Just another scratchbuilt glider

[joe yap]

I had a thought of catching thermal with a lightweight glider over hot sandy beaches, some months ago. I wanted to build a very lightweight glider, while using my 4 tiny Airtechnic AT-90 servos. However, I also thought of the method of launching to good height and found that discus style launch is the most practical method over our relatively narrow beach lines. So a DLG concept was adopted.

I also want to have a full house model so that I have the luxury of mixing spoilerons for more decisive landings, which is very important when flying over tight air and land spaces. The search the internet and found the Garnet,http://www.soaringusa.com/products/p...ategory_id=294, which should fit the bill. Not wanting to spend more cash, I used the specs and designed my own model. I remembered I chose Mark Drela's AG series airfoils, but I can't remember which one.

I started and finished the wing a 2 months ago but left it aside for my other projects. Only last week, I picked up some leftover materials and finished up the rest of the model.

Constructions are mainly balsa built-up structure with carbon wing spars and tail boom. Fuselage is balsa box construction with fibreglass reinforcements. Tail surfaces are sanded down from 1/8" thick balsa sheet.

The specs are as below:

Wingspan : 60"
Wingarea : 360sqin
AUW : 10.4oz
Wing loading : 4.16oz/sqft
Airfoil : AG series transitioning from root to tip
Servos : 4x AT-90
Battery : 4 cell 300mah nicd pack
Functions : aileron/spoilerons,elevator, rudder

I maidened it yesterday evening in very gusty conditions. The plane is currently slightly nose heavy and I didn't get very long flights. My launches are about 3-4 HDB storey high at the moment. Nevertheless, the model flies very well and the AG airfoil really allows the model to float down right to super slow speed. I did get a few small bumps to thermal today but yet to hit a real good one. Also, I need to further fine tune the model in order to get it best out of it. Right now, I'm looking for smaller Rx battery to get the CG right.

[msc]

Hi Joe,
That's a very nice version of the Garnet, even the AUW is about the same 10.4oz Vs 10.0oz.
Let me know when are you heading for the sandy beaches....my Bug is ready and I will take care to prevent landing in the waters again.

[Tony]

Hi Joe,

You are indeed a very prolific builder. Hardly does your hobby knife ever get to cool off from one build before it is being applied to yet another. Keep it up. Cheers.

[joe yap]

Just learnt something today. During one of the launches today, I managed to lobe the model hard enough to cause the ailerons to flutter. During the process, one of the aileron servo got stripped. These tiny servos won't be able to handle the loads of big control surfaces like this at high speeds, so more care must be taken during the launch.

This somehow also affect the launch height unless the launch can further be perfected so as to gain more altittude by getting the correct launch trajectory than excessive speeds. So if you are a newbie in DLG like me, I'd suggest you use stronger servos for your DLG models with big control surfaces.

I didn't want to go through the trouble of changing and re-routing the servo and so I stripped down one of my dead servos on another model to cannibalise its gears for replacements. I'm rather pleased that I used Hot-melt glue to install the servos in place previously. To remove them, I just need to iron over the structures to loosen them.

BTW, I'd just replaced the 300mah Nicad with 3 alkaline AAA batteries solder in series. With this, the CG is spot on without further ballast and AUW is now reduced to under 10oz.

[Sunstorm]

Hi Joe;

qn:
How does one determine the servo size for control surface size? is there a guideline for this?

Build qn;
Where the carboon rod tail boom joins the vert stab, did you have to make a notch? If so, how did you do it without splintering the carbon rod? did you use a dremel?

[randomtask]

Cool man, more DLG buddies

My B900 is duly repaired and just waiting to get the control lines in. We can go through some launches together.

Cheers,
Adnan

[joe yap]

Hi Joe;

qn:
How does one determine the servo size for control surface size? is there a guideline for this?

Build qn;
Where the carboon rod tail boom joins the vert stab, did you have to make a notch? If so, how did you do it without splintering the carbon rod? did you use a dremel?

Mainly 'agaration', but you can read other people's thread on thier servo selection or go by recommended servo sizes from kit manufacturers.

The vertical fin is epoxied into the notches cut out from the tail end of the CF boom, using my Dremel spin-off tool. Just tape the end with masking tape, mark out and cut.

The horizontal stabiliser is mounted over a small pylon, which is also epoxied onto the tail boom.

[plug&fly]

Alamak...

Another one....?

[Sunstorm]

Mainly 'agaration', but you can read other people's thread on thier servo selection or go by recommended servo sizes from kit manufacturers.

The vertical fin is epoxied into the notches cut out from the tail end of the CF boom, using my Dremel spin-off tool. Just tape the end with masking tape, mark out and cut.

The horizontal stabiliser is mounted over a small pylon, which is also epoxied onto the tail boom.

Thanks. Let's hope this coming beach soaring outing would be a better one!
I got 2 sub-1 metre gliders to try out.

[joe yap]

Still early for the Southwest monsoon. The winds are all over the place.

[Ghostfit]

Another one....?

Joe builds his gliders faster then you can change your underwear !


...But we love seeing them ! ...keep them coming Joe, I need your glider inspirational fix to keep me going in-between the NE monsoons.

[plug&fly]

How? Did you get any thermal last Sunday? Your persistence is remarkable. I would have given up and just bungeed it. Anyway had to leave early to fetch the children from religious class. Just curious. But that lil bird floated ever so slowly and gently ... even saw you catch it in mid air and relaunching it. Awesome man..all that swinging and pivoting would have given a me backache if not a headache...hehehe.

[joe yap]

I did got one near the circular road, which lasted over 3 minutes. But I had a bad landing earlier which caused a crack in one of the wings aft spar. After some flying, it got worst and I had to abort flying further. As usual, I only start to get ground level thermal after 11am.

[randomtask]

Hey Joe,

When's the next time you gonna fly the Garnet? Finding DLG kakis

Cheers,
Adnan

[joe yap]

Hey Joe,

When's the next time you gonna fly the Garnet? Finding DLG kakis

Cheers,
Adnan

I'll be on short leave from thus Thursday to next Tuesday. We can meet up somewhere.