FT Explorer plan modification for depron

[buzuc]

Hi everyone
I'm currently modifying the FT Explorer's plan to fit the thickness of depron (as I'm in France I don't have access to DTF).
So, I extracted the pages in dxf and I'm modifying the drawing in Autocad.

I thought that the only thing I would have to do is change the width of the "cavities" but it seems that their width is not consistant.
Here are two screenshots of the first page of the plan showing the width of the cavities.



It's not really an issue but I just don't understand how their size were calculated. What I thought was that the width should be equal to the thickness of the material but it seems that's not the case...

Any explanation?

 

[TEAJR66]

Something got lost in conversion?

Not sure what happened. The cavities should be 3/16" (~5mm or 4.7625mm). There really is not much need for conversion. I have used standard plans to build an FT Racer and Versa Wing with 6mm foam. Since the foam is malleable, the tabs you can squish and the A/B folds just need to be worked a little to get them to form nicely. The 6mm foam I used did not have a covering so I skinned the outside with packing tape then built as per the normal FT Build Techniques. 4, 5, or 6mm depron should work nicely with no plans modification.

Let us know how it works and post pictures.

 

[buzuc]

Something got lost in conversion?

Nope: I measured on the pdf and it's the same

Not sure what happened.

Me neither!

Let us know how it works and post pictures.

Of course I will. It's not my first FT build but this one is special: I'm preparing the plans for my 9 yo son whose birthday is next week and it will be part of his birthday gift along with a transmitter, batteries, servos, motor...

 

[RodrigoDeLucca]

No need to change the thickness of the folds on the plans. I've built my explorer with 5mm depron without major issues.

The only thing I would recommend is to change the nose/tail, since depron has no paper, the technique where you leave the paper on the edges of the foam and use it to glue to other parts does not work well. This is used on the tail boom and on the rounded nose. You could make the tail boom sides shorter and widen the top, doing the same thing with the nose (easy to do with AutoCAD offset). I haven't done so in my build and it turned out good enough.

 

[shiitake]

If i am correct the cavities are on purpose < 5mm because when you use a laser printer for cutting foam, the foam itself melts a bit away so the cavity gets wider than the cut. The designs are originally made for a laser printer I think.

But indeed as anybody else says. don't worry too much about 1mm too much..

 

[localfiend]

If i am correct the cavities are on purpose < 5mm because when you use a laser printer for cutting foam, the foam itself melts a bit away so the cavity gets wider than the cut. The designs are originally made for a laser printer I think.

But indeed as anybody else says. don't worry too much about 1mm too much..

It makes for a stronger corner to have the width a bit tighter than the thickness. Everything is snug that way, and shouldn't ever start out loose. I use .17" for all a/b fold cuts on my plans, which is 4.318mm.

 

[buzuc]

The width of the cavities is not an issue. I think my explanation was unclear.

The issue is the difference between the cavities' dimensions. This plane has quite a few tight fit and I think that it will be difficult to get this right if the cavities are not the same dimensions.

 

[Craftydan]

Buzuc,

I believe those dimensional differences are intentional, depending on where that joint is. In either case, the joint can be made using the 5mm paper backed foam, but the smaller cavity will be far tighter than the larger one, resulting in a more crushed joint that pushes/bows out more, where the larger cavity will close more cleanly without crushing and have a sharper, cleaner look.

In the end, I think you are approaching this with far more precision than is warranted. This is not a bad thing as your attention to detail will give you a better build in the end, but you're getting locked up in analysis-paralysis. These models are designed intentionally with a lot of slop in how it is built to accommodate builders lacking skill and patience.

Go ahead and build it to plan, fixing unforeseen issues as you go. If your careful examination up to this point is any indicator, you will do just fine.

 

[buzuc]

I came to the same conclusion. But, it will be the first complete build for my son and I really don't want that experience to turn in a trial and error that could be frustating when you begin. That's what happened when I scratch built the Tiny trainer though I could manage it as I have enough experience.

Anyway I will do my best and show him what "real" modelism is

 

[RodrigoDeLucca]

What is the thickness of the depron you will use? I had a bit of a tight fit of the tail section on it's slot. Best approach was to run it against the edge of the table and then use some soap to get it in.
You've built with depron before so I guess you know to coat every outside surface with packing tape as a way not to crack it.
I'll be home on Friday and I can post a picture of the issues I had when building this plane out of depron.
Rgds,

 

[buzuc]

What is the thickness of the depron you will use? I had a bit of a tight fit of the tail section on it's slot.

Sorry for the late answer: I was very busy refurbishing my bathroom and kids' bedrooms...

I'm using 6mm depron and everything if fine except what I came to this week-end:

The servos do not fit in the boom!

I wanted to install them in the main frame but I will have an issue with the push-rods that will run very close to the prop... The other solution would be to install rudder and elevator servos at the bottom of the rudder but I'm worried about the amount of weight I will have to add to balance the plane properly.

What do you think?

 

[Craftydan]

Buzuc,

I'd run the pushrods inside the tail boom, bending them out to line up with the control surfaces and servos. Pushrods don't have to be straight, they just can't be allowed to flex. There are pushrod kits available all over that have a matched pushrod and plastic sleeve -- mount the sleeve so it routes the rod where you want it to go, making sure it no longer flexes (glued down where it might) then run the pushrod through the sleeve.

RC builders have been using them for ages, particularly on ailerons when the servos were too big to fit into the wings. It can't do sharp bends well, but it's surprising what you can accomplish with a few gentle bends. The sleeve forces the pushrod around the gentle bends, but because the sleeve can't flex, every mm the pushrod moves into the sleeve on the servo side, a mm or rod will move out of the sleeve on the control side. As long as the entry and exit points on the sleeve are mounted properly and close to their linking points, they have no room left to flex.

The kits aren't terribly expensive, however if you don't have a source of thin nylon tubing, you can cobble together a series of pushrod guides using coffee stirrers as sleeves. You'd have to be more creative about making sure it doesn't have room to flex inside as it bends around corners, but it can be done.

 

[TooJung2Die]

Buzuc,
I'd run the pushrods inside the tail boom, bending them out to line up with the control surfaces and servos. Pushrods don't have to be straight, they just can't be allowed to flex. There are pushrod kits available all over that have a matched pushrod and plastic sleeve -- mount the sleeve so it routes the rod where you want it to go, making sure it no longer flexes (glued down where it might) then run the pushrod through the sleeve.

Found these pushrod guides in a three pack of dollar store shower caps. Each shower cap has a 2 foot section of 0.14" OD tubing with couplers. Stiff yet flexible. The wife was about to throw these away. Silly woman. :black_eyed: If you don't use the shower caps they'll make colorful parachutes.
Jon

 

[buzuc]

@Craftydan: That's what I wanted to do, with more than twenty years of RC Gliders' practise I know how to install push rods. I wanted to know if somebody already came to the same issue (servos that don't fit in boom) and what was the best way to solve the problem. Thanks for the reminder anyway: Your explanations are clear as usual:applause:

@TooJung2Die: What a great finding! I will go to the euro shop (I'm on the other side of the pond) on my way back home tonight to see if I can find the same kind of shower caps or any other stuff that may contain potential pushrods tubing...

 

[rkal]

Hi everyone
I'm currently modifying the FT Explorer's plan to fit the thickness of depron (as I'm in France I don't have access to DTF).
So, I extracted the pages in dxf and I'm modifying the drawing in Autocad.

I thought that the only thing I would have to do is change the width of the "cavities" but it seems that their width is not consistant.
Here are two screenshots of the first page of the plan showing the width of the cavities.

View attachment 73579 View attachment 73580

It's not really an issue but I just don't understand how their size were calculated. What I thought was that the width should be equal to the thickness of the material but it seems that's not the case...

Any explanation?

Hi buzuc

Great work
Is it possible to download Yours depron plans ?

Best Regards