It's another day in paradise here (in the office dreaming on flying tho) and it got me thinking.

I know that a few years ago retracts got left behind on pattern ships, mainly to save weight and I think a couple of comments from Chip Hyde was enough to sway all and sundry.

Are they worthwhile fitting to planes these days? Or have the good old retract days passed us by?

Seems to me the next thing we're all going to see to shave another two ounces out of our ships is a monowheel arrangement, ala a Motorglider!!!

I wish they would come back!
If you fly from a rough grass patch,as I do, the currently-fashionable carbon legs/fus mounting,is a total PIA---if the leg doesn't eventually delaminate from vertical shocks,its lack of fore-and-aft flexibility will eventually damage the mounting plate, and if you introduce soft-mounting into the bolts (eg Rawlbolts or similar),sooner or later they'll pull out and the belly pan suffers----at least with retracts all that happened was the repeated leg straightening.....
It's a pity we're such appearance/fashion slaves----a torsion-wire U/C saves a lot of grief!

There's nothing that says any of us has to use fixed gear or retracts. I have a friend who has built every plane, including the 2 last year with retracts.

You may have to buy a true "KIT" as opposed to the carbon, painted in the mold but hey, you can do it.

It has been well documented that the molds for Supra Retracts were bought by Great Planes (I think that is them anyway) so the retracts available are supposed to be essentially the same.

However, the game has changed in such a way as drag is a good thing now, and fixed gear is a good way to get it, to slow the plane down a bit and help keep constant speed.

Personally, IMO I don't see retracts making a big comeback. I didn't think I would like fixed gear but having gotten used to it, is sooo nice to put plane together, to haul in my pickup, and to move on the flightline, plus they are soooo much easier to put on a plane.

Ed

Well for me, up until I started flying this Impact in June, I've always had retracts. I just like the way they look. The only problem I had was prop clearance. For that reason alone, unless someone comes up with some stellar lightweight struts, it's hard to see them coming back for AMA. Of course, this is why I've now become a big supporter of the much talked about BPA! Now I can have my retracts one weekend and my big props the next ;-)

Joe W.

Ok Joe,for the uninformed what does BPA stand for?

BPA = Ballistic Pattern Association, e.g. super fast rocket ships from the past.

I think the current crop of slow and bulky pattern aircraft would not benefit much from retracts.

To get retracts to come back, all you have to do is get Cristophe to start using them again!....Then magically they will reappear....
GregGrigsby

Gregg, thats' exaclty what I'm on about.

Soo tempting to go back to retracts, and lets face it prop clearance isn't that much of an issue once you add an extra blade or two to your plane.

Retracts were great when we were trying to squeeze as much performance from a .61 as possible. A clean plane helped us out a bit. Today, we have no limit on displacement, so we actually have too much power in some cases. To the point that we are running 3 - 4 blade props to add drag to our already widebody planes. It will take another rules change that somehow would make retracts attractive again before people will change back. Personally, I like the fixed gear. I can remember beating up my retacts on a grass field all week practicing and having them jam or the nose gear fold up on landing in a contest. Nothing looks cooler than retracts, but from a practical standpoint. No thanks.

Is there any debate with regard to aerodynamic effects? If you take a nice, long, bolly electric gear with wheel pants...this is a fair amount of drag force begin imparted well below the cg? Does this create more of a need for positive incidence in the wing or up elevator for level flight...this could also have adverse drag effects when trying to yaw in level flight.

Also, and perhaps more importantly, what is the effect on vertical cg? If one particular airframe were equipped with a long fixed gear, then later fitted with retracts, would the fixed gear version show a stronger tendency to roll upright during knife edge flight? With the retracts in the up position, the vertical cg would/should be closer to the aerodynamic center of the fuse side (in knife edge flight).

I did the retract thing back in the 70's. I got back into pattern in the 90's using fixed and I haven't looked back since.

I think the Bolly swept gear is a very good choice. The gear is designed to flex and give. They will take a surpisingly high impact load before breaking or tearing up the airplane. I have a set that were in a crash that totaled the airplane and the gear split length wise. I repaired them with thin c/a to the split and put one layer of light c.fiber on the bottom with thin c/a and they are still serviceable on my new airplane.

May not be the lightest gear on the market but are the more durable and shock forgiving.

Wayne Galligan

As for aerodynamics.... the biggest factor I have seen is the wheel pants. If the pants are not lined up it can have an influence on trim and some drag issues. I am sure it may influence knife edge some. Retracts have issues with a big hole in the bottom of the wing so there is probably a wash on the influence of trim on eiither set up.

Retracts have always impressed me. They look very scale while going in and popping out on landing. I have a .40 avistar form hobbico so retracts I think are out of the question with my high wing. I'm currently trying to fix up a small 400 class heli airwolf style body and am thinking of placeing retracts. do mico sized retracts exist or do you think for such a small aircraft I should rig someting up to pick up all the wheels with one servo. Thanks for the insights guys, very informative.

Heli_Flight

I did a bit more of a hunt on the retract story.

Seems a while back that Pete Goldsmith was messing around with his Carrera and found that an aircraft with fixed gear flew FASTER, and rolled better.

He attributed this to to having less upset airflow over the centre section of the wing as the cutouts were now gone.

Seems to me if you wanted the best of both worlds we'd be looking at covers over the retract holes, which is all getting a little bit fiddly for a ship that's gotta work, every time.

but, food for thought, no?

My newest bird has fixed gear but I've always done retracts. I think I've figured out how to get the max benefit from them in setup. Cosmetically, fixed are nice on the ground and workbench, retracts look great in the air. But the BIG reason to use retracts is the simple fact that if you build your plane to last you 1000+ flights you have to think a bit differently and keep it simple and flexible. In this case, I will guarantee you that somewhere over that 1000+ flights you'll have an inopportune deadstick or have to land downwind. Being able to suck up the gear and belly land it is a defensive act. With fixed gear you have a high chance of a major repair. With retracts, its no biggie.

So, to get the most out of retracts, here's the formula:
1. mount retracts for 7 degree forward rake. This gets the wheels farther ahead of the CG (but still not as far as some fixed) AND it better distributes the landing loads so your gear gets bent much less often
2. Use the central 3/16" titanium struts because they are lighter than the 5/32" steel and they are 1" longer, so you can mount the retract further out on the wing and improve your clearance. I can use a 19" prop on my Symphony with no problem.
3. Keep the C-plate mount light. Use 1/8" ac ply or 1/4" lite ply with lightening holes. bond it to only one false rib. You can use a doubler at the bond joint to improve the bond

I've done both ways and retract are not heavier than fixed when installed in foam wings.

Heli. I knew a guy who had retracts in a 40 size trainer like the Avistar. Cessna made a version of the 182 that had retracts. The axis of rotation of the main gear made a ''V'' and they folded back into the fuselage.

This inspired me to design a setup for a pattern plane with fuselage mounted retracts that acted the same way. My main reason was that wing mounted gear would require much longer struts. An added advantage would to be to reduce the problem Rendegade mentioned since the wells would show a lower profile to the airflow. Fixed gear became popular about the time I came up with it, and it was never built.

BTW. The 182 RG was MUCH faster than the fixed gear version, and the wells were open.

Not to go off topic, but as you can see by my Avatar, I have a new Cessna 182. The older 182RG version is not MUCH faster than the new (and streamlined) 182. Maybe 5-10kts. I totally agree with Dreadnaut, it was MUCH faster than the same older version of the 182 built at the same time, but when the engineers found out they could cheat the wind and leave the gear out, that's what they opted for. When you add insurance, maintenance, etc, Cessna dumped retracts on ALL their single planes. So did Cirrus and Columbia. Their speeds are nearly the same as a retract version without the liability issues. Powerplants haven't changed any HP-wise, unlike pattern planes. I agree that our model engine HP is excessive and we're looking for something to "drag" us down a little bit.

My pattern planes have always been fixed gear! Now, if they could just make them longer (and readily available) for the electric prop clearance, I'd be happy.

Yeah, I build fixed now, but if you like tinkering, retracts are fun!

when u get the retracts RIGHT, they are a joy 2 watch especially one with tricycle retracts operating using 1 servo.My cosmos has trike retracts,and hell....she's fast man.

Gee, I wonder if retracts would affect judging?

Depends on the judges unfortunately. No matter how hard we try to get every one on the same page, same chapter, same book,..... individual interpretations and scoring habits persist. It's much better than it used to be but we still have quite aways to go

MattK

PS- retracts would be a cinch to build long legged. Cut the steel strut about 1" below the coil and epoxy a .24 x .16" carbon tube in place. Torsional strength can be had with a length of 1000 carbon roving ca'd in place, spiral wound around the carbon strut. You will remove about 2 ozs of steel weight from them, making them comparable in weight to the lightest fixed gear. I've done it and it works fine. The bonus is improved or cleaner air flow under the stab, particularly when using a gear door. QED

OK, My turn to go a little off topic here. I got to the long strut thing by thinking of the old navy F4U Corsair. It occured to me that the reason for the inverse gull wing design was to keep the LG struts shorter by lowering the spar at the gear attachment points. But then, we are not slamming our pattern planes to the deck of a moving airstrip.

In the future I just might do that fuselage mounted thing. Why not? I'll probably try MTK's CF tube idea too.

On the bottom end, a small block of maple was drilled out to go over the CF tube, and ca'd in place. Then I drilled and tapped for an alluminum bolt to serve as axle. Worked extremely well and has been durable. Removed approximately 75 grams of steel strut but added about 20 of CF, maple blocks and alluminum bolts. And it was pretty cheap to boot. CF tubing in this size is far stiffer than steel or titanium particularly at longer length required for large prop clearance. No more rubber ducky effect in cross wind.

One thing I have found with CF tubing is that mounted at an angle, as if one installed it on a fuse, they won't hold up well unless supported internally with some carbon rod. Work particularly well when mounted vertically as in a retractable assembly

MattK