Design

[bjt4888]

Here is an excellent video of AMA Penny Plane construction. I believe that this has been posted on the SO forum previously. Several steps demonstrated in the video are done "free hand" and may be difficult for a novice. However, the concepts and demonstration are very good and a few additional pieces pinned-down, weighted and measured and held with simple jigs prior to gluing would make accurate construction easier for a beginner. This video is from the public space of the internet, but, of course, we all should thank the creator Ben Saks. A number of questions related to construction of a "bucket prop" can be answered by viewing the following sections:

22:30 - cutting and soaking the blades
35:00 - bending the blades around a form (The video indicates to allow 1 hr. drying time. I usually allow to dry overnight.)
1:08 - setting pitch and attaching blades

The video shows a pitch gauge being constructed. See the Ray Harlan Indoor Specialties website for his simple pitch gauge. Ray's gauge is specifically designed for a plastic commercial propeller that has a "hole" for the shaft. You can modify this design to hold a shaft for a bucket prop.

See my attached pictures of another way to build a simple pitch gauge. The gauge in the attached picture has a short piece of 1/16" x 1/18" basswood with a very thin groove filed along its length to accept the shaft wire and with dental bands holding the shaft in place. The cotton ball holds the blade in place so that it can be glued to the blade. I install the prop shaft/spar in the gauge and the blade in the gauge without glue. There are marks on the blade for the end of the shaft. I then glue the end of the shaft to the blade with one drop of glue and the root of the blade to the blade. After this glue has dried, I add a few additional drops of glue. Super glue (CA) is fine if you want to be done quickly, otherwise, thin carpenters glue (elmers yellow, thinned a little with water) us usually used as it does not shrink like Duco Cement. Glue shrinkage at these joints is a bad thing as it will usually alter the blade pitch and make pitch between the two blades uneven. I like this type of pitch gauge for models like this one as I can see the prop spar better as I am gluing it to the blade.

bjt4888

[InfiniCuber]

Here is an excellent video of AMA Penny Plane construction. I believe that this has been posted on the SO forum previously. Several steps demonstrated in the video are done "free hand" and may be difficult for a novice. However, the concepts and demonstration are very good and a few additional pieces pinned-down, weighted and measured and held with simple jigs prior to gluing would make accurate construction easier for a beginner. This video is from the public space of the internet, but, of course, we all should thank the creator Ben Saks. A number of questions related to construction of a "bucket prop" can be answered by viewing the following sections:

22:30 - cutting and soaking the blades
35:00 - bending the blades around a form (The video indicates to allow 1 hr. drying time. I usually allow to dry overnight.)
1:08 - setting pitch and attaching blades

The video shows a pitch gauge being constructed. See the Ray Harlan Indoor Specialties website for his simple pitch gauge. Ray's gauge is specifically designed for a plastic commercial propeller that has a "hole" for the shaft. You can modify this design to hold a shaft for a bucket prop.

See my attached pictures of another way to build a simple pitch gauge. The gauge in the attached picture has a short piece of 1/16" x 1/18" basswood with a very thin groove filed along its length to accept the shaft wire and with dental bands holding the shaft in place. The cotton ball holds the blade in place so that it can be glued to the blade. I install the prop shaft/spar in the gauge and the blade in the gauge without glue. There are marks on the blade for the end of the shaft. I then glue the end of the shaft to the blade with one drop of glue and the root of the blade to the blade. After this glue has dried, I add a few additional drops of glue. Super glue (CA) is fine if you want to be done quickly, otherwise, thin carpenters glue (elmers yellow, thinned a little with water) us usually used as it does not shrink like Duco Cement. Glue shrinkage at these joints is a bad thing as it will usually alter the blade pitch and make pitch between the two blades uneven. I like this type of pitch gauge for models like this one as I can see the prop spar better as I am gluing it to the blade.

bjt4888

I don't think you put the link for the video... xP

[bjt4888]

Sorry. Here's the link to the video referenced in my post above. I also see that I have a couple of typos. Obviously, I'm gluing the blade to the prop spar, etc. Sorry about that. Typing too fast.

Bjt4888

https://vimeo.com/68616979

[bernard]

In Elastic Launched Glider, offsetting the rudder was enough to make our glider turn. Why do we have to change more for Wright Stuff to get our planes to turn?

[jander14indoor]

Much more complicated things going on when you add rubber power.
Big issue is that huge prop and the non-linear rubber.
First issue is turn
- Early in the flight the prop torque is very strong giving the plane a strong left roll and turn. If not compensated for, it will roll the plane into the ground on launch. Thus longer left wing and washin in left wing.
- Early in the flight the thrust from the prop and the rudder dominate turn radius.
- Later in the flight, when power drops,
- Goal is to balance forces so the turn stays relatively constant.
Next issue is climb angle
- early in flight, you have so much power from the prop that you'll powerstall unless you give the plane a lot of down elevator. Thus prop needs down angle.
- later, frankly the bulk of flight, you need best lift which requires the elevator to hold the nose up.

So, more variables to manage to get a good flight, thus more adjustments to make to control turn.

Jeff Anderson
Livonia, MI

[torqueburner]

So here is a fresh topic. I've noticed that there are different ways to trim the plane. For example, some planes have the stabilizer fixed on the tailboom, and adjust the wing incidence to trim. Others, including the ones we are flying, have an adjustable stab. We set the wing with a small amount of positive incidence (about 1 degree), and adjust the stabilizer incidence to trim.

It would seem to me that trimming with the wing will also change the downthrust angle, while trimming with the stab does not. Am I correct? And is there any reason to prefer one of these trimming methods to the other?

[jander14indoor]

If I had to chose, I'd make the stab adjustable. No real strong reason.
But I avoid having to make that choice by having both wing and stab on posts and adjustable. I do that more to allow complete breakdown of the plane for stowage in the transport box then for adjustability. I then generally set the wing and make most of the rest of the adjustments with the stab. Only go back to wing if I see evidence of power stall.

There is a risk to that approach. More adjustments means more risk of error in a competition. I've known some coaches to have their students build with the adjustability while developing/testing, and then to lock in most of the adjustments before the competition, only leaving the critical few needed to adjust for ceiling height.

Regards,
Jeff Anderson
Livonia, MI

[bernard]

Our team is almost done with our plane. Does anyone have recommendations for starting to test the plane? In Elastic Launched Glider last year we started with just letting the glider glide easily without launching it. Is there a similar approach people use with Wright Stuff to make sure the plane doesn't break on the first test?

[InfiniCuber]

Our team is almost done with our plane. Does anyone have recommendations for starting to test the plane? In Elastic Launched Glider last year we started with just letting the glider glide easily without launching it. Is there a similar approach people use with Wright Stuff to make sure the plane doesn't break on the first test?

I would suggest that you first try tossing it lightly with the propeller on (no rubber) and if it seems to glide well, put some rubber on and do some trim flights, many times I have done 30 turns with a 15:1 winder (it may depend on the thickness of your rubber, but really only if it is SUPER thin or thick). That should help you trim a bit, then go with higher winds, trim. Etc!

[bernard]

Our team is almost done with our plane.anyone have recommendations for starting to test the plane? In Elastic Launched Glider last year we started with just letting the glider glide easily without launching it. Is there a similar approach people use with Wright Stuff to make sure the plane n't break on the first test?

I would suggest that you first try tossing it lightly with the propeller on (no rubber) and if it seems to glide well, put some rubber on andsome trim flights, many times I have done 30 turns with a 15:1 winder (it may depend on the thickness of your rubber, but really only if it is SUPER thin or thick). That should help you trim a bit, then go with higher winds, trim. Etc!

Thanks for your suggestion! Could you explain what you mean by trim?