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General control line discussion => Open Forum => Topic started by: Brian Massey on February 11, 2012, 11:02:33 AM

Title: Scaling Down Plans
Post by: Brian Massey on February 11, 2012, 11:02:33 AM

I want to scale down Trophy Trainer plans to build a 25 size stunter. The full size TT flys well with an LA 46, so how much should I reduce it to have a plane an LA 25 will haul well?? I'm thinking it should wind up being 65-70% of the full size TT??

Thanks,

Brian

Title: Re: Scaling Down Plans
Post by: builditright on February 11, 2012, 03:03:26 PM

Brian,

Give me a call, I still kit the Trophy Trainer so I can reduce the plans and parts files to the
size you want and cut you whichever parts or even a kit if you want. If you only want plans then
I can provide that also. let me know.

My Telephone is: 386-447-4247

Title: Re: Scaling Down Plans
Post by: Geoff Goodworth on February 11, 2012, 05:31:40 PM

I'd suggest scale to 90% of original. That gives a wing area of ~457 sq in. If you are talking 65–70% of span, you are into FP 10 territory.

Title: Re: Scaling Down Plans
Post by: Bill Little on February 11, 2012, 05:39:07 PM

I'm with Geoff!  Probably 85%-90% should do well.  Of course it depends on which ".25" you are using! ;D

BIG Bear
RNMM/AMM

Title: Re: Scaling Down Plans
Post by: builditright on February 11, 2012, 08:09:52 PM

Quote from: Bill Little on February 11, 2012, 05:39:07 PM

I'm with Geoff!  Probably 85%-90% should do well.  Of course it depends on which ".25" you are using! ;D

BIG Bear
RNMM/AMM

I agree with both of you guys but I did it @ 82% giving it a little over 44.50" span and approx 413 Sq's
I think that should be good for a 25

Title: Re: Scaling Down Plans
Post by: Brian Massey on February 11, 2012, 10:46:50 PM

Quote from: Bill Little on February 11, 2012, 05:39:07 PM

I'm with Geoff!  Probably 85%-90% should do well.  Of course it depends on which ".25" you are using! ;D

BIG Bear
RNMM/AMM

I'm planning on powering the plane with an LA 25 I just purchased. It's used (the seller said it has about a half gallon of fuel run through it) and it came complete with muffler, prop and an RC motor mount. It has an RC carb, but I've borrowed a couple of venturis to try out, then I'll order the size I like.

I'm not sure how big/heavy a plane the 25 will pull, 40-42 inch span . . . 425-450 Sq. inches . . . 38-40 oz???

I may look at several sizes as I have a local print shop that copies plans for $1.40 per page.

Brian

Title: Re: Scaling Down Plans
Post by: Geoff Goodworth on February 11, 2012, 10:59:06 PM

The 42" span Brodak Shoestring has ~395 sq in and an FP 20 flies that at 30 oz with plenty of authority. Pat Johnston went to some lengths to build his FP 25 powered '57 Nobler light enough.

That's why I think 450–475 sq in should be the target for FP and LA 25s. Build light, aim for about 32 oz and it should be good

Title: Re: Scaling Down Plans
Post by: Bill Little on February 12, 2012, 01:56:10 PM

Quote from: Brian Massey on February 11, 2012, 10:46:50 PM

I'm planning on powering the plane with an LA 25 I just purchased. It's used (the seller said it has about a half gallon of fuel run through it) and it came complete with muffler, prop and an RC motor mount. It has an RC carb, but I've borrowed a couple of venturis to try out, then I'll order the size I like.

I'm not sure how big/heavy a plane the 25 will pull, 40-42 inch span . . . 425-450 Sq. inches . . . 38-40 oz???

I may look at several sizes as I have a local print shop that copies plans for $1.40 per page.

Brian

Hi Brian,

With the parameters given you can use about any design you like to reduce, from the Impact to the Barnstormer( but I think the Barnstormer would be fine, full size, with the LA .25).

A "Thunder Gazer" might be perfect for reducing.  Any way you want to go, just don't use a wing that has too thin of an airfoil.

BIG Bear
RNMM/AMM

Title: Re: Scaling Down Plans
Post by: Brian Massey on February 13, 2012, 01:26:04 PM

Thanks for all the feedback, I can't wait to get it started.

Brian