KMP Harvard 84" - RCCanada - Canada Radio Controlled Hobby Forum
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Old 11-30-2019, 10:27 PM   #1
RSVenture
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KMP Harvard 84"


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Have a KMP Harvard. Glass fuselage, built up wings, elevators, rudder.
Specs:
Weight: 22 lbs
Engine: 50 - 60cc gas
Wing Span: 84"
C of G: 25% to 28% of chord from leading edge

I installed a DLE 55, electric start. All servos/elecronics are as far forward as possible, as well as the receiver, ignition, starter batteries. Ignition box is mounted on front of firewall under the cowl.
I was very happy to find that my AUW was 21lbs 13 ozs. Yeah.
Then came time to balance. Being a short nosed Warbird, I expected to need "some" nose weight. But, it is soooo tail heavy I could hardly believe it. It took 4 lbs of lead at very front of the cowl to balance. This really did surprised me.
I am hoping someone will tell me the C of G is off, (manual is same as their 30cc model, just some an addendum added) but to date I have not found any info regarding a tail heavy issue even mentioned anywhere.
Has anyone had any experience with one of these, or any suggestions on how to overcome this large amount of nose weight.
Any suggestions would be appreciated. As is this is destine to become a "static" display.
Arnold
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Hangar 9 B25 Twin G46 electrics
MAAC #42080
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Old 12-01-2019, 12:10 AM   #2
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Re: KMP Harvard 84"

Pretty much all KMP models with glass fuses are tail heavy. Especially the shorter nose radial engine style models like Beaver and Texan/Harvard.
Are the wings and horizontal stab built up balsa ? How is the hookup from the elevator and rudder to servos,
Pushrods or pull-pull or ?
For every oz you save in the tail you can probably dump 6-8 oz of lead in the front.

Last edited by stegl; 12-01-2019 at 12:19 AM.
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Old 12-01-2019, 01:31 AM   #3
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Re: KMP Harvard 84"

Wings, stab, rudder, and elevators are built up balsa, solartex covered.
Hookups are pull, pull.
I've been considering removing the covering to see if I could safely shave a few ozs off.
Received a message from another member who indicated he had to add 4 lbs to his also when he built it, but it flew fine.
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Hangar 9 B25 Twin G46 electrics
MAAC #42080
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Old 12-01-2019, 03:13 AM   #4
stegl
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Re: KMP Harvard 84"

Even if the servos are as far forward as you can get them but they are still behind the CG ; that is still weight behind. This is were servo weight can become important. selecting ( quit often) servo brands by weight can make a difference. Many servo users just look at the torque of a servo and very often don’t compare brands ,taking weight into consideration.
Servo brass or steel gears can make a servo as heavy as lead but if looking at titanium geared servos with comparable torque , you can save as much as 40% or more . It will cost but then you din’t Have as much of a flying lead brick. I guess it is called research.
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Old 12-01-2019, 09:07 AM   #5
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Re: KMP Harvard 84"

You might want to cut the servo tray and custom fit it to move the servos as far forward as possible. If the tail wheel assembly is made of metal get rid of it and replace with a hefty plastic one. I did both these things and shaved 2lbs of nose weight off my 90" Spitfire
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Old 12-01-2019, 10:19 AM   #6
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Re: KMP Harvard 84"

Thanks for the tips fellows. It does seem like what I thought was near completion of this model, is turning into a "let's start again" project. Fun and games.
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Hangar 9 B25 Twin G46 electrics
MAAC #42080
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Old 12-01-2019, 01:41 PM   #7
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Re: KMP Harvard 84"

Not sure if the glass fuse was finished but some had gel coat over the glass cloth and this adds a ton of weight at the back. Reason for gel coat ( in my books) it seals the poor job done with the glass cloth. Gets rid of pinholes and stiffens the fuse. Gel coat is ok if done correctly but gotta be thin and done properly takes time and expertise; and time is money.
My European Beaver is built correctly with a light fuse but the moulded wings are heavy . Since most of the weight is forward , balancing weight in the nose isn’t too bad.

Excelsious has some good points.
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Old 12-01-2019, 06:28 PM   #8
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Re: KMP Harvard 84"

Here are some photos of the lead I had in the nose of my Kmp Harvard. I used a cookie tin to give it that shape.
When I spoke to Andy from KMP he did indicate the model will need a fair but of nose weight.
Great looking model! What color scheme did you get?
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Old 12-01-2019, 07:30 PM   #9
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Re: KMP Harvard 84"

Same color scheme as in the photo.
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Hangar 9 B25 Twin G46 electrics
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Old 12-02-2019, 01:21 AM   #10
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It is normal to be tail heavy. 30cc is the minimum on your plane. 50cc is required to fly with power to get you out of trouble. Make sure you keep the speed up at all time and no sharp turn. The Texan is among the worst for wing tip stall in a turn. The 4lbs of lead with a 30cc is normal. That is topical warbird trend. As for fibreglass I have a Hawker Seafury 66 inches wingspan with an OS120 four stock with. Fibreglass fuselage only and I had to add 3lbs in the nose. My 30cc Bearcat has 6 1/2lbs in the nose but that is with my Radial engine only.
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