propbuster

My Feedback: (1)

Hi Guys! Whats the best way to make lightening holes in sheet balsa without splintering the edges?

Pecanpatch

Hey,
I draw my circle with a circle template and a ball point pin. then I put a undersize hole in the middle of that, smaller than finish size , but big enough for one of my dremel drum sander arbors to go inside.

then I will weight down the balsa so it cant move with the hole part hangin off the table.....

I then use my dremel tool with both hands to keep it steady. Use the drum sander very carefully to sand up close to the ink mark.
If you really want to be precise, after the dremel use a dowel wrapped with finer sand paper to sand the hole even closer/smoother.

I hope this helps

CoosBayLumber

My Feedback: (1)

In my opinion now, I have taken the attitude that the Scale Flyers have long since done. Don't work with lightening holes anymore. For the weight saved is wasted in loss of strength. We weighed all of the cut out wood on a glider a friend was making up. For a two metere wingspan, the wood weighed in at 2-3 grams. Yes, not even a whole ounce. As radio gear and covering is now measured in Grams instead of ounces, the effort was wasted then.

This was validated by a series of tests in the Aero forum near end of summer 2007.

Wm.

Jim Thomerson

Small holes are easily cut using a piece of brass tubing. Shave the inside with a # 11 blade to sharpen it, and make some saw notches around the cutting edge.

RCPAUL

My Feedback: (1)

Sometimes, large holes can be cut using a hole saw at high speed ina drill press. Back up the balsa with a board.

Paul

propbuster

My Feedback: (1)

Thanks for all the advice guys! Has anyone tried using Forstner bits?

rainedave

My Feedback: (1)

Forstner bits will work if you clamp the balsa between two pieces of light ply. That will prevent the balsa from tearing and splitting.

One of my favorite quotes in this hobby (don't know who coined it) is, "The goal is not to find one place to lose an ounce, it's to find twenty-eight places to lose a gram."

David

KidEpoxy

Depending on the size of the holes you're talking about...

Are you stuck on round?
Use the Sharp Brass Tube method at the 'corners' of triangular-hexagonal holes, maybe 1/4 to 3/8"d
and then just run the #11 Xacto & ruler to 'connect the dots',
using tangent to the radii of the holes the brass made.

If you are swiss cheesing a large area with symetric holes,
make a template from scrap sheet for locating the brass tube holes.

You can also use this to cut holes that leave diagnol brace type webbing with decent/uniform radiused corners

Red B.

I agree, lightening holes are a waste of time and often weakens the structure. Sanding is often as effective and doesn't compromise strength as much as lightening holes sometimes do.

Icleanh2o

I like to punch holes in my ribs to equalize the pressure between the bays with a cheap hand held hole punch. Ang if you have money to blow Whitney makes a hand help punch with different sizes of punch sets.


Rick

gcb

If you are specifically talking wings, consider strip ribs.

George

propbuster

My Feedback: (1)

The holes will be in some 5/16 sheet for the horz. stab on my Dad's Sun Fli 4 he's building from scratch. He's going with sheet balsa rather than a built up one, and thought lightening holes would help compensate for the added weight. I thought I remembered reading somewhere about using Forstner bits as a good way to do this.

rainedave

My Feedback: (1)

Be sure to add cap strips on the ends of the parts with the grain running chordwise to prevent twisting and warping.

David

combatpigg

My Feedback: (3)

Years ago I needed to mass produce circular end caps for bladder tube compartments out of 3/16" balsa. I made an arbor that clamped a #11 Xacto blade off to the side with a spring loaded pilot. It worked very well, but you had to make sure that the wood you are cutting doesn't move one iota.

digital_trucker

A better way is to build up the tail surfaces and sheet them..stronger than solid sheet at a fraction of the weight.

Walther

My Feedback: (1)

Lightening holes are best made with a burr in a dremel tool of the size you need It is also a good way to make holes for push rod or servo wire.

combatpigg

My Feedback: (3)

I don't think you can do much better on a small to medium sized model than to just take some contest grade 3/16"-1/4"-3/8" balsa and make a solid sheet tail surface. with no holes. Airfoil the part not just to make it look nice but to also make it lighter.....but forget about the holes, they won't add up to anything if you use light wood.

KidEpoxy

I dont think I need Contest Balsa, I need Contest Glue

No matter how hard I try to be sparing with the glue, seems like half a 4oz bottle of elmers is gone before the plane is ready for cover.... and thats a bad thing.

Built up tail shoould be lighter,
unless you are like me & use 2 tablespoons of elmers just to connect a couple 1/4in sticks.

Guess what I am tryin to get around to is
watch the weight added for the glue of a built up & skin, vs the weight of balsa cut out of a slab

airraptor

My Feedback: (66)

28 lighting holes at 1 gram each = one ounce.

so leave the holes in and just use lighter fasteners like Ti or aluminum. carbon landing gear, carbon puch rods, do you really need MG gear servos, light weight wheels, xoar props over apc, plastic spinner over aluminum. see what i am getting at.

mgnostic

Usually if it needs to be lightweight I have to go with the guys in the built up club. For cutting holes though I do use a tool that came from a scientific supply company. It is a set of brass tubes with handles that were intended to bore holes through corks so that glass tubing could be inserted. The tubes are sharpened from the inside out. That is the bevel is on the inside. Have to be sure to use a backer to keep from splitting the wood and go gently twisting the tube as you go.

Silvaire

My Feedback: (50)

I do understand what you mean by using too much glue. With Titebond type glue, try using a small artist's paint brush to apply the glue - and in sparing amounts just where you want it.

Try making up some test pieces using less and less glue. With a good fit you will be surprised how little glue you need to get an acceptable bond.

Where I seem to apply too much glue is when laminating doublers. Does anyone have a particularly good method for using a minimal amount of glue for laminating?

Arlen

digital_trucker

I just squiggle the glue on, put the two laminations together, and apply pressure and move them in circles against each other to make sure the surfaces are totally covered. Wipe of all excess glue that squeezes out.

combatpigg

My Feedback: (3)

3M77 works well for doublers.

rainedave

My Feedback: (1)

When laminating balsa I thin the wood glue with just a little water and squeegee it on both surfaces. The water helps the glue get into the wood grain so it takes less glue to make a strong bond (old cabinetmaking method). But, get the glue too watery and the balsa will ripple. Practice.

David

Andrew

Here are two approaches I have used. The first, which I use a lot, consists of an internal frame of 1/8" stock sheeted with 1/16". It is light, but very stiff and not prone to warping. The second has already been mentioned == go the built up route.