driscollies
Seaman Apprentice
- Joined
- Nov 19, 2016
- Messages
- 42
questions about aftermarket aluminum outboard brackets: design, fabrication, for a Starcraft Chieftain
Hello,
I am thinking about ditching my old I/O and putting on an aluminum outboard bracket, something like an Armstrong bracket or something. I was hoping I might be able to ask a few questions!
1) the big question seems to be, single or twin? I plan on mostly going in the lakes/bays and stuff, where I'm never more than probably a mile or two offshore. However, it would be nice to be able to go into the ocean just a little on calm days. A twin almost doubles the cost because of materials and whatnot. For the most part, I feel like twins are just for convenience: Put on two 75hp motors instead of one 150hp motor, and if one goes out, the other one is already on there and you can limp home. But is there any merit to doing something like.... put a 150hp on there, and 99% of the time it'll be fine. And for the one time it's not, IF that happens to be in the middle of the ocean, keep a spare 50hp or something belowdecks? Like, even build a special compartment in the bow? because, really, how often are you going to have to need it, PLUS, as a added bonus, the weight of a motor up there will help counterbalance the extra leverage of the bracket. Seems like the slim chance of ever needing that extra engine is worth the extra work that it might be to haul a dead 150hp up and mount a 50hp.
2) local builders: Good or bad? If I have a local fab shop that can cut hundreds off the price (local discount, no shipping, etc), is that a viable way to go about things? I assume strength is paramount here, but a good aluminum welder should be able to make an equally strong bracket. But shape.... I think that places like Armstrong definitely have the knowledge about subtleties that will make the boat perform much better. But is that really worth a few hundred? If the angle is just a little off, how much will I really notice? Of course, if it's about safety, that's a whole different animal. But I assume strength is the important component for safety, and she shape is more about performance. I'd happily risk losing a quarter mile per hour of top speed or a tiny bit in fuel economy to save a ton of money up front. Plus, I feel like, a lot of "mistakes" in angles and stuff can be made up via engine positioning, right?
3) shape: Speaking of shape, I have a few questions about the shape of these guys. First off, am I correct in assuming that they're, essentially, hollow boxes? And that they can be filled with flotation foam or something for buoyancy? I've seen some that go all the way down and match the hull shape coming off the back, essentially just becoming an extension of the hull. But most of them I see are basically just boxes bolted onto the back. Why the discrepancy? Is one shape better than the other? Is there a downside to just the box model? I assume that, on boats where the transom in the same for their I/O and outboard models, the goal is just to recreate the transom angle a little further back. Then again, some of them are exactly beam width. Am I correct in assuming that these are intended to be swim platforms, and all you really need is the box if you don't want a swim platform?
4) Speaking of further back: How far back should these go? Most of the ones I've seen are WIDE. Like, 2-3 feet wide (that is, they add 2-3 feet straight off the back). That seems like it's designed to accommodate the engine tilting up. Is this strictly necessary? For example, if I have an engine that doesn't tilt (no such thing, that I know of. Just asking a theoretical question to get a sense of whether the length is critical or not), would I need that much room? I feel like, from a pure functional standpoint, the bare minimum you would need would be enough to bolt the outboard on, and that's it. Beyond this, the bare minimum you'd need would be enough to tilt the engine back. Any other reason for a long bracket?
5) materials: Looks like the standard is 1/8" 5052 aluminum. Is that right?
6) other: Anything else I'm failing to consider? Thoughts on going local?
7) I'm just thinking.... in order to combine all of the "minimalist" elements of a number of brackets, the absolute bare-bones approach would be an aluminum bar that just sticks out about 6 inches from the transom (enough to bolt an outboard on). If you don't need to tilt your engine, and are fine with a single, this seems like it would work just fine.
However, for most people, this isn't enough. But if we use that as a starting point, and add features as necessary, we can get to the true minimalist bracket. So add length, so you can tilt your motor. Now you have an unsupported platform coming off the back. So add supports. How you have a platform with angle aluminum connecting the platform. I saw someone on iBoats did this, and the response was mixed, but a lot of it seemed to stem from his use of bolts to hold the supports in place. Would welding change things? I'm also thinking, he just had free-standing supports. What about keeping a lot of the functionality of the hollow square bracket, but making it into a triangle? So instead of doing the open-air supports like that guy had, doing a fully enclosed triangular prism bracket? It would still be hollow, and could be filled with foam, and wouldn't it be stronger anyways, as well as cutting out half the material?
8) Conclusion. The big thing I can't figure out is why these are so expensive. I'm wondering about the pros and cons of having a local guy fabricate one for me. My paramount concern is safety, but if I can get an equally-safe but slightly less efficient bracket for significantly cheaper, I would take a loss of performance. It's not like I'm a boat racer, I just want to get out to fish! I will also say, even doing a traditional square bracket would be much cheaper locally. It just wouldn't be from a "known" builder. Just wondering how terrible this is!
I would appreciate any and all feedback, from "you know nothing, let me tell you why you're the stupidest person who has ever lived" to "let's talk about this, here are my thoughts, we can engage in a conversation and maybe end up learning something cool". I guess the only feedback that's not useful is purely positive feedback! ha. I assume I'm missing a lot of knowledge here, and I'd like to learn everything I can
Thank you in advance for your time
Hello,
I am thinking about ditching my old I/O and putting on an aluminum outboard bracket, something like an Armstrong bracket or something. I was hoping I might be able to ask a few questions!
1) the big question seems to be, single or twin? I plan on mostly going in the lakes/bays and stuff, where I'm never more than probably a mile or two offshore. However, it would be nice to be able to go into the ocean just a little on calm days. A twin almost doubles the cost because of materials and whatnot. For the most part, I feel like twins are just for convenience: Put on two 75hp motors instead of one 150hp motor, and if one goes out, the other one is already on there and you can limp home. But is there any merit to doing something like.... put a 150hp on there, and 99% of the time it'll be fine. And for the one time it's not, IF that happens to be in the middle of the ocean, keep a spare 50hp or something belowdecks? Like, even build a special compartment in the bow? because, really, how often are you going to have to need it, PLUS, as a added bonus, the weight of a motor up there will help counterbalance the extra leverage of the bracket. Seems like the slim chance of ever needing that extra engine is worth the extra work that it might be to haul a dead 150hp up and mount a 50hp.
2) local builders: Good or bad? If I have a local fab shop that can cut hundreds off the price (local discount, no shipping, etc), is that a viable way to go about things? I assume strength is paramount here, but a good aluminum welder should be able to make an equally strong bracket. But shape.... I think that places like Armstrong definitely have the knowledge about subtleties that will make the boat perform much better. But is that really worth a few hundred? If the angle is just a little off, how much will I really notice? Of course, if it's about safety, that's a whole different animal. But I assume strength is the important component for safety, and she shape is more about performance. I'd happily risk losing a quarter mile per hour of top speed or a tiny bit in fuel economy to save a ton of money up front. Plus, I feel like, a lot of "mistakes" in angles and stuff can be made up via engine positioning, right?
3) shape: Speaking of shape, I have a few questions about the shape of these guys. First off, am I correct in assuming that they're, essentially, hollow boxes? And that they can be filled with flotation foam or something for buoyancy? I've seen some that go all the way down and match the hull shape coming off the back, essentially just becoming an extension of the hull. But most of them I see are basically just boxes bolted onto the back. Why the discrepancy? Is one shape better than the other? Is there a downside to just the box model? I assume that, on boats where the transom in the same for their I/O and outboard models, the goal is just to recreate the transom angle a little further back. Then again, some of them are exactly beam width. Am I correct in assuming that these are intended to be swim platforms, and all you really need is the box if you don't want a swim platform?
4) Speaking of further back: How far back should these go? Most of the ones I've seen are WIDE. Like, 2-3 feet wide (that is, they add 2-3 feet straight off the back). That seems like it's designed to accommodate the engine tilting up. Is this strictly necessary? For example, if I have an engine that doesn't tilt (no such thing, that I know of. Just asking a theoretical question to get a sense of whether the length is critical or not), would I need that much room? I feel like, from a pure functional standpoint, the bare minimum you would need would be enough to bolt the outboard on, and that's it. Beyond this, the bare minimum you'd need would be enough to tilt the engine back. Any other reason for a long bracket?
5) materials: Looks like the standard is 1/8" 5052 aluminum. Is that right?
6) other: Anything else I'm failing to consider? Thoughts on going local?
7) I'm just thinking.... in order to combine all of the "minimalist" elements of a number of brackets, the absolute bare-bones approach would be an aluminum bar that just sticks out about 6 inches from the transom (enough to bolt an outboard on). If you don't need to tilt your engine, and are fine with a single, this seems like it would work just fine.
However, for most people, this isn't enough. But if we use that as a starting point, and add features as necessary, we can get to the true minimalist bracket. So add length, so you can tilt your motor. Now you have an unsupported platform coming off the back. So add supports. How you have a platform with angle aluminum connecting the platform. I saw someone on iBoats did this, and the response was mixed, but a lot of it seemed to stem from his use of bolts to hold the supports in place. Would welding change things? I'm also thinking, he just had free-standing supports. What about keeping a lot of the functionality of the hollow square bracket, but making it into a triangle? So instead of doing the open-air supports like that guy had, doing a fully enclosed triangular prism bracket? It would still be hollow, and could be filled with foam, and wouldn't it be stronger anyways, as well as cutting out half the material?
8) Conclusion. The big thing I can't figure out is why these are so expensive. I'm wondering about the pros and cons of having a local guy fabricate one for me. My paramount concern is safety, but if I can get an equally-safe but slightly less efficient bracket for significantly cheaper, I would take a loss of performance. It's not like I'm a boat racer, I just want to get out to fish! I will also say, even doing a traditional square bracket would be much cheaper locally. It just wouldn't be from a "known" builder. Just wondering how terrible this is!
I would appreciate any and all feedback, from "you know nothing, let me tell you why you're the stupidest person who has ever lived" to "let's talk about this, here are my thoughts, we can engage in a conversation and maybe end up learning something cool". I guess the only feedback that's not useful is purely positive feedback! ha. I assume I'm missing a lot of knowledge here, and I'd like to learn everything I can
Thank you in advance for your time
