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Old May 25, 2012, 10:32 AM
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Tacking my M

Karl,
The boat always had the unusual trick of "leaping" into a tack. In a breeze, the bow would literally jump up and around. You would think that for a long bowed boat that might be helpful. It may be just because the pivot point is just so far aft.
I carefully centered the 1/4 chord above the CG of the bulb but not the LCG of the whole boat. I wanted to be sure I didn't induce any twist in the keel foil by building in a moment between bulb and fin. By not taking into account the entire boat's LCG I may have the problem you mention.
On the other hand it just might be rig related and I tacked better with a slight sheet ease after a tack.
The boat was really more like a 36" (it's predecessor was my 36/600 "Barney" design) with a stretched bow- the keel/ rig is literally about 3" aft of any other boat of the time . My M is 7" wide and 19.5" from bottom of the hull to bottom of bulb. Can't recall the overall weight. I found that with the semi balanced swing rig, an arm winch was (barely) adequate. Watertightness was always my bugaboo until I found that my very light keel box laminate leaked through the cloth weave ! A reason for gel coat.
Poor boat has sat for a dozen or so years and needs a reason the be sailed.
TP

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Originally Posted by klkirkman View Post
Tom,

I think I can explain why your boats tacks badly with the aft keel. What you have created is a situation not entirely unlike our canards in that the keel blade pitch center ( roughly the 1/4 chord) is aft of the LCG of the boat. If what we found is correct, if you slid the keel blade forward until the 1/4 chord line was directly above the LCG , the tacking would greatly improve. After building many different boats to explore this one particular variable, we found that placing the keel 1/4 chord directly above the LCG resulted in the very best tacking performance because the keel was not contributing to the directional stability at that location, and hence had minimum additional induced drag.

Karl
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Old May 25, 2012, 11:16 AM
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Joined May 2012
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Keel twist and other matters

Tom,

Perhaps I was too hasty my comment, but I believe it is safe to say that to turn with the least induced drag, I suspect you want the boat to pivot about its composite LCG, not he LCG of any particular component. Also, to my eyeball of your picture, the blade 1/4 chord looke aft of the bulb LCG itself because of the largeer root chord. I sippose that is why it is best to measure things instead of just bursting out with a quick answer.

As to keel twist, we found that if we laid up our blades with 45-degree diagonal ribbons of CG , we could move the shear center of the blade so that it acted is of it slanted aft of the simple geometrical center for a homogeneous shape, In fact we made blades that actually resisted the keel bulb twisting moment to the point of slighty over correcting for it. That is to say, if you heeled the boat on a stand, the keel TE went to windward slightly, even though the bulb LCG as aft of the blade. It took us a long time to figure that one out, perhaps because it is so counter intuitive.

Karl
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Old May 25, 2012, 11:32 AM
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Joined Mar 2012
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foils

That's pretty cool. Our outside plies are +- 45s. Now if we could just figure out a way to couple the keel's fiber orientation to turn bending forces into a cupping of the fin to become asymmetric (on both tacks!) Or would that just be added drag? The VOR boats have amazingly intense (short chord and curvy) asym foil sections on their daggerboards.



Quote:
Originally Posted by klkirkman View Post
Tom,

Perhaps I was too hasty my comment, but I believe it is safe to say that to turn with the least induced drag, I suspect you want the boat to pivot about its composite LCG, not he LCG of any particular component. Also, to my eyeball of your picture, the blade 1/4 chord looke aft of the bulb LCG itself because of the largeer root chord. I sippose that is why it is best to measure things instead of just bursting out with a quick answer.

As to keel twist, we found that if we laid up our blades with 45-degree diagonal ribbons of CG , we could move the shear center of the blade so that it acted is of it slanted aft of the simple geometrical center for a homogeneous shape, In fact we made blades that actually resisted the keel bulb twisting moment to the point of slighty over correcting for it. That is to say, if you heeled the boat on a stand, the keel TE went to windward slightly, even though the bulb LCG as aft of the blade. It took us a long time to figure that one out, perhaps because it is so counter intuitive.

Karl
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Old May 25, 2012, 11:57 AM
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Keel diagonal layup

Tom,

I need to emphasize that to achieve what we did, the CF strips are all plus or all minus 45, not plus and minus 45. If they were plus and minus, the biasing of the sheer center would not occur because they would balance one another.

Also regarding cambered foils, the VOR is a different animal in lots of ways, and I am not convinced that getting lift on a Marblehead by camber makes a big gain. If you look at Abbott et al ( NACA Foils data ), you will see that at low loadings, the advantage of camber over angle of attack is not a big deal, it has more to do with obtaining larger lifts, Since the M class needs a certain amount of foil area to satisfy the requirements to hold the bulb rigidly a long way from the hull, the lift coefficients may be small enought to preclude the advantage for camber, Certainly, people have tried TE flaps in keels and as far as I was aware when we left the sport, they were not worth the penalties.

Karl
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Old May 25, 2012, 12:03 PM
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Joined May 2012
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Leaping in a tack

The leaping you observe is consistent with sudden/excessive rudder drag, I think I am correct that putting the rudder over is like dragging a bucket well above the CG of the boat, the lead tries to keep going and gives a bow up pitching moment.

It also may indicate excessive rudder throw - recall that in my view with a well balanced boat, you are not trying to turn the boat with the rudder , you are trying to make it directionally unstable briefly and letting the aero momends tack the boat.

Karl
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Old May 26, 2012, 09:36 AM
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Marblehead?

I came across this thread doing some research into a boat I just recieved. My wife came across it and bought it for me, because she is just an awesome wife. I have many rc cars/trucks over the years but never a sailboat. I do enjoy sailing, so I would like to get this thing going. I just nothing about how it is supposed to be rigged and it needs a little TLC. So I am looking for any info that might help me. Here is what I can tell you. It is made my Reynolds Mfg out of Orlando, FL(they went out of business in 1983 I found). The model is listed as Marblehead R.O.D, boat # 95. It has been registered with AMYA and has numbers 2519 and 2310, with the latter being on sails, although the 2519 sticker is much newer. I have sent an email to Standley Goodwin also and waiting for response. If anyone can point me in a direction that help me with rigging and working n the boat, it would be greatly appreciated. Name: sailboat1.jpg
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Old May 26, 2012, 11:44 AM
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United States, MA, Wenham
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Quote:
Originally Posted by Jasonbug56 View Post
I came across this thread doing some research into a boat I just recieved. My wife came across it and bought it for me, because she is just an awesome wife. I have many rc cars/trucks over the years but never a sailboat. I do enjoy sailing, so I would like to get this thing going. I just nothing about how it is supposed to be rigged and it needs a little TLC. So I am looking for any info that might help me. Here is what I can tell you. It is made my Reynolds Mfg out of Orlando, FL(they went out of business in 1983 I found). The model is listed as Marblehead R.O.D, boat # 95. It has been registered with AMYA and has numbers 2519 and 2310, with the latter being on sails, although the 2519 sticker is much newer. I have sent an email to Standley Goodwin also and waiting for response. If anyone can point me in a direction that help me with rigging and working n the boat, it would be greatly appreciated. Attachment 4890294

Attachment 4890295

You just scored on one of the better R/C sailboats in existance. Congratulations.

I have one word for you.
Patience.

We will get you running, but please treat that boat with patience and respect. I'm going sailing. We'll help later on.
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Old May 26, 2012, 09:35 PM
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Ok, Step 1.

take the rig off of the boat, and store it hanging somewhere as I have mine in this photo. Basically, put your rig into storage.

Send a screw into the wall (or a nail), and hang the rig by the backstay. Let off on all of your halyards so the sails are floppy. Tight sails in storage are the quickest way to destroy your sails.

You have no reason to fool around with the rig when the boat itself isn't ready (I can see your rudder is either not installed or hanging obsurely)



Are you comfortable installing the rudder?
What do the electronics inside the boat look like?
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Old May 26, 2012, 10:41 PM
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Reynolds Marblehead

Reynolds 1969 published literature indicates that the Marblehead should have a displacement of 18 pounds. It also says that the kit, less radio and sails retailed for $69.95!!! Sails added $30 to the price of the kit.

Boat was originally a free sailed model, with a rudder hung aft of the keel.
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Old May 27, 2012, 07:39 AM
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Joined Jan 2007
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Here's one of our races.
I got a real bad start on this particular one, but made up some ground to finish 5th out of 9.

Mske sure to switch to HD mode.
Vintage Marblehead Race @ Redds Pond May 26, 2012 (5 min 24 sec)
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Last edited by breakwater; May 27, 2012 at 09:47 PM.
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Old May 27, 2012, 09:37 PM
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Tom, we should check out the creek behind St. John's to see if it is still sailable now that it is a nature marsh, and put a date on the calendar for racing; sounds like Gregg and Mike would be willing to come down. I don't think it would be possible to host non-midshipman oriented racing on the Academy grounds.

Karl, great to hear you are still around and interested in sharing the Bone history. I have given away most of the bits and pieces you gave me years ago but we still have one of your original towing tank models at the USNA lab. - John Z
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Old May 30, 2012, 03:09 PM
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Rig off

Ok, I have the rig off and stored. I feel fine working on the boat, especially with a little guidance. The electronics look ok, I am going to take a receiver off one my cars to test everything later today. I took a picture of the inside and where the rudder is mounted, which is the problem. The board that rudder tube goes through has come un-attached. I have worked the the board back down the tube, not sure if it is far enough. The outside of the hull around rudder is pretty rough in my opinion, not sure how much it matters. looks to me that this rudder position was an add on by a previous owner.
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Old May 31, 2012, 11:28 AM
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[QUOTE=Jasonbug56;21754101 I took a picture of the inside and where the rudder is mounted, which is the problem. The board that rudder tube goes through has come un-attached. I have worked the the board back down the tube, not sure if it is far enough.[/QUOTE]

Getting the rudder thwart back in there properly isnt' too much work, especially if you already have the piece.
For the best diagram and description, check out page #29 of the US1M construction guide. http://www.theamya.org/boats/us1m/pdf/us1mconst.pdf


When gluing the piece back in, I recommend not using epoxy, but rather a product called 4200 from 3M. It is a one-part adhesive sealant.
http://www.3m.com/product/informatio...e-Sealant.html

Apply it in liberal amounts, and use a fine-pointed detail paint-brush to apply. That way it wont' smear everywhere. Let it cure before touching it!
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Old May 31, 2012, 11:29 AM
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Quote:
Originally Posted by Jasonbug56 View Post
The outside of the hull around rudder is pretty rough in my opinion, not sure how much it matters
Float the boat in a pool/pond for several hours, on an anchor. (just use string and a weight)

After a few hours you'll find out if it matters or not.
(watch it obviously so you don't ruin your electronics)
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Last edited by breakwater; May 31, 2012 at 11:42 AM.
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Old Jun 02, 2012, 08:44 PM
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Did the US1M guide help you get the rudder thwart back in? Let us know.
That resource is probably the best building guide going, so I hope it did. Can't find much better material than that!
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