Fun with fiberglass

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Includes: Highlander, Escapade, Summit and SuperSTOL.

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Re: Fun with fiberglass

Postby Allan » Thu Mar 26, 2015 10:07 am

That's a good article in Kitplanes as it has some real numbers. My superstol build is well on the way and with an aircraft friend we have come up with something we hope will work. Until we test it, probably a couple months??.....there isn't much point in talking about it.
A photo of the outside, obviously it's all in the internals and exit cowl doors. I want those few extra knots AND I want to increase my cooling effciency here in an often hot climate.
Having trouble loading photos(lack of knowledge and patience) but I think I can get one up.
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Re: Fun with fiberglass

Postby moving2time » Thu Mar 26, 2015 12:22 pm

Allan, I remember reading that article. It was very interesting. Can you explain what your thoughts are with the mods you are making to your cowl? Was this something that you decided on following your reading the article in Kitplanes? I need to go back and read that article again myself. Seems I remember they went through some trial and error. Maybe not so much error as just tweaking. I plan to modify my landing gear similar to the way you appear to be modifying yours although I was thinking of using foam for the airfoil. It appears that you are using wood, maybe balsa? Do you plan to extend the trailing edge to fair it out? That is probably the most important element to the mod to maximize reducing the drag. Question is how much can you draw out the trailing edge to create a smooth transition and not restrict getting into or exiting the cabin? I hope it works for you. Please keep us informed of the progress. Specially the cowl mods. BTW, Your photo was great. once you figure it out it isn't that difficult. Great ideas!
Rick, The weather still isn't going in the right direction. UGH. Joe B
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Re: Fun with fiberglass

Postby kenryan » Thu Mar 26, 2015 3:21 pm

Alan, is this for a Rotax installation? If so, are you giving up the limp home feature built into the cooling system, that allows one to limp home at reduced power in the event of a failure of the water coolant system? I mention this because it doesn't look like you have much cooling air for the cylinders.
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Re: Fun with fiberglass

Postby Johnny C! » Fri Mar 27, 2015 10:37 am

What is this "Limp Home Mode" that you speak of?

John

kenryan wrote:Alan, is this for a Rotax installation? If so, are you giving up the limp home feature built into the cooling system, that allows one to limp home at reduced power in the event of a failure of the water coolant system? I mention this because it doesn't look like you have much cooling air for the cylinders.
There are many things that happen really fast when you are
flying an airplane. There is no sense in rushing any of the others.

I would much rather be looking down at the runway, than up at it.

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Re: Fun with fiberglass

Postby kenryan » Fri Mar 27, 2015 11:09 am

The Rotax 9 series engines rely on cooling from not just the coolant that circulates through the heads, but also air that blows over the fins on the cylinders. The design is intended to allow for emergency flight at reduced power in the event of a failure of the water cooling portion of the system, for instance, if you boiled your coolant off.

Edited to add:

Specifically, here's what Rob Seaton (Rotech) said on the Rotax Engine Forum:

"The Rotax was certified with fins on the cylinders as it is a 'get-home' redundant feature; if the coolant system fails you can operate at a lower power setting and the engine will run for hours."

Link: http://www.rotax-owner.com/en/rotax-forum/4-general-discussion/5087-thermo-bob-coolant-thermostat#9538
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Re: Fun with fiberglass

Postby Allan » Sat Mar 28, 2015 9:00 pm

It's a rotax 912 turbo. Whilst we have thought about cylinder cooling for normal ops and cool air for turbo etc the emphasis has been to work on an efficient cooling system that we can control with cowl flap doors. I wasn't aware of the limp home feature. Just completed a rotax heavy maintenance course and it's clear that any over temps need to be considered carefully due engine top end softening. I would happily sacrifice my engine if needs be but at this point the superstol would be rapidly looking for a landing to sort the issue out.
I will give this more thought thanks.
I am not sure of forum etiquette here but it feels this maybe hi jacking fun with fibreglass...is that ok? It does revolve around air flow mods and tidy ups.
For instance the generic jabiru cowl that was supplied with my kit has been dropped several inches hence the gearbox tunnel on top. A new bottom end designed to allow for the internal cooling ducts and volume changes to the radiator air flows for divergent air flow (slower air flow picks up more heat) from the front end including a curve for prop wash whilst not exceeding 7 degrees anywhere to avoid internal duct turbulence. As it passes through the radiators it appears that heating the air actually removes what I would have thought would be turbulent flow through the radiators and critically there has to be some length after the radiators to be able to reduce flows during cruise hence cowl flap doors for oil cooler and water sides. Has to be split by the gear legs and that also limits the length of cowls behind radiators. Exit cowls are fenced.
Engine has full monitoring on new style heads, chats, egts, cylinder barrel temp, air box temps, turbo inlet temps, oil and water and may even stick a couple cheap probes into the cooling air flow to work out the deltas over the radiators.
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Re: Fun with fiberglass

Postby Allan » Sat Mar 28, 2015 9:25 pm

Regarding gear legs there are several points. The fairings you see on the legs are an aircraft hard foam that I have tested for heat resistance (using Oratex fabric with heat and pressure to stick and set the glues) and whist it can be cut and sanded to shape the very dial finish isn't perfectly smooth. This doesn't matter to me, it is still going to be a very much bush plane that wants to preserve stol and yet manage the distances I need to cover here.
The top of the gear legs will disappear into the area behind the radiator cooling system and the belly line behind the gear a dropped and inch or two to make a sweet line through to the back. Obviously gear movement must be taken into account.
The other mod with all the cowl changes is that there is a smooth line along the sides from the nose over the top of the top of shock legs (allowing for movement) through to the rear of the plane. This effectively widens the front door frame by and inch or so, (and widens the Firewall a little) basically gets rid of the flat area on the side of the cowls back to the cabin. Rear cabin door is standard.
Rear of the gear legs will have a folded light ally trailing eve and there will be a definite step set into the legs for cabin access. Shock strut will be faired.
There are rolled flying wires coming from NZ for the tail. As well as less drag than wires will allow my later trimming if desired.
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Re: Fun with fiberglass

Postby Allan » Sat Mar 28, 2015 9:33 pm

This shot gives an idea of the new cowl lines.
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Re: Fun with fiberglass

Postby rmullins » Sun Mar 29, 2015 12:42 pm

No Allen, I don't think you've hijacked "Fun with fiberglass" at all. All this discussion fits right in with my original post of making fairings and other go fast mods. It's really great to see what you and others are up to. Still not very good flying conditions here yet so yesterday I got out the fiberglass saw...
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Re: Fun with fiberglass

Postby Allan » Mon Mar 30, 2015 7:33 am

Thanks. Will give you an update as I get this flying. Right now it's just a good idea........well hopefully better than that!!
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Re: Fun with fiberglass

Postby danerazz » Mon Mar 30, 2015 7:43 am

Allan,

I see you put airfoil shaped false ribs on your tail. I had suggested this earlier to much dissent, but I am really anxious to see what you think of it once you are flying.

Looks great!
Dane

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Re: Fun with fiberglass

Postby moving2time » Mon Mar 30, 2015 12:03 pm

Allen, thank you so much for filling in some of the details. As Rick mentioned, we are talking about things that may clean up the Highlander and I think this is a great topic. The Highlander and SS are great aircraft intended to get into places that other aircraft can't get into but that doesn't mean that both couldn't benefit from cleaning up unnecessary drag. The landing gear legs are a huge area and I'm certain that cleaning up the drag in that area will help a lot. Your ideas are very much like what I have sketched up myself for when I build my Highlander. I have also thought about the tail surfaces but I am not so sure that your approach will be very effective at reducing drag and may even affect the efficiency of the control surfaces. Trust me, I do not intend to insult your ideas regarding your attempt to clean up the tail surfaces but I questions the way it will work for you in practice. The built up fixed stabilizer surfaces appear to return back to the rear tube basically creating a fat trailing edge which I believe will destroy the air flow into the control surface. The airfoil of the stabilizers including their trailing control surfaces should be a smooth airfoil to be effective. I am not an aeronautical engineer but I have never seen the tail surfaces built up like you have done. As far as I understand, the shape of the airfoil is not all that critical when your only goal is to reduce drag. The two goals of the airfoil in reducing the drag are that the airfoil be smooth and the trailing edge terminate such that airflow separates from the trailing edge smoothly into the airflow trailing airflow. What you are creating is an undulating shape where the leading shape (stabilizer) does not carry the airfoil over and into the leading edge of the control surface. Perhaps the air will separate from the surface area of the stabilizers where they transition into the control surfaces and continue flow over the control surfaces but I believe that their will be a lot of turbulence created right in front of the control surfaces and significantly reduce control effectiveness. Hopefully someone on our forum will have more education in this area than I do and be able to make some constructive comments. I hope I am wrong because you look like you have a fair amount of work done in that area and your solution is much simpler than trying to build in a true airfoil and would be a great solution if effective. Sorry to sound so critical. I'm just trying to make a constructive observation. Good luck. I am always looking to learn. Joe B
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Re: Fun with fiberglass

Postby Johnny C! » Mon Mar 30, 2015 12:34 pm

Thanks!

Great thread!

John

kenryan wrote:The Rotax 9 series engines rely on cooling from not just the coolant that circulates through the heads, but also air that blows over the fins on the cylinders. The design is intended to allow for emergency flight at reduced power in the event of a failure of the water cooling portion of the system, for instance, if you boiled your coolant off.

Edited to add:

Specifically, here's what Rob Seaton (Rotech) said on the Rotax Engine Forum:

"The Rotax was certified with fins on the cylinders as it is a 'get-home' redundant feature; if the coolant system fails you can operate at a lower power setting and the engine will run for hours."

Link: http://www.rotax-owner.com/en/rotax-forum/4-general-discussion/5087-thermo-bob-coolant-thermostat#9538
There are many things that happen really fast when you are
flying an airplane. There is no sense in rushing any of the others.

I would much rather be looking down at the runway, than up at it.

Duane Sorenson & Rick Norton Gone West 6/8/09. Godspeed
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Re: Fun with fiberglass

Postby Allan » Wed Apr 01, 2015 2:43 am

True re the tail feathers, and the method won't generate the best surface. Yes looks good! Look at a tiger moth is probably the best. Will be gap sealed although it's interesting to note that a relatively small deflection gives a nice total curve.
The flying wires will be rolled and also gives me nice adjustment.
Engine will have the required air flow over the cylinders plus there will be probes to confirm correct temps.

How close are people getting their slats to fit on the wing fronts at the trailing edge?
Had mine pre built. One has a twist and lifts about 5/16 on the out board of the outboard slat. Good bottom match.
The other side is slightly low and consistently both slats are close to 1/4 proud. Would be a definite 1/4 proud if the bottom of the slat is matched like the other wing.
Twist would be a derivet to fix and the othe slats look like they need their mounts rotated slightly, ie spacers don't fix the angular problem!

Stol is still priority and straying outside the lines is time costly in the build............
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