Mefisto build (BLEJZYK)

[Konrad]

Yep, that was me with the Hammer. Absolute joy to fly, though I admit that I do lack a decent comparison basis as this is my first real full house glider. It flew well as set up, just needed a bit of trim to fine tune. I bungled the elevator comp for crow, which made landing a bit more interesting, but that was entirely my fault as I rushed through the setup on Saturday morning to get out to Sunset Beach. This is a great event to look at gliders and talk to folks. Helped me a lot to have some more experienced eyes look over the glider before tossing it off a cliff...

The Heron was a great suggestion and I would recommend it to anyone trying to get into a full house setup. I don’t actually use the motor much if at all, but it’s a great insurance policy to get out of “situations“...

Have to say a great thank you to many folks here on the forum, so much good input for building and setup. I’ll take Konrad's earlier hint and do a write up on the build. Reading through many of these here and on RCGroups has helped me a lot in figuring out what to do.

Ralf

Ralf, Its been 6 months or so. Are you still enjoying your Hammer? I'm interested in how your 3D printed tail mount is working. Also have you experimented with "V" tail angles other than the ubiquitous 110°.

My Mefisto with 99° really tracks well. I do show a bit of spiral instability if flown real real slow as mine has turned in on itself a bit prematurely. So with the full size "V" tail and the 99° I think I'm at the spiral stability limit. As I have some hanger rash I'm thinking of cutting down some of the V tail area. This will clean up the damage and maybe move away from the low speed spiral instability issue.

All the best,
Konrad

 

[RalfH]

Hi Konrad, haven't been flying as much as I would like lately. Between work travel and offshore winds when I'm in town it has been a bit bleak the last 2 months or so. Still like the plane a lot, it flies great and is fairly versatile in different conditions. Though I will show up at the next ISR with something a bit more in line with the rest of the field...

The mount is working well for me, my main reason for building it that way was to be able to remove the tail for transport. Could have done that with some plywood as well, but then i had this newly acquired 3D printer toy...

I don't think I'm a good enough flyer to blame all my sloppy turns on the v-tail angle, so I haven't played around with changing that. I would probably do a few things different next time around to save weight and make the pushrod connection a bit sleeker. Some of that was limited by my CAD skills and reaching "good enough".
In hindsight it would have been nice to not epoxy in the surfaces and be able to switch mounts with different angles to try what works best. Or just make a separate set to swap.

Waiting for a couple of snowed-in weekends to get to all the projects I have in mind...

Ralf

 

[Konrad]

Snowed in weekends!! How far up in the hills are you in sunny California?

 

[Konrad]

... Though I will show up at the next ISR with something a bit more in line with the rest of the field...

...
Ralf

Is that a promiss or a threat. Don't leave us hanging like that! What have you got, or what are you looking at. The ISR is only a few month away.

 

[RalfH]

Got a Twister Now I just need to make sure I'm in town that weekend. And fly more...

And yeah, the likelihood of snowed in weekends is solidly at zero.

 

[Konrad]

Looks like I'll be out gunned, again!

All the ebst,
Konrad

 

[RalfH]

dont worry, you fly way better than me...

 

[Konrad]

That has yet to be seen!

All the best,
Konrad

 

[Konrad]

Yesterday while I was slumming it over at RCGoofs (I was looking for "Blejzyk" entries) I came across this. Really KST DS225 and DS213 servos for the Mefisto? DON'T do use them in the Mefisto! (Wait I'd like to see how anybody could fit those servos in this small airframe).
The Mefisto works best if kept light. No need for servos larger than 9 grams.

Servo recommendations for a Blejzyk Mefisto please - RC Groups

Question Servo recommendations for a Blejzyk Mefisto please Thermal Soaring

www.rcgroups.com

These servos have been working great. They are a rugged 9 gram (nominal) 8mm servo, perfect for most 1.5m to 2.4m ships.

JX PDI-0902MG Servo - 2.6 Kg (36.11 oz in), .07 sec - High Voltage

Digital control, high torque and a metal gear train make this servo an attractive choice but the thin profile (8mm) is really where it shines. A great servo for lighter gliders, thermal ships, and entry level DLG's at a great price.

alofthobbies.com

If using modern battery chemistry (LiFe) these servos work well at 7.4V.
See my review about using them at lower voltages.

KS HD47MG Servo - 1.2Kg (16.66 oz in), .10/sec - High Voltage

High voltage (4.8 to 7.4V) digital servo with a coreless motor and tiny weight with reliable metal gears and good specs makes this a very nice servo that could sell for a lot higher price at some other store.

alofthobbies.com

 

[Konrad]

Adding a bit to my post #80 I'm finding that due to storage or temperature / humidity changes my trailing edges (TE) often warp a bit.

I think a lot of this can be traced to the fact that there is no TE sub spar. This is easy to deal with on a varnished surface. I like to use two "MoneyKote" iron set at just above 100°C and a damp paper towel. The damp towel supplies the steam. I find that it helps if the wife is in a good mood as I often need a second set of hands.

I place the damp towel over the TE on both the top and bottom surface. I then heat both the top and bottom surface with the irons keeping the towel between them and the surface. Move the towel and iron trying to heat the surface evenly (You won't but the idea is to try). With the surface heated twist the control surface counter to the twist you are try to remove. I often find that a holding the end of the control surface between two straight edges helps keep the TE straight. You will want to hold the counter twist about 10% to 15% more than the original twist. Let the surface cool for about 5 minutes. Set aside for about a 1/2 hour later to see if the counter twist took. If it didn't repeat the heating and twisting. If it is good I like to come back with some WBPU and try to seal the face of the surface pocket. (I'll even reclamp the TE while this coat of WBPU dries).

This process works well, but I do find that I often need to repeat this through out the flying season.

Note: The wet paper towel supplies the steam and limits the heat to the boiling point of water to protect the foam core of the wing. If the towel dries out this protection is lost!

All the best,
Konrad

 

[Luis94]

Finished my Mefisto and ready for Maiden Flight...
Thanks to this thread ..made my build much easier...??

View attachment 4713

 

[Luis94]

 

[Konrad]

Looks fantastic! Much better than mine.

 

[Luis94]

Thanks..??
Do you think its ok to maiden it with the C.G at 77mm ....?

 

[Konrad]

Are you use to flying slope gliders? But yes 77mm is safe. I recall I once I misrigged my ballast weights and shifted the CG much further aft and the Mefisto few fine. It was I that had the jitters not the plane.

But if you are new to slope I'd try to add nose weight just for the maiden. Get the trim and throws under control and than remove the weights to bring the CG back to 77mm.

 

[Luis94]

Are you use to flying slope gliders? But yes 77mm is safe. I recall I once I misrigged my ballast weights and shifted the CG much further aft and the Mefisto few fine. It was I that had the jitters not the plane.

But if you are new to slope I'd try to add nose weight just for the maiden. Get the trim and throws under control and than remove the weights to bring the CG back to 77mm.

Ok,,thanks for the advice...
Think i will do just that,
Slope is the only type of flying i do..?

 

[Konrad]

Then 77mm Is safe. With the set up values I show in the first post.

 

[Tahoed]

Thread wake up time. The Mefisto is next up. I'm going with a 2 piece wing and since I'm partial to the wood look on these planes, I'm using this stuff from Varathane
The product, and an example of the color.

 

[gp49]

Thread wake up time. The Mefisto is next up. I'm going with a 2 piece wing and since I'm partial to the wood look on these planes, I'm using this stuff from Varathane
The product, and an example of the color.

Ed, is that a tow release hole in the nose of your Hobie?

BTW, I'm finishing a Art Hobby Thermic JK, 2.5m. Added flaps and stuck some HS08 servos in it. Wood finish on these planes is supper nice!.

 

[Tahoed]

Ed, is that a tow release hole in the nose of your Hobie?

BTW, I'm finishing a Art Hobby Thermic JK, 2.5m. Added flaps and stuck some HS08 servos in it. Wood finish on these planes is supper nice!.

Apparently so....It came to me that way. I haven't bothered to install a release yet. The deck was a mess, so I used a piece of Basswood to cover it up.