Thread Tools
Mar 25, 2008, 06:19 AM
I'm not flying backwards!
Tony65x55's Avatar
Quote:
Originally Posted by Rolland Benson
Tony

Is there there a wood spar in the center wing section? I have 3 hours 45 minutes flight time on mine now and have noticed the center section is showing stress wrinkles.
I had some flat bamboo from a placemat and have added this to the wing as a turbulator strip in the center section. This has stiffened the wing and it looks like it will survive for awhile longer.

I don't know if this is something I have done, but the ideal CG is closer to 25% of the root chord, back from the leading edge. I tried it farther back, but flies much better with it forward. I thought most of the data I had read on the KFm wing had it more rearward than this. Beats me, but it works

The plane is flying well. It loops and even got it to fly a little upside down.

Flight times with the 1500 ma battery are an easy 30 minutes guaranteed. I had one flight today that I landed after 38 minutes and still had reserve power.

Thanks
Rolland
Hi Rolland. No, in the interest of keeping it light and not anticipating aerobatics with it, I didn't design it with a wood spar in the center section. Ooops! You can add tremendous strength to it by simply running a strip of fiber reinforced 3/4" packing tape, top and bottom, across the center section about 1/4" forward of the step. This will seriously increase the load bearing ability of the wing and is very light, just make sure it's stuck down well.

You sussed it right. KFm airfoils do like a rearward CG, 33-38% and my calcs show 2.75" as the optimum starting CG but if 25% is working for you, don't worry about it. You're certainly getting great flight times. Imagine what it will be like when boomer season starts!

Tony
Sign up now
to remove ads between posts
Mar 25, 2008, 06:21 AM
I'm not flying backwards!
Tony65x55's Avatar
Quote:
Originally Posted by Dakrat
Hmm... That's why I was wondering about, dropping the bamboo and Miniwaxing the bottom of the wing and and Fuse....
Dak, see my comments to Rolland in the previous post. Minwax and glass will work BUT KEEP IT LIGHT! Sailplanes thrive on light.

Tony
Mar 26, 2008, 05:42 AM
Sky good, Earth bad!
Dakrat's Avatar
Started my build last night, got everything cut out and I hot wired out the mono block.
Looks like this is going to be an easy build, Foaminator, your fuse is much bigger then the plans, what width is yours?

I have to get a good idea for a paint scheme, hmm what's easy to see 500ft up?

Dak...
Mar 26, 2008, 08:38 AM
I'm not flying backwards!
Tony65x55's Avatar
I like black on the bottom, yellow on the top.

Tony
Mar 28, 2008, 05:00 AM
Sky good, Earth bad!
Dakrat's Avatar
Ok guys,
I almost have this one together but this is my first V-tail. I noticed that most of you guys are putting the V-tail together first then attaching it to the top. The plans call for the tail placed on the sides of the fuse. Which method is better?
I was using a string (*16in) to get the distance between the stabs. I needed 4 hands to do the mock up and figure out where I was going to put the control rods through the fuse.
Tomorrow I will glue the wings together and go fly it once I get the V-tail all settled!
Thanks...
Dak...
Mar 28, 2008, 06:50 AM
I'm not flying backwards!
Tony65x55's Avatar
Side is structurally stronger, top might be easier maybe? Take a couple strips of foam or balsa 16" long, tape their edges to the edges of the fins and then glue the fins into their side supports with 5 minute epoxy. Only needs two hands and guarantees perfect alignment. When dry, remove the tape.

Tony
Mar 29, 2008, 03:39 PM
Sky good, Earth bad!
Dakrat's Avatar
Ok, got the tail on last night to the side rail, that was a bit of a pain... Used tape/string method by tacking down tail with Ca glue then epoxy. All there is to do is to install the push rods and pin horns... I did however give it a chuck across the room, seems to work but I have to admit that the wings are a bit "floppy. I will fly it once or twice to get the CG but I think that this is a good candidate for WBPU and glass. I am just going to glass the bottom of the wing and the Poly joints on top.

Anyway, my 45 deg cuts on the poly's were a bit off on one wing so I had to smooth out the joints with some light weight spackle. I will take some pic's befor the first crash/ I mean maiden...
Apr 02, 2008, 04:19 PM
Sky good, Earth bad!
Dakrat's Avatar
Got the glider together, took it out for a test run but and stalled it out and cracked the fuse in half! Well glued it back together and WBPU glassed it last night. I also put in a carbon spar in the wing it was just too floppy for my liking. I'm off again to test glide it again...
Dak...
Apr 03, 2008, 02:35 PM
Registered User
I'm in Jekyll Island Georgia this week on spring break with the family so I took the Blu-Sail along. This is the first chance I have had to fly it and not freeze doing it.

The plane is performing excellent and I am getting in some flying that is not in my backyard. I have flown this in fairly high costal winds and near no wind conditions here. The results are really good. In near no wind I got 42 minutes before coming in. No need to go dead in a strange area and loose a plane. In the high wind conditions it still flies great, you just have to be more on top of it. The landings were a problem at first, landing close by. I have found at least here flying off of a nice soccer field that coming in a little faster under power makes it all come together.

The best part of this plane is that it can be flown under alot of different wind conditions. Everything from flying backwards in high wind at low throttle to good penetration with more throttle. In low wind it flies great with very little throttle and can stay airborne a long time.

To date I have not found conditions to thermal it yet, just a few updrafts off the coast.
Apr 03, 2008, 02:44 PM
Registered User
Reguarding the issue of the wing being a little floppy as designed I have used some bamboo in the center of the wing.

1 I placed skewer material on the front and rear edges of the wing in the center. This helped some, but moved the stress point out.

2 I then found some bamboo slats from a placemat and taped them to the top of the wing about 15% back from the leading edge. They are a primative turbulator, but also reinforce the wing center section further out.

The wing still flexes, but doesn't seem floppy. This is alowing me to loop now with out wing failure. I have also got it to fly upside down for awhile this way.
Apr 03, 2008, 06:32 PM
I'm not flying backwards!
Tony65x55's Avatar
Sounds like you're having fun. I wish it was me.

Tony
Apr 04, 2008, 06:02 AM
Sky good, Earth bad!
Dakrat's Avatar
I had much success this time around!
I was flying with a 800mah 2cell and 900mah 3cell both performed rather well, but it is still winter up here so no chance of thermalling.

I did dorked it into the ground/snow again hot dogging close to the ground.
The miniwax/glass held up extremely well, I am sold on that stuff!!!
I can't wait till it gets warmer; I may try it near the beach at the edge of town.

Dak
Apr 04, 2008, 06:53 AM
I'm not flying backwards!
Tony65x55's Avatar
Whoo-hoo Dak! You got it. We're watching the winter leave now and I might even get out flying this weekend. I bet you have some great places to slope soar in Anchorage.

Tony
Apr 04, 2008, 07:16 PM
Sky good, Earth bad!
Dakrat's Avatar
Quote:
Originally Posted by Tony65x55
I bet you have some great places to slope soar in Anchorage.

Tony
Yeah, I sure hope so, I need to hook up with some guys who have done this to tune me into the good spots around town. What kinds of winds can you slope soar in?

Dak
Apr 04, 2008, 09:59 PM
I'm not flying backwards!
Tony65x55's Avatar
Quote:
Originally Posted by Dakrat
Yeah, I sure hope so, I need to hook up with some guys who have done this to tune me into the good spots around town. What kinds of winds can you slope soar in?

Dak
Truthfully, it depends how good you are and the penetration of your plane. I'd go pretty light at first.

Tony


Quick Reply
Message:

Thread Tools