I've been working on a design for a 5m Horten IV on and off for a the last several months. I did the inital aerodynamic design work using the Nurflügel and FLZ_Vortex programs. Once I had the aerodynamic design worked out I "built" a 3d model in Rhino. Finally, I'm now generating "cut files". At this point I've cut out a couple of sheets of parts.

Here's a list of some of the design challenges on the Ho IV:

• Making the center section scale enough.
• Making it light and stiff enough to resist flutter--I know I shouldn't mention that word!
• Dealing with a very small wing tip airfoil and the associated low Reynolds numbers.
• Driving the outer elevon (there are three elevons per wing panel). The wing is simply too small to fit a real servo out there.
• Fitting a tow release

I could probably go on for a long time...This is definitely a difficult plane to model.

If anyone is interested I'll discuss the design and/or post some more screen shots of the model in Rhino. I don't intend to do a build thread at this point since I just don't have the time. As a matter of fact I may be looking for someone who is interested in building the Ho IV.

Brian

p.s. Here are some intersting Ho IV model links:
http://forum.retroplane.net/viewtopi...er=asc&start=0
http://www.retroplane.net/forum/viewtopic.php?t=3610
http://www.retroplane.net/forum/viewtopic.php?t=1672

Brian,

Of course I'm interested.

Re Servo fit up.

You might want to consider doing Pull Pull on those outer control surfaces.
With three separate smaller servos located near the wing break. ( Plug - in joint )

I have been using KEVLAR thread in some of this summers Foamys for Rudder and Elevator.

Used them an a FalClone 60 foamy ( Falcon56 alike) and have tons of flights on it
using kelvar thread. It's been THE Buddy Box trainer here this summer.

I bought a 1000yd spool a few yrs back and have also been using it for
wrapping Pultruded CF tubing to prevent split out.
http://www.thethreadexchange.com/

Yep it's yet another challenge.

Tow release I expect it be on the bottom somewhere.
A strong mounted metal plate with a hole and a sliding pin inside might be a way to go.

I believe the Horten IV presents THE greatest challenge for sailplane modelers.

What can I do to help ?
Another plug or some CAD fiddling ?

L8r

Bob

Brian,

I'd definitely be interested. Looks like a really cool project. Having flown your other works of art, I can only imagine how well this one will perform!

How about doing a molded center section to ease some of the torture of pulling off the scale eye candy stuff?

Mike

Brian, not to steer you away from this one, but any thought about a 5 meter HO 3? Yours looked to fly awesome.

Hey Bob,

How are things going with you?

I had thought about using a pull-pull system. I've done pull-pull systems on both elevators and rudders but non on ailerons (or elevons for that matter). Do you have any good pictures and/or drawings of the system you described below?

You might be right about putting the tow release on the bottom--as opposed to directly on the nose. I wonder if it could be slightly (~3/8" or so) off-center? Thoughts?

I have to disagree with you about the Ho IV being the most difficult scale sailplane. I'd have to give that honor to the Ho VI since it has a crazy high aspect ratio.

Thanks for the offer of help but--other than the pull-pull information--I'm good with things for the moment.

Brian

Originally Posted by birdofplay

Brian,

Of course I'm interested.

Re Servo fit up.

You might want to consider doing Pull Pull on those outer control surfaces.
With three separate smaller servos located near the wing break. ( Plug - in joint )

I have been using KEVLAR thread in some of this summers Foamys for Rudder and Elevator.

Used them an a FalClone 60 foamy ( Falcon56 alike) and have tons of flights on it
using kelvar thread. It's been THE Buddy Box trainer here this summer.

I bought a 1000yd spool a few yrs back and have also been using it for
wrapping Pultruded CF tubing to prevent split out.
http://www.thethreadexchange.com/

Yep it's yet another challenge.

Tow release I expect it be on the bottom somewhere.
A strong mounted metal plate with a hole and a sliding pin inside might be a way to go.

I believe the Horten IV presents THE greatest challenge for sailplane modelers.

What can I do to help ?
Another plug or some CAD fiddling ?

L8r

Bob

Originally Posted by yyz

Brian,

I'd definitely be interested. Looks like a really cool project. Having flown your other works of art, I can only imagine how well this one will perform!

How about doing a molded center section to ease some of the torture of pulling off the scale eye candy stuff?

Mike

Hey Mike,

No!!!!! Not for the prototype anyway. This thing will be be made out of wood where ever possible. Maybe at some point in the future there will be an easy-build kit.

Brian

Originally Posted by s2000

Brian, not to steer you away from this one, but any thought about a 5 meter HO 3? Yours looked to fly awesome.

Hey Dennis,

Only 5 meters? If/when I design and build another Ho III I think I'll go 30% bigger. Doesn't 30% and 6.15 meters sound better? However, if I go there I'll either need to get a source for longer joiner tubes or work out a completely different system to mount the wing panels to the center section. Any thoughts?

Brian

While I agree that bigger is better too large of a model Sailplane makes you
ultra dependent on an available LARGE tug.

IMHO thats why scale sailplanes are not as popular as I believe that could be.

It's difficult to become proficient at flying ones model if the opportunity
only presents itself half dozen times a season.

Bob

CPDude:
How are you?

I've been working on a large Ho - IV for a long time: dreaming, drawing, redreaming. redrawing, etc.

I'd love to do a build log for you.
I think you have had lots of offers......????
I've done several build logs, latest one is Ray Hays ASK on his site

I have in my file the formula for CG, Cpres, etc for wings. I also have almost all books by, for, of the Horton Brothers.

Carbon fiber spars, CF on LE and TE's The inner ribs will be quite thick/deep!!!!
Al rod and Al tube - 1.5 inch

CG location will give you a rather accurate location for the Tow hook. The evelon at the time is not really a problem for servo mounting - with push-rods and bell crank. I had to use that method for my 1/4 scale Janter. 4" in chord at tip.

Would love to discuss more of the methods I planned on using for mine.

I have compuFoil and can knock out all of the ribs in a few hours, ready for laser cutting by my cutter or you might want to cut them, right? BTW what did you do with your homemade laser cutter???
cheers
Jim

Originally Posted by cpdude

Hey Mike,

No!!!!! Not for the prototype anyway. This thing will be be made out of wood where ever possible. Maybe at some point in the future there will be an easy-build kit.

Brian

What if someone helped you do the mold?

There is no way you can't do this plane! Check this shot out:

@Jim - What size Ho IV where/are you working on? I was only able to squeeze in 7/8" wing joiner tube in mine. What did you use to figure out the wing twist? As far as doing the build log...I've got a bit more work to do before I at the point were I need to make a decision.

My homemade laser is what I'm current using. I upgraded it to 60 Watts and higher quality optics. It's working great!

Brian

Brian,
Of course I'm interested too. I look forward to following your progress. Sadly there are really no opportunities to fly large ships like this that require towing around here (would have to go to Elmira and that is 3-4 hrs away ).
I still hope to finish the projects I have on the board (have actually gotten back into a steady build routine) so I fully intend to order the HoXII soon.
Best Regards,
-Eric

Originally Posted by ohmite

Brian,
Of course I'm interested too. I look forward to following your progress. Sadly there are really no opportunities to fly large ships like this that require towing around here (would have to go to Elmira and that is 3-4 hrs away ).
I still hope to finish the projects I have on the board (have actually gotten back into a steady build routine) so I fully intend to order the HoXII soon.
Best Regards,
-Eric

Hey Eric,

I could always design a powered center section for the Ho IV wing panels. Just a thought!

About the Ho XII...just let me know when you are ready and I'll be more than happy to cut one for you.

Brian

Brian,

If you're going to do a 5 meter version, why not jump up a bit and do a full 1:3 scale? That would take it to 6.8 meters with, and I'm guessing, roughly the same about of work and slightly more material.

People aren't going to be hand launching a 5 m glider so it already assumes that it will be powered or towed.

Just a thought (at the expense of more work for you) ,

Mike

Hey Mike,

You're killing me! That's right...just a little bit more work. You've got me thinking now. How does 40% sound? Maybe just go full size!

On a serious note. I think 1:3 scale is very doable and darn if it probably wouldn't fly better too. However, at this point I'm committed to the 25% (~5m) version. Maybe next time...or maybe after the 6.15m Horten III.

Brian