H37C strut dimensions

[QP Chuck]

OK, I'm still struggling with my strut problem. I have not been able to find a source for a new strut but several people have told me that straightening a bronze strut (like mine) is not particularly difficult for a well-equipped machine shop. Problem is my strut is bent both sideways and fore-and-aft, so I will need to know all the pertinent dimensions to give to the shop guys.

I have gotten no response from Dahmer Marine, evidently the fabricators Hunter used. Their web page still works and Ed Shenck suggested a model number on the Dahmer site, but that model might be for an H33. Do any of you H37C owners know for sure which model number is correct or know of some other source where I can get the correct measurements? HELP!

 

[Ed Schenck]

From the attached pictures I think that you can deduce the strut dimensions. You can see the Dahmer name but not the part number unfortunately. But my old folding prop had a 15" diameter. So from that you can see that dimension 'C' on the Dahmer diagram( http://dahmermarine.com/Struts.htm ) must be 7 and 7/8" or part number 2005. It cannot be part 2006, the forward vertical dimension is not 9 and 3/4". I thought we documented that around here somewhere. I'll look some more.

 

[Ed Schenck]

Follow-up: now I am concerned because I found this: http://forums.hunter.sailboatowners.com/showthread.php?p=448294&highlight=dahmer strut . I found other entries stating that the H-34(2006) is the right part. But then you see where someone states that the H-34 had the wrong angle for his boat. Is there no way for you to look at your strut and get the number off of it?

 

[Water Bill]

Chuck, this past summer we snapped the strut off at the base on our 1984 H37. We were referred to General Propeller in Bradenton, FL (www.gpcprop.com). Using Dahmer's H34 drawings they fabricated a stainless steel strut. Upon test fitting the strut to our boat we found it was 1/4 in too long. At the bottom of Dahmer's drawings there is a disclaimer that reads "specifications and designs are subject to change without notice". Is it possible that there were minor changes from hull to hull and year to year? General Propeller was able to take specs from our original strut and modify our new strut. Of course we had the advantage of working with the machinist on a one on one basis because we live in Bradenton, making changes relatively quick. I do recall in your first post you indicated you did not want S/S. If you decide to contact them refer to invoice # 58578. Whereas they have noted the specs from our strut keeping in mind the possible changes.

 

[Steve Dion]

Did you check Southeastern Foundries?

http://www.vizseek.com/vizspace/vizspace.aspx?uid=89ddd4a5-f5b4-4f8d-a613-27e83a86fe6f

I believe that Dahmer has closed their doors but cannot verify this.

 

[Don12364]

Self Help?

Presumably the boat is already out of the water. If it is not then it will certainly have to come out to have this job done. (I might try living dangerously and doing it between tides but this cannot be recommended.)

Starting from the Dahmer page on their web site and armed with the knowledge that it is a 1" shaft (if it is a 1" shaft?), then there are only 5 choices. See extract from Dahmer web page below.
Now, regardless of how mangled your strut might be, it will surely be possible to deduce the dimension 'C' as these only came in approx 2" steps! (6"; 7 7/8"; 9 3/4"; 11 1/4".
Then one does not need to be Sherlock Holmes as the size of the flange is something of a giveaway.
As a last resort you could even weigh it.
Then again I would expect your strut to have its number either stamped or moulded on the side or possibly on top of the flange.

Now any competent marine fabricator could weld one up in 316 stainless for you but surely the guys recommended by Ollie Lee have been there, done that etc. and already have the dimensions.
All the probable ones are 18° or 18.5° angle and the 0.5° can be adjusted by 1/16" packing under one end of the flange anyway.
If you don't feel able to measure your installation to sufficient accuracy yourself then commission someone who can. They may also be able to advise on whether straightening your present strut is feasible.
Any reasonably competent engineer could measure it up from scratch and make a drawing from which a strut could be made.

BTW If you do have one made I would recommend having the bore to be 1½" so one can use a 1" ID x 1 ½" OD cutless bearing which has a sufficiently thick sleeve to be removable without taking the prop shaft out of the boat each time it needs changing. I had my strut bored out for this reason.

 

[Ed Schenck]

Well now I am really confused. This was driving me crazy so I drove three hours to visit Ladylove this afternoon. Pictures with a rule are attached. I took a picture of the part number but you really cannot make it out. The best guess is "H-98". There is nothing on the Dahmer site by that number. Using the two measurements of 6" and 7" you can calculate the angle. And the base exactly matches part #2051. So dimensions A, C, D, and E are matches.

A fellow sailor's H37C had been right next to mine but it was gone! It is a fin keel boat and I wanted to check to see if it might be different. No luck.

Had to add a personal picture showing why the Steeler's won. You have to have the shirt AND the bottle! Oh, and I did accomplish more than just take pictures after a three hour drive.

 

[Mathurin]

Ed, Just to put some oil on the fire about the strut question, I dove to have a look at our strut today, and H-34 is clearly stamped on it.

 

[Steve Dion]

That is amazing. The H34 was not in production until about the time that the H37C was ending production (1983)

 

[Ed Schenck]

So who dove, Phillipe or Dad? And how are you guys doing down there. I suppose the water is warm and clear.

Regardless, the number H-34 makes no sense. On the Dahmer site the H-34 has a 'C' value, the short length, of 9 3/4". As you can see mine is less than 7". And my strut has no number like that.

P.S. could it be the difference between a shoal draft and fin keel? But why?

 

[Blaise]

Just to throw a little more confusion into the mix, Midnight Sun is a 79, like Ladylove, but I have an 18" diameter prop, and from Ed's pictures, It doesn't look like it would fit on Ed's boat. My strut is original. I have about 1 1/2" tip clearance.

 

[Mathurin]

I (Philippe) dove to have a look at the strut, as a matter of fact, I had to pull the prop out. I happened that the key was too long. We never realised it before, but the nuts weren't sitting on the prop, they where sitting on the key shaft. So when we were putting the engine in reverse, the prop would back up one eight of an inch and vibrate. I took a long time to figure out what it was. And since we decided to take some vacations here in the Turks & Caicos, I decided to clean the hull as well.

Anyone interested in a smalll spiny lobster ?

 

[Steve Dion]

Normally accepted prop tip clearance is 15% of the prop diameter. Based on this "theory" an 18" prop should have about 2.7 inches of clearance. Less clearance may cause more noise from the prop and can also induce additional prop walk (especially in reverse).

 

[Jim Legere]

I will try to get down to the boat yard and take some measurements and maybe make a sketch of the strut on my boat...when the rain stops - its blowing a gale here right now.

 

[Blaise]

Prop walk

Normally accepted prop tip clearance is 15% of the prop diameter. Based on this "theory" an 18" prop should have about 2.7 inches of clearance. Less clearance may cause more noise from the prop and can also induce additional prop walk (especially in reverse).

Ah, reverse. Don't really know what that is with a folding prop. In all seriousness, I know what the prop tip theory is, but have noticed no difference in noise or prop walk. I think that maybe the low shaft rpm is the reason.

 

[guidera48]

Re: Prop walk

Hey Chuck
My office desk is 25 feet from my boat (in my parking lot). Tell me what you need and I will try to help. Pictures, scaled drawing, etc..
Jose

 

[Ed Schenck]

Chuck has not written anything anywhere since his original post here on 1/23. Where are you Chuck? But I would like to see pictures with measurements similar to what I posted when you have the time. Thanks Jose.

 

[guidera48]

I checked my strut and it is a H33. It says so on it . I double checked the measurements and they are as per their drawing + or - 1/8". I was going to remove it to check it out but the two nylock nuts are tight and I am afraid to start torquing on the nuts and have the studs start turning on me. Better leave well enought alone.

 

[Ed A]

I think if you take the demensions, remove the strutt. make a drawing with the angles under the boat and the length of hte shaft, distance from hull etc. and send the whole works to general Prop in bradenton fla. I will bet that they can do it.

 

[Ed Schenck]

Thanks Jose, your measurements were taken a little differently but really are the same as mine. I was always pretty confident it was an H33. But then I couldn't find that on the strut. And then I went and measured it from the base instead of from the hull which further confused the issue.

So Ed, how would General Prop duplicate our struts? Stainless? We discussed this once, whether better to have it soft and bendable or hard where it might tear out the bottom.