HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 08, 2014, 12:05 AM
Registered User
Joined Jul 2014
40 Posts
Discussion
Building an Allegro 100

Some of you may have heard about my little project on BayRC, well I decided to spread the word onto RCgroups. Here is the start of my journey.

Best Regards,

Throwbot,

Hello Thermalers, after building a Pickle DLG plane and being extremely happy with the results, I have decided to build a replacement for my Oly IIS. Hope you find this interesting.

Best Regards,

Throwbot

STRATEGY - Replace my Oly IIS with another Polyhedral plane built with the foam core, carbon boom method that we built our DLG Pickle with (see BayRC | Hand Launch | Bay Area Home Built Design).

TACTIC - Take the design of the original Drela Allegro (not the Allego-Lite) and scale it up from 2 meters to 100 inches. The wing is strong so just expand the wingspan and keep the chords like the 2m Allegro. Leave out a spoiler since the plane should be so light that it can be slowed down by doing a porpoise up/down movements. Rely heavily on the expertise of Grim Surveyor and Dbaya
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 08, 2014, 12:06 AM
Registered User
Joined Jul 2014
40 Posts
Re: Building an Allegro 100

PROJECT PLAN
PUT PROGRESS ON BAYRC
READ ALL DRELLA DESIGNS - at Charles River
MAKE PLANS
MAKE EXTRA FLAT BUILDING BOARD
TEST HOTWIRE SKILLS by making extra Pickle fin.
FIND TEMPLATES FOR ALLEGRO AIRFOILS
BUY MATERIAL FOR WING & SPARS & JOINERS
Lightweight fiberglass for wings
Joiner boxes
CUT FOAM
MAKE JOINER BOXES
MAKE SPARS
MAKE STAB
MAKE FIN
MAKE WING GRAPHICS/DESIGN TO PAINT ON MYLAR
MAKE WINGS
TEST WING ON MY OLD OLYII (D & G do not recommend this, but I think it might be fun to get this flying sooner.
BUY PARTS FOR FUSELAGE
MAKE POD/BOOM FUSELAGE
BUY FITTINGS/SERVOS
FINISH PLANE
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:08 AM
Registered User
Joined Jul 2014
40 Posts
More Details on Allegro 100

BOOMS - Not too expensive from http://goodwinds.com/carbon/wrapped/tail-booms.html use the $33 Dancer boom.

CHORDS - Match the same chords as the Allegro 2m which keeps the Reynolds numbers the same for my Allegro 100 as the normal Allegro 2m

DIHEDRAL ANGLES - keep the angles the same on my Allegro 100 to the Allegro 2M angles.

FIBERGLASS - Dbaya and Grim have 1.5 oz glass. We can use multiple layers of that for the wing skins.

GRAPHICS - Stick on cut out Monokote. Paint wing molds white with Duplicolor

JOINER BOXES - 1.5 oz or any old scraps from D & G

POD - Use Grim's new DLG pod mold (see Bay Area Built Design thread). The Allegro nose looks too stubby so this will be an improvement. He built this pod in the same manner as this thread describes http://www.rcgroups.com/forums/showthread.php?t=2011861.

SPAR - Use Drela's built up spar, but make it out of a pultruded rectangle. Grim will help me engineer this. D &G already has spar material already, both the carbon caps and the shear web. We can wrap it in 1.5 glass, with a bit of kevlar thread on the joints, which I also have.

TEMPLATES - Juzwuz makes the best templates. We can buy a set for probably $25. I'll assume they are HT08 and HT12 for the tail and while I am at it buy the the AG19, AG18, A17, and AG16 all at the same chord as the normal Allegro.

WING MOUNTING - I was reading about the Supra, that had a pretty smooth wing mounting, it would probably be more complicated to build than the two post technic of the DLG world.

WINGSPAN - Multiply the 2m Allegro by 1.25 to get a 98.5" plane.
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:10 AM
Registered User
Joined Jul 2014
40 Posts
Discussions on Design of Allegro 100

Hello Dbaya & Grim,

I am happy with the wing using the same chords as the Allegro 2m, but now I am looking at the planform vs the bubble dancer. It looks the wing has a slightly different shape so I superimposed the Bubble Dancer in pink on the Allegro 100. I did this using the an eye ball guess of the center of lift on both wings (not matching the root chord). This comes up with new questions:

BOOM LENGTH: Should I increase this to match closer to the Bubble Dancer? It probably needs a longer arm of momentum to turn the plane.

FIN WIDTH: Should I make it stubbier like the Bubble Dancer? If so do I need a different size of the HT08 airfoil?

STAB WIDTH: Same question as the Fin, except the HT12 airfoil.

POD: I am guessing that Grim's pod is 14.5". This length would make it about as stubby as a scaled up pod of the Allegro 2m. To make it as proportionally long as the Bubble Dancer's, it would need to be 19.5".

DIHEDRAL ANGLE: I am happy that it is matching the Bubble Dancer by keeping the old angles of the Allegro 2m.

Thanks,

Throwbot
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:11 AM
Registered User
Joined Jul 2014
40 Posts
These types of planes are pretty Impressive. Got to see them perform at the big contest in Fresno. They float and to my disbelief, can handle the wind. I got to fly Toms Danny a couple weeks ago. Launched high with just a high start, climbed out fast on a winter thermal. The simple spoiler is very effective.

I like the proportions of the pink fuse. Fin and nose length look perfect. Longer booms good Idea for better tracking.

Don't be affraid to add spoilers and even a ballast tube. I'm pretty sure this model will be around for a while! Looking forward to helping you and watching your progress.
Dbaya
Composites Specialist
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:11 AM
Registered User
Joined Jul 2014
40 Posts
Discussion on Tails

For the tails what we want to do is maintain the same tail volume coefficient. There are two ways to do this, increase the boom length and make the tails bigger. I would target the TVC by increasing the boom length and then if it doesn't look right, shorten it a bit and make the tails bigger. I am recommending this approach because the chords are being kept constant.

Grim
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:12 AM
Registered User
Joined Jul 2014
40 Posts
Follow Along with Charles River Sites Plans on Allegro 2m

reat stuff Kyle! I'm looking forward to following along.

Here's a link to the online plans at the Charles River website for anyone interested in following along here. http://www.charlesriverrc.org/articles.htm
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:13 AM
Registered User
Joined Jul 2014
40 Posts
Hi Grim,

Let me know if you want me to post my questions via email and then I can post the answers on RCgroups. Whatever is easier for you.

So I like the TVC theory. So in practical application does that mean I should use the same planform for the stab and the fin as the black lines above (the Allegro 2m), but use the proportional boom length of the Bubble Dancer (in pink above)? Dbaya liked the look the pink lines.

Also, TomRC suggested I run the design through a tool I emailed you about (written up in RCSD) to check for stability. But, you have built a lot of scratch plans so I am happy to take you advice and perhaps skip that step. TomRC also suggesting building on a very very flat building board and then proceeded to give me a slightly warped building board so I think his motives could be suspect...just kidding ;-).

Thanks,

Throwbot

PS: Thanks Dbaya for the mention. This Thermal group needs a little action and I can guarantee, my Allegro 100 will provide the thrill of victory and hopefully miss the agony of defeat, you know like a lawn dart.
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:50 AM
Registered User
Joined Jul 2014
40 Posts
Grim Says be sure to check the X Country thread on BayRC, I think it is called XC 10 #2 Here are some random notes that will be used later in the construction.

BOOM WRAP - 3x with 1.5 Oz Fiberglass. Then wrap with electrical tape with sticky side out to make a nice shape, but try to soak up extra epoxy with paper towels before you wrap. You also can use Peal-Ply.

JOINER MOLD - make a trough using a plug stuck on a two boards that meet at an 11 degree angle. Use something like clay to stick it with. Wax and PVA release base board and plug. Cover with chopped fiberglass, epoxy, thick cabosil, and fiberglass cloth, make it about 1/4" thick. When it hardens, saw off the two ends so that the two ends of the mold are open. Polish out trough with polishing compound, wet sand, fee coat plexir? wax?,

JOINER - lay in 12K tow, wet and pack in. cram in as much as you can, then over lay two plexglass panels to flatten it down into the mold. Clamp and when hard cut off two ends of excess 12K that stick out beyond the mold edge.

SPAR - Use an aluminum window bar that is nice and straight and has a long 90 degree angle running down it that allows you to line up the spar caps and the balsa spacers all up against the bottom and the 90 degree edge.

JOINER BOX - Be sure to wrap the ends of the joiner box and the base with kevlar tow.
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 12:54 AM
Registered User
Joined Jul 2014
40 Posts
Sophisticated Cad Drawing of Plug Mold

Here is a diagram of the plug mold.
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 08, 2014, 10:38 AM
Registered User
George Franklin's Avatar
Joined Feb 2013
439 Posts
I built a 90 inch span version. Changed a few things. I like flaps better than spoilers and I reduced the tip cord. Reduced the tip cord to increase the aspect ratio, but reducing the tip cord was a mistake. Mine is a little heavy too. But all things considered this is my best sailplane.
George Franklin is offline Find More Posts by George Franklin
Reply With Quote
Old Aug 14, 2014, 02:52 PM
AMA 353531
rdeis's Avatar
United States, CO, Colorado Springs
Joined Aug 2003
6,564 Posts
Quote:
Originally Posted by Throwbot View Post
For the tails what we want to do is maintain the same tail volume coefficient. There are two ways to do this, increase the boom length and make the tails bigger. I would target the TVC by increasing the boom length and then if it doesn't look right, shorten it a bit and make the tails bigger. I am recommending this approach because the chords are being kept constant.

Grim
Look for Don Stackhouse's talk about tail length and dynamic stability. Longer boom is generally desirable rather than increased surfaces, but there's a sweet spot to it.
rdeis is offline Find More Posts by rdeis
Reply With Quote
Old Aug 20, 2014, 01:16 AM
Registered User
Joined Jul 2014
40 Posts
Nice Work

Quote:
Originally Posted by George Franklin View Post
I built a 90 inch span version. Changed a few things. I like flaps better than spoilers and I reduced the tip cord. Reduced the tip cord to increase the aspect ratio, but reducing the tip cord was a mistake. Mine is a little heavy too. But all things considered this is my best sailplane.
Wow, what a nice plane. Looks like you modified the Allegro Lite, which as me worried since I am modifying the Allegro 2m so foam cores may end up being even heavier. I noticed you about doubled the nose length. I too was wondering why Drela had such a short nose, but I am only adding about 30% more length. Thanks for commenting.
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 20, 2014, 01:24 AM
Registered User
Joined Jul 2014
40 Posts
SHOPPING LIST 1-29-14

TEST FIN (for my Pickle DLG)
MYLAR - Thick MylarŪ (PET Polyester Film) for wings 36" x 12", 0.010" polyester
http://www.eplastics.com/Plastic/Clear_ ... ER-CLR-010 get enough for Allegro
TAIL BAG - Polyester
NYLON TUBES 5m length of 18: bag $10 + $1 tax + $3 shipping http://www.acpsales.com/Nylon-Vacuum-Bag-Tubes.html
BAG SEALER - 4x = 40" Quick Lock Seal x 4 = $48
VALUES - apc? / /Grim or Dbaya - do you have the old ones?
VACUUM BAG - http://www.acpsales.com/Nylon-Vacuum-Bag-Tubes.htmlm or Aerospace Livermore
FOAM - $20 4x8 Sheet, Dow Styrofoam Blue 25lb. non-hi-load foam) (40 Hiload would also work). http://www.whitecap.com/products/595270290 buy at White Cap 595 Brennan Street, San Joose. M-F 6-5, closed S & S.
ALUMINUM BEAMS - to check that my building board is flat. Amazon 48" x 1/8 x 1 for $13 each, got two $26. With two long straight edges you can eyeball that each direction of the building board is flat (the straightedges look parallel in both directions).
SMALL WOODEN ROLLERS - where do you buy these to squeeze out extra resin
FIBERGLASS - use 3/4 oz, Kevlar over hinges, carbon fiber unidirectional a a flat "spar". Plus a little carbon on the bottom that hits the ground. Put a little carbo stick in it as well.

REAL WING
WING BAG - Polyester (not MYLAR) .010”x24x48 Polyester Sheet 8 sheets $80 + ~$10 shipping
RESIN - I have some 3 year old West Systems 105 with 206 hardener. Is this still good. It is slightly amber. Or should I order new stuff from Greg Loehr - Resin Research West - 321-223-5276gl10@aol.com
CARBON FIBER SPREAD TOW TAPE - I have that.
FIBERGLASS - 1.5 Oz from Dbaya or from Aircraft Spruce. Size assume 100" + 10" extra x 10" width x 4. More if it needs to be on a bias.

FUSE
BOOM - DANCER - http://goodwinds.com/carbon/wrapped/tail-
booms.html $33 Dancer, but will probably use Hyper flight 22-9, 100cm (trimmed to 88cm or 34.6"), OD 22mm, OD Little 9mmm Weight 30g, $70 for two shipped.http://www.hyperflight.co.uk/products.a ... arbon-boom
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Old Aug 20, 2014, 01:26 AM
Registered User
Joined Jul 2014
40 Posts
Thanks for the tip rdeis
Throwbot is offline Find More Posts by Throwbot
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Allegro Lite Electric+std fuselage andersgj Electric Sailplanes 131 Oct 21, 2014 09:12 AM
Discussion Recommendation for an Airframe or build to suit an OS GT22 Gasser MerlinV Scale Fuel Planes 5 Sep 27, 2014 03:20 AM
Discussion Help in identifying an old 100" glider ORANATOR Slope 12 Sep 28, 2013 10:15 PM
build Allegro-Lite Thomas Wang Thermal 299 May 19, 2010 06:23 AM
Building Lessons Learned from building my Allegro-Lite thelocust Thermal 10 Apr 13, 2005 10:41 PM