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Old Nov 26, 2008, 11:15 AM
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Cambridge, MA USA
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Quote:
Originally Posted by Glauco
Thanks Mark and Tom, will go for a wider center spar. Would you suggest widening the tip spars too?
The tip spars are adequately stiff for F3J.
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Old Nov 26, 2008, 10:03 PM
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Thanks again Mark.

Took the day off today since the weather was about as perfect as it gets here in the Midwest for the end of November and was able to make a few tests with the bagged Supra.
First was a couple of 2 man F3J tows. With almost no wind I can say the wing took it easily. A little later we setup the F3B winch, set to 150 meters. Again at the same wind conditions there was no problems for "51".
So I'm happy to say this plane can easily take good F3J tows in light conditions. The new one with the wider spar will be used for higher wind conditions.
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Old Nov 26, 2008, 11:59 PM
MSgt, USAF Ret.
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USA, WA, Spokane
Joined Nov 2003
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Glauco,

Thanks for all the data/testing!

No sure when I'll get started, currently I'm working on an Aegea II and a 2 meter version of the Supra but I'll continue to follow this thread.

Thanks again,

Jim
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Old Nov 28, 2008, 01:06 PM
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A couple of pictures taken by photographer expert Chris Lee from our last flying day. You can read some reports about our day here
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Old Nov 28, 2008, 01:57 PM
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Time for some more pictures of the stab and fin. Need to add another disclaimer. The methods I use are not always the fast ones. Most of the time I'll spend a few extra hours to get that 1% better looking piece or what I think to be a more precise part, can't control myself

For most the construction it was used only MGS epoxy. The fast hardener actually cures in about 5 hours and the slow one in 24. You can't rush this type of construction.

On the stab I just wetted the rods with the least amount of epoxy I could to make sure it would stick to the foam. Also glued both top and bottom rods at once so didn't want to create a mess with the bottom ones. Transparent tape glued to the beds is your fiend to avoid all sticking up together.
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Old Nov 28, 2008, 03:59 PM
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USA, WA, Spokane
Joined Nov 2003
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Glauco,

Thanks for the detailed build photos! If there's one thing I've learned from all the Supra build photos it's this: I need more "hold down" weight....

Keep them photos coming,

Jim
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Old Nov 28, 2008, 06:58 PM
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Vancouver, Canada
Joined Jan 2008
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Glauco, I'm curious why you don't use weblets instead of the carbon rods?

I find weblets to be less labour intensive and plenty strong...maybe liter as well.


T.D.
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Old Nov 29, 2008, 08:28 AM
Mario S. de Lucca
Brasil
Joined Oct 2005
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Glauco

Very nice job..... great model

Im finishing my new 2,6m standart class (like a RES)... I`ve told to you when you stay here in Brasil.... I will post some pictures at planador@grupos....

Best regards
Mario
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Old Nov 29, 2008, 09:31 AM
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Quote:
Originally Posted by T.D.
Glauco, I'm curious why you don't use weblets instead of the carbon rods?

T.D.
T.D., after many years building Dr. Drela's designs including several Supergees, an Allegro, a composite Bubble Dancer and two Supras I learned the best way to avoid problems is following exactly the plans and that is how the stab was designed, with carbon rods.
I understand many new hand launch planes are now build with weblets only and I'm planing on building one with them but for right now I'll just stick to the plans.


Hello Mario, good luck with your Standard class glider.
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Old Nov 29, 2008, 05:02 PM
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USA, WA, Spokane
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Quote:
Originally Posted by Glauco
Hope we can build them together. I also would like to build this new batch with the molded Supra square joiners but I'm a bit afraid of changing the plans. Does anyone know of any problems using the square joiners instead of the 3/8" round ones?
Construction would be much easier without having to build those basswood joiner boxes.

For the stab and fin I just tiled them but for the wings it was enlarged of the supra_wing.pdf file. I work in a construction company and just asked the drafters to plot to full scale. Took them a couple of tries but the result was perfect.
Glauco,

Here's the thread I found with a diagram on post 10 showing how to build boxed joiners.
http://www.rcgroups.com/forums/showthread.php?t=920053

Jim
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Old Dec 03, 2008, 04:36 PM
VHO
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Armidale NSW Australia
Joined Feb 2007
563 Posts
Foam Weights

Glauco,

Been building Supras as well, nice to get them light, but I seem to be working behind the 8 ball on weight.

Weights of foam are significantly different to your posts. On vertical tail, 15g bare, 16g with glass facings only. Horizontal tail 17g with rods and balsa centre block (and no filler).. Been using foam with 50psi (350kPa) rating (called SP by Dow) for tail feathers, and also 400 kPa (called RTM in Australia, and stamped that by Dow) for wings. Templates printed by Profili and cut with 0.020" wire using Phil Barnes methods.

I seem to be able to match the covering weights, but by starting 4-5g too heavy wind up not surprisingly with weights around 27-28g rather than the target of 24g...

What do you do to get the foam 4-5g lighter? It is really to HiLoad 60 specs?

Hutton
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Last edited by VHO; Dec 03, 2008 at 04:39 PM. Reason: typos
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Old Dec 03, 2008, 07:43 PM
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Quote:
Originally Posted by VHO

What do you do to get the foam 4-5g lighter? It is really to HiLoad 60 specs?

Hutton
I got the foam cores CNC cut from Les Horvath and I understand Dr. Drela did the same. They are Hi Load 60 but bigger parts have more variation. For example the target for the center panel foam is 165 g. The two wings I've done one was 138.7 g and the other 133.8 g.
Also the way I check the weight is when the core is absolutely only what will be bagged, meaning all the sanding, trimming and cutting are done.

I would guess the manufacturing in Australia is a bit different than here, enough to add a few grams.
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Old Dec 04, 2008, 01:40 AM
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San Diego
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Quote:
Originally Posted by VHO
What do you do to get the foam 4-5g lighter? It is really to HiLoad 60 specs?

Hutton
Foam densities can vary significantly. The manufacturer only has to make sure that the foam has enough density to meet the required R value and compressive strength. If it has a higher density it still meets the functional specification.

If you are really trying to build the lightest model possible you will probably have to shop around for the lightest batch of foam you can find. Kind of like looking for contest grade balsa . . .
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Old Dec 04, 2008, 04:17 AM
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DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,112 Posts
fin sections

Hi All, Hutton,

I can't see the section for the top of the fin on the plans (the .pdfs from CRRC site).

Lower section is drawn but the top?

Chris.
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