, 2016, 09:46:34 AM »

whoa, Rush don't "rush to judgment!" Guess I did not explain myself very well. I wanted a smaller plane that would weigh less as to line pull and be more portable. Would probably use Axi 2826-10 with 3300Mah 4 cell battery if I went electric or OS La .46 or Veco .45 if needed more nose weight. Scale factor : take wing area you want and divide by the original wing area and then take the Sq root of that result to give you the % reduction you need to arrive at the desired wing area. I was told of this formula by John Pond the ultimate Old time Free flight master. Thank you all for your replies. Best, Guy

Mark Scarborough · « **Reply #13 on:** August 13, 2016, 12:47:50 PM »

Quote from: guy markham on August 13, 2016, 09:46:34 AM

whoa, Rush don't "rush to judgment!" Guess I did not explain myself very well. I wanted a smaller plane that would weigh less as to line pull and be more portable. Would probably use Axi 2826-10 with 3300Mah 4 cell battery if I went electric or OS La .46 or Veco .45 if needed more nose weight. Scale factor : take wing area you want and divide by the original wing area and then take the Sq root of that result to give you the % reduction you need to arrive at the desired wing area. I was told of this formula by John Pond the ultimate Old time Free flight master. Thank you all for your replies. Best, Guy

I think the point being made is that scaling it to some dimension may not retain the flying qualities of the original

Howard Rush · « **Reply #14 on:** August 13, 2016, 01:03:09 PM »

Quote from: guy markham on August 13, 2016, 09:46:34 AM

whoa, Rush don't "rush to judgment!" Guess I did not explain myself very well. I wanted a smaller plane that would weigh less as to line pull and be more portable. Would probably use Axi 2826-10 with 3300Mah 4 cell battery if I went electric or OS La .46 or Veco .45 if needed more nose weight.

Sorry to waste your time with extra information. Just ignore it.

Quote from: guy markham on August 13, 2016, 09:46:34 AM

Scale factor : take wing area you want and divide by the original wing area and then take the Sq root of that result to give you the % reduction you need to arrive at the desired wing area. I was told of this formula by John Pond the ultimate Old time Free flight master.

I was told of this formula in high school.

Brett Buck · « **Reply #15 on:** August 13, 2016, 01:34:43 PM »

Quote from: Howard Rush on August 13, 2016, 01:03:09 PM

I was told of this formula in high school.

Or failing, that, the first response to this post.
Brett

Tim Wescott · « **Reply #16 on:** August 13, 2016, 06:22:49 PM »

Quote from: Howard Rush on August 12, 2016, 07:55:55 PM

He also axed about electric.

It's an interesting question. If one were scaling down an airplane into which little real design effort had gone and for which little competition reputation exists, the scaled down airplane might work as well or better than the big one. Scaling down a name-brand airplane like the Max Bee and matching the aerodynamic and inertial properties of the original would be more difficult.

<snip>

Getting the copy scaled right and flying well could be a lot of work. It may take a few prototypes. Copying the original Max Bee and its propulsion system is a pretty sure bet.

Yes, but...

If I were to take a completely blank piece of paper and design a stunter with a target area of 600 square inches, ignoring anything that's out there, it would probably work a lot less well than if I took an Impact and scaled it down to that size. It might prove that such a reduced-size Impact would, indeed, need some tweaking before it flew as well as the best that could be done at 600 square inches -- but it would probably be less tweaking than if I just started from scratch.

Guy Markham · « **Reply #17 on:** August 13, 2016, 08:34:33 PM »

Thanks, Tim and I say Amen to your statement ! Can we all put this to bed now?

Igor Burger · « **Reply #18 on:** August 14, 2016, 02:52:03 AM »

Pat got it right, all versions of "Max" (means Max, Max II, Max Bee) got name after OS Max .46 for which they are downscaled from larger model "Next". All Max II and Max Bee differ mostly in fuselage dimensions - Max Bee has improved side areas for better behavior in wind and turbulence. So you not need to change anything, just make it light. That is the point. I know several versions of non-piped Maxes with OS .46, funny is that they used the same prop which I flew afterward with electric version - 3 blade 11x5, but IC version with full carbon blades.

The difference between Max and Next was length of wing tip what made it aproximately 10% of wing area if I remember well.

Electric version of Max II flew in WCh Landres 2008 with AXI 2826 and 6 cell LiFe 2300mah (equivalent of 5 cell lipo 2300) battery and placed 2nd (the same model which flew in 2002 Sebnitz and placed 10th with OS Max LA .46). So with lighter Lipol you have good chance. The weight with LiFe cells was somewhere at 1650 or 1700. Actual Max Bee flights with 6 cell LiPo 2700 at 1800 or 1850.

And regarding downscaling - if you want make minimal changes in design, probably the best way is make shorter (spanwise) wing and tail. Do not touch controlls or fuselage dimmension (nose length, wing - tail length, vertical motor, wing and tail position). If you want you can make height of the fuselage smaller. However this will not save too much weight. I recomend to make it as it is, just do it as light as possible. It will allow weaker (low power) powertrain and it will save even more weight. You will get what you ask for, the downside will be model more sensitive for turbullence.

http://www.netax.sk/hexoft/stunt/the_max_ii.htm

Guy Markham · « **Reply #19 on:** August 14, 2016, 07:28:45 AM »

Thank you Igor ever so much! You just made my day

Again Thank you ... Please have Tania send me the parts list and prices to me at spitfire@silcom.com

Igor Burger · « **Reply #20 on:** August 14, 2016, 07:41:24 AM »

Guy. I will forward it to Tania, but you should know that the kit is not oriented for lightest model, it is more contest oriented, with exact composite wing and tail, means exact and strong, but little heavier for strong powertrain. I think you can do it lighter as a foam/balsa version in vacuum bag.

Guy Markham · « **Reply #21 on:** August 14, 2016, 08:32:37 AM »

Quote from: Igor Burger on August 14, 2016, 07:41:24 AM

Guy. I will forward it to Tania, but you should know that the kit is not oriented for lightest model, it is more contest oriented, with exact composite wing and tail, means exact and strong, but little heavier for strong powertrain. I think you can do it lighter as a foam/balsa version in vacuum bag.
[
Yes I was going to do that but still all the fuselage parts except the controls which Tania sent before. Best, Guy

\