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Old Jun 29, 2012, 08:41 PM
Good, fast or cheap, pick two
robh's Avatar
Napa, California
Joined Jul 2006
2,604 Posts
Question
Build changes to an Oly II SX to keep it light, with gear?

I've got and Oly II SX ready to build and I've spent quite a bit of time scanning the plans, and various sets of online instructions, and I'm about to launch into this. I would like to know if anyone has any hints/ suggestions on how to possibly lighten the build so that when I add in the gear I don't end up with something too heavy. Of course, gear will be kept as light as possible. I'm considering building up the tail, rather than cutting holes in the solid rudder and stab surfaces that are supplied, in order to lighten them. The weight of the solid wing joiner rod is probably what started me thinking- that sucker is heavy!. I know that this is a great sailplane already and I'm not meaning to infer that there is anything at all incorrect with the design, I'm just wondering... and if you say to build it as is I'm happy to do so!

All ideas and suggestions are welcomed, in advance!
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Last edited by robh; Jun 29, 2012 at 11:02 PM. Reason: typo
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Old Jun 30, 2012, 10:32 AM
Gasbags & Gussets
jswain's Avatar
Riverside, Ca
Joined Feb 2009
1,196 Posts
less is better than more

Quote:
Originally Posted by robh View Post
I've got and Oly II SX ready to build and I've spent quite a bit of time scanning the plans, and various sets of online instructions, and I'm about to launch into this. I would like to know if anyone has any hints/ suggestions on how to possibly lighten the build so that when I add in the gear I don't end up with something too heavy. Of course, gear will be kept as light as possible. I'm considering building up the tail, rather than cutting holes in the solid rudder and stab surfaces that are supplied, in order to lighten them. The weight of the solid wing joiner rod is probably what started me thinking- that sucker is heavy!. I know that this is a great sailplane already and I'm not meaning to infer that there is anything at all incorrect with the design, I'm just wondering... and if you say to build it as is I'm happy to do so! All ideas and suggestions are welcomed, in advance!
Hi.
The design is what it is - a d-box woody- that will take at the very least a moderate (compared to a composite model) winch launch while using a two part wing for easier transport. The wing rod is heavy but the only alternative for this configuration is a CF rod which is OK for a e-power glider but not as durable for winch launches.
.
I would suggest gluing some small (1/8" by 1/32")carbon fibre rod along both the vertical and horizontal stablizer hinge lines to resist cracking these wood surfaces when transporting or harsh landing at the fuse/flying surface intersections.

Fuselage Weight wise, use epoxy only where the plans or directions say (wing spars,wing root rod bays, and fuse ply laminations ?) and CA or wood/carpenters glue everywhere else. The built up tail is really a ketchup vs. mustard choice, the flat wood provided i believe would be more durable (not stronger, but damage wise from storage and transporting) and faster to finish.

For what its worth, as built per instructions my BigBirdXL (which is a kissing cousin your model) flys really well, weighs in at the published specs, really covers a lot of ground(due to airfoil selection)and without worry of folding the wings(Dbox/wing rod) and all for about 200$ <= Thats a great DEAL in my book

best wishes, have fun, and post your results- we'd be interested in your project .
john s..
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Last edited by jswain; Jun 30, 2012 at 11:25 AM. Reason: spelling
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Old Jun 30, 2012, 02:30 PM
Good, fast or cheap, pick two
robh's Avatar
Napa, California
Joined Jul 2006
2,604 Posts
Hi John,

Hey thanks very much for your reply and comments. I think that I will look into a CF rod to replace the steel one supplied in the kit, as I'm not planning winch launching it. I am going to use the spare NEU 1105 as the motor though, and it hopefully won't put too much stress on the wing joint when under power. Thinking...

Good idea on the CF rod... heading to the hobby shop this afternoon and will pick some up.

As for the tail surfaces, I'm going to pickup the wood needed so that I can do a built-up tail. I've got the solid pieces supplied in the kit, and they are not heavy at all, but I'm trying to keep the tail end as light as possible. I will weigh the built up tail, and compare it to the supplied solid wood, and see how I make out. Who knows, I may end up so darn close to the supplied solid wood...we'll see!

Lastly, I'm not trying to imply that there is anything at all wrong with the kit as it stands. I'm just trying to see if I can get it as light as possible with the gear installed. I'm sure that she will be a winner no matter what I do.

Thanks again, and I'll post the progress that I make!

Rob
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Old Jun 30, 2012, 02:48 PM
Gasbags & Gussets
jswain's Avatar
Riverside, Ca
Joined Feb 2009
1,196 Posts
looking forward to this

Quote:
Originally Posted by robh View Post
Hi John, Hey thanks very much for your reply and comments. ....Lastly, I'm not trying to imply that there is anything at all wrong with the kit as it stands. I'm just trying to see if I can get it as light as possible with the gear installed. I'm sure that she will be a winner no matter what I do.
Thanks again, and I'll post the progress that I make!Rob
Hi Rob, it was understood your trying for the lightest setup and not questioning the design. Woody's inherently will weigh more and thats the trade off of build it youself $'s vs. carbon/foam Arf $'s.
I think by the time you put in the motor and battery and CF wing rod it will be close to the non-powered glider all-up flying weight.

2~3 oz of nose lead seems to be a manadatory 'gotch-ya' when all is said and done to get the cg right on any unpowered glider so why not put in a motor/battery combo instead and skip the winch

Best wishes, john s.
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