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mccarthy(at)jefnet.com
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 Posted: Sat Oct 02, 2010 3:29 am Post subject: HKS |
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I should have been a little more specific on my original post, I know better after being a long time lurker. I purchased the HKS with 50hrs on it that was on a trike with a 71" arplast ?sp I believe, it was reduced to a one blade when I got it. The real trick here is the gear box. I had to pitch the borrowed 68" Warp to 17 1/2 degrees to get the static rpm to 6000rpm, which I consider to be already marginal. It's the higher thrust line that I'm worried about. I might be able to turn the gear box down, and shim up the motor a bit,to get the 68" to fit, and after reading Richard's post, I wonder if a 4 blade might work as well. I'm not sure if a longer prop up higher,or a shorter blade lower is best, that's why I put it out there. I see a lot of 912 drivers are using 72", which Daryl said would work on this HKS, and thought that was the way to go at first. I'm hoping to get it up in the air again in the next week or so to try it as is. I think the HP rating should be fine for this bird, as it will only be a single seater with cargo space. I bought the Slingshot to replace the Firestar 5 rib, that couldn't be upgraded to a four stroke, and had no room to carry anything. Flying the Slingshot is nothing short of a hoot, I look forward to dialing it in, just as the original Firestar/377 is.
Thanks again,
| Quote: | | Tom McCarthy N514 TM Zenith 601HD 240 hrs N414 TM Kolb Firestar 377, 594 hrs N863 GB Kolb Slingshot 154 hrs |
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neilsenrm(at)gmail.com
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| Posted: Sat Oct 02, 2010 5:01 am Post subject: HKS |
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Tom
I don't know much about the HKS or the Slingshot but I have played around with props on my VW powered MKIIIC. I would recommend the longer prop. You just get more thrust with the longer prop and you are a bit low on power so why not make it as efficient as possible. The down side might be the the long prop will not have the speed range of a shorter prop. I still think you can pitch the prop for cruise which will give you maybe less than optimal RPMs for takeoff but overall more thrust. This is really a black art but Kolbs like long slow props. Kolbs also like lower thrust lines as possible but the higher thrust line is better if you use it all with a longer prop. Also check with the HKS guy I know they put a HKS on a Slingshot.
Rick Neilsen
1st Redrive VW Powered MKIIIC
On Sat, Oct 2, 2010 at 7:26 AM, McCarthy Tom <mccarthy(at)jefnet.com (mccarthy(at)jefnet.com)> wrote:
[quote] I should have been a little more specific on my original post, I know better after being a long time lurker. I purchased the HKS with 50hrs on it that was on a trike with a 71" arplast ?sp I believe, it was reduced to a one blade when I got it. The real trick here is the gear box. I had to pitch the borrowed 68" Warp to 17 1/2 degrees to get the static rpm to 6000rpm, which I consider to be already marginal. It's the higher thrust line that I'm worried about. I might be able to turn the gear box down, and shim up the motor a bit,to get the 68" to fit, and after reading Richard's post, I wonder if a 4 blade might work as well. I'm not sure if a longer prop up higher,or a shorter blade lower is best, that's why I put it out there. I see a lot of 912 drivers are using 72", which Daryl said would work on this HKS, and thought that was the way to go at first. I'm hoping to get it up in the air again in the next week or so to try it as is. I think the HP rating should be fine for this bird, as it will only be a single seater with cargo space. I bought the Slingshot to replace the Firestar 5 rib, that couldn't be upgraded to a four stroke, and had no room to carry anything. Flying the Slingshot is nothing short of a hoot, I look forward to dialing it in, just as the original Firestar/377 is.
Thanks again,
| Quote: | | Tom McCarthy N514 TM Zenith 601HD 240 hrs N414 TM Kolb Firestar 377, 594 hrs N863 GB Kolb Slingshot 154 hrs |
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get="_blank">http://www.matronics.com/Navigator?Kolb-List
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GeoB
Joined: 16 Jun 2009
Posts: 207
Location: Fresno, CA
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| Posted: Sat Oct 02, 2010 11:58 pm Post subject: HKS |
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| Quote: | I bought the Slingshot to replace the Firestar 5 rib, that couldn't be
upgraded to a four stroke
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I have a Firestar I with 5 ribs, that I have never flown. I have been planning to install a Generac on it. Could you tell me why the 5 rib couldn't be upgraded to a 4-stroke?
Thanks
GeoB
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GeoB
"Members of Congress should be compelled to wear uniforms like NASCAR drivers, so we could identify their corporate sponsors" |
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JetPilot
Joined: 10 Jan 2006
Posts: 1246
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| Posted: Sun Oct 03, 2010 9:38 am Post subject: Re: HKS |
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Being that you do not have an excess of power, you will probably be better off with a longer prop. A shorter prop with more blades is great for producing high speed thrust, but is very inefficient at the slow speeds where your Kolb will fly. You will just be giving away performance and HP with a shorter prop.
As far as the higher thrust line, I have never flown a slingshot, so I can no help you much on the specifics of how that model will be affected by thrust line. The better thrust and performance of a larger prop as slower speeds applies to all planes ( when kept within reason, and Daryl at warp drive knows his stuff and will not let you go too big ). I have a fairly high thrust line on my MK III and it does not bother me at all, you just have to be aware of it. Dealing with a high thrust line becomes second nature with a few hours in the airplane and I do not even think about it anymore, I just fly and enjoy the plane and the great acceleration and climb  In my plane, I would not give up any performance for a lower thrust line in my Kolb, dealing with the higher thrust line it is just a non issue for me.
Mike
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"NO FEAR" - If you have no fear you did not go as fast as you could have !!!
Kolb MK-III Xtra, 912-S |
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mccarthy(at)jefnet.com
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| Posted: Mon Oct 04, 2010 7:41 am Post subject: HKS |
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I have a Firestar I with 5 ribs, that I have never flown. I have been planning
to install a Generac on it. Could you tell me why the 5 rib couldn't be upgraded
to a 4-stroke?
Thanks
Geo
George,
First of all, I make no claims to be an authority on Kolbs, that job clearly belongs to several others on this list that I have great respect for and appreciate very much. My post should have read, "I" wouldn't upgrade a 5 rib Firestar with a four stroke. I believe that Homer designed it only with the 377 Rotax in mind, and I would be cautious to add any more weight on top, and even more afraid of the vibrations that the Generac will create on the entire airframe. When I bought this Firestar many years ago, it had 178 hours on it and I weighed 180 LBS, and the plane weighed 325 LBS, its performance was incredible, all with 35 HP Rotax. I now weigh 215LBS before breakfast, and the performance is still very adequate. If you read between the lines, I guess what I'm saying is to consider a 377 instead of the Generac, it has done well for me over 500 hours. I have experimented quite a bit along the way with different motors, and the 377 performed overall the best "for me". Just for reference, I found that the 447 was OK, but did the same thing using more gas, and felt overpowered, and could exceed my VNE of 90 in a blink. Believe it or not, the smoothest motor was a 2SI 460(new Cayuna), but I got tired of it being finicky and put it on the shelf- If you were local, I would let you try it for yourself. I flew 2 1/2 hours yesterday low and slow- until I couldn't feel my bottom side anymore, and still love the Firestar as much as when I got it. I'll have to part with it soon as 3 planes do not fit well in the hanger.
Tom McCarthy
N514 TM Zenith 601HD 240 hrs
N414 TM Kolb Firestar 377, 594 hrs
N863 GB Kolb Slingshot 154 hrs
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mccarthy(at)jefnet.com
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| Posted: Mon Oct 04, 2010 8:09 am Post subject: HKS |
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| Quote: | Tom, Your signature states that you have 154 hours in a Slingshot. What engine have you been flying the slingshot with prior to installing the HKS? The reason I ask is that what you are accustomed to will have some bearing on what your expectations are for the HKS powered Slingshot. Thom,
Sorry for being misleading about the hours, the plane has 154 hours, I only put 8 on it, and that was with a borrowed 532 Rotax with a 2.58 gearbox and a 66"GSC 3 blade prop I had laying around. The motor never ran properly from the start, with cooling issues and a dead spot 5100 and 5900 RPM. What I saw I did like very much, max climb on a standard day 1400fpm, and it got to 80mph quickly, but started to overheat immediately, so I never saw a top end. I'm curious about one thing Thom, is you motor mounted parallel with the frame, or lifted up in the back around 7degrees? After my first couple flights, I talked to 2 other slingshot owners, and they both told me to raise the motor in the back about 1 1/2 inches to improve the thrust line, which I did and it made quite a difference.With a perfect forecast for the week, and around a busy work schedule, I hope to get it back in the air.
Thanks again,
Tom McCarthy
N514 TM Zenith 601HD 240 hrs
N414 TM Kolb Firestar 377, 594 hrs
N863 GB Kolb Slingshot 154 hrs
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mccarthy(at)jefnet.com
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| Posted: Mon Oct 04, 2010 8:14 am Post subject: HKS |
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| Quote: | Being that you do not have an excess of power, you will probably be better off with a longer prop. A shorter prop with more blades is great for producing high speed thrust, but is very inefficient at the slow speeds where your Kolb will fly. You will just be giving away performance and HP with a shorter prop.
Mike,
I tend to agree that a longer prop is the way to go. I'll start out with this borrowed 68" 3 blade Warp and go from there.
Tom McCarthy
N514 TM Zenith 601HD 240 hrs
N414 TM Kolb Firestar 377, 594 hrs
N863 GB Kolb Slingshot 154 hrs
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[quote][b]
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slyck(at)frontiernet.net
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| Posted: Mon Oct 04, 2010 11:43 am Post subject: HKS |
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that is still a lot of prop for the HKS. My suzuki is rated somewhere around 58 hp and I settled on a two blade 70" warp.It is a perfect match.
BB
On 4, Oct 2010, at 12:12 PM, McCarthy Tom wrote:
[quote]
| Quote: | Being that you do not have an excess of power, you will probably be better off with a longer prop. A shorter prop with more blades is great for producing high speed thrust, but is very inefficient at the slow speeds where your Kolb will fly. You will just be giving away performance and HP with a shorter prop.
Mike,
I tend to agree that a longer prop is the way to go. I'll start out with this borrowed 68" 3 blade Warp and go from there.
Tom McCarthy
N514 TM Zenith 601HD 240 hrs
N414 TM Kolb Firestar 377, 594 hrs
N863 GB Kolb Slingshot 154 hrs
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[b]
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