HPA Shark... Part 2

[Pit]

Too long neglected, I hope to resume a log of this build started in Nov. 2009 and mentioned recently in the "What did you do..." topic.  A link to the Wayback HPA "Shark" thread:
https://web.archive.org/web/20130912210347/http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=2806.0

As I mentioned in the 'What did you do' thread, I canned the original fuselage design as being too impractical opting for a more conventional sequence(?) for me.  So far, I've gotten the basic structure framed up, but I've found that nerve damage has made handling of small sticks somewhat of a major issue - things take a LOT more time and patience.

More to follow, along with progress pics.

[Pit]

A partially built up fuselage.  Drew up a workable sketch and cut wood, finding that my paws no longer appreciate working with small sticks but I'll stick tuit... .  It is not much longer than many peanut size fuselages, but for the  purpose of this exercise (proof of concept) it should suffice.

IF everything works, I'll be drawing up a regular plan.

[Pit]

A peek of the layout so far.  The fuselage top and bottom formers have yet to be added, and I'll be starting the booms this evening.

Then, figuring out how to join the works together...

The concept has the canard and main wing on the same datum, which worked on my chuck glider, but the canard will interfere with the rubber motor (will be adjustable).  I plan to move it a bit more to the top of the fuselage nose.

[Ratz (Bruce)]

Moving the elevator high may be a good choice as this puts the vorticies from the elevator above the wing in flight which is a stabilizing factor. Even a hint of dihedral in the elevator may be ok too.

Your mileage may vary...

Bruce

[Pit]

Dihedral in the canard is def in the cards.  Worked very well in my RUTANGO and other ducks that I've built.

[Ratz (Bruce)]

Well if you get some success with it and a basic plan, I will certainly build one.

Bruce

[PB_guy]

I like different looking models. How about a cookup?
ian

[Ratz (Bruce)]

Here is the image again.

[Pit]

I finally found the data sheet that I make up for nearly all of my builds and added the weights together.  The current weight of all the bits in my last photo surprised me somewhat as I have not paid any heed in selecting "good" wood except for choosing stiffness where needed.  The fuselage frame is only 8.75in, so I think a more practical size would be to enlarge the plan to 24" span.

The total so far is a whopping 3.8 grams.

[Ratz (Bruce)]

So the drawback of this design is limited to prop diameter stuck between the fins. At the time of the initial design a rubber model prop was not in the thinking.

Bruce

[Pit]

This proto should accept a 6 inch prop, should be adequate for the 19" flat span with 57 in² area.  I've also increased the wingspan, removed the wing anhedral and added dihedral to the tip panels.  I don't think the HPA Concept's wing planform would work for a rubber model, based on the apparent span and wing area.

I drew up the booms and fins today and hope to get them built by the weekend.  Finishing up the fuselage will take a bit more time as I've still got to figure out how to get everything stuck together .  As I previously mentioned, this build is being done mostly "in the air" .

[Ratz (Bruce)]

The air is right. The original was done in coffee...

All good.

[Don McLellan]

Hi Pete,

A very interesting (different) looking airplane.  Will you be posting the drawing?  I'm with Ian, maybe a CU?  Or maybe post the plan.

Cheers,
Don

[Pit]

Hi Pete,

A very interesting (different) looking airplane.  Will you be posting the drawing?  I'm with Ian, maybe a CU?  Or maybe post the plan.

Cheers,
Don

Hey Don, how are you doing?

Once I get this puppy built and figured out how best to get all the parts where they will work the way they're supposed to and at least one half way successful flight, yes, I will be updating my sketches to a workable plan and make it available.

I've had a load of life issues piled on my plate lately, so it might take a bit before anything concrete transpires.

[Pit]

Couldn't sleep, went for a walk (nice weather but too windy), went home for a second breakfast and got to work making templates and started redrawing my sketches into some semblance of a plan.  Those booms, at the scale I'm building this puppy are really minuscule, tho thankfully they are basically box shaped.  I'm using 1mm balsa for the base, that will attach directly to the underside of the airfoil, with a lamination of 0.8mm as "bottom planking" for added stiffness.  The sides will be 0.8mm and the top deck 1mm.  Fins and sub-rudders are 1mm.  I have already cut and laminated the base and bottom and cut the fins.

I really should find time to learn how to use my CNC cutter (came also with a laser head), but I'm still clearing up the cave.  At least I can now comfortably walk the length of the room without creating a disaster .

[Pit]

Gotten one of the booms mostly finished and fitted and the other started.  I'll add the top sheeting to them once the wings are attached to the fuselage (at least that is the plan... ).  The one boom weighs a little over 1 gram, including the part for the top deck, so once finished and sanded, they should be at or a bit below 1 gram.  I experimented (read: wasted a bit of time) using a stiff balsa core with foam (hollowed) form sections, but was not satisfied with the weight or the overall ruggedness (tho much easier to make).

[Crabby]

Pit great going. I am riveted!

[Pit]

Hi Crabby!

I mentioned in the original thread (linked in the first post here) that I made a '"'few" alterations to the concept.  The concepts' wing would be a bit lacking in area for a viable rubber powered plane.  Also, the anhedral could pose stability problems, hence the flat center section and tip dihedral.  There may be some issue with the size of the canard, but "area and span" can be added, if needed, without much trouble.

Like I said earlier, this pup is just based on Sundance's concept.

[Pit]

Completed the booms, including the top sheeting.  Sanded and fitted, weighing 1 gram apiece.  The lightest I got on the two previous attempts was 1.5 grams apiece and are very robust.

[Pit]

I  wanted to add a photo to my last post, but either the "modify" button is not restored or I exceeded the time limit.  Anyway, here it is...

[Don McLellan]

Looking good Pete!  Your weight for the booms is excellent.

[Pit]

A bit more done, that actually took way to much time.  Attached the wing mount plates - getting them aligned was a real PITA as the fuselage wasn't quite as straight as I would normally achieve.  Also glued the sub-fins in place - alignment was also a bit tricky, but I think (hope?) I got it.  Started adding the curved former bits, with the side bits done and a few on the bottom.  Quit when my eyes started to see four of everything .

Still, I just HAD to clip the wings to the fuselage with my trusty mini clothes pins and throw the works on the scale.  I'm not quite believing what it showed (7.95 grams, incl clothespins), but the pup does seem quite light.  Hopefully, once the rest of the formers, stringers, and nose cone are done, I don't go over my target of 12 grams (minus tissue).

[OZPAF]

What a wild looking beast Pete. It all looks neat to my eyes.

John

[Pit]

Fully stringered, nose plug rough shaped and canard mount in place.  The main wing needs three small parts and a bit of sanding,then covering can start.  I haven't decided whether to plunge form the canopy/after deck as one piece or to use a chunk of super light block (hollowed) for the rear portion.

Weight as shown is still within my target of 12 grams at 10 - and some of that 10 grams will be reduced when everything is fully shaped.

[Ratz (Bruce)]

12 grams and what is the wing area? It should perform well. Trimming will be interesting and a bit of an education.

Were you going to add the wings leading edge root and trailing edge extensions?

Bruce