Zweibox HLG

[philly]

Mind showing a sketch of this spruce/balsa idea. I need ideas for light but strong.
Just received a reply from FAI and they will ship with a cheaper option when/if available. I guess the priority mail is a default.  Ordered.

[OZPAF]

Here is the plan of my 12" version on the HPA Builders Plan gallery

https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=10962

The idea was taken from a Larry Connover series of HLG's for the beginner - named "Skimmers".

John

[philly]

Interesting idea using a paper covering, had not seen that before. I dunno how I would make a compound shape with it around the elliptical plan-form and over the airfoil. And is my paper clay free? Light enough? I do have some fiberglass and resin "in stock" so will go that route. Will keep the paper idea in the back of my head for another day.
Tnx for the spruce/balsa idea Oz. I do have a piece of 16 lb. balsa I can use for the fuselage and might try that as I think it might be lighter than using spruce @ ...is it ~27 lb/cu.ft? Your way stronger of course. If I was an engineer maybe could calculate the optimum spruce to balsa sizes to optimize the strength to weight ratio.
Another option, I have a tapered carbon shaft coming for another project. The cut off (excess) length may be enough for a Zweibox tail.
Gusts to 50mph and 1.3" rain yesterday. Not missing any flying weather.

 

[dosco]

Interesting idea using a paper covering, had not seen that before. I dunno how I would make a compound shape with it around the elliptical plan-form and over the airfoil. And is my paper clay free? Light enough? I do have some fiberglass and resin "in stock" so will go that route. Will keep the paper idea in the back of my head for another day.

Initially I was thinking you could reinforce the root at the 1/4 or 1/3 chord with diamond shaped bits of paper. Covering could be pretty straightforward with 1 piece on the top, and 1 on the bottom.

Anyhow, no worries, just something to think about.

Gusts to 50mph and 1.3" rain yesterday. Not missing any flying weather.

You must be on the eastern seaboard ... yes, it was pretty horrible here in Maryland as well.

-Dave

[dosco]

Phil:
Here's another one for your memory bank (the paper and white glue made me think of it ... I've been thinking of trying this with Kraft paper and balsa). If you already knew it, please ignore.

You can use white glue (it works for Elmer's Carpenter's Glue as well) as a "heat activated instant adhesive."

Put glue on each surface to be joined, wipe off excess. Let dry.

When you're ready to join the bits, get your covering iron (or an old clothes iron) hot.

Put the two pieces together, and heat them with the iron (press them together using the iron). Make sure they get hot ... the glue will "activate" (I'm not sure if it melts or what). Keep the bits together until cool.

Done.

I've used this method to affix "D-tube" sheeting to wing leading edges.

Cheers-
Dave

[scooterjay]

Wow! I bought a boxful of model mags in 1990 and one had Oldenkamps article and plans for Zweibox in it. I probably built 50 of them since. I discovered it likes a rearward CG. I'd add more left rudder to counter any stalling.  Think I'll start building a few just for nostalgia!

[dosco]

Wow! I bought a boxful of model mags in 1990 and one had Oldenkamps article and plans for Zweibox in it. I probably built 50 of them since. I discovered it likes a rearward CG. I'd add more left rudder to counter any stalling.  Think I'll start building a few just for nostalgia!

Cool! I hope you post some pics.

If you've read through my rambling thread, you will see that I agree about the aft CG.

Regards-
Dave

[scooterjay]

As soon as I find a suitable razor plane. My old one has been MIA for many years, and the plastic Master Airscrew one I bought is junk!

[philly]

What do you see in flight that makes you feel the CG needs to be "more back" than the plans suggest? My complete WAG is if it is not flying correct with the plans specified CG (within reason) the wing or tail angles/ decalage is likely wrong?  Now if we could do the dive test the RC guys do that might help decide its neutral,negative, or positive longitudinal stability.
Not sayin' your wrong, just looking to learn something new regarding CG placement.

[dosco]

What do you see in flight that makes you feel the CG needs to be "more back" than the plans suggest? My complete WAG is if it is not flying correct with the plans specified CG (within reason) the wing or tail angles/ decalage is likely wrong?  Now if we could do the dive test the RC guys do that might help decide its neutral,negative, or positive longitudinal stability.
Not sayin' your wrong, just looking to learn something new regarding CG placement.

The amount of "up elevator warp" I had to put into the H. stab to get it to *not* nose-dive, which was alleviated by removal of noseweight. (granted this is in calm air ... in rough air, I'd plan on adding both noseweight (clay) and elevator trim).

To your point, there are several things of which I am not aware:

> I do not know if my fuselage stick has the correct decalage built in ... it could be really incorrect (1 or 2 degrees is, unfortunately, 3/5ths of not much)

> I do not know if my airfoils are "correct" which affects dynamic stability

   >> My wing "airfoil" is really a triangle with a Phillips Entry LE

   >> My stab airfoils ... hard to say ... rounded LE and "thinned aft section," but probably not "airfoils" in the truest sense

#2 Zweibox is still in yet-to-be-finished-or-assembled-pieces after my move. Work has been insanity lately, am trying to break free one day and grind on it a bit.

-Dave