Rubber Band Power

[mbauer]

Gluing the Fuselage Pod Top Skin:


Right Nacelle. Will soon know it it fits properly or if needing a major re-design. Rubber band tube is inside and slightly below the wing. Will be major issue if the wing doesn't fit to the nacelle:




This part needed re-drawn. In luck, the green fits perfectly. The blue not so much. after the use of a hobby knife, green stayed put. Re-draw then print new part, problem fixed-took 3.5 hours of print/test fit/draw/print.


Front view of finished pod. Note spar markings for the outer nacelles? Wasted time. The spars will be covered by the wing skin when ready to locate the nacelles to the printed area on the skins:

Boy oh boy did I feel smart....

Main fuselage the markings are the only way to align everything. Not so much the nacelles:


Closeup front view:


Mike

[mbauer]

Just checked the Nacelle Fit. Going to have to print some small 1/2" wide trim strips. gaps on the underside, but looks like it is a great fit.

More photos leading to the fit test.

Glue the wing spar to fuselage Pod:


Rolling paper tube for rubber band. Sheet size was 31" x 19" wide:


Paper tube ready for spray glue. Only short section will see the 3m Super 77 adhesive spray. Good stuff, works better over the long time than others:


Sliding left wing onto spar and fitting for glue application:


Now for an issue.

The wing tabs would not stay in the cut slits on the fuselage, a big gap was hard to close. Finally glued the trailing edge, it kept popping loose, so decided to use masking tape to hold it where it needed to align at.

The to add more fun to what should have been an easy attachment, the fuselage side decided to "oil" can inwards. This caused the tabs to pop out before I could glue everything together. Then success, glued and finally done, set the Pod with the wings attached down for drying. POP! Whole lower wing root and front half of top side popped out.

At this stage that was a huge issue! Ever try to glue tabs and have this happen? Then you know that when trying to re-insert the tabs, wet with glue they sometimes are impossible to insert. Wet, soft bendable, just won't work easily.

Well, these were not that wet and soft yet, knew I had one chance to get done or the need to pull apart and hope for a second try when everything was dry.

What I did was drill a small hole in the fuselage side-opposite the wet glue connection. Great now to find something to insert through the fuselage to "push" the oil can back into proper position.

Just happen to have a piece of .078 music wire that is being used for the landing gear. Pushed this through the small hole, and applied pressure to the offending side. "POP" everything was back together. Wow, that was easy!

Now to hold it until the glue dries. Wait, what? Hold till the glue dries? Laziness is the mother of all inventions; why not set the model down so that the wire is supporting the weight and holding everything in place while the glue dries?

Using a box and my large quilting ruler, that is what this photo shows. Model is leaning against a lazyboy "recliner" as the glue dries. Left it overnight. The next day everything was perfect!:


The Nacelle is almost complete. Short section of top skin to glue. Time to glue the rear rubber band mount. Why wait till now?

If it is not glued properly, the fuselage will twist. If the fuselage is made till this pint, it helps to align the mount because it is basically done:


Rubber bands added next.

Rubber bands are 56" long. All three per each side weigh in at 1oz.

Nacelle done rubber bands mounted, total weight 3.8oz with rubber bands installed:


Nacelle Fit test; Some issues the top of the rubber abdn tube applies pressure to the lower wing surface. This forces the wing up into the top of the airfoil shape. There is a 1/4" gap along the bottom. Will need to cut some trim strips to fix. It is a design issue, but the tube will help hold the wing once glued. Don't see any adverse issues with just gluing and calling it ok.

Using a 12" propeller will have .65" clearance according to AutoCAD. Should have some get up and go!:


More photos as the build continues. Cut, glue fold, install rubber abnd, tube and bands.

After it is made should be fast and easy to complete model. Slide everything together for fit and verify everything is straight. Once fit is complete, will glue everything at once so it all dries together. Maintaining alignment with out moving around to do each piece.

Mike

[mbauer]

Made it to the part test fit step. Will need to create under wing fairings to fix the gap at the bottom of wing/nacelle connection. Looks like it will have the .6578" prop clearance the drawing shows it should have, not a good thing if the 12" props strike the cockpit pod.







Once everything is glued, the landing gear will complete the build process.

Learned some new stuff on this design. Will be the last rubber band project for awhile. Need to get other projects back on track.

Plan on seeing a Spitfire, Hurricane, FW190 and ME109 as the next project, will be some time before getting started. Then back to US fighters: F4f, F6f. P39.

Been working up some instructions. Once complete, will list on eBay offering kits for sale.

Mike

[mbauer]

Finished the P38 last night. Had to reprint the landing gear.

Lots of taxi power, wound up both props just a little, it moved quickly for how many winds were available.

Nose wheel was to big or the main wheels were to small. Decided the nose wheel would be easier to adjust so, it was downsized from the correct "scale" size. 2.5" down to 2".

But after weight and balance, found out it actually is the location of the main wheels. The main landing gears need to be moved back.

I drew the gear and located it from the drawings. Should have used common practice to at least check their location. 5 degree back from CG location. They are nowhere close to where they should be.

Since they are firmly glued in position, surgery is not an option.

The nacelles have been re-drawn already, fixed an issue with the lower engine cowl being wider than the top. Almost ready to print the new nacelles and remove the old, would correct both issues. But, already working on my Jet Paper Airplane project-this will go on hold for awhile.

The biggest issue fixed when drawing the nacelles? Corrected the rubber band tube mount/wing interference inside the nacelle. This was a basic re-draw of the whole nacelle. The only thing that stayed the same? the length.

P38 Specs:
Wingspan: 57.5"
Rubber Band: 1/4"W x 57"L @ 6 loops
Propeller Diameter: 12"
Build Weight: 1lb .09oz
Ready To Fly Weight: 1lb 7.4oz

A couple of photos of it added to the "Pile".




Thank you for checking my thread out. Will re-visit in the future.

Mike

[Don Boose]

You sure have produced a lot of flying models, Mike! That's quite an array.

Is that a Dyna-jet I see on the yellow flying wing?

Have you tried flying the P-38 yet?

Don

[mbauer]

Mentioned the rivets in one of the posts. Here are a couple photos of the pattern used from the drawing that I found.

The cut you can see on the nose is the access door for the weights added to balance.


Want to say a Big THANK YOU to AirDave- He brought to my attention something I was over looking. Notice in this photo the wing is not distorted until the tip. By bringing the wing spar right to point of distortion, that ends up being the area instead of inboard portion of the wing! Big issue was cured with a simple fix. Thank you Dave! My thinking at the time was the spar didn't need to go all the way to the tip, as such save a little weight. The turbulence from the resulting distortion probably would result in a poor performing flight.


Mike

[airdave]

wow, I actually helped in some way?!


I always wonder about the rounded wing tip ends on most aircraft.
Why do wings always end that way.?
Why not end flat, with the last rib?
Whats beyond that point, isnt wing shape...doesn't do much as a wing surface.
Its just extra material, extra construction, extra weight.
Spitfires and Mustangs look cool with their clipped wings.
Air Racers clip the ends of the wings.
There must be something to my logic?
and it sure would make paper model airplanes a lot easier to build!

[mbauer]

Originally Posted by Don Boose

You sure have produced a lot of flying models, Mike! That's quite an array.

Is that a Dyna-jet I see on the yellow flying wing?

Have you tried flying the P-38 yet?

Don

Hi Don,

No, the pulsejet is a Hobby King Redhead. Purchased 2015 with electronic ignition.

That project will now be moved to the flight stage. Welding up an aluminum frame for the power system on Monday at work. The wood used for that particular prototype was to see if the "power skid" system would work. Wood wouldn't last very long with that engine running!

It will be several days yet before I can fly outside. Took these photos when I saw your question on flight. Ice is off most side roads, we've been driving on solid ice since Nov.

What is great? Last week the fence posts were just starting to show, it has been cold until Tues., when it finally warmed up. About time we got rain instead of snow, the rain really has been knocking the snow down! These photos were taken at 0633 this morning:

Notice fire ring is clean? Threw an outdoor Alaska beachwear party for my Daughter on her birthday, 1st week of March. Everybody had to wear swimming suits on the outside of their normal winter gear. Ice chairs around the perimeter. Had built in beer holders. Temp was -18deg F until the day of the party warmed up to above zero. Ice chairs didn't work as well. Beer/spirit coolers worked great; stopped everything from freezing. Used a cutting torch to cut the designs in the ring.






Going to be some time before can fly outside! Main reason still working on projects in the house.

Mike

[mbauer]

Been thinking how to make a B-25 Bomber with rubber power.

Looked at using some fishing swivels, but those won't work, they are called swivels for a reason. What I need is a universal joint, actually two per propeller.

After a search, all I could find are heavy metal ones used for RC cars and Boats, decided to search for how to make them: Found a couple of different ways to make using parts from sharpie style markers.

Youtube is a huge resource

Better yet I have several plastic tubes that should work top create what I need, plenty of music wire from 1/32" dia to 1/8"dia., carbon fiber in all kinds of diameter, aluminum and brass tubing in small dia. as well. A combo of them all should work for what is needed.

My digital scale will be in use to verify the lightest combination of materials to use. This has to be be super light weight.

If this works a B-17 and B-29 or any multi-engine can be done.

As I start this, not sure where it will end up, but think the answer is in plain view, only option is to start the design of the airplane model and fit the u-joints to see.

Will it fly?

Going to add weight to an already heavy paper design, most of the weight will be aft of the CG. Lots of technical challenges are in the future, but willing to give it a try.

Only one way to find out if it will work: Time to start designing!

AutoCAD computer is starting up!

Mike

[southwestforests]

It is as interesting watching the design process happen as watching the model come together.