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Post  bamboozler on Fri Sep 23, 2016 5:53 pm

I'm building a Brodak Li'l Jumpin' Bean and the Stab, Elevator, Rudder & Fin are all 1/16" balsa. Is this too thin? How's it worked for others or have you gone to thicker balsa?

Thanks for any input.
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Post  akjgardner on Fri Sep 23, 2016 6:20 pm

I would either laminate two sheets of 1/16 or use 1/8. The strenght would out weigh the weight , I would think
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Post  RknRusty on Fri Sep 23, 2016 6:23 pm

I built a Brodak Bean in 2011 or so, and the stab/elevator/fin never broke. I used the plane to learn to fly loops, so everything else broke, but the 1/16" balsa tail feathers are still in my scrap box. Look at the plane in my avatar, that's the Bean after I resurrected it into the .061 powered ReFried Bean.

One day testing a Medallion and a balloon tank, during a lazy 8, I finally pulled the stock bellcrank platform out and through all the ribs in the inboard wing.

To address your question, I Ultracoted the stab and painted the elevator. I also needed nose weight, so if you go thicker you may unnecessarily end up with a lead sled. But that was before I understood how heavy enamel(Rustoleum) paint can be. Be sure and brace the B/C platform to keep it in place.

I hope you'll post some pictures and a progress report.
Rusty

Box stock, it was a good little trainer.
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Post  Cribbs74 on Fri Sep 23, 2016 8:26 pm

Build it per plans 1/16 is fine. Mr. Goldberg didn't sell/design poor airframes.

I put my bean through hell and like Rusty's bird the stab and elevator are the same as the day I built it.

Ron

Edit: besides a 1/8 stab will look out of place.
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Post  bamboozler on Sat Sep 24, 2016 1:27 am

Thanks for the replies, I'll leave it stock with 1/16".

The bellcrank platform did worry me and it's too late for a picture because all the sheeting is on but all I did was cut a piece of balsa the same size as the plywood and glue it between the bellcrank platform and wing sheeting - very strong with almost no weight gain. :-)
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Post  RknRusty on Sat Oct 01, 2016 12:07 am

I was digging through my scrap box today looking for some 1/8" plywood, and whaddya know came out? My Li'l Jumpin Bean's entire empennage. Still hinged  with the vertical fin all intact. I confirmed that, sure enough, all of its parts were 1/16" balsa, the only surviving major part of the Bean, prior to its conversion to the Refried Bean, which still hangs in the shop with its wing CA tacked on for the sake of display.

Just for the sake of nostalgia on my part, here's what the Bean morphed into with twin tail booms, mostly new wing parts, and a plywood beam mount nose. I made sure all the measurements between prop and LE and TE to stab-hinge were the same as the bean. I also added fixed flaps for more wing area and bolted a Norvel .061 on it. Didn't have to rebalance it at all.

Here is one of its few flights before the OB wing folded. It was my first flight with a Norvel and I was a little scared of it, so I overloaded it with a 5.5x3 prop. You can hear it straining under the load a few times.

https://youtu.be/RobymeDXZkc

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Post  roddie on Sat Oct 01, 2016 2:23 pm

I guess the consensus is; as-designed 1/16" sheet works.. and is plenty durable. I wouldn't think so.. but the tail is what usually survives in an operational mishap. I personally would substitute hard C-grain balsa, if the wood supplied was soft. It's discouraging how easy it is for a model to be damaged in transit/storage. It's more likely to be damaged under these circumstances.. than it is being flown.
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Post  Ken Cook on Sat Oct 01, 2016 3:30 pm

3/32" is what the original kit had and it was C grain. I substituted a piece of bass as the elevator joiner piece even though it really wasn't two pieces. My kit was from the early 60's.
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Post  bamboozler on Sun Oct 02, 2016 5:30 am

I noticed a couple of other mistakes on the Brodak drawing. The wing tips are one-piece instead of three making them very weak. The leadout guide hidden lines are missing making it look like the leadouts go on the top.
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Post  Ken Cook on Sun Oct 02, 2016 6:35 am

They're certainly not mistakes, they're cost saving measures. Laser cutting is expensive and every minute counts. To manufacture a wing tip like the stock Goldberg kit would cost a lot more not to mention use more wood, Unfortunately, the cost savings goes in their pockets and we in turn are impacted on the negatives and the strength and durability of the end product.
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Post  RknRusty on Sun Oct 02, 2016 7:55 am

Ken Cook wrote:            They're certainly not mistakes, they're  cost saving measures. Laser cutting is expensive and every minute counts. To manufacture a wing tip like the stock Goldberg kit would cost a lot more not to mention use more wood, Unfortunately, the cost savings goes in their pockets and we in turn are impacted on the negatives and the  strength and durability of the end product.

The Brodak Baby Flite Streak's vertical stab is another example of improper grain orientation. I cut a new one of slightly thicker balsa with the grain properly oriented, and rather than mounting it with an offset to the outside, I sanded an airfoil on the inboard side. Even after all the trauma it's been through with my willingness to train beginners on it, it's still a great flying airframe.

I wish I'd found something else for my beginner friends to fly. As I mentioned in my 1/2A Day report, it now weighs 9.9 ounces, but with a strong power plant it's still an amazing flyer. Sorry I keep veering off topic, but I jus luvs my babies.
Rusty

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Post  bamboozler on Sun Oct 02, 2016 8:33 am

Ken Cook wrote:            They're certainly not mistakes, they're  cost saving measures. Laser cutting is expensive and every minute counts. To manufacture a wing tip like the stock Goldberg kit would cost a lot more not to mention use more wood, Unfortunately, the cost savings goes in their pockets and we in turn are impacted on the negatives and the  strength and durability of the end product.

The drawing is in error vs. Goldberg. Laser cutting the three piece tips with proper grain direction would use less wood and as fast the machine operates no slow down there. Laser is not new anymore it's a standard, a given, expected and again the machines fast.
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Post  706jim on Sun Oct 02, 2016 10:22 am

I built one of these several years ago and powered it with a Black Widow. Never got around to flying it.

Is this thing going to be manageable for a senior citizen who hasn't flown ukie for several years?

Figure I'll put a photo of it in a month or two in the engine of the month section.
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Post  RknRusty on Sun Oct 02, 2016 10:38 am

706jim wrote:I built one of these several years ago and powered it with a Black Widow. Never got around to flying it.

Is this thing going to be manageable for a senior citizen who hasn't flown ukie for several years?

Figure I'll put a photo of it in a month or two in the engine of the month section.
Yeah, Jim, I think it'll suit you fine, but I do recommend turning circles in the house at about 4 to 4-1/2 seconds per turn until you can do about 30 of them without getting too dizzy. That should be the equivalent of 2 minutes of flight on 35' lines. The higher your nitro, the shorter your run time will be. I never got much over 90 seconds of flight with 35%.
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