LOLOLOL

Oh man, glass and paint total airframe! I'm thinking HOK candy.....

man, that is so cool [8D]

-M

I am scratch building an EVO Pentathlon. Its going to be interesting, and, very rewarding to say the least. As soon as I get enough parts cut, I will post some pics. I dont plan on building the short pipe version as of yet, that may change. I want to say to all the other builders, keep the pics comming, they are a great help, thanks.

Neil Hunt

Uh oh......

Dad is building a test plane...so to speak. The scratch part of the project is to test some built up frames versus foam core. We'll see how it goes...but it's only a test and will definitely not be available anytime soon...sorry. It will be interesting to see how it all turns out.


Mark Hunt

On another note.....The dog and I have actually started building a Pentathlon Evo. I have started working on the foam cores. Once these are all sheeted, capped, and rough sanded, I will start on the fuse.


-mark

Mark.. in your CAD drawings, I saw NO foam.

Interesting....

Mark, you should have seen Bryan Hebert's current project. 100% built-up and sheeted. As usual his attention to detail and craftsmanship were second to none. Built-up definitely can work, though. From what I understand of the processes he used, it was very similar to the way composite planes are made, but with a balsa/glass sandwich for the fuse. I can't wait to see his finished product, which from what I understand isn't too far off!

How about this way for DEPS?

Looks interesting. Also looks as though it will now just clear you pipe tunnel.

I have got most all of the sheeting done and I am now working on the fuse.



-Mark

Did you vacuum bag? What PSI?

Yes, I used a vacuum setup at 4-5 in Hg. I have used more in the past, but these cores were lightened and I did not want to risk more pressure. Everything seems to have come out fine.


-mark

Your DEPS servo mount is very clever and clearly very light, but I've have to tell you I would not put that in my plane for fear that it might break loose. Most likely it will be OK, but the fact that a failure means the loss of elevator would be too big of a risk for me. Among the things I want to make SURE don't fail the elevator ranks pretty high.

Keith B

Thanks for the feedback. What do you feel is the week point?

I see nothing wrong with that setup for the DEPS..there shouldnt be any lateral forces on it. Should work fine. We really don't stress our elevators like many think we do. I've been running a 48oz heli tail rotor servo (9254) on the elevator and never had an issue. That setup should be mroe than strong enough...

Neat idea.

Arch

The weak point is where your CF tubes go into the balsa strips at the side. You have a minimum of material above and below the hole, and balsa is not good in shear with the grain. If those will be tied into the fuselage sides in some way along their entire length, they may be ok, but I'd still put reinforcements above and below the holes. Make sure the servo cannot twist in the vertical plane under load.

This leads to another point. My experience (and some other peoples) with DEPS in balsa airplanes is not good. Every flight means another change in trim, and you HOPE you get it right on your trim pass because you are real busy after that. The first flight of the day is also an experience, as it WILL be out of trim, especially when the humidity or temperature has changed a lot. I will not build another balsa pattern plane with DEPS. It is easy to set up if you have to change servos. but the flight to flight trim change is a real annoyance. Two servos in the tail is my standard from now on, because the trim never changes. DEPS seems to work ok in composite airplanes, given they don't seem to expand and contract as much relative to the CF pushrods.

I have three concerns with the setup.

1. As Jon Lowe mentioned the anchor points of the carbon rods in the side wood strips is a concern. A) the strip could break where the wood is weakened due to the drilled holes and B) given stress from the elevator pushing up (or down ) flex could cause the rods to pull out of the holes.

2. Though there have been comments that the stresses on our elevator servos are not that great, I have seen in a DEPS systems slight movement of the elevator servo torquing (rotating slightly) when the elevator is pushed to an extreme position. Granted this probably means the elevator is pushing too far, but it demonstrates that resistance causes the elevator servo to want to twist and from the picture it appears that the rods will not be great against this twisting action. If I could put my hand on it I may feel differently.

3. The hole drilled through the ply that allows the rod to slip through (beautifully done btw) is also a concern. From my point of view you’ve completely separated the middle layers of the ply laminate at the ends and I’m not sure how much pressure it would take to cause those separated middle layers from slipping out. The only support they have is from glue on their neighboring layers above and below, and the surface area above and below the end ply section is very small (particularly the front joint). I hope that made sense.

Your work is beautiful and perhaps like Arch said will be fine, I’m just giving you my opinion. It’s worth what you paid for it.

A good idea might be to build another such mount and push it to the breaking point to see how much it will withstand.

Good luck,
Keith B

Perhaps consider that the base of the servo plate will be about 1/8" away from the base of the pipe tunnel. You might add a sheet of hard balsa (thickness to be determined) to the base of the plate so that it can be glued directly to bottom sheet of the pipe tunnel when it is installed.

By the way, you may want to add a light piece of 1/8" square balsa to the backside of each of the balsa formers so that it will be in direct contact with the bottom sheet of the pipe tunnel. That would strengthen you balsa formers where they are weakest. Sorry about the thin section there.....


-mark

Decided to build the vertical fin and fixture.....child labor[:@]

Dad sheeted it though!


-mark

Hi Mark,

How much does the build up rudder vs the foam core weigh?

G

George,

I just weighed the vertical fin and tailpost quickly...as seen in the picture, it is sheeted, but lacks the light 1/4 balsa leading edge. It weighs 0.8oz. Not sure how this compares to foam.

Rudder is next.


Mark

Rudder time.

Weight of rudder without leading edge bevel or final sanding - 1.0oz. (sorry, my scale is only good to .1oz.).

Sorry I didn't get a picture of it, but I did build the rudder fixture over a plan and wax paper.


-mark

Mark,
What is the purpose in chopping part of the rudder off?
Thanks
Greg

Mark
Bring it over and I'll weigh it for you at work. My Denver balance is accurate to 1mg or 0.001 GM. Your scale at 0.1oz comes out to 2.835Gm (jk)

Eddie

Hey Eddie!

Is your Pentathlon an Evo? How is it coming? I'm getting mine ready to spray later today.

G

Here is another picture/s of the vertical fin and rudder.

-mark

George
Mine is a "vintage" Pentathlon. I'm not very far with it, Life keeps cutting into my free time( as you know that's about normal for me[:@] )

Eddie