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Author Topic: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?  (Read 965 times)

Offline YellowJacket

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Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« on: January 08, 2023, 09:45:42 PM »
Any advice on a backward prop reducing the thrust enough to gently fly this plane C/L?  The plans on this little plane contained a plywood firewall and bellcrank/control horn but no instructions for any of it.  This is an older kit I had framed up and sheeted the first two sections of the fuse to make it rigid.  I also beefed up the wing with gussets at the ribs and a plywood LE/TE wing joiner to give the plane more heft.

My concern is that even with the extra weight added in airframe strengthening, that TD is going to produce too much power.

I have heard of turning props backward to reduce thrust but not sure how that would behave on an .020 and would like anyone’s thoughts on it.

I plan to use this as a trainer for my two sons as it will simply go round and round, no stunts, should have an nice, stable flight with gentle, post engine glide, and look really pretty (will add scale detail to it).

Also, since it came with red colored tissue, I will not have to use color dope and would like anyone’s advice on how many coats of thinned clear and /or sanding sealer I should use to have a fuel proof finish.

Thanks in advance for your replies.

Offline Dan McEntee

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #1 on: January 08, 2023, 10:23:36 PM »
  Turning the prop around is an old free flighter's trimming trick, to allow a decent engine run but reduce thrust but mainly reduces torque also for early test flights under power. Once you get the airplane in the ball park for climb and transition, turn the prop back to normal, reduce power with the needle valve and work your way back up to full power. It will do the same thing for a small control line model also. Unless you are flying over that mythical field of tall grass, and stick and tissue model won't survive the riggers of learning to even fly round and round. Lots of plans and some kits still available for the Cox and Norvel engines in use now. I recommend the SIG 1/2A Skyray with the engine mount retained with rubber bands.  If finish is kept to a minimum with one coat or dope on the airframe and a couple of extra coats around the nose, the TD.020 might even fly it for straight and level flight. If it's not enough power, then swap out the engine for a babe Bee .049. The Skyray can be scratch built very easily also if you have some materials on hand and use the kit to make patterns to build more. That makes for more time flying and less time building while you get started n your other projects.
  Have fun!!
   Dan McEntee
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Offline Dave Hull

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #2 on: January 09, 2023, 01:17:42 AM »
I second Dan's thoughts:  the SIG Baby Skyray is an excellent first-flight trainer with a Baby Bee

Dave

Offline YellowJacket

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #3 on: January 09, 2023, 09:19:45 AM »
Thank you for your feedback and agree with you about the Sky Ray.  The problem is that Sig is offline now and not sure when they will be back up.  I only know bits and pieces from the Hobby Shop owner near my neighborhood, so I thought I would make do with what I have laying around so my boys can fly as soon as it warms and winds are calm.

I will purchase two Sky Rays as soon as they are available again, so not dismissing your advice at all.

Regards,

Greg

Offline Dan McEntee

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #4 on: January 09, 2023, 10:08:25 AM »
Thank you for your feedback and agree with you about the Sky Ray.  The problem is that Sig is offline now and not sure when they will be back up.  I only know bits and pieces from the Hobby Shop owner near my neighborhood, so I thought I would make do with what I have laying around so my boys can fly as soon as it warms and winds are calm.

I will purchase two Sky Rays as soon as they are available again, so not dismissing your advice at all.

Regards,

Greg

    While i would like to see you support the local hobby shop, have you contacted SIG and tried ordering direct? SIG is going through some tough times and some big changes, but others have reported here that they are able to make purchases with them directly. If they are not shipping kits at the current time, I'm sure that there are some 1/2A Skyray kits sitting on shelves around the country that people may part with, and plans can be copied and mailed pretty cheaply. Try calling SIG direct.  Some shops may just be trying to be cautious and are not ordering anything from them out of fear that they won't be getting anything. Kit prices have gone up but they are even more inflated on eBay but you could keep your eyes open there also.
  Type at you later,
   Dan  McEntee
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Offline John Skukalek

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #5 on: January 09, 2023, 04:00:14 PM »
Brodak does have a number of 1/2a kits for plank wing type airplanes similar to the skyray

Offline Mark Mc

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #6 on: January 09, 2023, 10:00:47 PM »
It only takes a few dollars in wood to build a Skyray.  Much cheaper than buying two kits.  Pat King has plans for what he calls a Skyray Racer.  The plans show the model built with bass wood, but dimensions are identical to the balsa version.  Just buy the .pdf from Pat and build it from balsa.  I just built two from the plans myself.

https://stunthanger.com/smf/pdk-llc-laser-cut-kits/skyray-racer/msg530151/#msg530151


Mark

Offline YellowJacket

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #7 on: January 10, 2023, 10:20:59 AM »
    While i would like to see you support the local hobby shop, have you contacted SIG and tried ordering direct? SIG is going through some tough times and some big changes, but others have reported here that they are able to make purchases with them directly. If they are not shipping kits at the current time, I'm sure that there are some 1/2A Skyray kits sitting on shelves around the country that people may part with, and plans can be copied and mailed pretty cheaply. Try calling SIG direct.  Some shops may just be trying to be cautious and are not ordering anything from them out of fear that they won't be getting anything. Kit prices have gone up but they are even more inflated on eBay but you could keep your eyes open there also.
  Type at you later,
   Dan  McEntee


I have not called them directly, but used to before I had to take pause from this hobby in early 2020.  The website says they are relocating, and apparently (according the hobby chop owner) they are going to outsource some things like the balsa shop.  I very much would like to support them and while have been blown away by the price increases I am seeing on kits now since jumping back in, I hope that at least a decent chunk of that is increased profits to help them, and not just supply chain inflation.

I will give them a call and see what they say.

I know I could save money building from plans (thank you for the suggestions from those who made them), but I would like to do my part to keep demand up for kit sales.  I would hate for more kit companies to leave the hobby and one day. all C/L kits only being available on ebay from estate sales.

 

Offline YellowJacket

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #8 on: January 10, 2023, 10:49:22 AM »
update...just called SIG and the only kit remaining is the Dewy Bird, so I ordered it.  Unfortunately, that plant is shut down and will close its doors at the end of this month.

The new SIG shop will be up at a different location, with new equipment, but no known timeline. 

Also, very sadly, SIG dope, fuel, and other things will never be sold again...perhaps kits only.

That may mean Brodak will be the only source of dope, although fuel can still be purchased elsewhere.

Greg

Offline Chuck Matheny

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Re: Fitting a TD .020 on Guillows SE 5A - mount prop backwards?
« Reply #9 on: January 11, 2023, 10:43:50 PM »
Any advice on a backward prop reducing the thrust enough to gently fly this plane C/L?  The plans on this little plane contained a plywood firewall and bellcrank/control horn but no instructions for any of it.  This is an older kit I had framed up and sheeted the first two sections of the fuse to make it rigid.  I also beefed up the wing with gussets at the ribs and a plywood LE/TE wing joiner to give the plane more heft.

My concern is that even with the extra weight added in airframe strengthening, that TD is going to produce too much power.

I have heard of turning props backward to reduce thrust but not sure how that would behave on an .020 and would like anyone’s thoughts on it.

I plan to use this as a trainer for my two sons as it will simply go round and round, no stunts, should have an nice, stable flight with gentle, post engine glide, and look really pretty (will add scale detail to it).

Also, since it came with red colored tissue, I will not have to use color dope and would like anyone’s advice on how many coats of thinned clear and /or sanding sealer I should use to have a fuel proof finish.

Thanks in advance for your replies.

If you are using the "rubber" prop you can depitch the blades manually just by giving them a twist...[just don't go into negative pitch territory].... H^^
If you see a clever way laying around your shop  to choke the intake about 50% then that's another idea


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