Scratch Build With Guillow's Wood

[kittyfritters]

Here's the other thing that has been on my workbench along with the Arrow and my other projects. It's a Bostonian for a local contest that I call the Irish Jumping Bean. This is a formal project using full EAYGA standards. (I have a prize for the first forum member who can tell us what that means.)

This model is built entirely with current production Guillow's wood. Here is a shot of the parts on the bench.



I stuck it together with a few dabs of "Green Glue" (Comes apart with a whiff of acetone.) for a "bones shot".



Since this is a bit delicate I decided to cover dry and shrink with alcohol instead of covering wet.



Here's how it looked before shrinking.



I got my pin down setup ready before shrinking the wing covering. It's a 95 degree day, about 82 in the garage, and I had to be all setup to work fast because the alcohol would start drying almost immediately.



Here's the wing wet and drying.



Fuselage is dry in this shot and waiting for a misting of Krylon #1305. That upper longeron should have been stiffer and I had to sister in another piece when I cut out the window holes.



The point about the Guillow's wood is that this model weighs, all up, just under 12 grams. It needs 2 grams of ballast to meet the minimum weight for the contest. Guillow's wood indeed!

The contest is tomorrow and I'll try not to forget my camera for video.

[stx44]

I am actually in the process of building my second Bostonian from leftover wood from my kits (well, leftover stringers and a bought sheet for the ribs, etc). The first, called a "Lil Sister" and from a plan from aeromodeller magazine, flies briliantly on a loop of 3/16 and a guillows 6 " prop. I thikn the plan is also available via HPA download.

The second is called "one knight in boston" and came from HPA plans gallery- its about the same stage as yours- shrinking the covering. I have the opposite weather issue tho- its cool and rainy here.

Is yours a self design? If not, where did you get the plan from? Its quite a neat looking little number.....

[kittyfritters]

Yes, this is my own design. Back in the 1950s there was a modeling book published that had a drawing of a contest type rubber powered model with the proportions and moments dimensioned in terms of wing span and wing area. This may not look like it but dimensionally this is the model in the drawing.

Here's what it looks like finished.





I switched to the North Pacific prop because it has a shallower pitch than the EB prop and is easier for a single loop of 1/16" rubber to swing. A small drag tab was added at the dihedral break on the left wing to insure a tight left turn. Someone suggested that with the triple tail I should have called it "Bostillation."

[kittyfritters]

Well, no video, except, maybe some rather embarrassing stuff that Dave Gee may post of it doing high-speed taxi runs around the gym floor.

It wouldn't R.O.G with 1/16" rubber for power so I changed to 3/32" rubber and back to the EB prop. I had damaged the stabilizer getting it out of the car, the first of eight separate times I broke the stabilizer in two hours, (Calls for some re-design here.) and had some trouble getting the trim right. I switched back to the North Pacific prop and it tried harder. Finally, I clipped off the tail skid to give it a better 3-point stance on the floor and that did it. I got a good flight, that managed to go behind one of the pillars and over the seating area, twice! Then the motor broke. I installed a new motor and while winding it that one broke. I re-tied it and tried it again. I made the last two flights of the contest and they were good enough for me to place 4th in a field of 14. Not disappointing for a model that I finished the night before the contest. I'll build a redesigned stabilizer for it and keep it for the next Bostonian contest.

[kittyfritters]

Here is a link to a video of a short flight of the Jumping Bean. We don't wind for maximum flights in this particular gym because of the giant ventilation fan near the ceiling. Even though it's not running when we fly it can chew up or hang up a model that hits it.

https://www.youtube.com/watch?v=8j9UN_zAeu4

[davidchoate]

Dont know the acronym, but I love it. Why such a large fuselage though? I always wanted to make one of thase superlight indoor planes, with the built up prop and all.

[kittyfritters]

The model was built to the rules of the Bostonian class. The rules encourage models with a somewhat scale like appearance even though they tend to be a bit portly.


Bostonian Rules

1. Maximum projected wingspan shall not exceed 16 inches (40.64 centimetres).

2. Maximum wing chord (measured parallel to the direction of flight) shall not exceed three (3) inches (7.62 centimetres).

3. The diameter of the propeller(s) shall not exceed six (6) inches (15.24 centimetres).

4. The length of the model excluding the propeller(s), but including the thrust bearing(s), shall not exceed 14 inches (35.56 centimetres). This measurement will be made in the direction of flight and will include surfaces, which extend beyond the thrust bearing or fuselage end because of a sweep or unusual mounting.

5. The fuselage structure must include a box, which has minimum dimensions of 1.5 inches x 2.5 inches x 3.0 inches (3.81 centimetres x 6.35 centimetres x 7.62 centimetres). The width (the horizontal dimension perpendicular to the line of flight) of the fuselage shall not exceed three inches (7.62 centimetres). The box must be enclosed within the fuselage structure and must be covered so as to restrict free air movement through the box. Normal sag of the framework between supports caused by the tension of the covering will not be considered as a violation of this rule.

6. The fuselage structure must be built-up so that the longitudinal members (the longerons) support the forces produced by the rubber motor. A solid or hollow motor stick with a lightweight structure added on is not acceptable.

7. The fuselage must have a transparent windshield and side windows of at least one (1) square inch (6.45 centimetres area each). An open cockpit design need not have side windows. But the windshield must meet the one (1) square inch rule (6.45 square centimetres) and must stand at least 3/4 inch (1.905 centimetres) above the top of the fuselage.

8. The model must have at least two (2) wheels of at least 3/4 inch (1.905 centimetres diameter, each on a separate leg, which rotate freely and support the model for takeoff and landing.

9. All flying surfaces must be covered on both sides or must be solid material with a thickness of at least 1/16 inch (1.58 mm) at the maximum point in each chord wise element.

10. The total projected area of the secondary horizontal surface(s), excluding that inside the fuselage, shall not exceed 24 square inches (154.8 square centimetres). This may be a conventional stabilizer and/or a canard surface.

11. The airframe, excluding the rubber motor(s), shall weigh at least seven (7) grams. (NOTE: All Bostonian contests I have seen were flown with a weight minimum of 14 grams. Makes a much sturdier airframe. And, yes, they are weighed at the beginning of the contest.)

Does that answer your question?

[paul]

Hi Howrad

Im in the process of building a combination of the Bostonian comprising of a Lil Sister/Pudgey and your Jumping Bean.

Cam you tell me what dihedral angle you have used or the measurement to the tip of the wing?

Thanks
Paul

[kittyfritters]

Hi Howrad

Im in the process of building a combination of the Bostonian comprising of a Lil Sister/Pudgey and your Jumping Bean.

Cam you tell me what dihedral angle you have used or the measurement to the tip of the wing?

Thanks
Paul

Paul,

The wing is as follows:
Span (Projected) 15-7/8 inches (403.23 mm),
Chord 3 inches (76.2 mm),
Airfoil, 1/4 inch thickness (6.35 mm), high point 1-3/8 inches (34.93 mm)from leading edge,
Incidence 1.5 degrees,
Wing tips 3 inches (76.2 mm) length, dihedral angle 30 degrees,
Washout 1/16 inch (1.6 mm)at the wing tips. The washout is entirely in the wing tip panels, the center panel is flat.

The model's left turn is achieved by a combination of left thrust adjustment and a small, clear, acetate drag tab 1/2 inch (12.7 mm) by 3/8 inch (9.53 mm) that hangs down from the trailing edge of the wing just inboard of the left dihedral break. The airfoil, with 8% thickness with the high point at 46% of chord is something one would expect to find on a super light stick model rather than something relatively heavy (14.7 grams) like this Bostonian, but in this case it works.

Hope this helps,

Howard

[zoomie]

This is a formal project using full EAYGA standards. (I have a prize for the first forum member who can tell us what that means.)

Over two months now and still no takers, so...

EAYGA = Every Average Yokel's Greatest Airplane

Am I even close?


zoomie

[kittyfritters]

This is a formal project using full EAYGA standards. (I have a prize for the first forum member who can tell us what that means.)

Over two months now and still no takers, so...

EAYGA = Every Average Yokel's Greatest Airplane

Am I even close?


zoomie

Zoomie,

No, but that has to be one of the most amusing attempts I've seen.

Howard

[kittyfritters]

Another try at a scratch build with Guillow's wood.

I (was) volunteered to take my grandson to Science Camp at the California Science Center this week. Since it is a rush hour drive through downtown there was no sense to driving home and back downtown to pick him up so I made a portable building board intending to sit in the food court at the museum and build models while he was in class.



So far, this has worked out well. On Monday and Tuesday I built a no-cal model. Today I started working on a "Presto", a 13.5 inch span model, designed in 1945, for the O.F.F.C. one design contest next Wednesday. This Wednesday I finished framing the wing and tail.



My work is going slower since the museum staff has noticed me and now come over to engage me in conversation while I work.

Took a view of my "workstation" and the overhead inspiration.







This design was "old fashioned" when it was drawn in 1945. It looks like it was designed in 1935. Improvements in structural design, like alignment formers, would make a contemporary version of this much easier to build. I would have found some other way rather than the box-on-box structure to do the high wing with green house design, but it has to be built according to the plans except where noted. With a total of about 4 hours work I now have something that is resembling a plane.

[davidchoate]

I eventually plan on a similar build. I have several plans for these type of planes. I cant help but notice the solid stabilizer. I have made several attempts at micro RC stuff, and have had difficulty with warpage on very small built up control surfaces, and in the end, the weight saved is minimal. I was just curious about youre reasons for not using a built tail?

[kittyfritters]

I eventually plan on a similar build. I have several plans for these type of planes. I cant help but notice the solid stabilizer. I have made several attempts at micro RC stuff, and have had difficulty with warpage on very small built up control surfaces, and in the end, the weight saved is minimal. I was just curious about youre reasons for not using a built tail?

The reason was that it is simply built according to plan. The plan specifies 1/32" sheet balsa tail surfaces. The contest rules allow built up tail surfaces but in this case I didn't think any weight saved would be worth the effort. The double vertical tails glued to the top of the stabilizer seem to create a light, rigid and warp free structure.

[davidchoate]

I have a plan for a peanut that involves laminating, and built up ribs in the wings; since I am low on $ to get the radio gear for my RC build, i'm thinking of giving it a go. I got all the stuff I need in stock, so I am going to try. I have the humid summer to help bend the wood. I dont even need water on some days.