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Jan 23, 2020, 10:42 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
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Discussion

A lighter Grand Esprit???


Hi guys, first, I have a set of .DXF cad plans for the Grand Esprit and own my own laser and have cut a full kit for it, with the intention of building it as soon as I can get a tail boom from Cloudsniffer. But, I have a question, The ribs are 3/32" and was wondering about cutting them out of 1/16" and capping them with thin carbon strips (.010-020") to make the plane lighter. I'm also thinking of some other things to light it with thinner spruce and carbon for the spars. Any thoughts on this?? And before anybody says there are better planes than the Grand Esprit, yes, there probably are, but I 'like' the Grand Esprit, I have the plans, I have a kit and the canopy (I would like to find a plastic nose for it though), so, I'm good to go with it.

SteveT.
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Jan 23, 2020, 11:00 PM
If it flies, I can crash it.
rocketsled666's Avatar
While I can't comment on the plane itself, using thinner ribs with CF cap strips will almost certainly result in a structure stronger than just the thicker rib alone. By quite a bit, I'd imagine. CF is a lot stronger than Balsa.

But do the math, the thinner rib with cap strip might weigh more than the thicker balsa rib. CF is a lot denser than Balsa. And don't forget to include the glue you need to stick the cap strip to the rib in that calculation... I think it's going to add up quick.

Consider more traditional balsa cap strips maybe?
Jan 23, 2020, 11:08 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
But .012" fabric (from which the strips would be cut) is less than a human hair thick, and it only needs a couple of drops of CA to adhere it to the top of the rib. The strips would be 1/16" wide by .012".

Or, I can get it in .008" with adhesive already on it.

SteveT.
Last edited by SteveT.; Jan 23, 2020 at 11:27 PM.
Jan 24, 2020, 01:24 AM
Registered User
Quote:
Originally Posted by SteveT.
But .012" fabric (from which the strips would be cut) is less than a human hair thick, and it only needs a couple of drops of CA to adhere it to the top of the rib. The strips would be 1/16" wide by .012".

Or, I can get it in .008" with adhesive already on it.

SteveT.
That is some seriously thick hair. Probably from Paul Bunyan.

You'd be much better off using thin, unidirectional, pre-cured carbon strips. Avoid woven carbon in this application where all the stress is one way. You can probably use much thinner than .008", too. It all seems like a lot of work, though. I suggest you cut a set of ribs out of 6 lb. wood and weigh them before you go to much trouble. Or you could cut a set of cardboard practice ribs, weigh them, and apply a factor to account for the difference in weight per unit area. My guess is that you won't find there's enough weight to worry about it. If you do want to lighten them up, thinner wood with cap strips might be a good way to go, but you'll have some extra joinery work.

If I was going to use carbon in one of these, I'd use it in the tail boom and spar caps. Glass is heavy and floppy, at least compared to carbon fiber. A high quality carbon tailboom would be lighter, and the increased stiffness wouod probably improve,the handling. The v-tail will impose significant torsional,loads, so it would be best if some of the fiber went around the boom diagonally. Tail booms with all fibers parallel to the axis of the boom can flex a surprising amount with a v-tail mounted on them.

Those wing joiners don't impress me. Maybe the two of them together woukd be enough for a 100 inch floater whose owner knows how to properly tap the winch pedal. Plus, at least to my eyes, the way the receiver tubes are mounted looks flimsy.

I'd be in favor of one wing rod, an ejector pin at least 5/16" in diameter, conventionally mounted between the spar caps. Anyway, you could get some ideas from the Bubble Dancer plans, though if you know how to tap the pedal, you probably don't need to wrap with Kevlar. Someone who's willing to tap probably doen't need a spar anywhere near that strong, either.

If I was going to avoid carbon, I'd probably use spar caps and shear webs. I'd probably go with 3/8 X 1/8 caps using wood that's much stronger than spruce for the first foot or so, then scarfing to spruce, and tapering the spruce as it got further out. I think you could probably make a wood spar that was stronger and lighter than the one shown.
Jan 24, 2020, 02:08 AM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Ooops... yes, you are correct, .012" would be 3-4 times the thickness of a human hair.

I have built original Grand Esprits and I have winch launched them with the winch I owned during the late 1970s.

Yes, the tail boom will be carbon, as it is a tail boom from CLM Pro.

As noted, the original ribs are 3/32 and I want to go to 1/16 and still retain the strength.

As to strips, I have not been able to find them and was going to cut the woven cloth diagonally to have long strands. If you know where I can get 1/16" wide carbon strips in approximately .010" thickness, please post a link.

SteveT.
Last edited by SteveT.; Jan 24, 2020 at 03:32 AM.
Jan 24, 2020, 06:21 AM
Registered User
whacker's Avatar
stevet

seems to me someone redid a set of airtronics or aerosphere plans a couple years ago and added a whole bunch of new data and Info to the drawing and uploaded it somewhere.


Not sure If that counts as a Grand Esprit , but maybe have a look for that, there may be a complete new wing design and fuse design there for you.

whacker
Jan 24, 2020, 07:30 AM
Sonoran Laser Art
Steve, do you know what a rib set weighs now and what the potential saving is? Have you built a stock one and know how it balanced? What the AUW is?

Many older designs require a lot of nose weight with today electronics. Then depending how much you can out is the airfoil still good?

If you add a carbon cap to 1/16 is it actually lighter than a 3/32 rib?

Just food for thought. The GE is a beautiful model and I can see how a lighter one would be attractive. A redesign with a similar planform would be cool.
Jan 24, 2020, 08:40 AM
Balsa breaks better
Thermaler's Avatar
I can speak from experience. Both my Grand and Super Esprit's flew VERY well as originally built.
Then I had a ouey with the Grand, it flew better after repairs were made. Need to repair it again.
Had the same experience with the Super.

A LITTLE extra weight is a good thing for them.

Rumor has had it that we fly the woodies too slow anyway . . .


Joe

Balsa Breaks Better
Woodies Forever
Jan 24, 2020, 03:03 PM
Registered User

Great Company


Hello:
Ditto on the two GE. I love mine. They have been sitting in shop too long since they were last in the air. Trans orange from the 70. Not brittle.

I get all my CF needs from a great company, They also have great booms!

My only concern is the their cost for shipping...……… for small orders

< http://cstsales.com/a-carbon-fiber-material.html >

good luck
cheers
Jim


Quote:
Originally Posted by SteveT.
Hi guys, first, I have a set of .DXF cad plans for the Grand Esprit and own my own laser and have cut a full kit for it, with the intention of building it as soon as I can get a tail boom from Cloudsniffer. But, I have a question, The ribs are 3/32" and was wondering about cutting them out of 1/16" and capping them with thin carbon strips (.010-020") to make the plane lighter. I'm also thinking of some other things to light it with thinner spruce and carbon for the spars. Any thoughts on this?? And before anybody says there are better planes than the Grand Esprit, yes, there probably are, but I 'like' the Grand Esprit, I have the plans, I have a kit and the canopy (I would like to find a plastic nose for it though), so, I'm good to go with it.

BTW: I carved a balsa nose block and hollowed it out and then coated it will Epoxy and sanded. Plastic nose cone is a out of date item. IMHO

SteveT.
Jan 24, 2020, 03:33 PM
Registered User
jtlsf5's Avatar
You're not going to get much value from lightening the GS, will just make it more squirrely when slowed down for landing. Both of the GS's I've owned flew just fine at the design weight. If you're going to make any mods I would suggest improving the spar structure. The plane was designed when hi-start launches were the norm, and you can easily overpower the wing structure with modern winches.

JT
Jan 24, 2020, 03:49 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Quote:
Originally Posted by whacker
stevet

seems to me someone redid a set of airtronics or aerosphere plans a couple years ago and added a whole bunch of new data and Info to the drawing and uploaded it somewhere.


Not sure If that counts as a Grand Esprit , but maybe have a look for that, there may be a complete new wing design and fuse design there for you.

whacker
I have the Aerosphere plans, and while there are a set of upgraded ribs (different airfoil), they are still cut from 3/32 balsa. And the fuselage is a bit different as it uses a lighter carbon tube.

SteveT.
Latest blog entry: My shop....
Jan 24, 2020, 03:54 PM
Registered User
whacker's Avatar
Nice 5/16 wing rod

One of the Dixie Pins, In as far as it will go between some 1/8 x 3/8 sitka, considering the Dihedral angle

Pass thru ribs , 3/32 is fine

Shear webbing 3/8 - > 1/4 - > 3/16 -> 1/8

1/16 ply doubler for and aft the first 6 inch or so from the root

wrap the wing rod tube box.

All easy of the shelf Technology. all been said by others before

I'll be watching the Build Thread


whacker
in the dead of winter
Jan 24, 2020, 03:55 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Quote:
Originally Posted by CloudSniffer
Steve, do you know what a rib set weighs now and what the potential saving is? Have you built a stock one and know how it balanced? What the AUW is?

Many older designs require a lot of nose weight with today electronics. Then depending how much you can out is the airfoil still good?

If you add a carbon cap to 1/16 is it actually lighter than a 3/32 rib?

Just food for thought. The GE is a beautiful model and I can see how a lighter one would be attractive. A redesign with a similar planform would be cool.
i have not weighed them, but again, I'm really not talking about a substantial cap strip (I.E. like a 1/16" balsa one), but rather just a really thin strip (think the thickness of tissue paper) on top and bottom just to keep the thinner wood together.

SteveT.
Latest blog entry: My shop....
Jan 24, 2020, 03:58 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Thread OP
Quote:
Originally Posted by jtlsf5
You're not going to get much value from lightening the GS, will just make it more squirrely when slowed down for landing. Both of the GS's I've owned flew just fine at the design weight. If you're going to make any mods I would suggest improving the spar structure. The plane was designed when hi-start launches were the norm, and you can easily overpower the wing structure with modern winches.

JT
As noted, I launched mine with a winch all the time, you just can't have a lead foot. That said, what's wrong with a hi-start?

SteveT.
Latest blog entry: My shop....
Jan 24, 2020, 10:50 PM
Registered User
Quote:
Originally Posted by SteveT.
Ooops... yes, you are correct, .012" would be 3-4 times the thickness of a human hair.

I have built original Grand Esprits and I have winch launched them with the winch I owned during the late 1970s.

Yes, the tail boom will be carbon, as it is a tail boom from CLM Pro.

As noted, the original ribs are 3/32 and I want to go to 1/16 and still retain the strength.

As to strips, I have not been able to find them and was going to cut the woven cloth diagonally to have long strands. If you know where I can get 1/16" wide carbon strips in approximately .010" thickness, please post a link.

SteveT.
If I was doing this, I wouldn't get the strips 1/16 wide because of the expense. I'd get a wider piece of unidirectional laminate and strip it like balsa. Actually, you have to be careful handing the .007" stuff or you'll strip it by accident. And .007" is probably overkill. On the other hand, you won't be able to strip the woven cloth the same way. You'll have to use a saw or thin cutoff wheel with lots of conductive dust flying around. And the woven stuff won't be,anywhere near as stiff, especially if you strip diagonally. You'd probably get better, but still not very good results with unidirectional e-glass! When you make the ribs thinner, they will be much floppier in the sideways,direction. Like less than a third as stiff. I suppose if you did a REALLY good job of gluing the cap strips, they might make up for this, though I haven't run the numbers. All this trouble to eliminate 1/32" of balsa! Consider that a full sheet (3 X 36 inches) of 1/32" really light balsa weighs about 5 grams.

I'm kind of surprised that the original design could survive a winch launch. It's very far from optimal, and you don't actually have to make it heavier to make it much stronger.


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