Yanmar mockup

[jhenson]

Here are a couple of pictures of the engine mockup fitted into my boat. I used a 2 X 4 frame to suspend the two jigs (one for shaft alignment and one for mount position) in the engine compartment. I have decided to cut out and replace the shaft tube to align it to the centerline of the boat.

Here are the two jigs together:



The vertical 2x4 is the position/height of the exaust riser, which seemed to me to be the most important reference for clearance aft.

Here I have the alignment jig removed after the position was resolved so I can take measurements of the beds. Since I have to special order the material for the beds, I plan to make some scrap lumber mockups of them in the meantime. It's way to cold here to work epoxy right now, and my extension cord is buried under 5" of ice from our recent ice storm.



Joe

[Scout]

Very nice work in the prep Joe, and thanks for sharing. If you are moving the shaft hole, does this mean you are also moving the cutlless bushing?

[jhenson]

If you are moving the shaft hole, does this mean you are also moving the cutlless bushing?

A little bit. This will be to correct a small misalignment of the shaft tube, but nothing drastic.

Joe

[Hirilondë]

The mechanics at work are always asking me to build mock ups of engines. They take some work, but are much easier to play around with than the real thing during lay out. When you move the real thing in later you will be glad for the time you spent. Looks good!

[Duncan]

The guy I got my Volvo MD1 from sent me this photo of his mock-up:



But when I asked him if I could have it, he said "it wasn't very well-built, so I didn't keep it".
It sure looked good to me!

[Tim]

Now that's a serious mockup!

Probably unnecessarily detailed, though...but it's too bad he didn't keep it, since it's pretty cool!

[Hirilondë]

WOW! We keep ours for a while at least, but none look like that. Overall width, height, length, acurate mount layout and the take off from the transmission is all they ask of me.

[Tim]

Here's the basic template I built to simulate my SB12 at the early stages. While the platform and its lower extensions, all of which simulates the critical location of the mounting flanges and exact center of the transmission coupling, is carefully measured and accurate, the 2x4 "oil pan" and extension on the top to represent the overall height of the engine in roughly the right location are pretty crude, since they were only for basic visualization.

Unless there's a very critical clearance issue, I normally just build the flat platform to align the mounts and foundations with the center of the shaft.

[jhenson]

Engine beds are just about ready for the hull:


The glued up blank is on the left and the mockups are on the left.



The blank before cutting:



After cutting:




Joe

[jhenson]

More Progress:

Yesterday:



Today:

[Hirilondë]

I don't mean to hijack Joe's thread, but seeing as it is an engine mock up thread, and many here might find the picture amusing I will post it here. This decorates part of the mechanic shop.




This is an original factory made mock up

edit: no idea why I can't get a full size photo to show up.

[Duncan]

Those look beautifully shaped, but isn't plywood weak edge-on?
(I'm wondering how well anchored your mounts will be, with the vibration).

Please feel free to educate me, I just vaguely remember screws pulling out of the edges of plywood.

[Figment]

I notice that the top surfaces have a shallow relief plowed down the middle. Do you plan to add a metal bar atop the glulams?

I'm not so worried about fastening into the end-grain. as an engineered lumber product, it's not really "grain" in the traditional sense, and potting bolts in a slug of epoxy would be an easy way to eliminate any doubt.

[jhenson]

I?ve used Tim?s Triton Daysailor work as my primary tool for the construction of these beds. He has generously given me some more specific guidance via email on them as well.. My thanks to him for maintaining these valuable sites and always responding to questions from people like me doing this stuff for the first time.

See: http://www.tritondaysailor.com/rebuildi ... ngine2.htm

On the Daysailor, he used threaded inserts to avoid the weakness inherent in plywood to hold lag bolts, especially after several loosening/ tightening cycles. That was the plan as of last week.

I recently made the decision due to various constraints to substitute marine BS1088 okume plywood for marine fir instead. Because of this, I was somewhat concerned about this lower grade fir getting wet at some point and the threaded inserts pulling from the plywood.

Dave Martin recently did an article about a repower of a Folkboat in the September/ October 2006 issue (see page 16). Dave was also very good about responding to my email inquiries about this project. His method of securing the mount bolts amounts to glassing in 3/8? x 2? mild steel flat bar over foam. The flat bar is then drilled and tapped for the engine mount bolts. I emailed him with my concerns about corrosion but he responded by saying that he seals the bolt holes with bedding compound to prevent the water intrusion and doesn?t even worry about priming the steel.

I honestly don?t know what the final metalwork will look like yet. I have a couple of options under consideration. Both involve the use of 3/8? x 2? flat bar. The rabbets that I cut in the tops of the beds are to inlay these pieces. I have a sample of mild steel that fits in them snuggly.

Option 1:

-drill 3/8?holes through 304 stainless flat bar and have stainless nuts welded to the underside of bars (or use the same threaded inserts as mentioned earlier and cover with the bars).

Option2:

-drill and tap mild steel flat bar as was done by Dave Martin on the Folkboat project. This material is readily available in my home town and is much easier for me to machine.

Maybe this is overkill on a engine that generates 13hp and weighs only about 250 pounds, but I want this installation to be bulletproof.


Joe

[Duncan]

I?ve used Tim?s Triton Daysailor work as my primary tool for the construction of these beds. He has generously given me some more specific guidance via email on them as well..

"Nobody ever got fired for buying IBM" - that sounds highly authoritative to me!

On the Daysailor, he used threaded inserts to avoid the weakness inherent in plywood to hold lag bolts, especially after several loosening/ tightening cycles.

The threaded inserts sounds like they address my (naive) question about how well the bolts would stay in. My engine mounts have cutouts where the washers and the nuts go on underneath. It seems to me this is a good idea, since the washers spread the force over more area.

I googled around a bit about "plywood strength" and found that it is notable for shear strength, i.e. sideways. Since your laminated plywood beds are turned sideways, that tells me that they're oriented in the direction of maximum strength. I imagine that with all that fiber and glue and all those layers, you have very strong beds that will take anything your engine dishes out.

ps. I did notice that someone had the bright idea of mounting a shock absorber to the top of the engine. Since my old single-cylinder vibrates like crazy, it caught my attention! It went at an angle from the lifting ring to the bridgedeck, and sounded like an interesting way to mitigate the vibration.

[jhenson]

It seems as though there a many, many variations on this engine bed theme. I tried to read everything I could and talk to as many people as possible. Everyone has a different opinion on the best way to do this. I've had too much time off from the project to think about this stuff. I was thinking yesterday that the last time I mixed epoxy was about 4 or 5 months ago.

Plywood seemed like the ticket for me. It is dimensionally stable, and relatively dense. This density seems like a good thing to help dampen vibration.

One other reference I used to help me was Ian Nicolson's book "Build Your Own Boat". He has a section on engine bearers that describes the concept of plywood bearers with imbeded steel flatbar.

[Tim]

I do like your idea of laying some material in on the top of the mounts. That's a good concept that I will keep in mind myself for future use. The foundations look very nice.

I am quite against the notion of using mild steel on a boat. I know it's done often, but these items are often found to be horribly corroded after some years. I've seen an awful lot of rusted steel fuel tanks, engine foundations, and chainplate arrangements, and think that we know better than to hope that a little sealant will cure all potential ills.

If you're going to use metal, I'd recommend stainless, despite its more challenging workability. You could use an appropriate aluminum alloy as well.

For that matter, I think you could also have excellent success by epoxying an appropriately sized strip of prefab fiberglass into your slots, and use either the threaded inserts or some nuts and washers epoxied on the underside. (If you use nuts, you can probably tap the fiberglass to match as well.) When you glass fully over the top of the foundations, including the strip of whatever, the end result will be extremely strong.

I'm very wary of the mild steel. It's just gone wrong far too many well-documented times for me to think that it's a good idea. Too often, it's chosen simply because it's inexpensive and easily available, and it works...for a while. When it stops working, you have a mess on your hands.

I think your work is too good to start introducing materials that have known shortcomings.

[Tim]

It seems as though there a many, many variations on this engine bed theme.

Indeed. There are as many ways to do it as there are builders. Some ways are better than others, but there are a lot of "right" ways.

It's easy to overthink many stages of any project. Everyone does this.

In general, I think high quality plywood beds, properly adhered with epoxy and then glassed in and fully encapsulated, are worthy for engine foundations because of the inherent strength of the material. As to the long-term grip of something like the threaded inserts, I believe it helps to consider that the forces imparted on the engine mount fasteners are in shear, not tension (unless you turn turtle...), so there is little inclination for them to pull upwards out of the wood. I don't know scientifically, but those threaded inserts installed in epoxy seem like they would pretty strong from all practical perspectives, and with no inclination to pull out with the anticipated loads.

That said, I have more faith in the ability of multi-ply, void-free plywood to hold these fasteners than more common fir. I am very impressed with the density and quality of the Meranti plywood that I normally use; it's as sound as solid wood (but stronger, since it's plywood).

So a little additional insurance in the manner in which you are anticipating going about things is not a bad thing at all, with your fir beds. In the end, what matters is that you are comfortable with the manner in which you've built them, and if that means a little overkill, there's nothing wrong with that.

[jhenson]

You could use an appropriate aluminum alloy as well.

Would 6061 be inappropriate for this application? I know that most marine grade aluminum is in the 5000 series, but I think 6061 might be stronger for holding threads.

Joe

[Tim]

Unfortunately, I don't know enough about the various alloys to really answer that question.

Some basic information that I found indicates that 6061 is harder than 5052, is slightly less corrosion resistant, and has better machinability than 5052. Based on that, it seems like a reasonable choice.

[keelbolts]

Two things:

First - Plywood is as strong and stable in all dimensions as most woods. The problem comes whenever you run a fastener into end grain wood. You ought to look at the West Epoxy site. They did a series of tests to determine if little things like keelbolts could be glued into wood. You'll want to read it for yourself, but the short answer is yes. Their tests indicate that you could, drill a hole big enough to drop a bolt down into head first and glue it in and, there you have it, studs on which to mount your motor mounts.

Second - Are you sure you want to cut out your shaft tube? Many a tube is not aligned w/ the centerline of the boat. A number of older boats, mine included, have quarter mounted props that are not in alignment with the centerline. Some believe it's useful to counteract the prop's tendency to "walk." Cutting your tube out, aside from, probably, being unnecessary, sounds like a huge project to bite off this close to sailing season.

[Tim]

Many a tube is not aligned w/ the centerline of the boat. A number of older boats, mine included, have quarter mounted props that are not in alignment with the centerline. Some believe it's useful to counteract the prop's tendency to "walk." Cutting your tube out, aside from, probably, being unnecessary, sounds like a huge project to bite off this close to sailing season.

While that's certainly true in many cases, the Triton is not one of the boats where the stern tube is intentionally aligned off-center; rather, in this case, it's simply sloppy construction. At least the engine beds are aligned with the angle of the stern tube, so the slight variance from dead center is effectively unimportant.

We did discuss this very specific issue in another thread here recently. Although I also advised that replacing the tube was probably unnecessary, at least because of this issue, I understand why Joe decided to replace it anyway. Some things just don't seem worth leaving alone, and when you're deeply into a complete rebuild of a boat, like Joe is, it often makes sense to redo things that might be OK, but that would be better if they were redone.

Link: Thread on Joe's Stern Tube Alignment

As it happens, replacing the stern tube in a Triton is a remarkably straightforward process, though certainly not one to enter into without the appropriate thought as to its necessity.

Link: Here's one way to do it.

[jhenson]

Duncan,

I have thought of using studs inbedded in the beds, but I sort of want to keep from that idea right now. I seems to me to be a nice feature to remove the eight bolts and have the ability to slide the engine forward past the bridge deck, secure the lifting eye, and remove it. Again, I may be over thinking this thing.

I ran into a bit of a snag yesterday when I went to order the threaded inserts that Tim used on the Triton Daysailor. The supplier is out of stock, and I'm told that they will probably no longer be available.



As my kids say, "my bad" for not getting all the necessary supplies for the project before I started.

An internet search did come up with some other suppliers of threaded inserts. For instance:

http://www.chrislynninserts.com/ezfixpages/specs.htm

The things are clearly meant for insertion into metal though, and the outside threads and adhesive are not designed specifically for plywood or thickened epoxy. Still, they look pretty close to the pictures of those Tim used. I cannot find the article on the West System website about epoxy and threaded metal parts you mentioned above. Can you send me a link?

I could thread them into aluminum flat bar, but I don't know how much concern galvanic corrosion comes into play. Stainless, I guess, becomes a good deal less passive (noble) in an oxygen deprived environment. Comments here are greatly appreciated.

The plot thickens......

The issue of the shaft tube really doesn't look all that difficult or scarry to me. Somehow, after my keel repair, all subsequent repairs seem do-able. Now watch, I'll get snagged on this one as bad as these engine beds.

Cutting your tube out, aside from, probably, being unnecessary, sounds like a huge project to bite off this close to sailing season.

I think we can safely say that the boat will miss this sailing season. I'm more on the J.F. Kennedy type plan of splashing this thing before the end of the decade. Even that looks in doubt.

Joe

[keelbolts]

You are a patient man.

[Duncan]

The problem comes whenever you run a fastener into end grain wood.

That was the thing I had "wondered" about. It was more of a casual question, but since engine vibration basically consists of jumping up and down, that force is 'trying' to pull the bolts out all the time.

I don't know enough about timber and plywood to make a practical assessment, it's the edge-on, end-grain that I got a funny feeling about.

Duncan,

I have thought of using studs inbedded in the beds, but I sort of want to keep from that idea right now. I seems to me to be a nice feature to remove the eight bolts and have the ability to slide the engine forward past the bridge deck, secure the lifting eye, and remove it. Again, I may be over thinking this thing.

I ran into a bit of a snag yesterday when I went to order the threaded inserts that Tim used on the Triton Daysailor. The supplier is out of stock, and I'm told that they will probably no longer be available.

I think the idea of removable studs is a great one - Murphy's Law, and all that. What if you overdrill and epoxy the hole? Wax the stud, thread a nut on the bottom end of it, and put the assembly in the hole to cure. The next day, you double-nut the stud and out it comes.

In this way, your nut at the bottom becomes the "threaded insert". I'm guessing that the slug of epoxy in the hole should also make a stronger bearing surface than the plywood itself. It should seep into the wood a bit , too, which ought to make the whole thing stronger? I suppose you might be able to find longer nuts or bigger ones, too (or even use several), so that you'd be just as well off as with the 'threaded insert'?

A friend of mine did this to mount the autopilot ram on a big boat - it's not the same thing as engine mounts, but I think the principle is fairly similar.

I think the primary purpose of the metal bar on top is more to spread the impact of the vibration over the whole top surface of the bed. This seems like a good idea, and threading/tapping it wouldn't hurt, but I am guessing that having nuts "embedded in the bed" with epoxy would be a pretty solid mounting point?

[Tim]

I ran into a bit of a snag yesterday when I went to order the threaded inserts that Tim used on the Triton Daysailor. The supplier is out of stock, and I'm told that they will probably no longer be available.

Well, that's a shame! Those were slick. I was frankly surprised, though, when I searched for them two years ago, at the difficulty in finding something that seemed like it should be so common.

McMaster-Carr offers a few sizes of stainless steel threaded inserts for wood, but unfortunately the largest internal threads are only 1/4-20.

Link: Threaded Inserts at McMaster

An internet search did come up with some other suppliers of threaded inserts. For instance:

http://www.chrislynninserts.com/ezfixpages/specs.htm

The things are clearly meant for insertion into metal though, and the outside threads and adhesive are not designed specifically for plywood or thickened epoxy. Still, they look pretty close to the pictures of those Tim used.

The same website, Chrislynn Inserts, also seems to have the very same sort of insert that I used: the "knife-thread" insert for plastic and wood. They have sizes (internal thread) up to 3/8-16. Unfortunately, they seem to be aluminum and brass only.

I wonder how a plain hex nut epoxied into the wood would work. Having never looked into this, I don't know how the ultimate strength would work out, but you might get some answers from West System tech support.


Here's the link to an article covering the testing of the threaded rod inserts in wood and epoxy:

Link: PDF File from Epoxyworks Magazine

The same writeup is also in The Gougeon Brothers on Boat Construction, which is what I referenced to you the other day.

[jhenson]

Ok, I have the begun on "plan B"

I called West System Tech Support today. I told them about imbedding both stainless nuts and inserts. I gave them the information about my plywood beds.

They indicated that nuts inbedded in thickened epoxy would be much stronger than the material around it. The plywood should fail long before the epoxy plug holding the nut. It seems that the threaded inserts are not necessary.

So the plan is:

1. Drill oversize holes in the position of the mount bolts. I failed to ask about the size and depth of the holes, but I'm thinking about 1" diameter holes to a depth of around 1". I don't know, maybe I'll go deeper and wider.

2. Abrade the outside edges of the stainless nuts with a 80 grit disc on my grinder

3. Construct a jig to hold the nuts in place with waxed dummy bolts

4. Fill the holes with a fairly thick epoxy/filler mix

5. Push the jig in place with nuts attached. Clamp down the jig.

6. Somewhere after the mix hardens and before it fully cures, back the bolts out of the nuts, and remove the jig.

7. Clean up the tops of the engine beds

8. Apply fiberglass bar over the holes (with ovesized holes predilled in the positon of the bolts).

9. Wax the dummy bolts again and refill the oversize holes.

10. On the same day, I will attempt the outside lamination of the entire bed structure, weather permitting.

11. Back out the dummy bolts again and fair the beds as necessary.

12. Go on the next "fun" job in this project.

If I hadn't already cut rabbets in the top of the beds, I might probably would just insert stainless studs as Duncan suggests. Now I have to fill these anyway, so this seems like the way to go.

Joe

[Tim]

The best laid plans of mice and men...

Sounds like you have a good "plan B", though. Thanks for the update!

[Figment]

Is this a tugboat or a sailboat? ;)

Seriously, that sounds like a GREAT "plan B"! I pity-da-foo motor that tries to shake those bolts loose!

[Duncan]

...as Duncan suggests...

Gosh that sounds ominous!

I just want to reiterate that anything I've said is "for discussions purposes only". I've never done this (or anything remotely like it), but it is very interesting as a learning experience (especially when it's your engine, not mine!).

But "pressing on regardless"... ;)

West System Tech Support...indicated that nuts inbedded in thickened epoxy would be much stronger than the material around it. The plywood should fail long before the epoxy plug holding the nut.

According to the photos in the article Tim linked, that's exactly what happened when they tested - the wood failed, and the epoxy "stuck like glue".


So the plan is:

1. Drill oversize holes in the position of the mount bolts. I failed to ask about the size and depth of the holes, but I'm thinking about 1" diameter holes to a depth of around 1". I don't know, maybe I'll go deeper and wider.

Deeper sounds better anyway - West reported:

The bolt imbedded 2" into the laminate required 8,908 lb of force to pull the bolt loose. The bolt imbedded 3" into the laminate required 13,948 lb.

Sounds to me like twice as deep = twice as strong, so there could be benefits to going in 3" vs. 1"?

2. Abrade the outside edges of the stainless nuts with a 80 grit disc on my grinder

3. Construct a jig to hold the nuts in place with waxed dummy bolts

Your engine bed mockup should do the trick?

4. Fill the holes with a fairly thick epoxy/filler mix

West used pure resin

5. Push the jig in place with nuts attached. Clamp down the jig.

6. Somewhere after the mix hardens and before it fully cures, back the bolts out of the nuts, and remove the jig.

Should be able to let it cure - the wax will prevent adhesion?

7. Clean up the tops of the engine beds

8. Apply fiberglass bar over the holes (with ovesized holes predilled in the positon of the bolts).

9. Wax the dummy bolts again and refill the oversize holes.

Could skip 7, 8 & 9 and do it all in one go? Also, aluminum might be better to spread the load over the whole top of the beds - fiberglass is not that strong sideways, but metals are.

...

[jhenson]

Should be able to let it cure - the wax will prevent adhesion?

Yep, I've already done this once before. My mast support beam is marvel of welded engineering. There are two bolts for the mast base that were tapped into the top of beam. Thats great, but nobody put barrier protection around the bolts, and the core was in contact with the sometime leaking bolt holes. So... I replaced the wet core with a 12" X 12" solid layup over the mast beam when I did my deck recore work. During the lamination process, I did this same techninque of waxed bolts. I got busy doing something else and forgot to remove them until a couple of weeks later. No problem, gobs of car wax on the threads and they come right out. I did breathe a sigh of relief though when this first one started to budge.

I just noticed that my post above laid out a "12 step" plan. There is some irony there, I think.

Joe

[jhenson]

Over the last several days, I have slowly been working on the engine beds. Last week, I drilled the holes and made a jig to hold the bolts. I use a syringe to inject a loose epoxy/filler mix into the holes.



Then yesterday, because of the angled beds. I added a thick mixture to the top of the poured plugs to bring them level with the top of the beds and thus prevent any large voids. I forgot to take pictures.

Today, I glued down the the fiberglass bar to the top recess on the engine beds. The drywall screws are temporary to give some clamping pressure.




Wow, I hope the jig was right!! I would hate to go through all this and find out the engine is to high.

Joe

[Figment]

Wow that looks STOUT! Most impressive. Nice work.

[bcooke]

Very nice work.

It almost makes me want to pull my engine so I can copy that.
Maybe next year :-)

-Britton

[jhenson]

Thanks guys!!! Much head scratching has gone into this project.

Joe

[jhenson]

I'm a long way from hearing the rumble from the engine, but it now rests on the new beds:

I constructed an oil drip pan under the beds that will still (hopefully) allow the use of a Vetus muffler under the engine. There is about 2 1/2" of clearance below the bottom of the pan, which should be enough to run some bilge pumb hoses and still allow for water to pass under to the bilge.

The area between the two beds got a couple of rounds of fairing compound to make them smooth enough to clean engine oil.









Joe

[Tim]

Nice looking work, Joe!

One more major checkmark on your project list.